Prepare nano proto code to be merged into protobuf repository.

12 files changed, 3973 insertions, 0 deletions

diff --git a/javanano/src/main/java/com/google/protobuf/nano/CodedInputByteBufferNano.java b/javanano/src/main/java/com/google/protobuf/nano/CodedInputByteBufferNano.java
new file mode 100644
index 00000000..c5fea5ae
--- /dev/null
+++ b/javanano/src/main/java/com/google/protobuf/nano/CodedInputByteBufferNano.java
@@ -0,0 +1,641 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2013 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf.nano;
+
+import java.io.IOException;
+
+/**
+ * Reads and decodes protocol message fields.
+ *
+ * This class contains two kinds of methods:  methods that read specific
+ * protocol message constructs and field types (e.g. {@link #readTag()} and
+ * {@link #readInt32()}) and methods that read low-level values (e.g.
+ * {@link #readRawVarint32()} and {@link #readRawBytes}).  If you are reading
+ * encoded protocol messages, you should use the former methods, but if you are
+ * reading some other format of your own design, use the latter.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public final class CodedInputByteBufferNano {
+  /**
+   * Create a new CodedInputStream wrapping the given byte array.
+   */
+  public static CodedInputByteBufferNano newInstance(final byte[] buf) {
+    return newInstance(buf, 0, buf.length);
+  }
+
+  /**
+   * Create a new CodedInputStream wrapping the given byte array slice.
+   */
+  public static CodedInputByteBufferNano newInstance(final byte[] buf, final int off,
+                                             final int len) {
+    return new CodedInputByteBufferNano(buf, off, len);
+  }
+
+  // -----------------------------------------------------------------
+
+  /**
+   * Attempt to read a field tag, returning zero if we have reached EOF.
+   * Protocol message parsers use this to read tags, since a protocol message
+   * may legally end wherever a tag occurs, and zero is not a valid tag number.
+   */
+  public int readTag() throws IOException {
+    if (isAtEnd()) {
+      lastTag = 0;
+      return 0;
+    }
+
+    lastTag = readRawVarint32();
+    if (lastTag == 0) {
+      // If we actually read zero, that's not a valid tag.
+      throw InvalidProtocolBufferNanoException.invalidTag();
+    }
+    return lastTag;
+  }
+
+  /**
+   * Verifies that the last call to readTag() returned the given tag value.
+   * This is used to verify that a nested group ended with the correct
+   * end tag.
+   *
+   * @throws InvalidProtocolBufferNanoException {@code value} does not match the
+   *                                        last tag.
+   */
+  public void checkLastTagWas(final int value)
+                              throws InvalidProtocolBufferNanoException {
+    if (lastTag != value) {
+      throw InvalidProtocolBufferNanoException.invalidEndTag();
+    }
+  }
+
+  /**
+   * Reads and discards a single field, given its tag value.
+   *
+   * @return {@code false} if the tag is an endgroup tag, in which case
+   *         nothing is skipped.  Otherwise, returns {@code true}.
+   */
+  public boolean skipField(final int tag) throws IOException {
+    switch (WireFormatNano.getTagWireType(tag)) {
+      case WireFormatNano.WIRETYPE_VARINT:
+        readInt32();
+        return true;
+      case WireFormatNano.WIRETYPE_FIXED64:
+        readRawLittleEndian64();
+        return true;
+      case WireFormatNano.WIRETYPE_LENGTH_DELIMITED:
+        skipRawBytes(readRawVarint32());
+        return true;
+      case WireFormatNano.WIRETYPE_START_GROUP:
+        skipMessage();
+        checkLastTagWas(
+          WireFormatNano.makeTag(WireFormatNano.getTagFieldNumber(tag),
+                             WireFormatNano.WIRETYPE_END_GROUP));
+        return true;
+      case WireFormatNano.WIRETYPE_END_GROUP:
+        return false;
+      case WireFormatNano.WIRETYPE_FIXED32:
+        readRawLittleEndian32();
+        return true;
+      default:
+        throw InvalidProtocolBufferNanoException.invalidWireType();
+    }
+  }
+
+  /**
+   * Reads and discards an entire message.  This will read either until EOF
+   * or until an endgroup tag, whichever comes first.
+   */
+  public void skipMessage() throws IOException {
+    while (true) {
+      final int tag = readTag();
+      if (tag == 0 || !skipField(tag)) {
+        return;
+      }
+    }
+  }
+
+  // -----------------------------------------------------------------
+
+  /** Read a {@code double} field value from the stream. */
+  public double readDouble() throws IOException {
+    return Double.longBitsToDouble(readRawLittleEndian64());
+  }
+
+  /** Read a {@code float} field value from the stream. */
+  public float readFloat() throws IOException {
+    return Float.intBitsToFloat(readRawLittleEndian32());
+  }
+
+  /** Read a {@code uint64} field value from the stream. */
+  public long readUInt64() throws IOException {
+    return readRawVarint64();
+  }
+
+  /** Read an {@code int64} field value from the stream. */
+  public long readInt64() throws IOException {
+    return readRawVarint64();
+  }
+
+  /** Read an {@code int32} field value from the stream. */
+  public int readInt32() throws IOException {
+    return readRawVarint32();
+  }
+
+  /** Read a {@code fixed64} field value from the stream. */
+  public long readFixed64() throws IOException {
+    return readRawLittleEndian64();
+  }
+
+  /** Read a {@code fixed32} field value from the stream. */
+  public int readFixed32() throws IOException {
+    return readRawLittleEndian32();
+  }
+
+  /** Read a {@code bool} field value from the stream. */
+  public boolean readBool() throws IOException {
+    return readRawVarint32() != 0;
+  }
+
+  /** Read a {@code string} field value from the stream. */
+  public String readString() throws IOException {
+    final int size = readRawVarint32();
+    if (size <= (bufferSize - bufferPos) && size > 0) {
+      // Fast path:  We already have the bytes in a contiguous buffer, so
+      //   just copy directly from it.
+      final String result = new String(buffer, bufferPos, size, "UTF-8");
+      bufferPos += size;
+      return result;
+    } else {
+      // Slow path:  Build a byte array first then copy it.
+      return new String(readRawBytes(size), "UTF-8");
+    }
+  }
+
+  /** Read a {@code group} field value from the stream. */
+  public void readGroup(final MessageNano msg, final int fieldNumber)
+      throws IOException {
+    if (recursionDepth >= recursionLimit) {
+      throw InvalidProtocolBufferNanoException.recursionLimitExceeded();
+    }
+    ++recursionDepth;
+    msg.mergeFrom(this);
+    checkLastTagWas(
+      WireFormatNano.makeTag(fieldNumber, WireFormatNano.WIRETYPE_END_GROUP));
+    --recursionDepth;
+  }
+
+  public void readMessage(final MessageNano msg)
+      throws IOException {
+    final int length = readRawVarint32();
+    if (recursionDepth >= recursionLimit) {
+      throw InvalidProtocolBufferNanoException.recursionLimitExceeded();
+    }
+    final int oldLimit = pushLimit(length);
+    ++recursionDepth;
+    msg.mergeFrom(this);
+    checkLastTagWas(0);
+    --recursionDepth;
+    popLimit(oldLimit);
+  }
+
+  /** Read a {@code bytes} field value from the stream. */
+  public byte[] readBytes() throws IOException {
+    final int size = readRawVarint32();
+    if (size <= (bufferSize - bufferPos) && size > 0) {
+      // Fast path:  We already have the bytes in a contiguous buffer, so
+      //   just copy directly from it.
+      final byte[] result = new byte[size];
+      System.arraycopy(buffer, bufferPos, result, 0, size);
+      bufferPos += size;
+      return result;
+    } else {
+      // Slow path:  Build a byte array first then copy it.
+      return readRawBytes(size);
+    }
+  }
+
+  /** Read a {@code uint32} field value from the stream. */
+  public int readUInt32() throws IOException {
+    return readRawVarint32();
+  }
+
+  /**
+   * Read an enum field value from the stream.  Caller is responsible
+   * for converting the numeric value to an actual enum.
+   */
+  public int readEnum() throws IOException {
+    return readRawVarint32();
+  }
+
+  /** Read an {@code sfixed32} field value from the stream. */
+  public int readSFixed32() throws IOException {
+    return readRawLittleEndian32();
+  }
+
+  /** Read an {@code sfixed64} field value from the stream. */
+  public long readSFixed64() throws IOException {
+    return readRawLittleEndian64();
+  }
+
+  /** Read an {@code sint32} field value from the stream. */
+  public int readSInt32() throws IOException {
+    return decodeZigZag32(readRawVarint32());
+  }
+
+  /** Read an {@code sint64} field value from the stream. */
+  public long readSInt64() throws IOException {
+    return decodeZigZag64(readRawVarint64());
+  }
+
+  // =================================================================
+
+  /**
+   * Read a raw Varint from the stream.  If larger than 32 bits, discard the
+   * upper bits.
+   */
+  public int readRawVarint32() throws IOException {
+    byte tmp = readRawByte();
+    if (tmp >= 0) {
+      return tmp;
+    }
+    int result = tmp & 0x7f;
+    if ((tmp = readRawByte()) >= 0) {
+      result |= tmp << 7;
+    } else {
+      result |= (tmp & 0x7f) << 7;
+      if ((tmp = readRawByte()) >= 0) {
+        result |= tmp << 14;
+      } else {
+        result |= (tmp & 0x7f) << 14;
+        if ((tmp = readRawByte()) >= 0) {
+          result |= tmp << 21;
+        } else {
+          result |= (tmp & 0x7f) << 21;
+          result |= (tmp = readRawByte()) << 28;
+          if (tmp < 0) {
+            // Discard upper 32 bits.
+            for (int i = 0; i < 5; i++) {
+              if (readRawByte() >= 0) {
+                return result;
+              }
+            }
+            throw InvalidProtocolBufferNanoException.malformedVarint();
+          }
+        }
+      }
+    }
+    return result;
+  }
+
+  /** Read a raw Varint from the stream. */
+  public long readRawVarint64() throws IOException {
+    int shift = 0;
+    long result = 0;
+    while (shift < 64) {
+      final byte b = readRawByte();
+      result |= (long)(b & 0x7F) << shift;
+      if ((b & 0x80) == 0) {
+        return result;
+      }
+      shift += 7;
+    }
+    throw InvalidProtocolBufferNanoException.malformedVarint();
+  }
+
+  /** Read a 32-bit little-endian integer from the stream. */
+  public int readRawLittleEndian32() throws IOException {
+    final byte b1 = readRawByte();
+    final byte b2 = readRawByte();
+    final byte b3 = readRawByte();
+    final byte b4 = readRawByte();
+    return ((b1 & 0xff)      ) |
+           ((b2 & 0xff) <<  8) |
+           ((b3 & 0xff) << 16) |
+           ((b4 & 0xff) << 24);
+  }
+
+  /** Read a 64-bit little-endian integer from the stream. */
+  public long readRawLittleEndian64() throws IOException {
+    final byte b1 = readRawByte();
+    final byte b2 = readRawByte();
+    final byte b3 = readRawByte();
+    final byte b4 = readRawByte();
+    final byte b5 = readRawByte();
+    final byte b6 = readRawByte();
+    final byte b7 = readRawByte();
+    final byte b8 = readRawByte();
+    return (((long)b1 & 0xff)      ) |
+           (((long)b2 & 0xff) <<  8) |
+           (((long)b3 & 0xff) << 16) |
+           (((long)b4 & 0xff) << 24) |
+           (((long)b5 & 0xff) << 32) |
+           (((long)b6 & 0xff) << 40) |
+           (((long)b7 & 0xff) << 48) |
+           (((long)b8 & 0xff) << 56);
+  }
+
+  /**
+   * Decode a ZigZag-encoded 32-bit value.  ZigZag encodes signed integers
+   * into values that can be efficiently encoded with varint.  (Otherwise,
+   * negative values must be sign-extended to 64 bits to be varint encoded,
+   * thus always taking 10 bytes on the wire.)
+   *
+   * @param n An unsigned 32-bit integer, stored in a signed int because
+   *          Java has no explicit unsigned support.
+   * @return A signed 32-bit integer.
+   */
+  public static int decodeZigZag32(final int n) {
+    return (n >>> 1) ^ -(n & 1);
+  }
+
+  /**
+   * Decode a ZigZag-encoded 64-bit value.  ZigZag encodes signed integers
+   * into values that can be efficiently encoded with varint.  (Otherwise,
+   * negative values must be sign-extended to 64 bits to be varint encoded,
+   * thus always taking 10 bytes on the wire.)
+   *
+   * @param n An unsigned 64-bit integer, stored in a signed int because
+   *          Java has no explicit unsigned support.
+   * @return A signed 64-bit integer.
+   */
+  public static long decodeZigZag64(final long n) {
+    return (n >>> 1) ^ -(n & 1);
+  }
+
+  // -----------------------------------------------------------------
+
+  private final byte[] buffer;
+  private int bufferStart;
+  private int bufferSize;
+  private int bufferSizeAfterLimit;
+  private int bufferPos;
+  private int lastTag;
+
+  /** The absolute position of the end of the current message. */
+  private int currentLimit = Integer.MAX_VALUE;
+
+  /** See setRecursionLimit() */
+  private int recursionDepth;
+  private int recursionLimit = DEFAULT_RECURSION_LIMIT;
+
+  /** See setSizeLimit() */
+  private int sizeLimit = DEFAULT_SIZE_LIMIT;
+
+  private static final int DEFAULT_RECURSION_LIMIT = 64;
+  private static final int DEFAULT_SIZE_LIMIT = 64 << 20;  // 64MB
+
+  private CodedInputByteBufferNano(final byte[] buffer, final int off, final int len) {
+    this.buffer = buffer;
+    bufferStart = off;
+    bufferSize = off + len;
+    bufferPos = off;
+  }
+
+  /**
+   * Set the maximum message recursion depth.  In order to prevent malicious
+   * messages from causing stack overflows, {@code CodedInputStream} limits
+   * how deeply messages may be nested.  The default limit is 64.
+   *
+   * @return the old limit.
+   */
+  public int setRecursionLimit(final int limit) {
+    if (limit < 0) {
+      throw new IllegalArgumentException(
+        "Recursion limit cannot be negative: " + limit);
+    }
+    final int oldLimit = recursionLimit;
+    recursionLimit = limit;
+    return oldLimit;
+  }
+
+  /**
+   * Set the maximum message size.  In order to prevent malicious
+   * messages from exhausting memory or causing integer overflows,
+   * {@code CodedInputStream} limits how large a message may be.
+   * The default limit is 64MB.  You should set this limit as small
+   * as you can without harming your app's functionality.  Note that
+   * size limits only apply when reading from an {@code InputStream}, not
+   * when constructed around a raw byte array.
+   * <p>
+   * If you want to read several messages from a single CodedInputStream, you
+   * could call {@link #resetSizeCounter()} after each one to avoid hitting the
+   * size limit.
+   *
+   * @return the old limit.
+   */
+  public int setSizeLimit(final int limit) {
+    if (limit < 0) {
+      throw new IllegalArgumentException(
+        "Size limit cannot be negative: " + limit);
+    }
+    final int oldLimit = sizeLimit;
+    sizeLimit = limit;
+    return oldLimit;
+  }
+
+  /**
+   * Resets the current size counter to zero (see {@link #setSizeLimit(int)}).
+   */
+  public void resetSizeCounter() {
+  }
+
+  /**
+   * Sets {@code currentLimit} to (current position) + {@code byteLimit}.  This
+   * is called when descending into a length-delimited embedded message.
+   *
+   * @return the old limit.
+   */
+  public int pushLimit(int byteLimit) throws InvalidProtocolBufferNanoException {
+    if (byteLimit < 0) {
+      throw InvalidProtocolBufferNanoException.negativeSize();
+    }
+    byteLimit += bufferPos;
+    final int oldLimit = currentLimit;
+    if (byteLimit > oldLimit) {
+      throw InvalidProtocolBufferNanoException.truncatedMessage();
+    }
+    currentLimit = byteLimit;
+
+    recomputeBufferSizeAfterLimit();
+
+    return oldLimit;
+  }
+
+  private void recomputeBufferSizeAfterLimit() {
+    bufferSize += bufferSizeAfterLimit;
+    final int bufferEnd = bufferSize;
+    if (bufferEnd > currentLimit) {
+      // Limit is in current buffer.
+      bufferSizeAfterLimit = bufferEnd - currentLimit;
+      bufferSize -= bufferSizeAfterLimit;
+    } else {
+      bufferSizeAfterLimit = 0;
+    }
+  }
+
+  /**
+   * Discards the current limit, returning to the previous limit.
+   *
+   * @param oldLimit The old limit, as returned by {@code pushLimit}.
+   */
+  public void popLimit(final int oldLimit) {
+    currentLimit = oldLimit;
+    recomputeBufferSizeAfterLimit();
+  }
+
+  /**
+   * Returns the number of bytes to be read before the current limit.
+   * If no limit is set, returns -1.
+   */
+  public int getBytesUntilLimit() {
+    if (currentLimit == Integer.MAX_VALUE) {
+      return -1;
+    }
+
+    final int currentAbsolutePosition = bufferPos;
+    return currentLimit - currentAbsolutePosition;
+  }
+
+  /**
+   * Returns true if the stream has reached the end of the input.  This is the
+   * case if either the end of the underlying input source has been reached or
+   * if the stream has reached a limit created using {@link #pushLimit(int)}.
+   */
+  public boolean isAtEnd() {
+    return bufferPos == bufferSize;
+  }
+
+  /**
+   * Get current position in buffer relative to beginning offset.
+   */
+  public int getPosition() {
+    return bufferPos - bufferStart;
+  }
+
+  /**
+   * Retrieves a subset of data in the buffer. The returned array is not backed by the original
+   * buffer array.
+   *
+   * @param offset the position (relative to the buffer start position) to start at.
+   * @param length the number of bytes to retrieve.
+   */
+  public byte[] getData(int offset, int length) {
+    if (length == 0) {
+      return WireFormatNano.EMPTY_BYTES;
+    }
+    byte[] copy = new byte[length];
+    int start = bufferStart + offset;
+    System.arraycopy(buffer, start, copy, 0, length);
+    return copy;
+  }
+
+  /**
+   * Rewind to previous position. Cannot go forward.
+   */
+  public void rewindToPosition(int position) {
+    if (position > bufferPos - bufferStart) {
+      throw new IllegalArgumentException(
+              "Position " + position + " is beyond current " + (bufferPos - bufferStart));
+    }
+    if (position < 0) {
+      throw new IllegalArgumentException("Bad position " + position);
+    }
+    bufferPos = bufferStart + position;
+  }
+
+  /**
+   * Read one byte from the input.
+   *
+   * @throws InvalidProtocolBufferNanoException The end of the stream or the current
+   *                                        limit was reached.
+   */
+  public byte readRawByte() throws IOException {
+    if (bufferPos == bufferSize) {
+      throw InvalidProtocolBufferNanoException.truncatedMessage();
+    }
+    return buffer[bufferPos++];
+  }
+
+  /**
+   * Read a fixed size of bytes from the input.
+   *
+   * @throws InvalidProtocolBufferNanoException The end of the stream or the current
+   *                                        limit was reached.
+   */
+  public byte[] readRawBytes(final int size) throws IOException {
+    if (size < 0) {
+      throw InvalidProtocolBufferNanoException.negativeSize();
+    }
+
+    if (bufferPos + size > currentLimit) {
+      // Read to the end of the stream anyway.
+      skipRawBytes(currentLimit - bufferPos);
+      // Then fail.
+      throw InvalidProtocolBufferNanoException.truncatedMessage();
+    }
+
+    if (size <= bufferSize - bufferPos) {
+      // We have all the bytes we need already.
+      final byte[] bytes = new byte[size];
+      System.arraycopy(buffer, bufferPos, bytes, 0, size);
+      bufferPos += size;
+      return bytes;
+    } else {
+      throw InvalidProtocolBufferNanoException.truncatedMessage();
+    }
+  }
+
+  /**
+   * Reads and discards {@code size} bytes.
+   *
+   * @throws InvalidProtocolBufferNanoException The end of the stream or the current
+   *                                        limit was reached.
+   */
+  public void skipRawBytes(final int size) throws IOException {
+    if (size < 0) {
+      throw InvalidProtocolBufferNanoException.negativeSize();
+    }
+
+    if (bufferPos + size > currentLimit) {
+      // Read to the end of the stream anyway.
+      skipRawBytes(currentLimit - bufferPos);
+      // Then fail.
+      throw InvalidProtocolBufferNanoException.truncatedMessage();
+    }
+
+    if (size <= bufferSize - bufferPos) {
+      // We have all the bytes we need already.
+      bufferPos += size;
+    } else {
+      throw InvalidProtocolBufferNanoException.truncatedMessage();
+    }
+  }
+}
diff --git a/javanano/src/main/java/com/google/protobuf/nano/CodedOutputByteBufferNano.java b/javanano/src/main/java/com/google/protobuf/nano/CodedOutputByteBufferNano.java
new file mode 100644
index 00000000..88df38d7
--- /dev/null
+++ b/javanano/src/main/java/com/google/protobuf/nano/CodedOutputByteBufferNano.java
@@ -0,0 +1,879 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2013 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf.nano;
+
+import java.io.IOException;
+import java.io.UnsupportedEncodingException;
+
+/**
+ * Encodes and writes protocol message fields.
+ *
+ * <p>This class contains two kinds of methods:  methods that write specific
+ * protocol message constructs and field types (e.g. {@link #writeTag} and
+ * {@link #writeInt32}) and methods that write low-level values (e.g.
+ * {@link #writeRawVarint32} and {@link #writeRawBytes}).  If you are
+ * writing encoded protocol messages, you should use the former methods, but if
+ * you are writing some other format of your own design, use the latter.
+ *
+ * <p>This class is totally unsynchronized.
+ *
+ * @author kneton@google.com Kenton Varda
+ */
+public final class CodedOutputByteBufferNano {
+  private final byte[] buffer;
+  private final int limit;
+  private int position;
+
+  private CodedOutputByteBufferNano(final byte[] buffer, final int offset,
+                            final int length) {
+    this.buffer = buffer;
+    position = offset;
+    limit = offset + length;
+  }
+
+  /**
+   * Create a new {@code CodedOutputStream} that writes directly to the given
+   * byte array.  If more bytes are written than fit in the array,
+   * {@link OutOfSpaceException} will be thrown.  Writing directly to a flat
+   * array is faster than writing to an {@code OutputStream}.
+   */
+  public static CodedOutputByteBufferNano newInstance(final byte[] flatArray) {
+    return newInstance(flatArray, 0, flatArray.length);
+  }
+
+  /**
+   * Create a new {@code CodedOutputStream} that writes directly to the given
+   * byte array slice.  If more bytes are written than fit in the slice,
+   * {@link OutOfSpaceException} will be thrown.  Writing directly to a flat
+   * array is faster than writing to an {@code OutputStream}.
+   */
+  public static CodedOutputByteBufferNano newInstance(final byte[] flatArray,
+                                              final int offset,
+                                              final int length) {
+    return new CodedOutputByteBufferNano(flatArray, offset, length);
+  }
+
+  // -----------------------------------------------------------------
+
+  /** Write a {@code double} field, including tag, to the stream. */
+  public void writeDouble(final int fieldNumber, final double value)
+                          throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_FIXED64);
+    writeDoubleNoTag(value);
+  }
+
+  /** Write a {@code float} field, including tag, to the stream. */
+  public void writeFloat(final int fieldNumber, final float value)
+                         throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_FIXED32);
+    writeFloatNoTag(value);
+  }
+
+  /** Write a {@code uint64} field, including tag, to the stream. */
+  public void writeUInt64(final int fieldNumber, final long value)
+                          throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_VARINT);
+    writeUInt64NoTag(value);
+  }
+
+  /** Write an {@code int64} field, including tag, to the stream. */
+  public void writeInt64(final int fieldNumber, final long value)
+                         throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_VARINT);
+    writeInt64NoTag(value);
+  }
+
+  /** Write an {@code int32} field, including tag, to the stream. */
+  public void writeInt32(final int fieldNumber, final int value)
+                         throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_VARINT);
+    writeInt32NoTag(value);
+  }
+
+  /** Write a {@code fixed64} field, including tag, to the stream. */
+  public void writeFixed64(final int fieldNumber, final long value)
+                           throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_FIXED64);
+    writeFixed64NoTag(value);
+  }
+
+  /** Write a {@code fixed32} field, including tag, to the stream. */
+  public void writeFixed32(final int fieldNumber, final int value)
+                           throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_FIXED32);
+    writeFixed32NoTag(value);
+  }
+
+  /** Write a {@code bool} field, including tag, to the stream. */
+  public void writeBool(final int fieldNumber, final boolean value)
+                        throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_VARINT);
+    writeBoolNoTag(value);
+  }
+
+  /** Write a {@code string} field, including tag, to the stream. */
+  public void writeString(final int fieldNumber, final String value)
+                          throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_LENGTH_DELIMITED);
+    writeStringNoTag(value);
+  }
+
+  /** Write a {@code group} field, including tag, to the stream. */
+  public void writeGroup(final int fieldNumber, final MessageNano value)
+                         throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_START_GROUP);
+    writeGroupNoTag(value);
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_END_GROUP);
+  }
+
+  /** Write an embedded message field, including tag, to the stream. */
+  public void writeMessage(final int fieldNumber, final MessageNano value)
+                           throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_LENGTH_DELIMITED);
+    writeMessageNoTag(value);
+  }
+
+  /** Write a {@code bytes} field, including tag, to the stream. */
+  public void writeBytes(final int fieldNumber, final byte[] value)
+                         throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_LENGTH_DELIMITED);
+    writeBytesNoTag(value);
+  }
+
+  /** Write a {@code uint32} field, including tag, to the stream. */
+  public void writeUInt32(final int fieldNumber, final int value)
+                          throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_VARINT);
+    writeUInt32NoTag(value);
+  }
+
+  /**
+   * Write an enum field, including tag, to the stream.  Caller is responsible
+   * for converting the enum value to its numeric value.
+   */
+  public void writeEnum(final int fieldNumber, final int value)
+                        throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_VARINT);
+    writeEnumNoTag(value);
+  }
+
+  /** Write an {@code sfixed32} field, including tag, to the stream. */
+  public void writeSFixed32(final int fieldNumber, final int value)
+                            throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_FIXED32);
+    writeSFixed32NoTag(value);
+  }
+
+  /** Write an {@code sfixed64} field, including tag, to the stream. */
+  public void writeSFixed64(final int fieldNumber, final long value)
+                            throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_FIXED64);
+    writeSFixed64NoTag(value);
+  }
+
+  /** Write an {@code sint32} field, including tag, to the stream. */
+  public void writeSInt32(final int fieldNumber, final int value)
+                          throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_VARINT);
+    writeSInt32NoTag(value);
+  }
+
+  /** Write an {@code sint64} field, including tag, to the stream. */
+  public void writeSInt64(final int fieldNumber, final long value)
+                          throws IOException {
+    writeTag(fieldNumber, WireFormatNano.WIRETYPE_VARINT);
+    writeSInt64NoTag(value);
+  }
+
+  /**
+   * Write a MessageSet extension field to the stream.  For historical reasons,
+   * the wire format differs from normal fields.
+   */
+//  public void writeMessageSetExtension(final int fieldNumber,
+//                                       final MessageMicro value)
+//                                       throws IOException {
+//    writeTag(WireFormatMicro.MESSAGE_SET_ITEM, WireFormatMicro.WIRETYPE_START_GROUP);
+//    writeUInt32(WireFormatMicro.MESSAGE_SET_TYPE_ID, fieldNumber);
+//    writeMessage(WireFormatMicro.MESSAGE_SET_MESSAGE, value);
+//    writeTag(WireFormatMicro.MESSAGE_SET_ITEM, WireFormatMicro.WIRETYPE_END_GROUP);
+//  }
+
+  /**
+   * Write an unparsed MessageSet extension field to the stream.  For
+   * historical reasons, the wire format differs from normal fields.
+   */
+//  public void writeRawMessageSetExtension(final int fieldNumber,
+//                                          final ByteStringMicro value)
+//                                          throws IOException {
+//    writeTag(WireFormatMicro.MESSAGE_SET_ITEM, WireFormatMicro.WIRETYPE_START_GROUP);
+//    writeUInt32(WireFormatMicro.MESSAGE_SET_TYPE_ID, fieldNumber);
+//    writeBytes(WireFormatMicro.MESSAGE_SET_MESSAGE, value);
+//    writeTag(WireFormatMicro.MESSAGE_SET_ITEM, WireFormatMicro.WIRETYPE_END_GROUP);
+//  }
+
+  // -----------------------------------------------------------------
+
+  /** Write a {@code double} field to the stream. */
+  public void writeDoubleNoTag(final double value) throws IOException {
+    writeRawLittleEndian64(Double.doubleToLongBits(value));
+  }
+
+  /** Write a {@code float} field to the stream. */
+  public void writeFloatNoTag(final float value) throws IOException {
+    writeRawLittleEndian32(Float.floatToIntBits(value));
+  }
+
+  /** Write a {@code uint64} field to the stream. */
+  public void writeUInt64NoTag(final long value) throws IOException {
+    writeRawVarint64(value);
+  }
+
+  /** Write an {@code int64} field to the stream. */
+  public void writeInt64NoTag(final long value) throws IOException {
+    writeRawVarint64(value);
+  }
+
+  /** Write an {@code int32} field to the stream. */
+  public void writeInt32NoTag(final int value) throws IOException {
+    if (value >= 0) {
+      writeRawVarint32(value);
+    } else {
+      // Must sign-extend.
+      writeRawVarint64(value);
+    }
+  }
+
+  /** Write a {@code fixed64} field to the stream. */
+  public void writeFixed64NoTag(final long value) throws IOException {
+    writeRawLittleEndian64(value);
+  }
+
+  /** Write a {@code fixed32} field to the stream. */
+  public void writeFixed32NoTag(final int value) throws IOException {
+    writeRawLittleEndian32(value);
+  }
+
+  /** Write a {@code bool} field to the stream. */
+  public void writeBoolNoTag(final boolean value) throws IOException {
+    writeRawByte(value ? 1 : 0);
+  }
+
+  /** Write a {@code string} field to the stream. */
+  public void writeStringNoTag(final String value) throws IOException {
+    // Unfortunately there does not appear to be any way to tell Java to encode
+    // UTF-8 directly into our buffer, so we have to let it create its own byte
+    // array and then copy.
+    final byte[] bytes = value.getBytes("UTF-8");
+    writeRawVarint32(bytes.length);
+    writeRawBytes(bytes);
+  }
+
+  /** Write a {@code group} field to the stream. */
+  public void writeGroupNoTag(final MessageNano value) throws IOException {
+    value.writeTo(this);
+  }
+
+  /** Write an embedded message field to the stream. */
+  public void writeMessageNoTag(final MessageNano value) throws IOException {
+    writeRawVarint32(value.getCachedSize());
+    value.writeTo(this);
+  }
+
+  /** Write a {@code bytes} field to the stream. */
+  public void writeBytesNoTag(final byte[] value) throws IOException {
+    writeRawVarint32(value.length);
+    writeRawBytes(value);
+  }
+
+  /** Write a {@code uint32} field to the stream. */
+  public void writeUInt32NoTag(final int value) throws IOException {
+    writeRawVarint32(value);
+  }
+
+  /**
+   * Write an enum field to the stream.  Caller is responsible
+   * for converting the enum value to its numeric value.
+   */
+  public void writeEnumNoTag(final int value) throws IOException {
+    writeRawVarint32(value);
+  }
+
+  /** Write an {@code sfixed32} field to the stream. */
+  public void writeSFixed32NoTag(final int value) throws IOException {
+    writeRawLittleEndian32(value);
+  }
+
+  /** Write an {@code sfixed64} field to the stream. */
+  public void writeSFixed64NoTag(final long value) throws IOException {
+    writeRawLittleEndian64(value);
+  }
+
+  /** Write an {@code sint32} field to the stream. */
+  public void writeSInt32NoTag(final int value) throws IOException {
+    writeRawVarint32(encodeZigZag32(value));
+  }
+
+  /** Write an {@code sint64} field to the stream. */
+  public void writeSInt64NoTag(final long value) throws IOException {
+    writeRawVarint64(encodeZigZag64(value));
+  }
+
+  // =================================================================
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code double} field, including tag.
+   */
+  public static int computeDoubleSize(final int fieldNumber,
+                                      final double value) {
+    return computeTagSize(fieldNumber) + computeDoubleSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code float} field, including tag.
+   */
+  public static int computeFloatSize(final int fieldNumber, final float value) {
+    return computeTagSize(fieldNumber) + computeFloatSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code uint64} field, including tag.
+   */
+  public static int computeUInt64Size(final int fieldNumber, final long value) {
+    return computeTagSize(fieldNumber) + computeUInt64SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code int64} field, including tag.
+   */
+  public static int computeInt64Size(final int fieldNumber, final long value) {
+    return computeTagSize(fieldNumber) + computeInt64SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code int32} field, including tag.
+   */
+  public static int computeInt32Size(final int fieldNumber, final int value) {
+    return computeTagSize(fieldNumber) + computeInt32SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code fixed64} field, including tag.
+   */
+  public static int computeFixed64Size(final int fieldNumber,
+                                       final long value) {
+    return computeTagSize(fieldNumber) + computeFixed64SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code fixed32} field, including tag.
+   */
+  public static int computeFixed32Size(final int fieldNumber,
+                                       final int value) {
+    return computeTagSize(fieldNumber) + computeFixed32SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code bool} field, including tag.
+   */
+  public static int computeBoolSize(final int fieldNumber,
+                                    final boolean value) {
+    return computeTagSize(fieldNumber) + computeBoolSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code string} field, including tag.
+   */
+  public static int computeStringSize(final int fieldNumber,
+                                      final String value) {
+    return computeTagSize(fieldNumber) + computeStringSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code group} field, including tag.
+   */
+  public static int computeGroupSize(final int fieldNumber,
+                                     final MessageNano value) {
+    return computeTagSize(fieldNumber) * 2 + computeGroupSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * embedded message field, including tag.
+   */
+  public static int computeMessageSize(final int fieldNumber,
+                                       final MessageNano value) {
+    return computeTagSize(fieldNumber) + computeMessageSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code bytes} field, including tag.
+   */
+  public static int computeBytesSize(final int fieldNumber,
+                                     final byte[] value) {
+    return computeTagSize(fieldNumber) + computeBytesSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code uint32} field, including tag.
+   */
+  public static int computeUInt32Size(final int fieldNumber, final int value) {
+    return computeTagSize(fieldNumber) + computeUInt32SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * enum field, including tag.  Caller is responsible for converting the
+   * enum value to its numeric value.
+   */
+  public static int computeEnumSize(final int fieldNumber, final int value) {
+    return computeTagSize(fieldNumber) + computeEnumSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sfixed32} field, including tag.
+   */
+  public static int computeSFixed32Size(final int fieldNumber,
+                                        final int value) {
+    return computeTagSize(fieldNumber) + computeSFixed32SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sfixed64} field, including tag.
+   */
+  public static int computeSFixed64Size(final int fieldNumber,
+                                        final long value) {
+    return computeTagSize(fieldNumber) + computeSFixed64SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sint32} field, including tag.
+   */
+  public static int computeSInt32Size(final int fieldNumber, final int value) {
+    return computeTagSize(fieldNumber) + computeSInt32SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sint64} field, including tag.
+   */
+  public static int computeSInt64Size(final int fieldNumber, final long value) {
+    return computeTagSize(fieldNumber) + computeSInt64SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * MessageSet extension to the stream.  For historical reasons,
+   * the wire format differs from normal fields.
+   */
+//  public static int computeMessageSetExtensionSize(
+//      final int fieldNumber, final MessageMicro value) {
+//    return computeTagSize(WireFormatMicro.MESSAGE_SET_ITEM) * 2 +
+//           computeUInt32Size(WireFormatMicro.MESSAGE_SET_TYPE_ID, fieldNumber) +
+//           computeMessageSize(WireFormatMicro.MESSAGE_SET_MESSAGE, value);
+//  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * unparsed MessageSet extension field to the stream.  For
+   * historical reasons, the wire format differs from normal fields.
+   */
+//  public static int computeRawMessageSetExtensionSize(
+//      final int fieldNumber, final ByteStringMicro value) {
+//    return computeTagSize(WireFormatMicro.MESSAGE_SET_ITEM) * 2 +
+//           computeUInt32Size(WireFormatMicro.MESSAGE_SET_TYPE_ID, fieldNumber) +
+//           computeBytesSize(WireFormatMicro.MESSAGE_SET_MESSAGE, value);
+//  }
+
+  // -----------------------------------------------------------------
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code double} field, including tag.
+   */
+  public static int computeDoubleSizeNoTag(final double value) {
+    return LITTLE_ENDIAN_64_SIZE;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code float} field, including tag.
+   */
+  public static int computeFloatSizeNoTag(final float value) {
+    return LITTLE_ENDIAN_32_SIZE;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code uint64} field, including tag.
+   */
+  public static int computeUInt64SizeNoTag(final long value) {
+    return computeRawVarint64Size(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code int64} field, including tag.
+   */
+  public static int computeInt64SizeNoTag(final long value) {
+    return computeRawVarint64Size(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code int32} field, including tag.
+   */
+  public static int computeInt32SizeNoTag(final int value) {
+    if (value >= 0) {
+      return computeRawVarint32Size(value);
+    } else {
+      // Must sign-extend.
+      return 10;
+    }
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code fixed64} field.
+   */
+  public static int computeFixed64SizeNoTag(final long value) {
+    return LITTLE_ENDIAN_64_SIZE;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code fixed32} field.
+   */
+  public static int computeFixed32SizeNoTag(final int value) {
+    return LITTLE_ENDIAN_32_SIZE;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code bool} field.
+   */
+  public static int computeBoolSizeNoTag(final boolean value) {
+    return 1;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code string} field.
+   */
+  public static int computeStringSizeNoTag(final String value) {
+    try {
+      final byte[] bytes = value.getBytes("UTF-8");
+      return computeRawVarint32Size(bytes.length) +
+             bytes.length;
+    } catch (UnsupportedEncodingException e) {
+      throw new RuntimeException("UTF-8 not supported.");
+    }
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code group} field.
+   */
+  public static int computeGroupSizeNoTag(final MessageNano value) {
+    return value.getSerializedSize();
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an embedded
+   * message field.
+   */
+  public static int computeMessageSizeNoTag(final MessageNano value) {
+    final int size = value.getSerializedSize();
+    return computeRawVarint32Size(size) + size;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code bytes} field.
+   */
+  public static int computeBytesSizeNoTag(final byte[] value) {
+    return computeRawVarint32Size(value.length) + value.length;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code uint32} field.
+   */
+  public static int computeUInt32SizeNoTag(final int value) {
+    return computeRawVarint32Size(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an enum field.
+   * Caller is responsible for converting the enum value to its numeric value.
+   */
+  public static int computeEnumSizeNoTag(final int value) {
+    return computeRawVarint32Size(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sfixed32} field.
+   */
+  public static int computeSFixed32SizeNoTag(final int value) {
+    return LITTLE_ENDIAN_32_SIZE;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sfixed64} field.
+   */
+  public static int computeSFixed64SizeNoTag(final long value) {
+    return LITTLE_ENDIAN_64_SIZE;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sint32} field.
+   */
+  public static int computeSInt32SizeNoTag(final int value) {
+    return computeRawVarint32Size(encodeZigZag32(value));
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sint64} field.
+   */
+  public static int computeSInt64SizeNoTag(final long value) {
+    return computeRawVarint64Size(encodeZigZag64(value));
+  }
+
+  // =================================================================
+
+  /**
+   * If writing to a flat array, return the space left in the array.
+   * Otherwise, throws {@code UnsupportedOperationException}.
+   */
+  public int spaceLeft() {
+    return limit - position;
+  }
+
+  /**
+   * Verifies that {@link #spaceLeft()} returns zero.  It's common to create
+   * a byte array that is exactly big enough to hold a message, then write to
+   * it with a {@code CodedOutputStream}.  Calling {@code checkNoSpaceLeft()}
+   * after writing verifies that the message was actually as big as expected,
+   * which can help catch bugs.
+   */
+  public void checkNoSpaceLeft() {
+    if (spaceLeft() != 0) {
+      throw new IllegalStateException(
+        "Did not write as much data as expected.");
+    }
+  }
+
+  /**
+   * If you create a CodedOutputStream around a simple flat array, you must
+   * not attempt to write more bytes than the array has space.  Otherwise,
+   * this exception will be thrown.
+   */
+  public static class OutOfSpaceException extends IOException {
+    private static final long serialVersionUID = -6947486886997889499L;
+
+    OutOfSpaceException(int position, int limit) {
+      super("CodedOutputStream was writing to a flat byte array and ran " +
+            "out of space (pos " + position + " limit " + limit + ").");
+    }
+  }
+
+  /** Write a single byte. */
+  public void writeRawByte(final byte value) throws IOException {
+    if (position == limit) {
+      // We're writing to a single buffer.
+      throw new OutOfSpaceException(position, limit);
+    }
+
+    buffer[position++] = value;
+  }
+
+  /** Write a single byte, represented by an integer value. */
+  public void writeRawByte(final int value) throws IOException {
+    writeRawByte((byte) value);
+  }
+
+  /** Write an array of bytes. */
+  public void writeRawBytes(final byte[] value) throws IOException {
+    writeRawBytes(value, 0, value.length);
+  }
+
+  /** Write part of an array of bytes. */
+  public void writeRawBytes(final byte[] value, int offset, int length)
+                            throws IOException {
+    if (limit - position >= length) {
+      // We have room in the current buffer.
+      System.arraycopy(value, offset, buffer, position, length);
+      position += length;
+    } else {
+      // We're writing to a single buffer.
+      throw new OutOfSpaceException(position, limit);
+    }
+  }
+
+  /** Encode and write a tag. */
+  public void writeTag(final int fieldNumber, final int wireType)
+                       throws IOException {
+    writeRawVarint32(WireFormatNano.makeTag(fieldNumber, wireType));
+  }
+
+  /** Compute the number of bytes that would be needed to encode a tag. */
+  public static int computeTagSize(final int fieldNumber) {
+    return computeRawVarint32Size(WireFormatNano.makeTag(fieldNumber, 0));
+  }
+
+  /**
+   * Encode and write a varint.  {@code value} is treated as
+   * unsigned, so it won't be sign-extended if negative.
+   */
+  public void writeRawVarint32(int value) throws IOException {
+    while (true) {
+      if ((value & ~0x7F) == 0) {
+        writeRawByte(value);
+        return;
+      } else {
+        writeRawByte((value & 0x7F) | 0x80);
+        value >>>= 7;
+      }
+    }
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a varint.
+   * {@code value} is treated as unsigned, so it won't be sign-extended if
+   * negative.
+   */
+  public static int computeRawVarint32Size(final int value) {
+    if ((value & (0xffffffff <<  7)) == 0) return 1;
+    if ((value & (0xffffffff << 14)) == 0) return 2;
+    if ((value & (0xffffffff << 21)) == 0) return 3;
+    if ((value & (0xffffffff << 28)) == 0) return 4;
+    return 5;
+  }
+
+  /** Encode and write a varint. */
+  public void writeRawVarint64(long value) throws IOException {
+    while (true) {
+      if ((value & ~0x7FL) == 0) {
+        writeRawByte((int)value);
+        return;
+      } else {
+        writeRawByte(((int)value & 0x7F) | 0x80);
+        value >>>= 7;
+      }
+    }
+  }
+
+  /** Compute the number of bytes that would be needed to encode a varint. */
+  public static int computeRawVarint64Size(final long value) {
+    if ((value & (0xffffffffffffffffL <<  7)) == 0) return 1;
+    if ((value & (0xffffffffffffffffL << 14)) == 0) return 2;
+    if ((value & (0xffffffffffffffffL << 21)) == 0) return 3;
+    if ((value & (0xffffffffffffffffL << 28)) == 0) return 4;
+    if ((value & (0xffffffffffffffffL << 35)) == 0) return 5;
+    if ((value & (0xffffffffffffffffL << 42)) == 0) return 6;
+    if ((value & (0xffffffffffffffffL << 49)) == 0) return 7;
+    if ((value & (0xffffffffffffffffL << 56)) == 0) return 8;
+    if ((value & (0xffffffffffffffffL << 63)) == 0) return 9;
+    return 10;
+  }
+
+  /** Write a little-endian 32-bit integer. */
+  public void writeRawLittleEndian32(final int value) throws IOException {
+    writeRawByte((value      ) & 0xFF);
+    writeRawByte((value >>  8) & 0xFF);
+    writeRawByte((value >> 16) & 0xFF);
+    writeRawByte((value >> 24) & 0xFF);
+  }
+
+  public static final int LITTLE_ENDIAN_32_SIZE = 4;
+
+  /** Write a little-endian 64-bit integer. */
+  public void writeRawLittleEndian64(final long value) throws IOException {
+    writeRawByte((int)(value      ) & 0xFF);
+    writeRawByte((int)(value >>  8) & 0xFF);
+    writeRawByte((int)(value >> 16) & 0xFF);
+    writeRawByte((int)(value >> 24) & 0xFF);
+    writeRawByte((int)(value >> 32) & 0xFF);
+    writeRawByte((int)(value >> 40) & 0xFF);
+    writeRawByte((int)(value >> 48) & 0xFF);
+    writeRawByte((int)(value >> 56) & 0xFF);
+  }
+
+  public static final int LITTLE_ENDIAN_64_SIZE = 8;
+
+  /**
+   * Encode a ZigZag-encoded 32-bit value.  ZigZag encodes signed integers
+   * into values that can be efficiently encoded with varint.  (Otherwise,
+   * negative values must be sign-extended to 64 bits to be varint encoded,
+   * thus always taking 10 bytes on the wire.)
+   *
+   * @param n A signed 32-bit integer.
+   * @return An unsigned 32-bit integer, stored in a signed int because
+   *         Java has no explicit unsigned support.
+   */
+  public static int encodeZigZag32(final int n) {
+    // Note:  the right-shift must be arithmetic
+    return (n << 1) ^ (n >> 31);
+  }
+
+  /**
+   * Encode a ZigZag-encoded 64-bit value.  ZigZag encodes signed integers
+   * into values that can be efficiently encoded with varint.  (Otherwise,
+   * negative values must be sign-extended to 64 bits to be varint encoded,
+   * thus always taking 10 bytes on the wire.)
+   *
+   * @param n A signed 64-bit integer.
+   * @return An unsigned 64-bit integer, stored in a signed int because
+   *         Java has no explicit unsigned support.
+   */
+  public static long encodeZigZag64(final long n) {
+    // Note:  the right-shift must be arithmetic
+    return (n << 1) ^ (n >> 63);
+  }
+}
diff --git a/javanano/src/main/java/com/google/protobuf/nano/ExtendableMessageNano.java b/javanano/src/main/java/com/google/protobuf/nano/ExtendableMessageNano.java
new file mode 100644
index 00000000..46cd86f3
--- /dev/null
+++ b/javanano/src/main/java/com/google/protobuf/nano/ExtendableMessageNano.java
@@ -0,0 +1,187 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2013 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf.nano;
+
+import java.io.IOException;
+
+/**
+ * Base class of those Protocol Buffer messages that need to store unknown fields,
+ * such as extensions.
+ */
+public abstract class ExtendableMessageNano<M extends ExtendableMessageNano<M>>
+        extends MessageNano {
+    /**
+     * A container for fields unknown to the message, including extensions. Extension fields can
+     * can be accessed through the {@link #getExtension} and {@link #setExtension} methods.
+     */
+    protected FieldArray unknownFieldData;
+
+    @Override
+    protected int computeSerializedSize() {
+        int size = 0;
+        if (unknownFieldData != null) {
+            for (int i = 0; i < unknownFieldData.size(); i++) {
+                FieldData field = unknownFieldData.dataAt(i);
+                size += field.computeSerializedSize();
+            }
+        }
+        return size;
+    }
+
+    @Override
+    public void writeTo(CodedOutputByteBufferNano output) throws IOException {
+        if (unknownFieldData == null) {
+            return;
+        }
+        for (int i = 0; i < unknownFieldData.size(); i++) {
+            FieldData field = unknownFieldData.dataAt(i);
+            field.writeTo(output);
+        }
+    }
+
+    /**
+     * Checks if there is a value stored for the specified extension in this
+     * message.
+     */
+    public final boolean hasExtension(Extension<M, ?> extension) {
+        if (unknownFieldData == null) {
+            return false;
+        }
+        FieldData field = unknownFieldData.get(WireFormatNano.getTagFieldNumber(extension.tag));
+        return field != null;
+    }
+
+    /**
+     * Gets the value stored in the specified extension of this message.
+     */
+    public final <T> T getExtension(Extension<M, T> extension) {
+        if (unknownFieldData == null) {
+            return null;
+        }
+        FieldData field = unknownFieldData.get(WireFormatNano.getTagFieldNumber(extension.tag));
+        return field == null ? null : field.getValue(extension);
+    }
+
+    /**
+     * Sets the value of the specified extension of this message.
+     */
+    public final <T> M setExtension(Extension<M, T> extension, T value) {
+        int fieldNumber = WireFormatNano.getTagFieldNumber(extension.tag);
+        if (value == null) {
+            if (unknownFieldData != null) {
+                unknownFieldData.remove(fieldNumber);
+                if (unknownFieldData.isEmpty()) {
+                    unknownFieldData = null;
+                }
+            }
+        } else {
+            FieldData field = null;
+            if (unknownFieldData == null) {
+                unknownFieldData = new FieldArray();
+            } else {
+                field = unknownFieldData.get(fieldNumber);
+            }
+            if (field == null) {
+                unknownFieldData.put(fieldNumber, new FieldData(extension, value));
+            } else {
+                field.setValue(extension, value);
+            }
+        }
+
+        @SuppressWarnings("unchecked") // Generated code should guarantee type safety
+        M typedThis = (M) this;
+        return typedThis;
+    }
+
+    /**
+     * Stores the binary data of an unknown field.
+     *
+     * <p>Generated messages will call this for unknown fields if the store_unknown_fields
+     * option is on.
+     *
+     * <p>Note that the tag might be a end-group tag (rather than the start of an unknown field) in
+     * which case we do not want to add an unknown field entry.
+     *
+     * @param input the input buffer.
+     * @param tag the tag of the field.
+
+     * @return {@literal true} unless the tag is an end-group tag.
+     */
+    protected final boolean storeUnknownField(CodedInputByteBufferNano input, int tag)
+            throws IOException {
+        int startPos = input.getPosition();
+        if (!input.skipField(tag)) {
+            return false;  // This wasn't an unknown field, it's an end-group tag.
+        }
+        int fieldNumber = WireFormatNano.getTagFieldNumber(tag);
+        int endPos = input.getPosition();
+        byte[] bytes = input.getData(startPos, endPos - startPos);
+        UnknownFieldData unknownField = new UnknownFieldData(tag, bytes);
+
+        FieldData field = null;
+        if (unknownFieldData == null) {
+            unknownFieldData = new FieldArray();
+        } else {
+            field = unknownFieldData.get(fieldNumber);
+        }
+        if (field == null) {
+            field = new FieldData();
+            unknownFieldData.put(fieldNumber, field);
+        }
+        field.addUnknownField(unknownField);
+        return true;
+    }
+
+    /**
+     * Returns whether the stored unknown field data in this message is equivalent to that in the
+     * other message.
+     *
+     * @param other the other message.
+     * @return whether the two sets of unknown field data are equal.
+     */
+    protected final boolean unknownFieldDataEquals(M other) {
+        if (unknownFieldData == null || unknownFieldData.isEmpty()) {
+            return other.unknownFieldData == null || other.unknownFieldData.isEmpty();
+        } else {
+            return unknownFieldData.equals(other.unknownFieldData);
+        }
+    }
+
+    /**
+     * Computes the hashcode representing the unknown field data stored in this message.
+     *
+     * @return the hashcode for the unknown field data.
+     */
+    protected final int unknownFieldDataHashCode() {
+        return (unknownFieldData == null || unknownFieldData.isEmpty()
+                ? 0 : unknownFieldData.hashCode());
+    }
+}
diff --git a/javanano/src/main/java/com/google/protobuf/nano/Extension.java b/javanano/src/main/java/com/google/protobuf/nano/Extension.java
new file mode 100644
index 00000000..a851daf8
--- /dev/null
+++ b/javanano/src/main/java/com/google/protobuf/nano/Extension.java
@@ -0,0 +1,722 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2013 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf.nano;
+
+import java.io.IOException;
+import java.lang.reflect.Array;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Represents an extension.
+ *
+ * @author bduff@google.com (Brian Duff)
+ * @author maxtroy@google.com (Max Cai)
+ * @param <M> the type of the extendable message this extension is for.
+ * @param <T> the Java type of the extension; see {@link #clazz}.
+ */
+public class Extension<M extends ExtendableMessageNano<M>, T> {
+
+    /*
+     * Because we typically only define message-typed extensions, the Extension class hierarchy is
+     * designed as follows, to allow a big amount of code in this file to be removed by ProGuard:
+     *
+     *            Extension          // ready to use for message/group typed extensions
+     *                Δ
+     *                |
+     *       PrimitiveExtension      // for primitive/enum typed extensions
+     */
+
+    public static final int TYPE_DOUBLE   = 1;
+    public static final int TYPE_FLOAT    = 2;
+    public static final int TYPE_INT64    = 3;
+    public static final int TYPE_UINT64   = 4;
+    public static final int TYPE_INT32    = 5;
+    public static final int TYPE_FIXED64  = 6;
+    public static final int TYPE_FIXED32  = 7;
+    public static final int TYPE_BOOL     = 8;
+    public static final int TYPE_STRING   = 9;
+    public static final int TYPE_GROUP    = 10;
+    public static final int TYPE_MESSAGE  = 11;
+    public static final int TYPE_BYTES    = 12;
+    public static final int TYPE_UINT32   = 13;
+    public static final int TYPE_ENUM     = 14;
+    public static final int TYPE_SFIXED32 = 15;
+    public static final int TYPE_SFIXED64 = 16;
+    public static final int TYPE_SINT32   = 17;
+    public static final int TYPE_SINT64   = 18;
+
+    /**
+     * Creates an {@code Extension} of the given message type and tag number.
+     * Should be used by the generated code only.
+     *
+     * @param type {@link #TYPE_MESSAGE} or {@link #TYPE_GROUP}
+     */
+    public static <M extends ExtendableMessageNano<M>, T extends MessageNano>
+            Extension<M, T> createMessageTyped(int type, Class<T> clazz, int tag) {
+        return new Extension<M, T>(type, clazz, tag, false);
+    }
+
+    /**
+     * Creates a repeated {@code Extension} of the given message type and tag number.
+     * Should be used by the generated code only.
+     *
+     * @param type {@link #TYPE_MESSAGE} or {@link #TYPE_GROUP}
+     */
+    public static <M extends ExtendableMessageNano<M>, T extends MessageNano>
+            Extension<M, T[]> createRepeatedMessageTyped(int type, Class<T[]> clazz, int tag) {
+        return new Extension<M, T[]>(type, clazz, tag, true);
+    }
+
+    /**
+     * Creates an {@code Extension} of the given primitive type and tag number.
+     * Should be used by the generated code only.
+     *
+     * @param type one of {@code TYPE_*}, except {@link #TYPE_MESSAGE} and {@link #TYPE_GROUP}
+     * @param clazz the boxed Java type of this extension
+     */
+    public static <M extends ExtendableMessageNano<M>, T>
+            Extension<M, T> createPrimitiveTyped(int type, Class<T> clazz, int tag) {
+        return new PrimitiveExtension<M, T>(type, clazz, tag, false, 0, 0);
+    }
+
+    /**
+     * Creates a repeated {@code Extension} of the given primitive type and tag number.
+     * Should be used by the generated code only.
+     *
+     * @param type one of {@code TYPE_*}, except {@link #TYPE_MESSAGE} and {@link #TYPE_GROUP}
+     * @param clazz the Java array type of this extension, with an unboxed component type
+     */
+    public static <M extends ExtendableMessageNano<M>, T>
+            Extension<M, T> createRepeatedPrimitiveTyped(
+                    int type, Class<T> clazz, int tag, int nonPackedTag, int packedTag) {
+        return new PrimitiveExtension<M, T>(type, clazz, tag, true, nonPackedTag, packedTag);
+    }
+
+    /**
+     * Protocol Buffer type of this extension; one of the {@code TYPE_} constants.
+     */
+    protected final int type;
+
+    /**
+     * Java type of this extension. For a singular extension, this is the boxed Java type for the
+     * Protocol Buffer {@link #type}; for a repeated extension, this is an array type whose
+     * component type is the unboxed Java type for {@link #type}. For example, for a singular
+     * {@code int32}/{@link #TYPE_INT32} extension, this equals {@code Integer.class}; for a
+     * repeated {@code int32} extension, this equals {@code int[].class}.
+     */
+    protected final Class<T> clazz;
+
+    /**
+     * Tag number of this extension.
+     */
+    public final int tag;
+
+    /**
+     * Whether this extension is repeated.
+     */
+    protected final boolean repeated;
+
+    private Extension(int type, Class<T> clazz, int tag, boolean repeated) {
+        this.type = type;
+        this.clazz = clazz;
+        this.tag = tag;
+        this.repeated = repeated;
+    }
+
+    /**
+     * Returns the value of this extension stored in the given list of unknown fields, or
+     * {@code null} if no unknown fields matches this extension.
+     *
+     * @param unknownFields a list of {@link UnknownFieldData}. All of the elements must have a tag
+     *                      that matches this Extension's tag.
+     *
+     */
+    final T getValueFrom(List<UnknownFieldData> unknownFields) {
+        if (unknownFields == null) {
+            return null;
+        }
+        return repeated ? getRepeatedValueFrom(unknownFields) : getSingularValueFrom(unknownFields);
+    }
+
+    private T getRepeatedValueFrom(List<UnknownFieldData> unknownFields) {
+        // For repeated extensions, read all matching unknown fields in their original order.
+        List<Object> resultList = new ArrayList<Object>();
+        for (int i = 0; i < unknownFields.size(); i++) {
+            UnknownFieldData data = unknownFields.get(i);
+            if (data.bytes.length != 0) {
+                readDataInto(data, resultList);
+            }
+        }
+
+        int resultSize = resultList.size();
+        if (resultSize == 0) {
+            return null;
+        } else {
+            T result = clazz.cast(Array.newInstance(clazz.getComponentType(), resultSize));
+            for (int i = 0; i < resultSize; i++) {
+                Array.set(result, i, resultList.get(i));
+            }
+            return result;
+        }
+    }
+
+    private T getSingularValueFrom(List<UnknownFieldData> unknownFields) {
+        // For singular extensions, get the last piece of data stored under this extension.
+        if (unknownFields.isEmpty()) {
+            return null;
+        }
+        UnknownFieldData lastData = unknownFields.get(unknownFields.size() - 1);
+        return clazz.cast(readData(CodedInputByteBufferNano.newInstance(lastData.bytes)));
+    }
+
+    protected Object readData(CodedInputByteBufferNano input) {
+        // This implementation is for message/group extensions.
+        Class<?> messageType = repeated ? clazz.getComponentType() : clazz;
+        try {
+            switch (type) {
+                case TYPE_GROUP:
+                    MessageNano group = (MessageNano) messageType.newInstance();
+                    input.readGroup(group, WireFormatNano.getTagFieldNumber(tag));
+                    return group;
+                case TYPE_MESSAGE:
+                    MessageNano message = (MessageNano) messageType.newInstance();
+                    input.readMessage(message);
+                    return message;
+                default:
+                    throw new IllegalArgumentException("Unknown type " + type);
+            }
+        } catch (InstantiationException e) {
+            throw new IllegalArgumentException(
+                    "Error creating instance of class " + messageType, e);
+        } catch (IllegalAccessException e) {
+            throw new IllegalArgumentException(
+                    "Error creating instance of class " + messageType, e);
+        } catch (IOException e) {
+            throw new IllegalArgumentException("Error reading extension field", e);
+        }
+    }
+
+    protected void readDataInto(UnknownFieldData data, List<Object> resultList) {
+        // This implementation is for message/group extensions.
+        resultList.add(readData(CodedInputByteBufferNano.newInstance(data.bytes)));
+    }
+
+    void writeTo(Object value, CodedOutputByteBufferNano output) throws IOException {
+        if (repeated) {
+            writeRepeatedData(value, output);
+        } else {
+            writeSingularData(value, output);
+        }
+    }
+
+    protected void writeSingularData(Object value, CodedOutputByteBufferNano out) {
+        // This implementation is for message/group extensions.
+        try {
+            out.writeRawVarint32(tag);
+            switch (type) {
+                case TYPE_GROUP:
+                    MessageNano groupValue = (MessageNano) value;
+                    int fieldNumber = WireFormatNano.getTagFieldNumber(tag);
+                    out.writeGroupNoTag(groupValue);
+                    // The endgroup tag must be included in the data payload.
+                    out.writeTag(fieldNumber, WireFormatNano.WIRETYPE_END_GROUP);
+                    break;
+                case TYPE_MESSAGE:
+                    MessageNano messageValue = (MessageNano) value;
+                    out.writeMessageNoTag(messageValue);
+                    break;
+                default:
+                    throw new IllegalArgumentException("Unknown type " + type);
+            }
+        } catch (IOException e) {
+            // Should not happen
+            throw new IllegalStateException(e);
+        }
+    }
+
+    protected void writeRepeatedData(Object array, CodedOutputByteBufferNano output) {
+        // This implementation is for non-packed extensions.
+        int arrayLength = Array.getLength(array);
+        for (int i = 0; i < arrayLength; i++) {
+            Object element = Array.get(array, i);
+            if (element != null) {
+                writeSingularData(element, output);
+            }
+        }
+    }
+
+    int computeSerializedSize(Object value) {
+        if (repeated) {
+            return computeRepeatedSerializedSize(value);
+        } else {
+            return computeSingularSerializedSize(value);
+        }
+    }
+
+    protected int computeRepeatedSerializedSize(Object array) {
+        // This implementation is for non-packed extensions.
+        int size = 0;
+        int arrayLength = Array.getLength(array);
+        for (int i = 0; i < arrayLength; i++) {
+            Object element = Array.get(array, i);
+            if (element != null) {
+                size += computeSingularSerializedSize(Array.get(array, i));
+            }
+        }
+        return size;
+    }
+
+    protected int computeSingularSerializedSize(Object value) {
+        // This implementation is for message/group extensions.
+        int fieldNumber = WireFormatNano.getTagFieldNumber(tag);
+        switch (type) {
+            case TYPE_GROUP:
+                MessageNano groupValue = (MessageNano) value;
+                return CodedOutputByteBufferNano.computeGroupSize(fieldNumber, groupValue);
+            case TYPE_MESSAGE:
+                MessageNano messageValue = (MessageNano) value;
+                return CodedOutputByteBufferNano.computeMessageSize(fieldNumber, messageValue);
+            default:
+                throw new IllegalArgumentException("Unknown type " + type);
+        }
+    }
+
+    /**
+     * Represents an extension of a primitive (including enum) type. If there is no primitive
+     * extensions, this subclass will be removable by ProGuard.
+     */
+    private static class PrimitiveExtension<M extends ExtendableMessageNano<M>, T>
+            extends Extension<M, T> {
+
+        /**
+         * Tag of a piece of non-packed data from the wire compatible with this extension.
+         */
+        private final int nonPackedTag;
+
+        /**
+         * Tag of a piece of packed data from the wire compatible with this extension.
+         * 0 if the type of this extension is not packable.
+         */
+        private final int packedTag;
+
+        public PrimitiveExtension(int type, Class<T> clazz, int tag, boolean repeated,
+                int nonPackedTag, int packedTag) {
+            super(type, clazz, tag, repeated);
+            this.nonPackedTag = nonPackedTag;
+            this.packedTag = packedTag;
+        }
+
+        @Override
+        protected Object readData(CodedInputByteBufferNano input) {
+            try {
+                switch (type) {
+                    case TYPE_DOUBLE:
+                        return input.readDouble();
+                    case TYPE_FLOAT:
+                        return input.readFloat();
+                    case TYPE_INT64:
+                        return input.readInt64();
+                    case TYPE_UINT64:
+                        return input.readUInt64();
+                    case TYPE_INT32:
+                        return input.readInt32();
+                    case TYPE_FIXED64:
+                        return input.readFixed64();
+                    case TYPE_FIXED32:
+                        return input.readFixed32();
+                    case TYPE_BOOL:
+                        return input.readBool();
+                    case TYPE_STRING:
+                        return input.readString();
+                    case TYPE_BYTES:
+                        return input.readBytes();
+                    case TYPE_UINT32:
+                        return input.readUInt32();
+                    case TYPE_ENUM:
+                        return input.readEnum();
+                    case TYPE_SFIXED32:
+                        return input.readSFixed32();
+                    case TYPE_SFIXED64:
+                        return input.readSFixed64();
+                    case TYPE_SINT32:
+                        return input.readSInt32();
+                    case TYPE_SINT64:
+                        return input.readSInt64();
+                    default:
+                        throw new IllegalArgumentException("Unknown type " + type);
+                }
+            } catch (IOException e) {
+                throw new IllegalArgumentException("Error reading extension field", e);
+            }
+        }
+
+        @Override
+        protected void readDataInto(UnknownFieldData data, List<Object> resultList) {
+            // This implementation is for primitive typed extensions,
+            // which can read both packed and non-packed data.
+            if (data.tag == nonPackedTag) {
+                resultList.add(readData(CodedInputByteBufferNano.newInstance(data.bytes)));
+            } else {
+                CodedInputByteBufferNano buffer =
+                        CodedInputByteBufferNano.newInstance(data.bytes);
+                try {
+                    buffer.pushLimit(buffer.readRawVarint32()); // length limit
+                } catch (IOException e) {
+                    throw new IllegalArgumentException("Error reading extension field", e);
+                }
+                while (!buffer.isAtEnd()) {
+                    resultList.add(readData(buffer));
+                }
+            }
+        }
+
+        @Override
+        protected final void writeSingularData(Object value, CodedOutputByteBufferNano output) {
+            try {
+                output.writeRawVarint32(tag);
+                switch (type) {
+                    case TYPE_DOUBLE:
+                        Double doubleValue = (Double) value;
+                        output.writeDoubleNoTag(doubleValue);
+                        break;
+                    case TYPE_FLOAT:
+                        Float floatValue = (Float) value;
+                        output.writeFloatNoTag(floatValue);
+                        break;
+                    case TYPE_INT64:
+                        Long int64Value = (Long) value;
+                        output.writeInt64NoTag(int64Value);
+                        break;
+                    case TYPE_UINT64:
+                        Long uint64Value = (Long) value;
+                        output.writeUInt64NoTag(uint64Value);
+                        break;
+                    case TYPE_INT32:
+                        Integer int32Value = (Integer) value;
+                        output.writeInt32NoTag(int32Value);
+                        break;
+                    case TYPE_FIXED64:
+                        Long fixed64Value = (Long) value;
+                        output.writeFixed64NoTag(fixed64Value);
+                        break;
+                    case TYPE_FIXED32:
+                        Integer fixed32Value = (Integer) value;
+                        output.writeFixed32NoTag(fixed32Value);
+                        break;
+                    case TYPE_BOOL:
+                        Boolean boolValue = (Boolean) value;
+                        output.writeBoolNoTag(boolValue);
+                        break;
+                    case TYPE_STRING:
+                        String stringValue = (String) value;
+                        output.writeStringNoTag(stringValue);
+                        break;
+                    case TYPE_BYTES:
+                        byte[] bytesValue = (byte[]) value;
+                        output.writeBytesNoTag(bytesValue);
+                        break;
+                    case TYPE_UINT32:
+                        Integer uint32Value = (Integer) value;
+                        output.writeUInt32NoTag(uint32Value);
+                        break;
+                    case TYPE_ENUM:
+                        Integer enumValue = (Integer) value;
+                        output.writeEnumNoTag(enumValue);
+                        break;
+                    case TYPE_SFIXED32:
+                        Integer sfixed32Value = (Integer) value;
+                        output.writeSFixed32NoTag(sfixed32Value);
+                        break;
+                    case TYPE_SFIXED64:
+                        Long sfixed64Value = (Long) value;
+                        output.writeSFixed64NoTag(sfixed64Value);
+                        break;
+                    case TYPE_SINT32:
+                        Integer sint32Value = (Integer) value;
+                        output.writeSInt32NoTag(sint32Value);
+                        break;
+                    case TYPE_SINT64:
+                        Long sint64Value = (Long) value;
+                        output.writeSInt64NoTag(sint64Value);
+                        break;
+                    default:
+                        throw new IllegalArgumentException("Unknown type " + type);
+                }
+            } catch (IOException e) {
+                // Should not happen
+                throw new IllegalStateException(e);
+            }
+        }
+
+        @Override
+        protected void writeRepeatedData(Object array, CodedOutputByteBufferNano output) {
+            if (tag == nonPackedTag) {
+                // Use base implementation for non-packed data
+                super.writeRepeatedData(array, output);
+            } else if (tag == packedTag) {
+                // Packed. Note that the array element type is guaranteed to be primitive, so there
+                // won't be any null elements, so no null check in this block.
+                int arrayLength = Array.getLength(array);
+                int dataSize = computePackedDataSize(array);
+
+                try {
+                    output.writeRawVarint32(tag);
+                    output.writeRawVarint32(dataSize);
+                    switch (type) {
+                        case TYPE_BOOL:
+                            for (int i = 0; i < arrayLength; i++) {
+                                output.writeBoolNoTag(Array.getBoolean(array, i));
+                            }
+                            break;
+                        case TYPE_FIXED32:
+                            for (int i = 0; i < arrayLength; i++) {
+                                output.writeFixed32NoTag(Array.getInt(array, i));
+                            }
+                            break;
+                        case TYPE_SFIXED32:
+                            for (int i = 0; i < arrayLength; i++) {
+                                output.writeSFixed32NoTag(Array.getInt(array, i));
+                            }
+                            break;
+                        case TYPE_FLOAT:
+                            for (int i = 0; i < arrayLength; i++) {
+                                output.writeFloatNoTag(Array.getFloat(array, i));
+                            }
+                            break;
+                        case TYPE_FIXED64:
+                            for (int i = 0; i < arrayLength; i++) {
+                                output.writeFixed64NoTag(Array.getLong(array, i));
+                            }
+                            break;
+                        case TYPE_SFIXED64:
+                            for (int i = 0; i < arrayLength; i++) {
+                                output.writeSFixed64NoTag(Array.getLong(array, i));
+                            }
+                            break;
+                        case TYPE_DOUBLE:
+                            for (int i = 0; i < arrayLength; i++) {
+                                output.writeDoubleNoTag(Array.getDouble(array, i));
+                            }
+                            break;
+                        case TYPE_INT32:
+                            for (int i = 0; i < arrayLength; i++) {
+                                output.writeInt32NoTag(Array.getInt(array, i));
+                            }
+                            break;
+                        case TYPE_SINT32:
+                            for (int i = 0; i < arrayLength; i++) {
+                                output.writeSInt32NoTag(Array.getInt(array, i));
+                            }
+                            break;
+                        case TYPE_UINT32:
+                            for (int i = 0; i < arrayLength; i++) {
+                                output.writeUInt32NoTag(Array.getInt(array, i));
+                            }
+                            break;
+                        case TYPE_INT64:
+                            for (int i = 0; i < arrayLength; i++) {
+                                output.writeInt64NoTag(Array.getLong(array, i));
+                            }
+                            break;
+                        case TYPE_SINT64:
+                            for (int i = 0; i < arrayLength; i++) {
+                                output.writeSInt64NoTag(Array.getLong(array, i));
+                            }
+                            break;
+                        case TYPE_UINT64:
+                            for (int i = 0; i < arrayLength; i++) {
+                                output.writeUInt64NoTag(Array.getLong(array, i));
+                            }
+                            break;
+                        case TYPE_ENUM:
+                            for (int i = 0; i < arrayLength; i++) {
+                                output.writeEnumNoTag(Array.getInt(array, i));
+                            }
+                            break;
+                        default:
+                            throw new IllegalArgumentException("Unpackable type " + type);
+                    }
+                } catch (IOException e) {
+                    // Should not happen.
+                    throw new IllegalStateException(e);
+                }
+            } else {
+                throw new IllegalArgumentException("Unexpected repeated extension tag " + tag
+                        + ", unequal to both non-packed variant " + nonPackedTag
+                        + " and packed variant " + packedTag);
+            }
+        }
+
+        private int computePackedDataSize(Object array) {
+            int dataSize = 0;
+            int arrayLength = Array.getLength(array);
+            switch (type) {
+                case TYPE_BOOL:
+                    // Bools are stored as int32 but just as 0 or 1, so 1 byte each.
+                    dataSize = arrayLength;
+                    break;
+                case TYPE_FIXED32:
+                case TYPE_SFIXED32:
+                case TYPE_FLOAT:
+                    dataSize = arrayLength * CodedOutputByteBufferNano.LITTLE_ENDIAN_32_SIZE;
+                    break;
+                case TYPE_FIXED64:
+                case TYPE_SFIXED64:
+                case TYPE_DOUBLE:
+                    dataSize = arrayLength * CodedOutputByteBufferNano.LITTLE_ENDIAN_64_SIZE;
+                    break;
+                case TYPE_INT32:
+                    for (int i = 0; i < arrayLength; i++) {
+                        dataSize += CodedOutputByteBufferNano.computeInt32SizeNoTag(
+                                Array.getInt(array, i));
+                    }
+                    break;
+                case TYPE_SINT32:
+                    for (int i = 0; i < arrayLength; i++) {
+                        dataSize += CodedOutputByteBufferNano.computeSInt32SizeNoTag(
+                                Array.getInt(array, i));
+                    }
+                    break;
+                case TYPE_UINT32:
+                    for (int i = 0; i < arrayLength; i++) {
+                        dataSize += CodedOutputByteBufferNano.computeUInt32SizeNoTag(
+                                Array.getInt(array, i));
+                    }
+                    break;
+                case TYPE_INT64:
+                    for (int i = 0; i < arrayLength; i++) {
+                        dataSize += CodedOutputByteBufferNano.computeInt64SizeNoTag(
+                                Array.getLong(array, i));
+                    }
+                    break;
+                case TYPE_SINT64:
+                    for (int i = 0; i < arrayLength; i++) {
+                        dataSize += CodedOutputByteBufferNano.computeSInt64SizeNoTag(
+                                Array.getLong(array, i));
+                    }
+                    break;
+                case TYPE_UINT64:
+                    for (int i = 0; i < arrayLength; i++) {
+                        dataSize += CodedOutputByteBufferNano.computeUInt64SizeNoTag(
+                                Array.getLong(array, i));
+                    }
+                    break;
+                case TYPE_ENUM:
+                    for (int i = 0; i < arrayLength; i++) {
+                        dataSize += CodedOutputByteBufferNano.computeEnumSizeNoTag(
+                                Array.getInt(array, i));
+                    }
+                    break;
+                default:
+                    throw new IllegalArgumentException("Unexpected non-packable type " + type);
+            }
+            return dataSize;
+        }
+
+        @Override
+        protected int computeRepeatedSerializedSize(Object array) {
+            if (tag == nonPackedTag) {
+                // Use base implementation for non-packed data
+                return super.computeRepeatedSerializedSize(array);
+            } else if (tag == packedTag) {
+                // Packed.
+                int dataSize = computePackedDataSize(array);
+                int payloadSize =
+                        dataSize + CodedOutputByteBufferNano.computeRawVarint32Size(dataSize);
+                return payloadSize + CodedOutputByteBufferNano.computeRawVarint32Size(tag);
+            } else {
+                throw new IllegalArgumentException("Unexpected repeated extension tag " + tag
+                        + ", unequal to both non-packed variant " + nonPackedTag
+                        + " and packed variant " + packedTag);
+            }
+        }
+
+        @Override
+        protected final int computeSingularSerializedSize(Object value) {
+            int fieldNumber = WireFormatNano.getTagFieldNumber(tag);
+            switch (type) {
+                case TYPE_DOUBLE:
+                    Double doubleValue = (Double) value;
+                    return CodedOutputByteBufferNano.computeDoubleSize(fieldNumber, doubleValue);
+                case TYPE_FLOAT:
+                    Float floatValue = (Float) value;
+                    return CodedOutputByteBufferNano.computeFloatSize(fieldNumber, floatValue);
+                case TYPE_INT64:
+                    Long int64Value = (Long) value;
+                    return CodedOutputByteBufferNano.computeInt64Size(fieldNumber, int64Value);
+                case TYPE_UINT64:
+                    Long uint64Value = (Long) value;
+                    return CodedOutputByteBufferNano.computeUInt64Size(fieldNumber, uint64Value);
+                case TYPE_INT32:
+                    Integer int32Value = (Integer) value;
+                    return CodedOutputByteBufferNano.computeInt32Size(fieldNumber, int32Value);
+                case TYPE_FIXED64:
+                    Long fixed64Value = (Long) value;
+                    return CodedOutputByteBufferNano.computeFixed64Size(fieldNumber, fixed64Value);
+                case TYPE_FIXED32:
+                    Integer fixed32Value = (Integer) value;
+                    return CodedOutputByteBufferNano.computeFixed32Size(fieldNumber, fixed32Value);
+                case TYPE_BOOL:
+                    Boolean boolValue = (Boolean) value;
+                    return CodedOutputByteBufferNano.computeBoolSize(fieldNumber, boolValue);
+                case TYPE_STRING:
+                    String stringValue = (String) value;
+                    return CodedOutputByteBufferNano.computeStringSize(fieldNumber, stringValue);
+                case TYPE_BYTES:
+                    byte[] bytesValue = (byte[]) value;
+                    return CodedOutputByteBufferNano.computeBytesSize(fieldNumber, bytesValue);
+                case TYPE_UINT32:
+                    Integer uint32Value = (Integer) value;
+                    return CodedOutputByteBufferNano.computeUInt32Size(fieldNumber, uint32Value);
+                case TYPE_ENUM:
+                    Integer enumValue = (Integer) value;
+                    return CodedOutputByteBufferNano.computeEnumSize(fieldNumber, enumValue);
+                case TYPE_SFIXED32:
+                    Integer sfixed32Value = (Integer) value;
+                    return CodedOutputByteBufferNano.computeSFixed32Size(fieldNumber,
+                            sfixed32Value);
+                case TYPE_SFIXED64:
+                    Long sfixed64Value = (Long) value;
+                    return CodedOutputByteBufferNano.computeSFixed64Size(fieldNumber,
+                            sfixed64Value);
+                case TYPE_SINT32:
+                    Integer sint32Value = (Integer) value;
+                    return CodedOutputByteBufferNano.computeSInt32Size(fieldNumber, sint32Value);
+                case TYPE_SINT64:
+                    Long sint64Value = (Long) value;
+                    return CodedOutputByteBufferNano.computeSInt64Size(fieldNumber, sint64Value);
+                default:
+                    throw new IllegalArgumentException("Unknown type " + type);
+            }
+        }
+    }
+}
diff --git a/javanano/src/main/java/com/google/protobuf/nano/FieldArray.java b/javanano/src/main/java/com/google/protobuf/nano/FieldArray.java
new file mode 100644
index 00000000..ab923a4d
--- /dev/null
+++ b/javanano/src/main/java/com/google/protobuf/nano/FieldArray.java
@@ -0,0 +1,273 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2014 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf.nano;
+
+
+/**
+ * A custom version of {@link android.util.SparseArray} with the minimal API
+ * for storing {@link FieldData} objects.
+ *
+ * Based on {@link android.support.v4.util.SpareArrayCompat}.
+ */
+class FieldArray {
+    private static final FieldData DELETED = new FieldData();
+    private boolean mGarbage = false;
+
+    private int[] mFieldNumbers;
+    private FieldData[] mData;
+    private int mSize;
+
+    /**
+     * Creates a new FieldArray containing no fields.
+     */
+    public FieldArray() {
+        this(10);
+    }
+
+    /**
+     * Creates a new FieldArray containing no mappings that will not
+     * require any additional memory allocation to store the specified
+     * number of mappings.
+     */
+    public FieldArray(int initialCapacity) {
+        initialCapacity = idealIntArraySize(initialCapacity);
+        mFieldNumbers = new int[initialCapacity];
+        mData = new FieldData[initialCapacity];
+        mSize = 0;
+    }
+
+    /**
+     * Gets the FieldData mapped from the specified fieldNumber, or <code>null</code>
+     * if no such mapping has been made.
+     */
+    public FieldData get(int fieldNumber) {
+        int i = binarySearch(fieldNumber);
+
+        if (i < 0 || mData[i] == DELETED) {
+            return null;
+        } else {
+            return mData[i];
+        }
+    }
+
+    /**
+     * Removes the data from the specified fieldNumber, if there was any.
+     */
+    public void remove(int fieldNumber) {
+        int i = binarySearch(fieldNumber);
+
+        if (i >= 0 && mData[i] != DELETED) {
+            mData[i] = DELETED;
+            mGarbage = true;
+        }
+    }
+
+    private void gc() {
+        int n = mSize;
+        int o = 0;
+        int[] keys = mFieldNumbers;
+        FieldData[] values = mData;
+
+        for (int i = 0; i < n; i++) {
+            FieldData val = values[i];
+
+            if (val != DELETED) {
+                if (i != o) {
+                    keys[o] = keys[i];
+                    values[o] = val;
+                    values[i] = null;
+                }
+
+                o++;
+            }
+        }
+
+        mGarbage = false;
+        mSize = o;
+    }
+
+    /**
+     * Adds a mapping from the specified fieldNumber to the specified data,
+     * replacing the previous mapping if there was one.
+     */
+    public void put(int fieldNumber, FieldData data) {
+        int i = binarySearch(fieldNumber);
+
+        if (i >= 0) {
+            mData[i] = data;
+        } else {
+            i = ~i;
+
+            if (i < mSize && mData[i] == DELETED) {
+                mFieldNumbers[i] = fieldNumber;
+                mData[i] = data;
+                return;
+            }
+
+            if (mGarbage && mSize >= mFieldNumbers.length) {
+                gc();
+
+                // Search again because indices may have changed.
+                i = ~ binarySearch(fieldNumber);
+            }
+
+            if (mSize >= mFieldNumbers.length) {
+                int n = idealIntArraySize(mSize + 1);
+
+                int[] nkeys = new int[n];
+                FieldData[] nvalues = new FieldData[n];
+
+                System.arraycopy(mFieldNumbers, 0, nkeys, 0, mFieldNumbers.length);
+                System.arraycopy(mData, 0, nvalues, 0, mData.length);
+
+                mFieldNumbers = nkeys;
+                mData = nvalues;
+            }
+
+            if (mSize - i != 0) {
+                System.arraycopy(mFieldNumbers, i, mFieldNumbers, i + 1, mSize - i);
+                System.arraycopy(mData, i, mData, i + 1, mSize - i);
+            }
+
+            mFieldNumbers[i] = fieldNumber;
+            mData[i] = data;
+            mSize++;
+        }
+    }
+
+    /**
+     * Returns the number of key-value mappings that this FieldArray
+     * currently stores.
+     */
+    public int size() {
+        if (mGarbage) {
+            gc();
+        }
+
+        return mSize;
+    }
+
+    public boolean isEmpty() {
+        return size() == 0;
+    }
+
+    /**
+     * Given an index in the range <code>0...size()-1</code>, returns
+     * the value from the <code>index</code>th key-value mapping that this
+     * FieldArray stores.
+     */
+    public FieldData dataAt(int index) {
+        if (mGarbage) {
+            gc();
+        }
+
+        return mData[index];
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (o == this) {
+            return true;
+        }
+        if (!(o instanceof FieldArray)) {
+            return false;
+        }
+
+        FieldArray other = (FieldArray) o;
+        if (size() != other.size()) {  // size() will call gc() if necessary.
+            return false;
+        }
+        return arrayEquals(mFieldNumbers, other.mFieldNumbers, mSize) &&
+                arrayEquals(mData, other.mData, mSize);
+    }
+
+    @Override
+    public int hashCode() {
+        if (mGarbage) {
+            gc();
+        }
+        int result = 17;
+        for (int i = 0; i < mSize; i++) {
+            result = 31 * result + mFieldNumbers[i];
+            result = 31 * result + mData[i].hashCode();
+        }
+        return result;
+    }
+
+    private int idealIntArraySize(int need) {
+        return idealByteArraySize(need * 4) / 4;
+    }
+
+    private int idealByteArraySize(int need) {
+        for (int i = 4; i < 32; i++)
+            if (need <= (1 << i) - 12)
+                return (1 << i) - 12;
+
+        return need;
+    }
+
+    private int binarySearch(int value) {
+        int lo = 0;
+        int hi = mSize - 1;
+
+        while (lo <= hi) {
+            int mid = (lo + hi) >>> 1;
+            int midVal = mFieldNumbers[mid];
+
+            if (midVal < value) {
+                lo = mid + 1;
+            } else if (midVal > value) {
+                hi = mid - 1;
+            } else {
+                return mid; // value found
+            }
+        }
+        return ~lo; // value not present
+    }
+
+    private boolean arrayEquals(int[] a, int[] b, int size) {
+        for (int i = 0; i < size; i++) {
+            if (a[i] != b[i]) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    private boolean arrayEquals(FieldData[] a, FieldData[] b, int size) {
+        for (int i = 0; i < size; i++) {
+            if (!a[i].equals(b[i])) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
diff --git a/javanano/src/main/java/com/google/protobuf/nano/FieldData.java b/javanano/src/main/java/com/google/protobuf/nano/FieldData.java
new file mode 100644
index 00000000..e5b69aad
--- /dev/null
+++ b/javanano/src/main/java/com/google/protobuf/nano/FieldData.java
@@ -0,0 +1,190 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2014 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf.nano;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * Stores unknown fields. These might be extensions or fields that the generated API doesn't
+ * know about yet.
+ */
+class FieldData {
+    private Extension<?, ?> cachedExtension;
+    private Object value;
+    /** The serialised values for this object. Will be cleared if getValue is called */
+    private List<UnknownFieldData> unknownFieldData;
+
+    <T> FieldData(Extension<?, T> extension, T newValue) {
+        cachedExtension = extension;
+        value = newValue;
+    }
+
+    FieldData() {
+        unknownFieldData = new ArrayList<UnknownFieldData>();
+    }
+
+    void addUnknownField(UnknownFieldData unknownField) {
+        unknownFieldData.add(unknownField);
+    }
+
+    UnknownFieldData getUnknownField(int index) {
+        if (unknownFieldData == null) {
+            return null;
+        }
+        if (index < unknownFieldData.size()) {
+            return unknownFieldData.get(index);
+        }
+        return null;
+    }
+
+    int getUnknownFieldSize() {
+        if (unknownFieldData == null) {
+            return 0;
+        }
+        return unknownFieldData.size();
+    }
+
+    <T> T getValue(Extension<?, T> extension) {
+        if (value != null){
+            if (cachedExtension != extension) {  // Extension objects are singletons.
+                throw new IllegalStateException(
+                        "Tried to getExtension with a differernt Extension.");
+            }
+        } else {
+            cachedExtension = extension;
+            value = extension.getValueFrom(unknownFieldData);
+            unknownFieldData = null;
+        }
+        return (T) value;
+    }
+
+    <T> void setValue(Extension<?, T> extension, T newValue) {
+        cachedExtension = extension;
+        value = newValue;
+        unknownFieldData = null;
+    }
+
+    int computeSerializedSize() {
+        int size = 0;
+        if (value != null) {
+            size = cachedExtension.computeSerializedSize(value);
+        } else {
+            for (UnknownFieldData unknownField : unknownFieldData) {
+                size += unknownField.computeSerializedSize();
+            }
+        }
+        return size;
+    }
+
+    void writeTo(CodedOutputByteBufferNano output) throws IOException {
+        if (value != null) {
+            cachedExtension.writeTo(value, output);
+        } else {
+            for (UnknownFieldData unknownField : unknownFieldData) {
+                unknownField.writeTo(output);
+            }
+        }
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (o == this) {
+            return true;
+        }
+        if (!(o instanceof FieldData)) {
+            return false;
+        }
+
+        FieldData other = (FieldData) o;
+        if (value != null && other.value != null) {
+            // If both objects have deserialized values, compare those.
+            // Since unknown fields are only compared if messages have generated equals methods
+            // we know this will be a meaningful comparison (not identity) for all values.
+            if (cachedExtension != other.cachedExtension) {  // Extension objects are singletons.
+                return false;
+            }
+            if (!cachedExtension.clazz.isArray()) {
+                // Can't test (!cachedExtension.repeated) due to 'bytes' -> 'byte[]'
+                return value.equals(other.value);
+            }
+            if (value instanceof byte[]) {
+                return Arrays.equals((byte[]) value, (byte[]) other.value);
+            } else if (value instanceof int[]) {
+                return Arrays.equals((int[]) value, (int[]) other.value);
+            } else if (value instanceof long[]) {
+                return Arrays.equals((long[]) value, (long[]) other.value);
+            } else if (value instanceof float[]) {
+                return Arrays.equals((float[]) value, (float[]) other.value);
+            } else if (value instanceof double[]) {
+                return Arrays.equals((double[]) value, (double[]) other.value);
+            } else if (value instanceof boolean[]) {
+                return Arrays.equals((boolean[]) value, (boolean[]) other.value);
+            } else {
+                return Arrays.deepEquals((Object[]) value, (Object[]) other.value);
+            }
+        }
+        if (unknownFieldData != null && other.unknownFieldData != null) {
+            // If both objects have byte arrays compare those directly.
+            return unknownFieldData.equals(other.unknownFieldData);
+        }
+        try {
+            // As a last resort, serialize and compare the resulting byte arrays.
+            return Arrays.equals(toByteArray(), other.toByteArray());
+        } catch (IOException e) {
+            // Should not happen.
+            throw new IllegalStateException(e);
+        }
+    }
+
+    @Override
+    public int hashCode() {
+        int result = 17;
+        try {
+            // The only way to generate a consistent hash is to use the serialized form.
+            result = 31 * result + Arrays.hashCode(toByteArray());
+        } catch (IOException e) {
+            // Should not happen.
+            throw new IllegalStateException(e);
+        }
+        return result;
+    }
+
+    private byte[] toByteArray() throws IOException {
+        byte[] result = new byte[computeSerializedSize()];
+        CodedOutputByteBufferNano output = CodedOutputByteBufferNano.newInstance(result);
+        writeTo(output);
+        return result;
+    }
+
+}
diff --git a/javanano/src/main/java/com/google/protobuf/nano/InternalNano.java b/javanano/src/main/java/com/google/protobuf/nano/InternalNano.java
new file mode 100644
index 00000000..90ca11d5
--- /dev/null
+++ b/javanano/src/main/java/com/google/protobuf/nano/InternalNano.java
@@ -0,0 +1,333 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf.nano;
+
+import java.io.UnsupportedEncodingException;
+import java.util.Arrays;
+
+/**
+ * The classes contained within are used internally by the Protocol Buffer
+ * library and generated message implementations. They are public only because
+ * those generated messages do not reside in the {@code protobuf} package.
+ * Others should not use this class directly.
+ *
+ * @author kenton@google.com (Kenton Varda)
+ */
+public final class InternalNano {
+
+  private InternalNano() {}
+
+  /**
+   * An object to provide synchronization when lazily initializing static fields
+   * of {@link MessageNano} subclasses.
+   * <p>
+   * To enable earlier versions of ProGuard to inline short methods from a
+   * generated MessageNano subclass to the call sites, that class must not have
+   * a class initializer, which will be created if there is any static variable
+   * initializers. To lazily initialize the static variables in a thread-safe
+   * manner, the initialization code will synchronize on this object.
+   */
+  public static final Object LAZY_INIT_LOCK = new Object();
+
+  /**
+   * Helper called by generated code to construct default values for string
+   * fields.
+   * <p>
+   * The protocol compiler does not actually contain a UTF-8 decoder -- it
+   * just pushes UTF-8-encoded text around without touching it.  The one place
+   * where this presents a problem is when generating Java string literals.
+   * Unicode characters in the string literal would normally need to be encoded
+   * using a Unicode escape sequence, which would require decoding them.
+   * To get around this, protoc instead embeds the UTF-8 bytes into the
+   * generated code and leaves it to the runtime library to decode them.
+   * <p>
+   * It gets worse, though.  If protoc just generated a byte array, like:
+   *   new byte[] {0x12, 0x34, 0x56, 0x78}
+   * Java actually generates *code* which allocates an array and then fills
+   * in each value.  This is much less efficient than just embedding the bytes
+   * directly into the bytecode.  To get around this, we need another
+   * work-around.  String literals are embedded directly, so protoc actually
+   * generates a string literal corresponding to the bytes.  The easiest way
+   * to do this is to use the ISO-8859-1 character set, which corresponds to
+   * the first 256 characters of the Unicode range.  Protoc can then use
+   * good old CEscape to generate the string.
+   * <p>
+   * So we have a string literal which represents a set of bytes which
+   * represents another string.  This function -- stringDefaultValue --
+   * converts from the generated string to the string we actually want.  The
+   * generated code calls this automatically.
+   */
+  public static String stringDefaultValue(String bytes) {
+    try {
+      return new String(bytes.getBytes("ISO-8859-1"), "UTF-8");
+    } catch (UnsupportedEncodingException e) {
+      // This should never happen since all JVMs are required to implement
+      // both of the above character sets.
+      throw new IllegalStateException(
+          "Java VM does not support a standard character set.", e);
+    }
+  }
+
+  /**
+   * Helper called by generated code to construct default values for bytes
+   * fields.
+   * <p>
+   * This is a lot like {@link #stringDefaultValue}, but for bytes fields.
+   * In this case we only need the second of the two hacks -- allowing us to
+   * embed raw bytes as a string literal with ISO-8859-1 encoding.
+   */
+  public static byte[] bytesDefaultValue(String bytes) {
+    try {
+      return bytes.getBytes("ISO-8859-1");
+    } catch (UnsupportedEncodingException e) {
+      // This should never happen since all JVMs are required to implement
+      // ISO-8859-1.
+      throw new IllegalStateException(
+          "Java VM does not support a standard character set.", e);
+    }
+  }
+
+  /**
+   * Helper function to convert a string into UTF-8 while turning the
+   * UnsupportedEncodingException to a RuntimeException.
+   */
+  public static byte[] copyFromUtf8(final String text) {
+    try {
+      return text.getBytes("UTF-8");
+    } catch (UnsupportedEncodingException e) {
+      throw new RuntimeException("UTF-8 not supported?");
+    }
+  }
+
+  /**
+   * Checks repeated int field equality; null-value and 0-length fields are
+   * considered equal.
+   */
+  public static boolean equals(int[] field1, int[] field2) {
+    if (field1 == null || field1.length == 0) {
+      return field2 == null || field2.length == 0;
+    } else {
+      return Arrays.equals(field1, field2);
+    }
+  }
+
+  /**
+   * Checks repeated long field equality; null-value and 0-length fields are
+   * considered equal.
+   */
+  public static boolean equals(long[] field1, long[] field2) {
+    if (field1 == null || field1.length == 0) {
+      return field2 == null || field2.length == 0;
+    } else {
+      return Arrays.equals(field1, field2);
+    }
+  }
+
+  /**
+   * Checks repeated float field equality; null-value and 0-length fields are
+   * considered equal.
+   */
+  public static boolean equals(float[] field1, float[] field2) {
+    if (field1 == null || field1.length == 0) {
+      return field2 == null || field2.length == 0;
+    } else {
+      return Arrays.equals(field1, field2);
+    }
+  }
+
+  /**
+   * Checks repeated double field equality; null-value and 0-length fields are
+   * considered equal.
+   */
+  public static boolean equals(double[] field1, double[] field2) {
+    if (field1 == null || field1.length == 0) {
+      return field2 == null || field2.length == 0;
+    } else {
+      return Arrays.equals(field1, field2);
+    }
+  }
+
+  /**
+   * Checks repeated boolean field equality; null-value and 0-length fields are
+   * considered equal.
+   */
+  public static boolean equals(boolean[] field1, boolean[] field2) {
+    if (field1 == null || field1.length == 0) {
+      return field2 == null || field2.length == 0;
+    } else {
+      return Arrays.equals(field1, field2);
+    }
+  }
+
+  /**
+   * Checks repeated bytes field equality. Only non-null elements are tested.
+   * Returns true if the two fields have the same sequence of non-null
+   * elements. Null-value fields and fields of any length with only null
+   * elements are considered equal.
+   */
+  public static boolean equals(byte[][] field1, byte[][] field2) {
+    int index1 = 0;
+    int length1 = field1 == null ? 0 : field1.length;
+    int index2 = 0;
+    int length2 = field2 == null ? 0 : field2.length;
+    while (true) {
+      while (index1 < length1 && field1[index1] == null) {
+        index1++;
+      }
+      while (index2 < length2 && field2[index2] == null) {
+        index2++;
+      }
+      boolean atEndOf1 = index1 >= length1;
+      boolean atEndOf2 = index2 >= length2;
+      if (atEndOf1 && atEndOf2) {
+        // no more non-null elements to test in both arrays
+        return true;
+      } else if (atEndOf1 != atEndOf2) {
+        // one of the arrays have extra non-null elements
+        return false;
+      } else if (!Arrays.equals(field1[index1], field2[index2])) {
+        // element mismatch
+        return false;
+      }
+      index1++;
+      index2++;
+    }
+  }
+
+  /**
+   * Checks repeated string/message field equality. Only non-null elements are
+   * tested. Returns true if the two fields have the same sequence of non-null
+   * elements. Null-value fields and fields of any length with only null
+   * elements are considered equal.
+   */
+  public static boolean equals(Object[] field1, Object[] field2) {
+    int index1 = 0;
+    int length1 = field1 == null ? 0 : field1.length;
+    int index2 = 0;
+    int length2 = field2 == null ? 0 : field2.length;
+    while (true) {
+      while (index1 < length1 && field1[index1] == null) {
+        index1++;
+      }
+      while (index2 < length2 && field2[index2] == null) {
+        index2++;
+      }
+      boolean atEndOf1 = index1 >= length1;
+      boolean atEndOf2 = index2 >= length2;
+      if (atEndOf1 && atEndOf2) {
+        // no more non-null elements to test in both arrays
+        return true;
+      } else if (atEndOf1 != atEndOf2) {
+        // one of the arrays have extra non-null elements
+        return false;
+      } else if (!field1[index1].equals(field2[index2])) {
+        // element mismatch
+        return false;
+      }
+      index1++;
+      index2++;
+    }
+  }
+
+  /**
+   * Computes the hash code of a repeated int field. Null-value and 0-length
+   * fields have the same hash code.
+   */
+  public static int hashCode(int[] field) {
+    return field == null || field.length == 0 ? 0 : Arrays.hashCode(field);
+  }
+
+  /**
+   * Computes the hash code of a repeated long field. Null-value and 0-length
+   * fields have the same hash code.
+   */
+  public static int hashCode(long[] field) {
+    return field == null || field.length == 0 ? 0 : Arrays.hashCode(field);
+  }
+
+  /**
+   * Computes the hash code of a repeated float field. Null-value and 0-length
+   * fields have the same hash code.
+   */
+  public static int hashCode(float[] field) {
+    return field == null || field.length == 0 ? 0 : Arrays.hashCode(field);
+  }
+
+  /**
+   * Computes the hash code of a repeated double field. Null-value and 0-length
+   * fields have the same hash code.
+   */
+  public static int hashCode(double[] field) {
+    return field == null || field.length == 0 ? 0 : Arrays.hashCode(field);
+  }
+
+  /**
+   * Computes the hash code of a repeated boolean field. Null-value and 0-length
+   * fields have the same hash code.
+   */
+  public static int hashCode(boolean[] field) {
+    return field == null || field.length == 0 ? 0 : Arrays.hashCode(field);
+  }
+
+  /**
+   * Computes the hash code of a repeated bytes field. Only the sequence of all
+   * non-null elements are used in the computation. Null-value fields and fields
+   * of any length with only null elements have the same hash code.
+   */
+  public static int hashCode(byte[][] field) {
+    int result = 0;
+    for (int i = 0, size = field == null ? 0 : field.length; i < size; i++) {
+      byte[] element = field[i];
+      if (element != null) {
+        result = 31 * result + Arrays.hashCode(element);
+      }
+    }
+    return result;
+  }
+
+  /**
+   * Computes the hash code of a repeated string/message field. Only the
+   * sequence of all non-null elements are used in the computation. Null-value
+   * fields and fields of any length with only null elements have the same hash
+   * code.
+   */
+  public static int hashCode(Object[] field) {
+    int result = 0;
+    for (int i = 0, size = field == null ? 0 : field.length; i < size; i++) {
+      Object element = field[i];
+      if (element != null) {
+        result = 31 * result + element.hashCode();
+      }
+    }
+    return result;
+  }
+
+}
diff --git a/javanano/src/main/java/com/google/protobuf/nano/InvalidProtocolBufferNanoException.java b/javanano/src/main/java/com/google/protobuf/nano/InvalidProtocolBufferNanoException.java
new file mode 100644
index 00000000..ff0af9df
--- /dev/null
+++ b/javanano/src/main/java/com/google/protobuf/nano/InvalidProtocolBufferNanoException.java
@@ -0,0 +1,93 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2013 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf.nano;
+
+import java.io.IOException;
+
+/**
+ * Thrown when a protocol message being parsed is invalid in some way,
+ * e.g. it contains a malformed varint or a negative byte length.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public class InvalidProtocolBufferNanoException extends IOException {
+  private static final long serialVersionUID = -1616151763072450476L;
+
+  public InvalidProtocolBufferNanoException(final String description) {
+    super(description);
+  }
+
+  static InvalidProtocolBufferNanoException truncatedMessage() {
+    return new InvalidProtocolBufferNanoException(
+      "While parsing a protocol message, the input ended unexpectedly " +
+      "in the middle of a field.  This could mean either than the " +
+      "input has been truncated or that an embedded message " +
+      "misreported its own length.");
+  }
+
+  static InvalidProtocolBufferNanoException negativeSize() {
+    return new InvalidProtocolBufferNanoException(
+      "CodedInputStream encountered an embedded string or message " +
+      "which claimed to have negative size.");
+  }
+
+  static InvalidProtocolBufferNanoException malformedVarint() {
+    return new InvalidProtocolBufferNanoException(
+      "CodedInputStream encountered a malformed varint.");
+  }
+
+  static InvalidProtocolBufferNanoException invalidTag() {
+    return new InvalidProtocolBufferNanoException(
+      "Protocol message contained an invalid tag (zero).");
+  }
+
+  static InvalidProtocolBufferNanoException invalidEndTag() {
+    return new InvalidProtocolBufferNanoException(
+      "Protocol message end-group tag did not match expected tag.");
+  }
+
+  static InvalidProtocolBufferNanoException invalidWireType() {
+    return new InvalidProtocolBufferNanoException(
+      "Protocol message tag had invalid wire type.");
+  }
+
+  static InvalidProtocolBufferNanoException recursionLimitExceeded() {
+    return new InvalidProtocolBufferNanoException(
+      "Protocol message had too many levels of nesting.  May be malicious.  " +
+      "Use CodedInputStream.setRecursionLimit() to increase the depth limit.");
+  }
+
+  static InvalidProtocolBufferNanoException sizeLimitExceeded() {
+    return new InvalidProtocolBufferNanoException(
+      "Protocol message was too large.  May be malicious.  " +
+      "Use CodedInputStream.setSizeLimit() to increase the size limit.");
+  }
+}
diff --git a/javanano/src/main/java/com/google/protobuf/nano/MessageNano.java b/javanano/src/main/java/com/google/protobuf/nano/MessageNano.java
new file mode 100644
index 00000000..164f317f
--- /dev/null
+++ b/javanano/src/main/java/com/google/protobuf/nano/MessageNano.java
@@ -0,0 +1,190 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2013 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf.nano;
+
+import java.io.IOException;
+import java.util.Arrays;
+
+/**
+ * Abstract interface implemented by Protocol Message objects.
+ *
+ * @author wink@google.com Wink Saville
+ */
+public abstract class MessageNano {
+    protected volatile int cachedSize = -1;
+
+    /**
+     * Get the number of bytes required to encode this message.
+     * Returns the cached size or calls getSerializedSize which
+     * sets the cached size. This is used internally when serializing
+     * so the size is only computed once. If a member is modified
+     * then this could be stale call getSerializedSize if in doubt.
+     */
+    public int getCachedSize() {
+        if (cachedSize < 0) {
+            // getSerializedSize sets cachedSize
+            getSerializedSize();
+        }
+        return cachedSize;
+    }
+
+    /**
+     * Computes the number of bytes required to encode this message.
+     * The size is cached and the cached result can be retrieved
+     * using getCachedSize().
+     */
+    public int getSerializedSize() {
+        int size = computeSerializedSize();
+        cachedSize = size;
+        return size;
+    }
+
+    /**
+     * Computes the number of bytes required to encode this message. This does not update the
+     * cached size.
+     */
+    protected int computeSerializedSize() {
+      // This is overridden if the generated message has serialized fields.
+      return 0;
+    }
+
+    /**
+     * Serializes the message and writes it to {@code output}.
+     *
+     * @param output the output to receive the serialized form.
+     * @throws IOException if an error occurred writing to {@code output}.
+     */
+    public void writeTo(CodedOutputByteBufferNano output) throws IOException {
+        // Does nothing by default. Overridden by subclasses which have data to write.
+    }
+
+    /**
+     * Parse {@code input} as a message of this type and merge it with the
+     * message being built.
+     */
+    public abstract MessageNano mergeFrom(CodedInputByteBufferNano input) throws IOException;
+
+    /**
+     * Serialize to a byte array.
+     * @return byte array with the serialized data.
+     */
+    public static final byte[] toByteArray(MessageNano msg) {
+        final byte[] result = new byte[msg.getSerializedSize()];
+        toByteArray(msg, result, 0, result.length);
+        return result;
+    }
+
+    /**
+     * Serialize to a byte array starting at offset through length. The
+     * method getSerializedSize must have been called prior to calling
+     * this method so the proper length is know.  If an attempt to
+     * write more than length bytes OutOfSpaceException will be thrown
+     * and if length bytes are not written then IllegalStateException
+     * is thrown.
+     */
+    public static final void toByteArray(MessageNano msg, byte[] data, int offset, int length) {
+        try {
+            final CodedOutputByteBufferNano output =
+                CodedOutputByteBufferNano.newInstance(data, offset, length);
+            msg.writeTo(output);
+            output.checkNoSpaceLeft();
+        } catch (IOException e) {
+            throw new RuntimeException("Serializing to a byte array threw an IOException "
+                    + "(should never happen).", e);
+        }
+    }
+
+    /**
+     * Parse {@code data} as a message of this type and merge it with the
+     * message being built.
+     */
+    public static final <T extends MessageNano> T mergeFrom(T msg, final byte[] data)
+        throws InvalidProtocolBufferNanoException {
+        return mergeFrom(msg, data, 0, data.length);
+    }
+
+    /**
+     * Parse {@code data} as a message of this type and merge it with the
+     * message being built.
+     */
+    public static final <T extends MessageNano> T mergeFrom(T msg, final byte[] data,
+            final int off, final int len) throws InvalidProtocolBufferNanoException {
+        try {
+            final CodedInputByteBufferNano input =
+                CodedInputByteBufferNano.newInstance(data, off, len);
+            msg.mergeFrom(input);
+            input.checkLastTagWas(0);
+            return msg;
+        } catch (InvalidProtocolBufferNanoException e) {
+            throw e;
+        } catch (IOException e) {
+            throw new RuntimeException("Reading from a byte array threw an IOException (should "
+                    + "never happen).");
+        }
+    }
+
+    /**
+     * Compares two {@code MessageNano}s and returns true if the message's are the same class and
+     * have serialized form equality (i.e. all of the field values are the same).
+     */
+    public static final boolean messageNanoEquals(MessageNano a, MessageNano b) {
+        if (a == b) {
+            return true;
+        }
+        if (a == null || b == null) {
+            return false;
+        }
+        if (a.getClass() != b.getClass()) {
+          return false;
+        }
+        final int serializedSize = a.getSerializedSize();
+        if (b.getSerializedSize() != serializedSize) {
+            return false;
+        }
+        final byte[] aByteArray = new byte[serializedSize];
+        final byte[] bByteArray = new byte[serializedSize];
+        toByteArray(a, aByteArray, 0, serializedSize);
+        toByteArray(b, bByteArray, 0, serializedSize);
+        return Arrays.equals(aByteArray, bByteArray);
+    }
+
+    /**
+     * Returns a string that is (mostly) compatible with ProtoBuffer's TextFormat. Note that groups
+     * (which are deprecated) are not serialized with the correct field name.
+     *
+     * <p>This is implemented using reflection, so it is not especially fast nor is it guaranteed
+     * to find all fields if you have method removal turned on for proguard.
+     */
+    @Override
+    public String toString() {
+        return MessageNanoPrinter.print(this);
+    }
+}
diff --git a/javanano/src/main/java/com/google/protobuf/nano/MessageNanoPrinter.java b/javanano/src/main/java/com/google/protobuf/nano/MessageNanoPrinter.java
new file mode 100644
index 00000000..4cca3d5e
--- /dev/null
+++ b/javanano/src/main/java/com/google/protobuf/nano/MessageNanoPrinter.java
@@ -0,0 +1,257 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2013 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf.nano;
+
+import java.lang.reflect.Array;
+import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+
+/**
+ * Static helper methods for printing nano protos.
+ *
+ * @author flynn@google.com Andrew Flynn
+ */
+public final class MessageNanoPrinter {
+    // Do not allow instantiation
+    private MessageNanoPrinter() {}
+
+    private static final String INDENT = "  ";
+    private static final int MAX_STRING_LEN = 200;
+
+    /**
+     * Returns an text representation of a MessageNano suitable for debugging. The returned string
+     * is mostly compatible with Protocol Buffer's TextFormat (as provided by non-nano protocol
+     * buffers) -- groups (which are deprecated) are output with an underscore name (e.g. foo_bar
+     * instead of FooBar) and will thus not parse.
+     *
+     * <p>Employs Java reflection on the given object and recursively prints primitive fields,
+     * groups, and messages.</p>
+     */
+    public static <T extends MessageNano> String print(T message) {
+        if (message == null) {
+            return "";
+        }
+
+        StringBuffer buf = new StringBuffer();
+        try {
+            print(null, message, new StringBuffer(), buf);
+        } catch (IllegalAccessException e) {
+            return "Error printing proto: " + e.getMessage();
+        } catch (InvocationTargetException e) {
+            return "Error printing proto: " + e.getMessage();
+        }
+        return buf.toString();
+    }
+
+    /**
+     * Function that will print the given message/field into the StringBuffer.
+     * Meant to be called recursively.
+     *
+     * @param identifier the identifier to use, or {@code null} if this is the root message to
+     *        print.
+     * @param object the value to print. May in fact be a primitive value or byte array and not a
+     *        message.
+     * @param indentBuf the indentation each line should begin with.
+     * @param buf the output buffer.
+     */
+    private static void print(String identifier, Object object,
+            StringBuffer indentBuf, StringBuffer buf) throws IllegalAccessException,
+            InvocationTargetException {
+        if (object == null) {
+            // This can happen if...
+            //   - we're about to print a message, String, or byte[], but it not present;
+            //   - we're about to print a primitive, but "reftype" optional style is enabled, and
+            //     the field is unset.
+            // In both cases the appropriate behavior is to output nothing.
+        } else if (object instanceof MessageNano) {  // Nano proto message
+            int origIndentBufLength = indentBuf.length();
+            if (identifier != null) {
+                buf.append(indentBuf).append(deCamelCaseify(identifier)).append(" <\n");
+                indentBuf.append(INDENT);
+            }
+            Class<?> clazz = object.getClass();
+
+            // Proto fields follow one of two formats:
+            //
+            // 1) Public, non-static variables that do not begin or end with '_'
+            // Find and print these using declared public fields
+            for (Field field : clazz.getFields()) {
+                int modifiers = field.getModifiers();
+                String fieldName = field.getName();
+
+                if ((modifiers & Modifier.PUBLIC) == Modifier.PUBLIC
+                        && (modifiers & Modifier.STATIC) != Modifier.STATIC
+                        && !fieldName.startsWith("_")
+                        && !fieldName.endsWith("_")) {
+                    Class<?> fieldType = field.getType();
+                    Object value = field.get(object);
+
+                    if (fieldType.isArray()) {
+                        Class<?> arrayType = fieldType.getComponentType();
+
+                        // bytes is special since it's not repeated, but is represented by an array
+                        if (arrayType == byte.class) {
+                            print(fieldName, value, indentBuf, buf);
+                        } else {
+                            int len = value == null ? 0 : Array.getLength(value);
+                            for (int i = 0; i < len; i++) {
+                                Object elem = Array.get(value, i);
+                                print(fieldName, elem, indentBuf, buf);
+                            }
+                        }
+                    } else {
+                        print(fieldName, value, indentBuf, buf);
+                    }
+                }
+            }
+
+            // 2) Fields that are accessed via getter methods (when accessors
+            //    mode is turned on)
+            // Find and print these using getter methods.
+            for (Method method : clazz.getMethods()) {
+                String name = method.getName();
+                // Check for the setter accessor method since getters and hazzers both have
+                // non-proto-field name collisions (hashCode() and getSerializedSize())
+                if (name.startsWith("set")) {
+                    String subfieldName = name.substring(3);
+
+                    Method hazzer = null;
+                    try {
+                        hazzer = clazz.getMethod("has" + subfieldName);
+                    } catch (NoSuchMethodException e) {
+                        continue;
+                    }
+                    // If hazzer does't exist or returns false, no need to continue
+                    if (!(Boolean) hazzer.invoke(object)) {
+                        continue;
+                    }
+
+                    Method getter = null;
+                    try {
+                        getter = clazz.getMethod("get" + subfieldName);
+                    } catch (NoSuchMethodException e) {
+                        continue;
+                    }
+
+                    print(subfieldName, getter.invoke(object), indentBuf, buf);
+                }
+            }
+            if (identifier != null) {
+                indentBuf.setLength(origIndentBufLength);
+                buf.append(indentBuf).append(">\n");
+            }
+        } else {
+            // Non-null primitive value
+            identifier = deCamelCaseify(identifier);
+            buf.append(indentBuf).append(identifier).append(": ");
+            if (object instanceof String) {
+                String stringMessage = sanitizeString((String) object);
+                buf.append("\"").append(stringMessage).append("\"");
+            } else if (object instanceof byte[]) {
+                appendQuotedBytes((byte[]) object, buf);
+            } else {
+                buf.append(object);
+            }
+            buf.append("\n");
+        }
+    }
+
+    /**
+     * Converts an identifier of the format "FieldName" into "field_name".
+     */
+    private static String deCamelCaseify(String identifier) {
+        StringBuffer out = new StringBuffer();
+        for (int i = 0; i < identifier.length(); i++) {
+            char currentChar = identifier.charAt(i);
+            if (i == 0) {
+                out.append(Character.toLowerCase(currentChar));
+            } else if (Character.isUpperCase(currentChar)) {
+                out.append('_').append(Character.toLowerCase(currentChar));
+            } else {
+                out.append(currentChar);
+            }
+        }
+        return out.toString();
+    }
+
+    /**
+     * Shortens and escapes the given string.
+     */
+    private static String sanitizeString(String str) {
+        if (!str.startsWith("http") && str.length() > MAX_STRING_LEN) {
+            // Trim non-URL strings.
+            str = str.substring(0, MAX_STRING_LEN) + "[...]";
+        }
+        return escapeString(str);
+    }
+
+    /**
+     * Escape everything except for low ASCII code points.
+     */
+    private static String escapeString(String str) {
+        int strLen = str.length();
+        StringBuilder b = new StringBuilder(strLen);
+        for (int i = 0; i < strLen; i++) {
+            char original = str.charAt(i);
+            if (original >= ' ' && original <= '~' && original != '"' && original != '\'') {
+                b.append(original);
+            } else {
+                b.append(String.format("\\u%04x", (int) original));
+            }
+        }
+        return b.toString();
+    }
+
+    /**
+     * Appends a quoted byte array to the provided {@code StringBuffer}.
+     */
+    private static void appendQuotedBytes(byte[] bytes, StringBuffer builder) {
+        if (bytes == null) {
+            builder.append("\"\"");
+            return;
+        }
+
+        builder.append('"');
+        for (int i = 0; i < bytes.length; ++i) {
+            int ch = bytes[i] & 0xff;
+            if (ch == '\\' || ch == '"') {
+                builder.append('\\').append((char) ch);
+            } else if (ch >= 32 && ch < 127) {
+                builder.append((char) ch);
+            } else {
+                builder.append(String.format("\\%03o", ch));
+            }
+        }
+        builder.append('"');
+    }
+}
diff --git a/javanano/src/main/java/com/google/protobuf/nano/UnknownFieldData.java b/javanano/src/main/java/com/google/protobuf/nano/UnknownFieldData.java
new file mode 100644
index 00000000..2032e1a6
--- /dev/null
+++ b/javanano/src/main/java/com/google/protobuf/nano/UnknownFieldData.java
@@ -0,0 +1,84 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2013 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf.nano;
+
+import java.io.IOException;
+import java.util.Arrays;
+
+/**
+ * Stores unknown fields. These might be extensions or fields that the generated
+ * API doesn't know about yet.
+ *
+ * @author bduff@google.com (Brian Duff)
+ */
+final class UnknownFieldData {
+
+    final int tag;
+    final byte[] bytes;
+
+    UnknownFieldData(int tag, byte[] bytes) {
+        this.tag = tag;
+        this.bytes = bytes;
+    }
+
+    int computeSerializedSize() {
+        int size = 0;
+        size += CodedOutputByteBufferNano.computeRawVarint32Size(tag);
+        size += bytes.length;
+        return size;
+    }
+
+    void writeTo(CodedOutputByteBufferNano output) throws IOException {
+        output.writeRawVarint32(tag);
+        output.writeRawBytes(bytes);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (o == this) {
+            return true;
+        }
+        if (!(o instanceof UnknownFieldData)) {
+            return false;
+        }
+
+        UnknownFieldData other = (UnknownFieldData) o;
+        return tag == other.tag && Arrays.equals(bytes, other.bytes);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = 17;
+        result = 31 * result + tag;
+        result = 31 * result + Arrays.hashCode(bytes);
+        return result;
+    }
+}
diff --git a/javanano/src/main/java/com/google/protobuf/nano/WireFormatNano.java b/javanano/src/main/java/com/google/protobuf/nano/WireFormatNano.java
new file mode 100644
index 00000000..a3405e55
--- /dev/null
+++ b/javanano/src/main/java/com/google/protobuf/nano/WireFormatNano.java
@@ -0,0 +1,124 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2013 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf.nano;
+
+import java.io.IOException;
+
+/**
+ * This class is used internally by the Protocol Buffer library and generated
+ * message implementations.  It is public only because those generated messages
+ * do not reside in the {@code protobuf} package.  Others should not use this
+ * class directly.
+ *
+ * This class contains constants and helper functions useful for dealing with
+ * the Protocol Buffer wire format.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public final class WireFormatNano {
+  // Do not allow instantiation.
+  private WireFormatNano() {}
+
+  static final int WIRETYPE_VARINT           = 0;
+  static final int WIRETYPE_FIXED64          = 1;
+  static final int WIRETYPE_LENGTH_DELIMITED = 2;
+  static final int WIRETYPE_START_GROUP      = 3;
+  static final int WIRETYPE_END_GROUP        = 4;
+  static final int WIRETYPE_FIXED32          = 5;
+
+  static final int TAG_TYPE_BITS = 3;
+  static final int TAG_TYPE_MASK = (1 << TAG_TYPE_BITS) - 1;
+
+  /** Given a tag value, determines the wire type (the lower 3 bits). */
+  static int getTagWireType(final int tag) {
+    return tag & TAG_TYPE_MASK;
+  }
+
+  /** Given a tag value, determines the field number (the upper 29 bits). */
+  public static int getTagFieldNumber(final int tag) {
+    return tag >>> TAG_TYPE_BITS;
+  }
+
+  /** Makes a tag value given a field number and wire type. */
+  static int makeTag(final int fieldNumber, final int wireType) {
+    return (fieldNumber << TAG_TYPE_BITS) | wireType;
+  }
+
+  public static final int EMPTY_INT_ARRAY[] = {};
+  public static final long EMPTY_LONG_ARRAY[] = {};
+  public static final float EMPTY_FLOAT_ARRAY[] = {};
+  public static final double EMPTY_DOUBLE_ARRAY[] = {};
+  public static final boolean EMPTY_BOOLEAN_ARRAY[] = {};
+  public static final String EMPTY_STRING_ARRAY[] = {};
+  public static final byte[] EMPTY_BYTES_ARRAY[] = {};
+  public static final byte[] EMPTY_BYTES = {};
+
+  /**
+   * Parses an unknown field. This implementation skips the field.
+   *
+   * <p>Generated messages will call this for unknown fields if the store_unknown_fields
+   * option is off.
+   *
+   * @return {@literal true} unless the tag is an end-group tag.
+   */
+  public static boolean parseUnknownField(
+      final CodedInputByteBufferNano input,
+      final int tag) throws IOException {
+    return input.skipField(tag);
+  }
+
+  /**
+   * Computes the array length of a repeated field. We assume that in the common case repeated
+   * fields are contiguously serialized but we still correctly handle interspersed values of a
+   * repeated field (but with extra allocations).
+   *
+   * Rewinds to current input position before returning.
+   *
+   * @param input stream input, pointing to the byte after the first tag
+   * @param tag repeated field tag just read
+   * @return length of array
+   * @throws IOException
+   */
+  public static final int getRepeatedFieldArrayLength(
+      final CodedInputByteBufferNano input,
+      final int tag) throws IOException {
+    int arrayLength = 1;
+    int startPos = input.getPosition();
+    input.skipField(tag);
+    while (input.readTag() == tag) {
+      input.skipField(tag);
+      arrayLength++;
+    }
+    input.rewindToPosition(startPos);
+    return arrayLength;
+  }
+
+}