Down-integrate from internal code base.

21 files changed, 960 insertions, 627 deletions

diff --git a/java/src/main/java/com/google/protobuf/AbstractMessage.java b/java/src/main/java/com/google/protobuf/AbstractMessage.java
index cc89173a..9f418f2b 100644
--- a/java/src/main/java/com/google/protobuf/AbstractMessage.java
+++ b/java/src/main/java/com/google/protobuf/AbstractMessage.java
@@ -30,6 +30,7 @@
 
 package com.google.protobuf;
 
+import com.google.protobuf.Descriptors.EnumValueDescriptor;
 import com.google.protobuf.Descriptors.FieldDescriptor;
 import com.google.protobuf.Descriptors.OneofDescriptor;
 import com.google.protobuf.Internal.EnumLite;
@@ -161,10 +162,18 @@ public abstract class AbstractMessage extends AbstractMessageLite
     Descriptors.Descriptor descriptor = entry.getDescriptorForType();
     Descriptors.FieldDescriptor key = descriptor.findFieldByName("key");
     Descriptors.FieldDescriptor value = descriptor.findFieldByName("value");
-    result.put(entry.getField(key), entry.getField(value));
+    Object fieldValue = entry.getField(value);
+    if (fieldValue instanceof EnumValueDescriptor) {
+      fieldValue = ((EnumValueDescriptor) fieldValue).getNumber();
+    }
+    result.put(entry.getField(key), fieldValue);
     while (iterator.hasNext()) {
       entry = (Message) iterator.next();
-      result.put(entry.getField(key), entry.getField(value));
+      fieldValue = entry.getField(value);
+      if (fieldValue instanceof EnumValueDescriptor) {
+        fieldValue = ((EnumValueDescriptor) fieldValue).getNumber();
+      }
+      result.put(entry.getField(key), fieldValue);
     }
     return result;
   }
diff --git a/java/src/main/java/com/google/protobuf/BooleanArrayList.java b/java/src/main/java/com/google/protobuf/BooleanArrayList.java
index 45492d2f..70e042f5 100644
--- a/java/src/main/java/com/google/protobuf/BooleanArrayList.java
+++ b/java/src/main/java/com/google/protobuf/BooleanArrayList.java
@@ -68,10 +68,17 @@ final class BooleanArrayList
   private int size;
 
   /**
-   * Constructs a new mutable {@code BooleanArrayList}.
+   * Constructs a new mutable {@code BooleanArrayList} with default capacity.
    */
   BooleanArrayList() {
-    array = new boolean[DEFAULT_CAPACITY];
+    this(DEFAULT_CAPACITY);
+  }
+
+  /**
+   * Constructs a new mutable {@code BooleanArrayList} with the provided capacity.
+   */
+  BooleanArrayList(int capacity) {
+    array = new boolean[capacity];
     size = 0;
   }
 
diff --git a/java/src/main/java/com/google/protobuf/BoundedByteString.java b/java/src/main/java/com/google/protobuf/BoundedByteString.java
index b4c3fb1b..934c9030 100644
--- a/java/src/main/java/com/google/protobuf/BoundedByteString.java
+++ b/java/src/main/java/com/google/protobuf/BoundedByteString.java
@@ -33,7 +33,6 @@ package com.google.protobuf;
 import java.io.IOException;
 import java.io.InvalidObjectException;
 import java.io.ObjectInputStream;
-import java.util.NoSuchElementException;
 
 /**
  * This class is used to represent the substring of a {@link ByteString} over a
@@ -47,7 +46,7 @@ import java.util.NoSuchElementException;
  *
  * @author carlanton@google.com (Carl Haverl)
  */
-class BoundedByteString extends LiteralByteString {
+final class BoundedByteString extends LiteralByteString {
 
   private final int bytesOffset;
   private final int bytesLength;
@@ -65,16 +64,7 @@ class BoundedByteString extends LiteralByteString {
    */
   BoundedByteString(byte[] bytes, int offset, int length) {
     super(bytes);
-    if (offset < 0) {
-      throw new IllegalArgumentException("Offset too small: " + offset);
-    }
-    if (length < 0) {
-      throw new IllegalArgumentException("Length too small: " + offset);
-    }
-    if ((long) offset + length > bytes.length) {
-      throw new IllegalArgumentException(
-          "Offset+Length too large: " + offset + "+" + length);
-    }
+    checkRange(offset, offset + length, bytes.length);
 
     this.bytesOffset = offset;
     this.bytesLength = length;
@@ -94,14 +84,7 @@ class BoundedByteString extends LiteralByteString {
   public byte byteAt(int index) {
     // We must check the index ourselves as we cannot rely on Java array index
     // checking for substrings.
-    if (index < 0) {
-      throw new ArrayIndexOutOfBoundsException("Index too small: " + index);
-    }
-    if (index >= size()) {
-      throw new ArrayIndexOutOfBoundsException(
-          "Index too large: " + index + ", " + size());
-    }
-
+    checkIndex(index, size());
     return bytes[bytesOffset + index];
   }
 
@@ -119,8 +102,8 @@ class BoundedByteString extends LiteralByteString {
   // ByteString -> byte[]
 
   @Override
-  protected void copyToInternal(byte[] target, int sourceOffset, 
-      int targetOffset, int numberToCopy) {
+  protected void copyToInternal(byte[] target, int sourceOffset, int targetOffset,
+      int numberToCopy) {
     System.arraycopy(bytes, getOffsetIntoBytes() + sourceOffset, target,
         targetOffset, numberToCopy);
   }
@@ -134,47 +117,8 @@ class BoundedByteString extends LiteralByteString {
     return new LiteralByteString(toByteArray());
   }
 
-  private void readObject(ObjectInputStream in) throws IOException {
+  private void readObject(@SuppressWarnings("unused") ObjectInputStream in) throws IOException {
     throw new InvalidObjectException(
         "BoundedByteStream instances are not to be serialized directly");
   }
-
-  // =================================================================
-  // ByteIterator
-
-  @Override
-  public ByteIterator iterator() {
-    return new BoundedByteIterator();
-  }
-
-  private class BoundedByteIterator implements ByteIterator {
-
-    private int position;
-    private final int limit;
-
-    private BoundedByteIterator() {
-      position = getOffsetIntoBytes();
-      limit = position + size();
-    }
-
-    public boolean hasNext() {
-      return (position < limit);
-    }
-
-    public Byte next() {
-      // Boxing calls Byte.valueOf(byte), which does not instantiate.
-      return nextByte();
-    }
-
-    public byte nextByte() {
-      if (position >= limit) {
-        throw new NoSuchElementException();
-      }
-      return bytes[position++];
-    }
-
-    public void remove() {
-      throw new UnsupportedOperationException();
-    }
-  }
 }
diff --git a/java/src/main/java/com/google/protobuf/ByteString.java b/java/src/main/java/com/google/protobuf/ByteString.java
index b092bc36..68f20d51 100644
--- a/java/src/main/java/com/google/protobuf/ByteString.java
+++ b/java/src/main/java/com/google/protobuf/ByteString.java
@@ -83,6 +83,13 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    */
   public static final ByteString EMPTY = new LiteralByteString(new byte[0]);
 
+  /**
+   * Cached hash value. Intentionally accessed via a data race, which
+   * is safe because of the Java Memory Model's "no out-of-thin-air values"
+   * guarantees for ints. A value of 0 implies that the hash has not been set.
+   */
+  private int hash = 0;
+
   // This constructor is here to prevent subclassing outside of this package,
   ByteString() {}
 
@@ -105,7 +112,38 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    *
    * @return the iterator
    */
-  public abstract ByteIterator iterator();
+  @Override
+  public final ByteIterator iterator() {
+    return new ByteIterator() {
+      private int position = 0;
+      private final int limit = size();
+
+      @Override
+      public boolean hasNext() {
+        return position < limit;
+      }
+
+      @Override
+      public Byte next() {
+        // Boxing calls Byte.valueOf(byte), which does not instantiate.
+        return nextByte();
+      }
+
+      @Override
+      public byte nextByte() {
+        try {
+          return byteAt(position++);
+        } catch (ArrayIndexOutOfBoundsException e) {
+          throw new NoSuchElementException(e.getMessage());
+        }
+      }
+
+      @Override
+      public void remove() {
+        throw new UnsupportedOperationException();
+      }
+    };
+  }
 
   /**
    * This interface extends {@code Iterator<Byte>}, so that we can return an
@@ -134,7 +172,7 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    *
    * @return true if this is zero bytes long
    */
-  public boolean isEmpty() {
+  public final boolean isEmpty() {
     return size() == 0;
   }
 
@@ -150,7 +188,7 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    * @throws IndexOutOfBoundsException if {@code beginIndex < 0} or
    *     {@code beginIndex > size()}.
    */
-  public ByteString substring(int beginIndex) {
+  public final ByteString substring(int beginIndex) {
     return substring(beginIndex, size());
   }
 
@@ -175,7 +213,7 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    *         argument is a prefix of the byte sequence represented by
    *         this string; <code>false</code> otherwise.
    */
-  public boolean startsWith(ByteString prefix) {
+  public final boolean startsWith(ByteString prefix) {
     return size() >= prefix.size() &&
            substring(0, prefix.size()).equals(prefix);
   }
@@ -189,7 +227,7 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    *         argument is a suffix of the byte sequence represented by
    *         this string; <code>false</code> otherwise.
    */
-  public boolean endsWith(ByteString suffix) {
+  public final boolean endsWith(ByteString suffix) {
     return size() >= suffix.size() &&
         substring(size() - suffix.size()).equals(suffix);
   }
@@ -309,8 +347,7 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    */
   public static ByteString readFrom(InputStream streamToDrain)
       throws IOException {
-    return readFrom(
-        streamToDrain, MIN_READ_FROM_CHUNK_SIZE, MAX_READ_FROM_CHUNK_SIZE);
+    return readFrom(streamToDrain, MIN_READ_FROM_CHUNK_SIZE, MAX_READ_FROM_CHUNK_SIZE);
   }
 
   /**
@@ -383,10 +420,10 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
 
       if (bytesRead == 0) {
         return null;
-      } else {
-        // Always make a copy since InputStream could steal a reference to buf.
-        return ByteString.copyFrom(buf, 0, bytesRead);
       }
+
+      // Always make a copy since InputStream could steal a reference to buf.
+      return ByteString.copyFrom(buf, 0, bytesRead);
   }
 
   // =================================================================
@@ -402,12 +439,10 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    * @param other string to concatenate
    * @return a new {@code ByteString} instance
    */
-  public ByteString concat(ByteString other) {
-    int thisSize = size();
-    int otherSize = other.size();
-    if ((long) thisSize + otherSize >= Integer.MAX_VALUE) {
+  public final ByteString concat(ByteString other) {
+    if (Integer.MAX_VALUE - size() < other.size()) {
       throw new IllegalArgumentException("ByteString would be too long: " +
-                                         thisSize + "+" + otherSize);
+          size() + "+" + other.size());
     }
 
     return RopeByteString.concatenate(this, other);
@@ -426,29 +461,29 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    * @return new {@code ByteString}
    */
   public static ByteString copyFrom(Iterable<ByteString> byteStrings) {
-    Collection<ByteString> collection;
+    // Determine the size;
+    final int size;
     if (!(byteStrings instanceof Collection)) {
-      collection = new ArrayList<ByteString>();
-      for (ByteString byteString : byteStrings) {
-        collection.add(byteString);
+      int tempSize = 0;
+      for (Iterator<ByteString> iter = byteStrings.iterator(); iter.hasNext();
+          iter.next(), ++tempSize) {
       }
+      size = tempSize;
     } else {
-      collection = (Collection<ByteString>) byteStrings;
+      size = ((Collection<ByteString>) byteStrings).size();
     }
-    ByteString result;
-    if (collection.isEmpty()) {
-      result = EMPTY;
-    } else {
-      result = balancedConcat(collection.iterator(), collection.size());
+
+    if (size == 0) {
+      return EMPTY;
     }
-    return result;
+
+    return balancedConcat(byteStrings.iterator(), size);
   }
 
   // Internal function used by copyFrom(Iterable<ByteString>).
   // Create a balanced concatenation of the next "length" elements from the
   // iterable.
-  private static ByteString balancedConcat(Iterator<ByteString> iterator,
-      int length) {
+  private static ByteString balancedConcat(Iterator<ByteString> iterator, int length) {
     assert length >= 1;
     ByteString result;
     if (length == 1) {
@@ -486,25 +521,10 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    * @throws IndexOutOfBoundsException if an offset or size is negative or too
    *     large
    */
-  public void copyTo(byte[] target, int sourceOffset, int targetOffset,
+  public final void copyTo(byte[] target, int sourceOffset, int targetOffset,
       int numberToCopy) {
-    if (sourceOffset < 0) {
-      throw new IndexOutOfBoundsException("Source offset < 0: " + sourceOffset);
-    }
-    if (targetOffset < 0) {
-      throw new IndexOutOfBoundsException("Target offset < 0: " + targetOffset);
-    }
-    if (numberToCopy < 0) {
-      throw new IndexOutOfBoundsException("Length < 0: " + numberToCopy);
-    }
-    if (sourceOffset + numberToCopy > size()) {
-      throw new IndexOutOfBoundsException(
-          "Source end offset < 0: " + (sourceOffset + numberToCopy));
-    }
-    if (targetOffset + numberToCopy > target.length) {
-      throw new IndexOutOfBoundsException(
-          "Target end offset < 0: " + (targetOffset + numberToCopy));
-    }
+    checkRange(sourceOffset, sourceOffset + numberToCopy, size());
+    checkRange(targetOffset, targetOffset + numberToCopy, target.length);
     if (numberToCopy > 0) {
       copyToInternal(target, sourceOffset, targetOffset, numberToCopy);
     }
@@ -534,8 +554,8 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    *
    * @return copied bytes
    */
-  public byte[] toByteArray() {
-    int size = size();
+  public final byte[] toByteArray() {
+    final int size = size();
     if (size == 0) {
       return Internal.EMPTY_BYTE_ARRAY;
     }
@@ -548,6 +568,10 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    * Writes the complete contents of this byte string to
    * the specified output stream argument.
    *
+   * <p>It is assumed that the {@link OutputStream} will not modify the contents passed it
+   * it. It may be possible for a malicious {@link OutputStream} to corrupt
+   * the data underlying the {@link ByteString}.
+   *
    * @param  out  the output stream to which to write the data.
    * @throws IOException  if an I/O error occurs.
    */
@@ -563,30 +587,20 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    * @throws IndexOutOfBoundsException if an offset or size is negative or too
    *     large
    */
-  void writeTo(OutputStream out, int sourceOffset, int numberToWrite)
+  final void writeTo(OutputStream out, int sourceOffset, int numberToWrite)
       throws IOException {
-    if (sourceOffset < 0) {
-      throw new IndexOutOfBoundsException("Source offset < 0: " + sourceOffset);
-    }
-    if (numberToWrite < 0) {
-      throw new IndexOutOfBoundsException("Length < 0: " + numberToWrite);
-    }
-    if (sourceOffset + numberToWrite > size()) {
-      throw new IndexOutOfBoundsException(
-          "Source end offset exceeded: " + (sourceOffset + numberToWrite));
-    }
+    checkRange(sourceOffset, sourceOffset + numberToWrite, size());
     if (numberToWrite > 0) {
       writeToInternal(out, sourceOffset, numberToWrite);
     }
-
   }
 
   /**
    * Internal version of {@link #writeTo(OutputStream,int,int)} that assumes
    * all error checking has already been done.
    */
-  abstract void writeToInternal(OutputStream out, int sourceOffset,
-      int numberToWrite) throws IOException;
+  abstract void writeToInternal(OutputStream out, int sourceOffset, int numberToWrite)
+      throws IOException;
 
   /**
    * Constructs a read-only {@code java.nio.ByteBuffer} whose content
@@ -618,7 +632,7 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    * @return new string
    * @throws UnsupportedEncodingException if charset isn't recognized
    */
-  public String toString(String charsetName)
+  public final String toString(String charsetName)
       throws UnsupportedEncodingException {
     try {
       return toString(Charset.forName(charsetName));
@@ -636,7 +650,7 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    * @param charset encode using this charset
    * @return new string
    */
-  public String toString(Charset charset) {
+  public final String toString(Charset charset) {
     return size() == 0 ? "" : toStringInternal(charset);
   }
 
@@ -657,7 +671,7 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    *
    * @return new string using UTF-8 encoding
    */
-  public String toStringUtf8() {
+  public final String toStringUtf8() {
     return toString(Internal.UTF_8);
   }
 
@@ -716,13 +730,51 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
   public abstract boolean equals(Object o);
 
   /**
-   * Return a non-zero hashCode depending only on the sequence of bytes
-   * in this ByteString.
+   * Base class for leaf {@link ByteString}s (i.e. non-ropes).
+   */
+  abstract static class LeafByteString extends ByteString {
+    @Override
+    protected final int getTreeDepth() {
+      return 0;
+    }
+
+    @Override
+    protected final boolean isBalanced() {
+      return true;
+    }
+
+    /**
+     * Check equality of the substring of given length of this object starting at
+     * zero with another {@code ByteString} substring starting at offset.
+     *
+     * @param other  what to compare a substring in
+     * @param offset offset into other
+     * @param length number of bytes to compare
+     * @return true for equality of substrings, else false.
+     */
+    abstract boolean equalsRange(ByteString other, int offset, int length);
+  }
+
+  /**
+   * Compute the hashCode using the traditional algorithm from {@link
+   * ByteString}.
    *
-   * @return hashCode value for this object
+   * @return hashCode value
    */
   @Override
-  public abstract int hashCode();
+  public final int hashCode() {
+    int h = hash;
+
+    if (h == 0) {
+      int size = size();
+      h = partialHash(size, 0, size);
+      if (h == 0) {
+        h = 1;
+      }
+      hash = h;
+    }
+    return h;
+  }
 
   // =================================================================
   // Input stream
@@ -1034,7 +1086,9 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    *
    * @return value of cached hash code or 0 if not computed yet
    */
-  protected abstract int peekCachedHashCode();
+  protected final int peekCachedHashCode() {
+    return hash;
+  }
 
   /**
    * Compute the hash across the value bytes starting with the given hash, and
@@ -1049,8 +1103,49 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    */
   protected abstract int partialHash(int h, int offset, int length);
 
+  /**
+   * Checks that the given index falls within the specified array size.
+   *
+   * @param index the index position to be tested
+   * @param size the length of the array
+   * @throws ArrayIndexOutOfBoundsException if the index does not fall within the array.
+   */
+  static void checkIndex(int index, int size) {
+    if ((index | (size - (index + 1))) < 0) {
+      if (index < 0) {
+        throw new ArrayIndexOutOfBoundsException("Index < 0: " + index);
+      }
+      throw new ArrayIndexOutOfBoundsException("Index > length: " + index + ", " + size);
+    }
+  }
+
+  /**
+   * Checks that the given range falls within the bounds of an array
+   *
+   * @param startIndex the start index of the range (inclusive)
+   * @param endIndex the end index of the range (exclusive)
+   * @param size the size of the array.
+   * @return the length of the range.
+   * @throws ArrayIndexOutOfBoundsException some or all of the range falls outside of the array.
+   */
+  static int checkRange(int startIndex, int endIndex, int size) {
+    final int length = endIndex - startIndex;
+    if ((startIndex | endIndex | length | (size - endIndex)) < 0) {
+      if (startIndex < 0) {
+        throw new IndexOutOfBoundsException("Beginning index: " + startIndex + " < 0");
+      }
+      if (endIndex < startIndex) {
+        throw new IndexOutOfBoundsException(
+            "Beginning index larger than ending index: " + startIndex + ", " + endIndex);
+      }
+      // endIndex >= size
+      throw new IndexOutOfBoundsException("End index: " + endIndex + " >= " + size);
+    }
+    return length;
+  }
+
   @Override
-  public String toString() {
+  public final String toString() {
     return String.format("<ByteString@%s size=%d>",
         Integer.toHexString(System.identityHashCode(this)), size());
   }
diff --git a/java/src/main/java/com/google/protobuf/CodedInputStream.java b/java/src/main/java/com/google/protobuf/CodedInputStream.java
index d201f7c5..adc91536 100644
--- a/java/src/main/java/com/google/protobuf/CodedInputStream.java
+++ b/java/src/main/java/com/google/protobuf/CodedInputStream.java
@@ -1056,20 +1056,6 @@ public final class CodedInputStream {
   private RefillCallback refillCallback = null;
 
   /**
-   * Ensures that at least {@code n} bytes are available in the buffer, reading
-   * more bytes from the input if necessary to make it so.  Caller must ensure
-   * that the requested space is less than BUFFER_SIZE.
-   *
-   * @throws InvalidProtocolBufferException The end of the stream or the current
-   *                                        limit was reached.
-   */
-  private void ensureAvailable(int n) throws IOException {
-    if (bufferSize - bufferPos < n) {
-      refillBuffer(n);
-    }
-  }
-
-  /**
    * Reads more bytes from the input, making at least {@code n} bytes available
    * in the buffer.  Caller must ensure that the requested space is not yet
    * available, and that the requested space is less than BUFFER_SIZE.
@@ -1180,86 +1166,97 @@ public final class CodedInputStream {
       }
     }
 
-    if (totalBytesRetired + bufferPos + size > currentLimit) {
+    // Verify that the message size so far has not exceeded sizeLimit.
+    int currentMessageSize = totalBytesRetired + bufferPos + size;
+    if (currentMessageSize > sizeLimit) {
+      throw InvalidProtocolBufferException.sizeLimitExceeded();
+    }
+
+    // Verify that the message size so far has not exceeded currentLimit.
+    if (currentMessageSize > currentLimit) {
       // Read to the end of the stream anyway.
       skipRawBytes(currentLimit - totalBytesRetired - bufferPos);
-      // Then fail.
       throw InvalidProtocolBufferException.truncatedMessage();
     }
 
-    if (size < BUFFER_SIZE) {
-      // Reading more bytes than are in the buffer, but not an excessive number
-      // of bytes.  We can safely allocate the resulting array ahead of time.
+    // We need the input stream to proceed.
+    if (input == null) {
+      throw InvalidProtocolBufferException.truncatedMessage();
+    }
+
+    final int originalBufferPos = bufferPos;
+    final int bufferedBytes = bufferSize - bufferPos;
+
+    // Mark the current buffer consumed.
+    totalBytesRetired += bufferSize;
+    bufferPos = 0;
+    bufferSize = 0;
 
-      // First copy what we have.
+    // Determine the number of bytes we need to read from the input stream.
+    int sizeLeft = size - bufferedBytes;
+    // TODO(nathanmittler): Consider using a value larger than BUFFER_SIZE.
+    if (sizeLeft < BUFFER_SIZE || sizeLeft <= input.available()) {
+      // Either the bytes we need are known to be available, or the required buffer is
+      // within an allowed threshold - go ahead and allocate the buffer now.
       final byte[] bytes = new byte[size];
-      int pos = bufferSize - bufferPos;
-      System.arraycopy(buffer, bufferPos, bytes, 0, pos);
-      bufferPos = bufferSize;
 
-      // We want to refill the buffer and then copy from the buffer into our
-      // byte array rather than reading directly into our byte array because
-      // the input may be unbuffered.
-      ensureAvailable(size - pos);
-      System.arraycopy(buffer, 0, bytes, pos, size - pos);
-      bufferPos = size - pos;
+      // Copy all of the buffered bytes to the result buffer.
+      System.arraycopy(buffer, originalBufferPos, bytes, 0, bufferedBytes);
 
-      return bytes;
-    } else {
-      // The size is very large.  For security reasons, we can't allocate the
-      // entire byte array yet.  The size comes directly from the input, so a
-      // maliciously-crafted message could provide a bogus very large size in
-      // order to trick the app into allocating a lot of memory.  We avoid this
-      // by allocating and reading only a small chunk at a time, so that the
-      // malicious message must actually *be* extremely large to cause
-      // problems.  Meanwhile, we limit the allowed size of a message elsewhere.
-
-      // Remember the buffer markers since we'll have to copy the bytes out of
-      // it later.
-      final int originalBufferPos = bufferPos;
-      final int originalBufferSize = bufferSize;
-
-      // Mark the current buffer consumed.
-      totalBytesRetired += bufferSize;
-      bufferPos = 0;
-      bufferSize = 0;
-
-      // Read all the rest of the bytes we need.
-      int sizeLeft = size - (originalBufferSize - originalBufferPos);
-      final List<byte[]> chunks = new ArrayList<byte[]>();
-
-      while (sizeLeft > 0) {
-        final byte[] chunk = new byte[Math.min(sizeLeft, BUFFER_SIZE)];
-        int pos = 0;
-        while (pos < chunk.length) {
-          final int n = (input == null) ? -1 :
-            input.read(chunk, pos, chunk.length - pos);
-          if (n == -1) {
-            throw InvalidProtocolBufferException.truncatedMessage();
-          }
-          totalBytesRetired += n;
-          pos += n;
+      // Fill the remaining bytes from the input stream.
+      int pos = bufferedBytes;
+      while (pos < bytes.length) {
+        int n = input.read(bytes, pos, size - pos);
+        if (n == -1) {
+          throw InvalidProtocolBufferException.truncatedMessage();
         }
-        sizeLeft -= chunk.length;
-        chunks.add(chunk);
+        totalBytesRetired += n;
+        pos += n;
       }
 
-      // OK, got everything.  Now concatenate it all into one buffer.
-      final byte[] bytes = new byte[size];
-
-      // Start by copying the leftover bytes from this.buffer.
-      int pos = originalBufferSize - originalBufferPos;
-      System.arraycopy(buffer, originalBufferPos, bytes, 0, pos);
+      return bytes;
+    }
 
-      // And now all the chunks.
-      for (final byte[] chunk : chunks) {
-        System.arraycopy(chunk, 0, bytes, pos, chunk.length);
-        pos += chunk.length;
+    // The size is very large.  For security reasons, we can't allocate the
+    // entire byte array yet.  The size comes directly from the input, so a
+    // maliciously-crafted message could provide a bogus very large size in
+    // order to trick the app into allocating a lot of memory.  We avoid this
+    // by allocating and reading only a small chunk at a time, so that the
+    // malicious message must actually *be* extremely large to cause
+    // problems.  Meanwhile, we limit the allowed size of a message elsewhere.
+    final List<byte[]> chunks = new ArrayList<byte[]>();
+
+    while (sizeLeft > 0) {
+      // TODO(nathanmittler): Consider using a value larger than BUFFER_SIZE.
+      final byte[] chunk = new byte[Math.min(sizeLeft, BUFFER_SIZE)];
+      int pos = 0;
+      while (pos < chunk.length) {
+        final int n = input.read(chunk, pos, chunk.length - pos);
+        if (n == -1) {
+          throw InvalidProtocolBufferException.truncatedMessage();
+        }
+        totalBytesRetired += n;
+        pos += n;
       }
+      sizeLeft -= chunk.length;
+      chunks.add(chunk);
+    }
 
-      // Done.
-      return bytes;
+    // OK, got everything.  Now concatenate it all into one buffer.
+    final byte[] bytes = new byte[size];
+
+    // Start by copying the leftover bytes from this.buffer.
+    System.arraycopy(buffer, originalBufferPos, bytes, 0, bufferedBytes);
+
+    // And now all the chunks.
+    int pos = bufferedBytes;
+    for (final byte[] chunk : chunks) {
+      System.arraycopy(chunk, 0, bytes, pos, chunk.length);
+      pos += chunk.length;
     }
+
+    // Done.
+    return bytes;
   }
 
   /**
diff --git a/java/src/main/java/com/google/protobuf/CodedOutputStream.java b/java/src/main/java/com/google/protobuf/CodedOutputStream.java
index 291bd20a..d8ebad21 100644
--- a/java/src/main/java/com/google/protobuf/CodedOutputStream.java
+++ b/java/src/main/java/com/google/protobuf/CodedOutputStream.java
@@ -53,7 +53,7 @@ import java.util.logging.Logger;
  * @author kneton@google.com Kenton Varda
  */
 public final class CodedOutputStream {
-  
+
   private static final Logger logger = Logger.getLogger(CodedOutputStream.class.getName());
 
   // TODO(dweis): Consider migrating to a ByteBuffer.
@@ -243,19 +243,6 @@ public final class CodedOutputStream {
   }
 
 
-  /**
-   * Write a group represented by an {@link UnknownFieldSet}.
-   *
-   * @deprecated UnknownFieldSet now implements MessageLite, so you can just
-   *             call {@link #writeGroup}.
-   */
-  @Deprecated
-  public void writeUnknownGroup(final int fieldNumber,
-                                final MessageLite value)
-                                throws IOException {
-    writeGroup(fieldNumber, value);
-  }
-
   /** Write an embedded message field, including tag, to the stream. */
   public void writeMessage(final int fieldNumber, final MessageLite value)
                            throws IOException {
@@ -428,7 +415,7 @@ public final class CodedOutputStream {
     try {
       efficientWriteStringNoTag(value);
     } catch (UnpairedSurrogateException e) {
-      logger.log(Level.WARNING, 
+      logger.log(Level.WARNING,
           "Converting ill-formed UTF-16. Your Protocol Buffer will not round trip correctly!", e);
       inefficientWriteStringNoTag(value);
     }
@@ -449,10 +436,10 @@ public final class CodedOutputStream {
    * Write a {@code string} field to the stream efficiently. If the {@code string} is malformed,
    * this method rolls back its changes and throws an {@link UnpairedSurrogateException} with the
    * intent that the caller will catch and retry with {@link #inefficientWriteStringNoTag(String)}.
-   * 
+   *
    * @param value the string to write to the stream
-   * 
-   * @throws UnpairedSurrogateException when {@code value} is ill-formed UTF-16. 
+   *
+   * @throws UnpairedSurrogateException when {@code value} is ill-formed UTF-16.
    */
   private void efficientWriteStringNoTag(final String value) throws IOException {
     // UTF-8 byte length of the string is at least its UTF-16 code unit length (value.length()),
@@ -510,18 +497,6 @@ public final class CodedOutputStream {
   }
 
 
-  /**
-   * Write a group represented by an {@link UnknownFieldSet}.
-   *
-   * @deprecated UnknownFieldSet now implements MessageLite, so you can just
-   *             call {@link #writeGroupNoTag}.
-   */
-  @Deprecated
-  public void writeUnknownGroupNoTag(final MessageLite value)
-      throws IOException {
-    writeGroupNoTag(value);
-  }
-
   /** Write an embedded message field to the stream. */
   public void writeMessageNoTag(final MessageLite value) throws IOException {
     writeRawVarint32(value.getSerializedSize());
@@ -685,20 +660,6 @@ public final class CodedOutputStream {
   }
 
   /**
-   * Compute the number of bytes that would be needed to encode a
-   * {@code group} field represented by an {@code UnknownFieldSet}, including
-   * tag.
-   *
-   * @deprecated UnknownFieldSet now implements MessageLite, so you can just
-   *             call {@link #computeGroupSize}.
-   */
-  @Deprecated
-  public static int computeUnknownGroupSize(final int fieldNumber,
-                                            final MessageLite value) {
-    return computeGroupSize(fieldNumber, value);
-  }
-
-  /**
    * Compute the number of bytes that would be needed to encode an
    * embedded message field, including tag.
    */
@@ -927,19 +888,6 @@ public final class CodedOutputStream {
   }
 
   /**
-   * Compute the number of bytes that would be needed to encode a
-   * {@code group} field represented by an {@code UnknownFieldSet}, including
-   * tag.
-   *
-   * @deprecated UnknownFieldSet now implements MessageLite, so you can just
-   *             call {@link #computeUnknownGroupSizeNoTag}.
-   */
-  @Deprecated
-  public static int computeUnknownGroupSizeNoTag(final MessageLite value) {
-    return computeGroupSizeNoTag(value);
-  }
-
-  /**
    * Compute the number of bytes that would be needed to encode an embedded
    * message field.
    */
@@ -1295,10 +1243,10 @@ public final class CodedOutputStream {
    * 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;
+    if ((value & (~0 <<  7)) == 0) return 1;
+    if ((value & (~0 << 14)) == 0) return 2;
+    if ((value & (~0 << 21)) == 0) return 3;
+    if ((value & (~0 << 28)) == 0) return 4;
     return 5;
   }
 
@@ -1316,17 +1264,16 @@ public final class CodedOutputStream {
   }
 
   /** 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;
+  public static int computeRawVarint64Size(long value) {
+    // handle two popular special cases up front ...
+    if ((value & (~0L << 7)) == 0L) return 1;
+    if (value < 0L) return 10;
+    // ... leaving us with 8 remaining, which we can divide and conquer
+    int n = 2;
+    if ((value & (~0L << 35)) != 0L) { n += 4; value >>>= 28; }
+    if ((value & (~0L << 21)) != 0L) { n += 2; value >>>= 14; }
+    if ((value & (~0L << 14)) != 0L) { n += 1; }
+    return n;
   }
 
   /** Write a little-endian 32-bit integer. */
diff --git a/java/src/main/java/com/google/protobuf/Descriptors.java b/java/src/main/java/com/google/protobuf/Descriptors.java
index 7cfc47f7..5e15cfbe 100644
--- a/java/src/main/java/com/google/protobuf/Descriptors.java
+++ b/java/src/main/java/com/google/protobuf/Descriptors.java
@@ -889,6 +889,11 @@ public final class Descriptors {
      */
     public String getFullName() { return fullName; }
 
+    /** Get the JSON name of this field. */
+    public String getJsonName() {
+      return jsonName;
+    }
+
     /**
      * Get the field's java type.  This is just for convenience.  Every
      * {@code FieldDescriptorProto.Type} maps to exactly one Java type.
@@ -1079,6 +1084,7 @@ public final class Descriptors {
 
     private FieldDescriptorProto proto;
     private final String fullName;
+    private final String jsonName;
     private final FileDescriptor file;
     private final Descriptor extensionScope;
 
@@ -1157,6 +1163,38 @@ public final class Descriptors {
       private final Object defaultDefault;
     }
 
+    // TODO(xiaofeng): Implement it consistently across different languages. See b/24751348.
+    private static String fieldNameToLowerCamelCase(String name) {
+      StringBuilder result = new StringBuilder(name.length());
+      boolean isNextUpperCase = false;
+      for (int i = 0; i < name.length(); i++) {
+        Character ch = name.charAt(i);
+        if (Character.isLowerCase(ch)) {
+          if (isNextUpperCase) {
+            result.append(Character.toUpperCase(ch));
+          } else {
+            result.append(ch);
+          }
+          isNextUpperCase = false;
+        } else if (Character.isUpperCase(ch)) {
+          if (i == 0) {
+            // Force first letter to lower-case.
+            result.append(Character.toLowerCase(ch));
+          } else {
+            // Capital letters after the first are left as-is.
+            result.append(ch);
+          }
+          isNextUpperCase = false;
+        } else if (Character.isDigit(ch)) {
+          result.append(ch);
+          isNextUpperCase = false;
+        } else {
+          isNextUpperCase = true;
+        }
+      }
+      return result.toString();
+    }
+
     private FieldDescriptor(final FieldDescriptorProto proto,
                             final FileDescriptor file,
                             final Descriptor parent,
@@ -1167,6 +1205,11 @@ public final class Descriptors {
       this.proto = proto;
       fullName = computeFullName(file, parent, proto.getName());
       this.file = file;
+      if (proto.hasJsonName()) {
+        jsonName = proto.getJsonName();
+      } else {
+        jsonName = fieldNameToLowerCamelCase(proto.getName());
+      }
 
       if (proto.hasType()) {
         type = Type.valueOf(proto.getType());
diff --git a/java/src/main/java/com/google/protobuf/DoubleArrayList.java b/java/src/main/java/com/google/protobuf/DoubleArrayList.java
index 90ebe109..bcc9d6ee 100644
--- a/java/src/main/java/com/google/protobuf/DoubleArrayList.java
+++ b/java/src/main/java/com/google/protobuf/DoubleArrayList.java
@@ -68,10 +68,17 @@ final class DoubleArrayList
   private int size;
 
   /**
-   * Constructs a new mutable {@code DoubleArrayList}.
+   * Constructs a new mutable {@code DoubleArrayList} with default capacity.
    */
   DoubleArrayList() {
-    array = new double[DEFAULT_CAPACITY];
+    this(DEFAULT_CAPACITY);
+  }
+
+  /**
+   * Constructs a new mutable {@code DoubleArrayList} with the provided capacity.
+   */
+  DoubleArrayList(int capacity) {
+    array = new double[capacity];
     size = 0;
   }
 
diff --git a/java/src/main/java/com/google/protobuf/FloatArrayList.java b/java/src/main/java/com/google/protobuf/FloatArrayList.java
index 293eaff6..033b5eed 100644
--- a/java/src/main/java/com/google/protobuf/FloatArrayList.java
+++ b/java/src/main/java/com/google/protobuf/FloatArrayList.java
@@ -67,10 +67,17 @@ final class FloatArrayList extends AbstractProtobufList<Float> implements FloatL
   private int size;
 
   /**
-   * Constructs a new mutable {@code FloatArrayList}.
+   * Constructs a new mutable {@code FloatArrayList} with default capacity.
    */
   FloatArrayList() {
-    array = new float[DEFAULT_CAPACITY];
+    this(DEFAULT_CAPACITY);
+  }
+
+  /**
+   * Constructs a new mutable {@code FloatArrayList} with the provided capacity.
+   */
+  FloatArrayList(int capacity) {
+    array = new float[capacity];
     size = 0;
   }
 
diff --git a/java/src/main/java/com/google/protobuf/GeneratedMessageLite.java b/java/src/main/java/com/google/protobuf/GeneratedMessageLite.java
index 4316efee..81e1862c 100644
--- a/java/src/main/java/com/google/protobuf/GeneratedMessageLite.java
+++ b/java/src/main/java/com/google/protobuf/GeneratedMessageLite.java
@@ -102,6 +102,11 @@ public abstract class GeneratedMessageLite<
    * @return {@code true} unless the tag is an end-group tag.
    */
   protected boolean parseUnknownField(int tag, CodedInputStream input) throws IOException {
+    // This will avoid the allocation of unknown fields when a group tag is encountered.
+    if (WireFormat.getTagWireType(tag) == WireFormat.WIRETYPE_END_GROUP) {
+      return false;
+    }
+    
     ensureUnknownFieldsInitialized();
     return unknownFields.mergeFieldFrom(tag, input);
   }
@@ -1173,6 +1178,10 @@ public abstract class GeneratedMessageLite<
     return new IntArrayList();
   }
   
+  protected static IntList newIntListWithCapacity(int capacity) {
+    return new IntArrayList(capacity);
+  }
+  
   protected static IntList newIntList(List<Integer> toCopy) {
     return new IntArrayList(toCopy);
   }
@@ -1180,10 +1189,14 @@ public abstract class GeneratedMessageLite<
   protected static IntList emptyIntList() {
     return IntArrayList.emptyList();
   }
-  
+
   protected static LongList newLongList() {
     return new LongArrayList();
   }
+
+  protected static LongList newLongListWithCapacity(int capacity) {
+    return new LongArrayList(capacity);
+  }
   
   protected static LongList newLongList(List<Long> toCopy) {
     return new LongArrayList(toCopy);
@@ -1197,6 +1210,10 @@ public abstract class GeneratedMessageLite<
     return new FloatArrayList();
   }
   
+  protected static FloatList newFloatListWithCapacity(int capacity) {
+    return new FloatArrayList(capacity);
+  }
+  
   protected static FloatList newFloatList(List<Float> toCopy) {
     return new FloatArrayList(toCopy);
   }
@@ -1209,6 +1226,10 @@ public abstract class GeneratedMessageLite<
     return new DoubleArrayList();
   }
   
+  protected static DoubleList newDoubleListWithCapacity(int capacity) {
+    return new DoubleArrayList(capacity);
+  }
+  
   protected static DoubleList newDoubleList(List<Double> toCopy) {
     return new DoubleArrayList(toCopy);
   }
@@ -1221,6 +1242,10 @@ public abstract class GeneratedMessageLite<
     return new BooleanArrayList();
   }
   
+  protected static BooleanList newBooleanListWithCapacity(int capacity) {
+    return new BooleanArrayList(capacity);
+  }
+  
   protected static BooleanList newBooleanList(List<Boolean> toCopy) {
     return new BooleanArrayList(toCopy);
   }
@@ -1237,6 +1262,10 @@ public abstract class GeneratedMessageLite<
     return new ProtobufArrayList<E>(toCopy);
   }
   
+  protected static <E> ProtobufList<E> newProtobufListWithCapacity(int capacity) {
+    return new ProtobufArrayList<E>(capacity);
+  }
+  
   protected static <E> ProtobufList<E> emptyProtobufList() {
     return ProtobufArrayList.emptyList();
   }
diff --git a/java/src/main/java/com/google/protobuf/IntArrayList.java b/java/src/main/java/com/google/protobuf/IntArrayList.java
index f7609cc9..f4e68ed8 100644
--- a/java/src/main/java/com/google/protobuf/IntArrayList.java
+++ b/java/src/main/java/com/google/protobuf/IntArrayList.java
@@ -67,10 +67,17 @@ final class IntArrayList extends AbstractProtobufList<Integer> implements IntLis
   private int size;
 
   /**
-   * Constructs a new mutable {@code IntArrayList}.
+   * Constructs a new mutable {@code IntArrayList} with default capacity.
    */
   IntArrayList() {
-    array = new int[DEFAULT_CAPACITY];
+    this(DEFAULT_CAPACITY);
+  }
+
+  /**
+   * Constructs a new mutable {@code IntArrayList} with the provided capacity.
+   */
+  IntArrayList(int capacity) {
+    array = new int[capacity];
     size = 0;
   }
 
diff --git a/java/src/main/java/com/google/protobuf/LiteralByteString.java b/java/src/main/java/com/google/protobuf/LiteralByteString.java
index c5a8512a..a18c2792 100644
--- a/java/src/main/java/com/google/protobuf/LiteralByteString.java
+++ b/java/src/main/java/com/google/protobuf/LiteralByteString.java
@@ -36,9 +36,8 @@ import java.io.InputStream;
 import java.io.OutputStream;
 import java.nio.ByteBuffer;
 import java.nio.charset.Charset;
-import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
-import java.util.NoSuchElementException;
 
 /**
  * This class implements a {@link com.google.protobuf.ByteString} backed by a
@@ -49,8 +48,7 @@ import java.util.NoSuchElementException;
  *
  * @author carlanton@google.com (Carl Haverl)
  */
-class LiteralByteString extends ByteString {
-
+class LiteralByteString extends ByteString.LeafByteString {
   private static final long serialVersionUID = 1L;
 
   protected final byte[] bytes;
@@ -82,77 +80,56 @@ class LiteralByteString extends ByteString {
   // ByteString -> substring
 
   @Override
-  public ByteString substring(int beginIndex, int endIndex) {
-    if (beginIndex < 0) {
-      throw new IndexOutOfBoundsException(
-          "Beginning index: " + beginIndex + " < 0");
-    }
-    if (endIndex > size()) {
-      throw new IndexOutOfBoundsException("End index: " + endIndex + " > " +
-          size());
-    }
-    int substringLength = endIndex - beginIndex;
-    if (substringLength < 0) {
-      throw new IndexOutOfBoundsException(
-          "Beginning index larger than ending index: " + beginIndex + ", "
-              + endIndex);
-    }
+  public final ByteString substring(int beginIndex, int endIndex) {
+    final int length = checkRange(beginIndex, endIndex, size());
 
-    ByteString result;
-    if (substringLength == 0) {
-      result = ByteString.EMPTY;
-    } else {
-      result = new BoundedByteString(bytes, getOffsetIntoBytes() + beginIndex,
-          substringLength);
+    if (length == 0) {
+      return ByteString.EMPTY;
     }
-    return result;
+
+    return new BoundedByteString(bytes, getOffsetIntoBytes() + beginIndex, length);
   }
 
   // =================================================================
   // ByteString -> byte[]
 
   @Override
-  protected void copyToInternal(byte[] target, int sourceOffset,
-      int targetOffset, int numberToCopy) {
+  protected void copyToInternal(
+      byte[] target, int sourceOffset, int targetOffset, int numberToCopy) {
     // Optimized form, not for subclasses, since we don't call
     // getOffsetIntoBytes() or check the 'numberToCopy' parameter.
+    // TODO(nathanmittler): Is not calling getOffsetIntoBytes really saving that much?
     System.arraycopy(bytes, sourceOffset, target, targetOffset, numberToCopy);
   }
 
   @Override
-  public void copyTo(ByteBuffer target) {
-    target.put(bytes, getOffsetIntoBytes(), size());  // Copies bytes
+  public final void copyTo(ByteBuffer target) {
+    target.put(bytes, getOffsetIntoBytes(), size()); // Copies bytes
+  }
+
+  @Override
+  public final ByteBuffer asReadOnlyByteBuffer() {
+    return ByteBuffer.wrap(bytes, getOffsetIntoBytes(), size()).asReadOnlyBuffer();
   }
 
   @Override
-  public ByteBuffer asReadOnlyByteBuffer() {
-    ByteBuffer byteBuffer =
-        ByteBuffer.wrap(bytes, getOffsetIntoBytes(), size());
-    return byteBuffer.asReadOnlyBuffer();
+  public final List<ByteBuffer> asReadOnlyByteBufferList() {
+    return Collections.singletonList(asReadOnlyByteBuffer());
   }
 
   @Override
-  public List<ByteBuffer> asReadOnlyByteBufferList() {
-    // Return the ByteBuffer generated by asReadOnlyByteBuffer() as a singleton
-    List<ByteBuffer> result = new ArrayList<ByteBuffer>(1);
-    result.add(asReadOnlyByteBuffer());
-    return result;
- }
-
- @Override
-  public void writeTo(OutputStream outputStream) throws IOException {
+  public final void writeTo(OutputStream outputStream) throws IOException {
     outputStream.write(toByteArray());
   }
 
   @Override
-  void writeToInternal(OutputStream outputStream, int sourceOffset,
-      int numberToWrite) throws IOException {
-    outputStream.write(bytes, getOffsetIntoBytes() + sourceOffset,
-        numberToWrite);
+  final void writeToInternal(OutputStream outputStream, int sourceOffset, int numberToWrite)
+      throws IOException {
+    outputStream.write(bytes, getOffsetIntoBytes() + sourceOffset, numberToWrite);
   }
 
   @Override
-  protected String toStringInternal(Charset charset) {
+  protected final String toStringInternal(Charset charset) {
     return new String(bytes, getOffsetIntoBytes(), size(), charset);
   }
 
@@ -160,13 +137,13 @@ class LiteralByteString extends ByteString {
   // UTF-8 decoding
 
   @Override
-  public boolean isValidUtf8() {
+  public final boolean isValidUtf8() {
     int offset = getOffsetIntoBytes();
     return Utf8.isValidUtf8(bytes, offset, offset + size());
   }
 
   @Override
-  protected int partialIsValidUtf8(int state, int offset, int length) {
+  protected final int partialIsValidUtf8(int state, int offset, int length) {
     int index = getOffsetIntoBytes() + offset;
     return Utf8.partialIsValidUtf8(state, bytes, index, index + length);
   }
@@ -175,7 +152,7 @@ class LiteralByteString extends ByteString {
   // equals() and hashCode()
 
   @Override
-  public boolean equals(Object other) {
+  public final boolean equals(Object other) {
     if (other == this) {
       return true;
     }
@@ -194,19 +171,16 @@ class LiteralByteString extends ByteString {
       LiteralByteString otherAsLiteral = (LiteralByteString) other;
       // If we know the hash codes and they are not equal, we know the byte
       // strings are not equal.
-      if (hash != 0
-          && otherAsLiteral.hash != 0
-          && hash != otherAsLiteral.hash) {
+      int thisHash = peekCachedHashCode();
+      int thatHash = otherAsLiteral.peekCachedHashCode();
+      if (thisHash != 0 && thatHash != 0 && thisHash != thatHash) {
         return false;
       }
 
       return equalsRange((LiteralByteString) other, 0, size());
-    } else if (other instanceof RopeByteString) {
-      return other.equals(this);
     } else {
-      throw new IllegalArgumentException(
-          "Has a new type of ByteString been created? Found "
-              + other.getClass());
+      // RopeByteString and NioByteString.
+      return other.equals(this);
     }
   }
 
@@ -219,65 +193,36 @@ class LiteralByteString extends ByteString {
    * @param length number of bytes to compare
    * @return true for equality of substrings, else false.
    */
-  boolean equalsRange(LiteralByteString other, int offset, int length) {
+  @Override
+  final boolean equalsRange(ByteString other, int offset, int length) {
     if (length > other.size()) {
-      throw new IllegalArgumentException(
-          "Length too large: " + length + size());
+      throw new IllegalArgumentException("Length too large: " + length + size());
     }
     if (offset + length > other.size()) {
       throw new IllegalArgumentException(
-          "Ran off end of other: " + offset + ", " + length + ", " +
-              other.size());
+          "Ran off end of other: " + offset + ", " + length + ", " + other.size());
     }
 
-    byte[] thisBytes = bytes;
-    byte[] otherBytes = other.bytes;
-    int thisLimit = getOffsetIntoBytes() + length;
-    for (int thisIndex = getOffsetIntoBytes(), otherIndex =
-        other.getOffsetIntoBytes() + offset;
-        (thisIndex < thisLimit); ++thisIndex, ++otherIndex) {
-      if (thisBytes[thisIndex] != otherBytes[otherIndex]) {
-        return false;
-      }
-    }
-    return true;
-  }
-
-  /**
-   * Cached hash value.  Intentionally accessed via a data race, which
-   * is safe because of the Java Memory Model's "no out-of-thin-air values"
-   * guarantees for ints.
-   */
-  private int hash = 0;
-
-  /**
-   * Compute the hashCode using the traditional algorithm from {@link
-   * ByteString}.
-   *
-   * @return hashCode value
-   */
-  @Override
-  public int hashCode() {
-    int h = hash;
-
-    if (h == 0) {
-      int size = size();
-      h = partialHash(size, 0, size);
-      if (h == 0) {
-        h = 1;
+    if (other instanceof LiteralByteString) {
+      LiteralByteString lbsOther = (LiteralByteString) other;
+      byte[] thisBytes = bytes;
+      byte[] otherBytes = lbsOther.bytes;
+      int thisLimit = getOffsetIntoBytes() + length;
+      for (
+          int thisIndex = getOffsetIntoBytes(), otherIndex = lbsOther.getOffsetIntoBytes() + offset;
+          (thisIndex < thisLimit); ++thisIndex, ++otherIndex) {
+        if (thisBytes[thisIndex] != otherBytes[otherIndex]) {
+          return false;
+        }
       }
-      hash = h;
+      return true;
     }
-    return h;
-  }
 
-  @Override
-  protected int peekCachedHashCode() {
-    return hash;
+    return other.substring(offset, offset + length).equals(substring(0, length));
   }
 
   @Override
-  protected int partialHash(int h, int offset, int length) {
+  protected final int partialHash(int h, int offset, int length) {
     return hashCode(h, bytes, getOffsetIntoBytes() + offset, length);
   }
 
@@ -297,70 +242,20 @@ class LiteralByteString extends ByteString {
   // Input stream
 
   @Override
-  public InputStream newInput() {
-    return new ByteArrayInputStream(bytes, getOffsetIntoBytes(),
-        size());  // No copy
+  public final InputStream newInput() {
+    return new ByteArrayInputStream(bytes, getOffsetIntoBytes(), size()); // No copy
   }
 
   @Override
-  public CodedInputStream newCodedInput() {
+  public final CodedInputStream newCodedInput() {
     // We trust CodedInputStream not to modify the bytes, or to give anyone
     // else access to them.
     return CodedInputStream.newInstance(this);
   }
 
   // =================================================================
-  // ByteIterator
-
-  @Override
-  public ByteIterator iterator() {
-    return new LiteralByteIterator();
-  }
-
-  private class LiteralByteIterator implements ByteIterator {
-    private int position;
-    private final int limit;
-
-    private LiteralByteIterator() {
-      position = 0;
-      limit = size();
-    }
-
-    public boolean hasNext() {
-      return (position < limit);
-    }
-
-    public Byte next() {
-      // Boxing calls Byte.valueOf(byte), which does not instantiate.
-      return nextByte();
-    }
-
-    public byte nextByte() {
-      try {
-        return bytes[position++];
-      } catch (ArrayIndexOutOfBoundsException e) {
-        throw new NoSuchElementException(e.getMessage());
-      }
-    }
-
-    public void remove() {
-      throw new UnsupportedOperationException();
-    }
-  }
-
-  // =================================================================
   // Internal methods
 
-  @Override
-  protected int getTreeDepth() {
-    return 0;
-  }
-
-  @Override
-  protected boolean isBalanced() {
-    return true;
-  }
-
   /**
    * Offset into {@code bytes[]} to use, non-zero for substrings.
    *
diff --git a/java/src/main/java/com/google/protobuf/LongArrayList.java b/java/src/main/java/com/google/protobuf/LongArrayList.java
index 298617ff..ebe62029 100644
--- a/java/src/main/java/com/google/protobuf/LongArrayList.java
+++ b/java/src/main/java/com/google/protobuf/LongArrayList.java
@@ -67,10 +67,17 @@ final class LongArrayList extends AbstractProtobufList<Long> implements LongList
   private int size;
 
   /**
-   * Constructs a new mutable {@code LongArrayList}.
+   * Constructs a new mutable {@code LongArrayList} with default capacity.
    */
   LongArrayList() {
-    array = new long[DEFAULT_CAPACITY];
+    this(DEFAULT_CAPACITY);
+  }
+
+  /**
+   * Constructs a new mutable {@code LongArrayList} with the provided capacity.
+   */
+  LongArrayList(int capacity) {
+    array = new long[capacity];
     size = 0;
   }
 
diff --git a/java/src/main/java/com/google/protobuf/MapFieldLite.java b/java/src/main/java/com/google/protobuf/MapFieldLite.java
index c17fa7b1..16d3e6d2 100644
--- a/java/src/main/java/com/google/protobuf/MapFieldLite.java
+++ b/java/src/main/java/com/google/protobuf/MapFieldLite.java
@@ -30,6 +30,8 @@
 
 package com.google.protobuf;
 
+import com.google.protobuf.Internal.EnumLite;
+
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
@@ -44,7 +46,7 @@ import java.util.Set;
  * This class is a protobuf implementation detail. Users shouldn't use this
  * class directly.
  */
-public class MapFieldLite<K, V> implements MutabilityOracle {
+public final class MapFieldLite<K, V> implements MutabilityOracle {
   private MutatabilityAwareMap<K, V> mapData;
   private boolean isMutable;
   
@@ -136,8 +138,9 @@ public class MapFieldLite<K, V> implements MutabilityOracle {
     if (a instanceof byte[]) {
       return LiteralByteString.hashCode((byte[]) a);
     }
-    if (a instanceof Internal.EnumLite) {
-      return Internal.hashEnum((Internal.EnumLite) a);
+    // Enums should be stored as integers internally.
+    if (a instanceof EnumLite) {
+      throw new UnsupportedOperationException();
     }
     return a.hashCode();
   }
diff --git a/java/src/main/java/com/google/protobuf/MessageLiteToString.java b/java/src/main/java/com/google/protobuf/MessageLiteToString.java
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/MessageLiteToString.java
diff --git a/java/src/main/java/com/google/protobuf/NioByteString.java b/java/src/main/java/com/google/protobuf/NioByteString.java
new file mode 100644
index 00000000..f71e41b2
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/NioByteString.java
@@ -0,0 +1,309 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// 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;
+
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InvalidObjectException;
+import java.io.ObjectInputStream;
+import java.io.OutputStream;
+import java.nio.ByteBuffer;
+import java.nio.InvalidMarkException;
+import java.nio.channels.Channels;
+import java.nio.charset.Charset;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * A {@link ByteString} that wraps around a {@link ByteBuffer}.
+ */
+final class NioByteString extends ByteString.LeafByteString {
+  private final ByteBuffer buffer;
+
+  NioByteString(ByteBuffer buffer) {
+    if (buffer == null) {
+      throw new NullPointerException("buffer");
+    }
+
+    this.buffer = buffer.slice();
+  }
+
+  // =================================================================
+  // Serializable
+
+  /**
+   * Magic method that lets us override serialization behavior.
+   */
+  private Object writeReplace() {
+    return ByteString.copyFrom(buffer.slice());
+  }
+
+  /**
+   * Magic method that lets us override deserialization behavior.
+   */
+  private void readObject(@SuppressWarnings("unused") ObjectInputStream in) throws IOException {
+    throw new InvalidObjectException("NioByteString instances are not to be serialized directly");
+  }
+
+  // =================================================================
+
+  @Override
+  public byte byteAt(int index) {
+    try {
+      return buffer.get(index);
+    } catch (ArrayIndexOutOfBoundsException e) {
+      throw e;
+    } catch (IndexOutOfBoundsException e) {
+      throw new ArrayIndexOutOfBoundsException(e.getMessage());
+    }
+  }
+
+  @Override
+  public int size() {
+    return buffer.remaining();
+  }
+
+  @Override
+  public ByteString substring(int beginIndex, int endIndex) {
+    try {
+      ByteBuffer slice = slice(beginIndex, endIndex);
+      return new NioByteString(slice);
+    } catch (ArrayIndexOutOfBoundsException e) {
+      throw e;
+    } catch (IndexOutOfBoundsException e) {
+      throw new ArrayIndexOutOfBoundsException(e.getMessage());
+    }
+  }
+
+  @Override
+  protected void copyToInternal(
+      byte[] target, int sourceOffset, int targetOffset, int numberToCopy) {
+    ByteBuffer slice = buffer.slice();
+    slice.position(sourceOffset);
+    slice.get(target, targetOffset, numberToCopy);
+  }
+
+  @Override
+  public void copyTo(ByteBuffer target) {
+    target.put(buffer.slice());
+  }
+
+  @Override
+  public void writeTo(OutputStream out) throws IOException {
+    writeToInternal(out, buffer.position(), buffer.remaining());
+  }
+
+  @Override
+  boolean equalsRange(ByteString other, int offset, int length) {
+    return substring(0, length).equals(other.substring(offset, offset + length));
+  }
+
+  @Override
+  void writeToInternal(OutputStream out, int sourceOffset, int numberToWrite) throws IOException {
+    if (buffer.hasArray()) {
+      // Optimized write for array-backed buffers.
+      // Note that we're taking the risk that a malicious OutputStream could modify the array.
+      int bufferOffset = buffer.arrayOffset() + buffer.position() + sourceOffset;
+      out.write(buffer.array(), bufferOffset, numberToWrite);
+      return;
+    }
+
+    // Slow path
+    if (out instanceof FileOutputStream || numberToWrite >= 8192) {
+      // Use a channel to write out the ByteBuffer.
+      Channels.newChannel(out).write(slice(sourceOffset, sourceOffset + numberToWrite));
+    } else {
+      // Just copy the data to an array and write it.
+      out.write(toByteArray());
+    }
+  }
+
+  @Override
+  public ByteBuffer asReadOnlyByteBuffer() {
+    return buffer.asReadOnlyBuffer();
+  }
+
+  @Override
+  public List<ByteBuffer> asReadOnlyByteBufferList() {
+    return Collections.singletonList(asReadOnlyByteBuffer());
+  }
+
+  @Override
+  protected String toStringInternal(Charset charset) {
+    byte[] bytes;
+    int offset;
+    if (buffer.hasArray()) {
+      bytes = buffer.array();
+      offset = buffer.arrayOffset() + buffer.position();
+    } else {
+      bytes = toByteArray();
+      offset = 0;
+    }
+    return new String(bytes, offset, size(), charset);
+  }
+
+  @Override
+  public boolean isValidUtf8() {
+    // TODO(nathanmittler): add a ByteBuffer fork for Utf8.isValidUtf8 to avoid the copy
+    byte[] bytes;
+    int startIndex;
+    if (buffer.hasArray()) {
+      bytes = buffer.array();
+      startIndex = buffer.arrayOffset() + buffer.position();
+    } else {
+      bytes = toByteArray();
+      startIndex = 0;
+    }
+    return Utf8.isValidUtf8(bytes, startIndex, startIndex + size());
+  }
+
+  @Override
+  protected int partialIsValidUtf8(int state, int offset, int length) {
+    // TODO(nathanmittler): TODO add a ByteBuffer fork for Utf8.partialIsValidUtf8 to avoid the copy
+    byte[] bytes;
+    int startIndex;
+    if (buffer.hasArray()) {
+      bytes = buffer.array();
+      startIndex = buffer.arrayOffset() + buffer.position();
+    } else {
+      bytes = toByteArray();
+      startIndex = 0;
+    }
+    return Utf8.partialIsValidUtf8(state, bytes, startIndex, startIndex + size());
+  }
+
+  @Override
+  public boolean equals(Object other) {
+    if (other == this) {
+      return true;
+    }
+    if (!(other instanceof ByteString)) {
+      return false;
+    }
+    ByteString otherString = ((ByteString) other);
+    if (size() != otherString.size()) {
+      return false;
+    }
+    if (size() == 0) {
+      return true;
+    }
+    if (other instanceof NioByteString) {
+      return buffer.equals(((NioByteString) other).buffer);
+    }
+    if (other instanceof RopeByteString) {
+      return other.equals(this);
+    }
+    return buffer.equals(otherString.asReadOnlyByteBuffer());
+  }
+
+  @Override
+  protected int partialHash(int h, int offset, int length) {
+    for (int i = offset; i < offset + length; i++) {
+      h = h * 31 + buffer.get(i);
+    }
+    return h;
+  }
+
+  @Override
+  public InputStream newInput() {
+    return new InputStream() {
+      private final ByteBuffer buf = buffer.slice();
+
+      @Override
+      public void mark(int readlimit) {
+        buf.mark();
+      }
+
+      @Override
+      public boolean markSupported() {
+        return true;
+      }
+
+      @Override
+      public void reset() throws IOException {
+        try {
+          buf.reset();
+        } catch (InvalidMarkException e) {
+          throw new IOException(e);
+        }
+      }
+
+      @Override
+      public int available() throws IOException {
+        return buf.remaining();
+      }
+
+      @Override
+      public int read() throws IOException {
+        if (!buf.hasRemaining()) {
+          return -1;
+        }
+        return buf.get() & 0xFF;
+      }
+
+      @Override
+      public int read(byte[] bytes, int off, int len) throws IOException {
+        if (!buf.hasRemaining()) {
+          return -1;
+        }
+
+        len = Math.min(len, buf.remaining());
+        buf.get(bytes, off, len);
+        return len;
+      }
+    };
+  }
+
+  @Override
+  public CodedInputStream newCodedInput() {
+    return CodedInputStream.newInstance(buffer);
+  }
+
+  /**
+   * Creates a slice of a range of this buffer.
+   *
+   * @param beginIndex the beginning index of the slice (inclusive).
+   * @param endIndex the end index of the slice (exclusive).
+   * @return the requested slice.
+   */
+  private ByteBuffer slice(int beginIndex, int endIndex) {
+    if (beginIndex < buffer.position() || endIndex > buffer.limit() || beginIndex > endIndex) {
+      throw new IllegalArgumentException(
+          String.format("Invalid indices [%d, %d]", beginIndex, endIndex));
+    }
+
+    ByteBuffer slice = buffer.slice();
+    slice.position(beginIndex - buffer.position());
+    slice.limit(endIndex - buffer.position());
+    return slice;
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/ProtobufArrayList.java b/java/src/main/java/com/google/protobuf/ProtobufArrayList.java
index 759368c9..d2f82ac5 100644
--- a/java/src/main/java/com/google/protobuf/ProtobufArrayList.java
+++ b/java/src/main/java/com/google/protobuf/ProtobufArrayList.java
@@ -60,6 +60,10 @@ class ProtobufArrayList<E> extends AbstractProtobufList<E> {
     list = new ArrayList<E>(toCopy);
   }
   
+  ProtobufArrayList(int capacity) {
+    list = new ArrayList<E>(capacity);
+  }
+  
   @Override
   public void add(int index, E element) {
     ensureIsMutable();
diff --git a/java/src/main/java/com/google/protobuf/RopeByteString.java b/java/src/main/java/com/google/protobuf/RopeByteString.java
index 2c332624..6e8eb724 100644
--- a/java/src/main/java/com/google/protobuf/RopeByteString.java
+++ b/java/src/main/java/com/google/protobuf/RopeByteString.java
@@ -69,7 +69,7 @@ import java.util.Stack;
  *
  * @author carlanton@google.com (Carl Haverl)
  */
-class RopeByteString extends ByteString {
+final class RopeByteString extends ByteString {
 
   /**
    * BAP95. Let Fn be the nth Fibonacci number. A {@link RopeByteString} of
@@ -151,21 +151,24 @@ class RopeByteString extends ByteString {
    * @return concatenation representing the same sequence as the given strings
    */
   static ByteString concatenate(ByteString left, ByteString right) {
-    ByteString result;
-    RopeByteString leftRope =
-        (left instanceof RopeByteString) ? (RopeByteString) left : null;
     if (right.size() == 0) {
-      result = left;
-    } else if (left.size() == 0) {
-      result = right;
-    } else {
-      int newLength = left.size() + right.size();
-      if (newLength < ByteString.CONCATENATE_BY_COPY_SIZE) {
-        // Optimization from BAP95: For short (leaves in paper, but just short
-        // here) total length, do a copy of data to a new leaf.
-        result = concatenateBytes(left, right);
-      } else if (leftRope != null
-          && leftRope.right.size() + right.size() < CONCATENATE_BY_COPY_SIZE) {
+      return left;
+    }
+
+    if (left.size() == 0) {
+      return right;
+    }
+
+    final int newLength = left.size() + right.size();
+    if (newLength < ByteString.CONCATENATE_BY_COPY_SIZE) {
+      // Optimization from BAP95: For short (leaves in paper, but just short
+      // here) total length, do a copy of data to a new leaf.
+      return concatenateBytes(left, right);
+    }
+
+    if (left instanceof RopeByteString) {
+      final RopeByteString leftRope = (RopeByteString) left;
+      if (leftRope.right.size() + right.size() < CONCATENATE_BY_COPY_SIZE) {
         // Optimization from BAP95: As an optimization of the case where the
         // ByteString is constructed by repeated concatenate, recognize the case
         // where a short string is concatenated to a left-hand node whose
@@ -177,9 +180,10 @@ class RopeByteString extends ByteString {
         // new parent node so that the depth of the result is the same as the
         // given left tree.
         ByteString newRight = concatenateBytes(leftRope.right, right);
-        result = new RopeByteString(leftRope.left, newRight);
-      } else if (leftRope != null
-          && leftRope.left.getTreeDepth() > leftRope.right.getTreeDepth()
+        return new RopeByteString(leftRope.left, newRight);
+      }
+
+      if (leftRope.left.getTreeDepth() > leftRope.right.getTreeDepth()
           && leftRope.getTreeDepth() > right.getTreeDepth()) {
         // Typically for concatenate-built strings the left-side is deeper than
         // the right.  This is our final attempt to concatenate without
@@ -187,20 +191,18 @@ class RopeByteString extends ByteString {
         // is yet another optimization for building the string by repeatedly
         // concatenating on the right.
         ByteString newRight = new RopeByteString(leftRope.right, right);
-        result = new RopeByteString(leftRope.left, newRight);
-      } else {
-        // Fine, we'll add a node and increase the tree depth--unless we
-        // rebalance ;^)
-        int newDepth = Math.max(left.getTreeDepth(), right.getTreeDepth()) + 1;
-        if (newLength >= minLengthByDepth[newDepth]) {
-          // The tree is shallow enough, so don't rebalance
-          result = new RopeByteString(left, right);
-        } else {
-          result = new Balancer().balance(left, right);
-        }
+        return new RopeByteString(leftRope.left, newRight);
       }
     }
-    return result;
+
+    // Fine, we'll add a node and increase the tree depth--unless we rebalance ;^)
+    int newDepth = Math.max(left.getTreeDepth(), right.getTreeDepth()) + 1;
+    if (newLength >= minLengthByDepth[newDepth]) {
+      // The tree is shallow enough, so don't rebalance
+      return new RopeByteString(left, right);
+    }
+
+    return new Balancer().balance(left, right);
   }
 
   /**
@@ -248,22 +250,14 @@ class RopeByteString extends ByteString {
    */
   @Override
   public byte byteAt(int index) {
-    if (index < 0) {
-      throw new ArrayIndexOutOfBoundsException("Index < 0: " + index);
-    }
-    if (index > totalLength) {
-      throw new ArrayIndexOutOfBoundsException(
-          "Index > length: " + index + ", " + totalLength);
-    }
+    checkIndex(index, totalLength);
 
-    byte result;
     // Find the relevant piece by recursive descent
     if (index < leftLength) {
-      result = left.byteAt(index);
-    } else {
-      result = right.byteAt(index - leftLength);
+      return left.byteAt(index);
     }
-    return result;
+
+    return right.byteAt(index - leftLength);
   }
 
   @Override
@@ -309,48 +303,36 @@ class RopeByteString extends ByteString {
    */
   @Override
   public ByteString substring(int beginIndex, int endIndex) {
-    if (beginIndex < 0) {
-      throw new IndexOutOfBoundsException(
-          "Beginning index: " + beginIndex + " < 0");
+    final int length = checkRange(beginIndex, endIndex, totalLength);
+
+    if (length == 0) {
+      // Empty substring
+      return ByteString.EMPTY;
     }
-    if (endIndex > totalLength) {
-      throw new IndexOutOfBoundsException(
-          "End index: " + endIndex + " > " + totalLength);
+
+    if (length == totalLength) {
+      // The whole string
+      return this;
     }
-    int substringLength = endIndex - beginIndex;
-    if (substringLength < 0) {
-      throw new IndexOutOfBoundsException(
-          "Beginning index larger than ending index: " + beginIndex + ", "
-              + endIndex);
+
+    // Proper substring
+    if (endIndex <= leftLength) {
+      // Substring on the left
+      return left.substring(beginIndex, endIndex);
     }
 
-    ByteString result;
-    if (substringLength == 0) {
-      // Empty substring
-      result = ByteString.EMPTY;
-    } else if (substringLength == totalLength) {
-      // The whole string
-      result = this;
-    } else {
-      // Proper substring
-      if (endIndex <= leftLength) {
-        // Substring on the left
-        result = left.substring(beginIndex, endIndex);
-      } else if (beginIndex >= leftLength) {
-        // Substring on the right
-        result = right
-            .substring(beginIndex - leftLength, endIndex - leftLength);
-      } else {
-        // Split substring
-        ByteString leftSub = left.substring(beginIndex);
-        ByteString rightSub = right.substring(0, endIndex - leftLength);
-        // Intentionally not rebalancing, since in many cases these two
-        // substrings will already be less deep than the top-level
-        // RopeByteString we're taking a substring of.
-        result = new RopeByteString(leftSub, rightSub);
-      }
+    if (beginIndex >= leftLength) {
+      // Substring on the right
+      return right.substring(beginIndex - leftLength, endIndex - leftLength);
     }
-    return result;
+
+    // Split substring
+    ByteString leftSub = left.substring(beginIndex);
+    ByteString rightSub = right.substring(0, endIndex - leftLength);
+    // Intentionally not rebalancing, since in many cases these two
+    // substrings will already be less deep than the top-level
+    // RopeByteString we're taking a substring of.
+    return new RopeByteString(leftSub, rightSub);
   }
 
   // =================================================================
@@ -391,7 +373,7 @@ class RopeByteString extends ByteString {
     List<ByteBuffer> result = new ArrayList<ByteBuffer>();
     PieceIterator pieces = new PieceIterator(this);
     while (pieces.hasNext()) {
-      LiteralByteString byteString = pieces.next();
+      LeafByteString byteString = pieces.next();
       result.add(byteString.asReadOnlyByteBuffer());
     }
     return result;
@@ -471,11 +453,10 @@ class RopeByteString extends ByteString {
     // hashCode if it's already computed.  It's arguable we should compute the
     // hashCode here, and if we're going to be testing a bunch of byteStrings,
     // it might even make sense.
-    if (hash != 0) {
-      int cachedOtherHash = otherByteString.peekCachedHashCode();
-      if (cachedOtherHash != 0 && hash != cachedOtherHash) {
-        return false;
-      }
+    int thisHash = peekCachedHashCode();
+    int thatHash = otherByteString.peekCachedHashCode();
+    if (thisHash != 0 && thatHash != 0 && thisHash != thatHash) {
+      return false;
     }
 
     return equalsFragments(otherByteString);
@@ -492,12 +473,12 @@ class RopeByteString extends ByteString {
    */
   private boolean equalsFragments(ByteString other) {
     int thisOffset = 0;
-    Iterator<LiteralByteString> thisIter = new PieceIterator(this);
-    LiteralByteString thisString = thisIter.next();
+    Iterator<LeafByteString> thisIter = new PieceIterator(this);
+    LeafByteString thisString = thisIter.next();
 
     int thatOffset = 0;
-    Iterator<LiteralByteString> thatIter = new PieceIterator(other);
-    LiteralByteString thatString = thatIter.next();
+    Iterator<LeafByteString> thatIter = new PieceIterator(other);
+    LeafByteString thatString = thatIter.next();
 
     int pos = 0;
     while (true) {
@@ -536,33 +517,6 @@ class RopeByteString extends ByteString {
     }
   }
 
-  /**
-   * Cached hash value.  Intentionally accessed via a data race, which is safe
-   * because of the Java Memory Model's "no out-of-thin-air values" guarantees
-   * for ints.
-   */
-  private int hash = 0;
-
-  @Override
-  public int hashCode() {
-    int h = hash;
-
-    if (h == 0) {
-      h = totalLength;
-      h = partialHash(h, 0, totalLength);
-      if (h == 0) {
-        h = 1;
-      }
-      hash = h;
-    }
-    return h;
-  }
-
-  @Override
-  protected int peekCachedHashCode() {
-    return hash;
-  }
-
   @Override
   protected int partialHash(int h, int offset, int length) {
     int toIndex = offset + length;
@@ -714,34 +668,34 @@ class RopeByteString extends ByteString {
    * <p>This iterator is used to implement
    * {@link RopeByteString#equalsFragments(ByteString)}.
    */
-  private static class PieceIterator implements Iterator<LiteralByteString> {
+  private static class PieceIterator implements Iterator<LeafByteString> {
 
     private final Stack<RopeByteString> breadCrumbs =
         new Stack<RopeByteString>();
-    private LiteralByteString next;
+    private LeafByteString next;
 
     private PieceIterator(ByteString root) {
       next = getLeafByLeft(root);
     }
 
-    private LiteralByteString getLeafByLeft(ByteString root) {
+    private LeafByteString getLeafByLeft(ByteString root) {
       ByteString pos = root;
       while (pos instanceof RopeByteString) {
         RopeByteString rbs = (RopeByteString) pos;
         breadCrumbs.push(rbs);
         pos = rbs.left;
       }
-      return (LiteralByteString) pos;
+      return (LeafByteString) pos;
     }
 
-    private LiteralByteString getNextNonEmptyLeaf() {
+    private LeafByteString getNextNonEmptyLeaf() {
       while (true) {
         // Almost always, we go through this loop exactly once.  However, if
         // we discover an empty string in the rope, we toss it and try again.
         if (breadCrumbs.isEmpty()) {
           return null;
         } else {
-          LiteralByteString result = getLeafByLeft(breadCrumbs.pop().right);
+          LeafByteString result = getLeafByLeft(breadCrumbs.pop().right);
           if (!result.isEmpty()) {
             return result;
           }
@@ -749,6 +703,7 @@ class RopeByteString extends ByteString {
       }
     }
 
+    @Override
     public boolean hasNext() {
       return next != null;
     }
@@ -758,15 +713,17 @@ class RopeByteString extends ByteString {
      *
      * @return next non-empty LiteralByteString or {@code null}
      */
-    public LiteralByteString next() {
+    @Override
+    public LeafByteString next() {
       if (next == null) {
         throw new NoSuchElementException();
       }
-      LiteralByteString result = next;
+      LeafByteString result = next;
       next = getNextNonEmptyLeaf();
       return result;
     }
 
+    @Override
     public void remove() {
       throw new UnsupportedOperationException();
     }
@@ -781,52 +738,11 @@ class RopeByteString extends ByteString {
     return new LiteralByteString(toByteArray());
   }
 
-  private void readObject(ObjectInputStream in) throws IOException {
+  private void readObject(@SuppressWarnings("unused") ObjectInputStream in) throws IOException {
     throw new InvalidObjectException(
         "RopeByteStream instances are not to be serialized directly");
   }
 
-  // =================================================================
-  // ByteIterator
-
-  @Override
-  public ByteIterator iterator() {
-    return new RopeByteIterator();
-  }
-
-  private class RopeByteIterator implements ByteString.ByteIterator {
-
-    private final PieceIterator pieces;
-    private ByteIterator bytes;
-    int bytesRemaining;
-
-    private RopeByteIterator() {
-      pieces = new PieceIterator(RopeByteString.this);
-      bytes = pieces.next().iterator();
-      bytesRemaining = size();
-    }
-
-    public boolean hasNext() {
-      return (bytesRemaining > 0);
-    }
-
-    public Byte next() {
-      return nextByte(); // Does not instantiate a Byte
-    }
-
-    public byte nextByte() {
-      if (!bytes.hasNext()) {
-        bytes = pieces.next().iterator();
-      }
-      --bytesRemaining;
-      return bytes.nextByte();
-    }
-
-    public void remove() {
-      throw new UnsupportedOperationException();
-    }
-  }
-
   /**
    * This class is the {@link RopeByteString} equivalent for
    * {@link ByteArrayInputStream}.
@@ -835,7 +751,7 @@ class RopeByteString extends ByteString {
     // Iterates through the pieces of the rope
     private PieceIterator pieceIterator;
     // The current piece
-    private LiteralByteString currentPiece;
+    private LeafByteString currentPiece;
     // The size of the current piece
     private int currentPieceSize;
     // The index of the next byte to read in the current piece
@@ -872,7 +788,7 @@ class RopeByteString extends ByteString {
     /**
      * Internal implementation of read and skip.  If b != null, then read the
      * next {@code length} bytes into the buffer {@code b} at
-     * offset {@code offset}.  If b == null, then skip the next {@code length)
+     * offset {@code offset}.  If b == null, then skip the next {@code length}
      * bytes.
      * <p>
      * This method assumes that all error checking has already happened.
diff --git a/java/src/main/java/com/google/protobuf/TextFormat.java b/java/src/main/java/com/google/protobuf/TextFormat.java
index 44d036c1..c99b5285 100644
--- a/java/src/main/java/com/google/protobuf/TextFormat.java
+++ b/java/src/main/java/com/google/protobuf/TextFormat.java
@@ -1074,6 +1074,18 @@ public final class TextFormat {
     private ParseException floatParseException(final NumberFormatException e) {
       return parseException("Couldn't parse number: " + e.getMessage());
     }
+    
+    /**
+     * Returns a {@link UnknownFieldParseException} with the line and column
+     * numbers of the previous token in the description, and the unknown field
+     * name, suitable for throwing.
+     */
+    public UnknownFieldParseException unknownFieldParseExceptionPreviousToken(
+        final String unknownField, final String description) {
+      // Note:  People generally prefer one-based line and column numbers.
+      return new UnknownFieldParseException(
+        previousLine + 1, previousColumn + 1, unknownField, description);
+    }
   }
 
   /** Thrown when parsing an invalid text format message. */
@@ -1121,6 +1133,45 @@ public final class TextFormat {
       return column;
     }
   }
+  
+  /**
+   * Thrown when encountering an unknown field while parsing
+   * a text format message.
+   */
+  public static class UnknownFieldParseException extends ParseException {
+    private final String unknownField;
+
+    /**
+     * Create a new instance, with -1 as the line and column numbers, and an
+     * empty unknown field name.
+     */
+    public UnknownFieldParseException(final String message) {
+      this(-1, -1, "", message);
+    }
+
+    /**
+     * Create a new instance
+     *
+     * @param line the line number where the parse error occurred,
+     * using 1-offset.
+     * @param column the column number where the parser error occurred,
+     * using 1-offset.
+     * @param unknownField the name of the unknown field found while parsing.
+     */
+    public UnknownFieldParseException(final int line, final int column,
+        final String unknownField, final String message) {
+      super(line, column, message);
+      this.unknownField = unknownField;
+    }
+
+    /**
+     * Return the name of the unknown field encountered while parsing the
+     * protocol buffer string.
+     */
+    public String getUnknownField() {
+      return unknownField;
+    }
+  }
 
   private static final Parser PARSER = Parser.newBuilder().build();
 
@@ -1388,7 +1439,8 @@ public final class TextFormat {
 
         if (field == null) {
           if (!allowUnknownFields) {
-            throw tokenizer.parseExceptionPreviousToken(
+            throw tokenizer.unknownFieldParseExceptionPreviousToken(
+              name,
               "Message type \"" + type.getFullName()
               + "\" has no field named \"" + name + "\".");
           } else {
diff --git a/java/src/main/java/com/google/protobuf/TextFormatEscaper.java b/java/src/main/java/com/google/protobuf/TextFormatEscaper.java
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/TextFormatEscaper.java
diff --git a/java/src/main/java/com/google/protobuf/UnsafeByteStrings.java b/java/src/main/java/com/google/protobuf/UnsafeByteStrings.java
new file mode 100644
index 00000000..c1997515
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/UnsafeByteStrings.java
@@ -0,0 +1,55 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// 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;
+
+import java.nio.ByteBuffer;
+
+/**
+ * Provides unsafe factory methods for {@link ByteString} instances.
+ *
+ * <p><strong>DISCLAIMER:</strong> The methods in this class should only be called if it is
+ * guaranteed that the the buffer backing the {@link ByteString} will never change! Mutation of a
+ * {@link ByteString} can lead to unexpected and undesirable consequences in your application,
+ * and will likely be difficult to debug. Proceed with caution!
+ */
+public final class UnsafeByteStrings {
+  private UnsafeByteStrings() {}
+
+  /**
+   * An unsafe operation that returns a {@link ByteString} that is backed by the provided buffer.
+   *
+   * @param buffer the Java NIO buffer to be wrapped.
+   * @return a {@link ByteString} backed by the provided buffer.
+   */
+  public static ByteString unsafeWrap(ByteBuffer buffer) {
+    return new NioByteString(buffer);
+  }
+}