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+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.
+// http://code.google.com/p/protobuf/
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Author: kenton@google.com (Kenton Varda)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// This file contains common implementations of the interfaces defined in
+// zero_copy_stream.h.  These implementations cover I/O on raw arrays,
+// strings, and file descriptors.  Of course, many users will probably
+// want to write their own implementations of these interfaces specific
+// to the particular I/O abstractions they prefer to use, but these
+// should cover the most common cases.
+
+#ifndef GOOGLE_PROTOBUF_IO_ZERO_COPY_STREAM_IMPL_H__
+#define GOOGLE_PROTOBUF_IO_ZERO_COPY_STREAM_IMPL_H__
+
+#include <string>
+#include <iosfwd>
+#include <google/protobuf/io/zero_copy_stream.h>
+#include <google/protobuf/stubs/common.h>
+
+
+namespace google {
+namespace protobuf {
+namespace io {
+
+// ===================================================================
+
+// A ZeroCopyInputStream backed by an in-memory array of bytes.
+class LIBPROTOBUF_EXPORT ArrayInputStream : public ZeroCopyInputStream {
+ public:
+  // Create an InputStream that returns the bytes pointed to by "data".
+  // "data" remains the property of the caller but must remain valid until
+  // the stream is destroyed.  If a block_size is given, calls to Next()
+  // will return data blocks no larger than the given size.  Otherwise, the
+  // first call to Next() returns the entire array.  block_size is mainly
+  // useful for testing; in production you would probably never want to set
+  // it.
+  ArrayInputStream(const void* data, int size, int block_size = -1);
+  ~ArrayInputStream();
+
+  // implements ZeroCopyInputStream ----------------------------------
+  bool Next(const void** data, int* size);
+  void BackUp(int count);
+  bool Skip(int count);
+  int64 ByteCount() const;
+
+
+ private:
+  const uint8* const data_;  // The byte array.
+  const int size_;           // Total size of the array.
+  const int block_size_;     // How many bytes to return at a time.
+
+  int position_;
+  int last_returned_size_;   // How many bytes we returned last time Next()
+                             // was called (used for error checking only).
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ArrayInputStream);
+};
+
+// ===================================================================
+
+// A ZeroCopyOutputStream backed by an in-memory array of bytes.
+class LIBPROTOBUF_EXPORT ArrayOutputStream : public ZeroCopyOutputStream {
+ public:
+  // Create an OutputStream that writes to the bytes pointed to by "data".
+  // "data" remains the property of the caller but must remain valid until
+  // the stream is destroyed.  If a block_size is given, calls to Next()
+  // will return data blocks no larger than the given size.  Otherwise, the
+  // first call to Next() returns the entire array.  block_size is mainly
+  // useful for testing; in production you would probably never want to set
+  // it.
+  ArrayOutputStream(void* data, int size, int block_size = -1);
+  ~ArrayOutputStream();
+
+  // implements ZeroCopyOutputStream ---------------------------------
+  bool Next(void** data, int* size);
+  void BackUp(int count);
+  int64 ByteCount() const;
+
+ private:
+  uint8* const data_;        // The byte array.
+  const int size_;           // Total size of the array.
+  const int block_size_;     // How many bytes to return at a time.
+
+  int position_;
+  int last_returned_size_;   // How many bytes we returned last time Next()
+                             // was called (used for error checking only).
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ArrayOutputStream);
+};
+
+// ===================================================================
+
+// A ZeroCopyOutputStream which appends bytes to a string.
+class LIBPROTOBUF_EXPORT StringOutputStream : public ZeroCopyOutputStream {
+ public:
+  // Create a StringOutputStream which appends bytes to the given string.
+  // The string remains property of the caller, but it MUST NOT be accessed
+  // in any way until the stream is destroyed.
+  //
+  // Hint:  If you call target->reserve(n) before creating the stream,
+  //   the first call to Next() will return at least n bytes of buffer
+  //   space.
+  explicit StringOutputStream(string* target);
+  ~StringOutputStream();
+
+  // implements ZeroCopyOutputStream ---------------------------------
+  bool Next(void** data, int* size);
+  void BackUp(int count);
+  int64 ByteCount() const;
+
+ private:
+  static const int kMinimumSize = 16;
+
+  string* target_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(StringOutputStream);
+};
+
+// Note:  There is no StringInputStream.  Instead, just create an
+// ArrayInputStream as follows:
+//   ArrayInputStream input(str.data(), str.size());
+
+// ===================================================================
+
+
+// ===================================================================
+
+// A generic traditional input stream interface.
+//
+// Lots of traditional input streams (e.g. file descriptors, C stdio
+// streams, and C++ iostreams) expose an interface where every read
+// involves copying bytes into a buffer.  If you want to take such an
+// interface and make a ZeroCopyInputStream based on it, simply implement
+// CopyingInputStream and then use CopyingInputStreamAdaptor.
+//
+// CopyingInputStream implementations should avoid buffering if possible.
+// CopyingInputStreamAdaptor does its own buffering and will read data
+// in large blocks.
+class LIBPROTOBUF_EXPORT CopyingInputStream {
+ public:
+  virtual ~CopyingInputStream();
+
+  // Reads up to "size" bytes into the given buffer.  Returns the number of
+  // bytes read.  Read() waits until at least one byte is available, or
+  // returns zero if no bytes will ever become available (EOF), or -1 if a
+  // permanent read error occurred.
+  virtual int Read(void* buffer, int size) = 0;
+
+  // Skips the next "count" bytes of input.  Returns the number of bytes
+  // actually skipped.  This will always be exactly equal to "count" unless
+  // EOF was reached or a permanent read error occurred.
+  //
+  // The default implementation just repeatedly calls Read() into a scratch
+  // buffer.
+  virtual int Skip(int count);
+};
+
+// A ZeroCopyInputStream which reads from a CopyingInputStream.  This is
+// useful for implementing ZeroCopyInputStreams that read from traditional
+// streams.  Note that this class is not really zero-copy.
+//
+// If you want to read from file descriptors or C++ istreams, this is
+// already implemented for you:  use FileInputStream or IstreamInputStream
+// respectively.
+class LIBPROTOBUF_EXPORT CopyingInputStreamAdaptor : public ZeroCopyInputStream {
+ public:
+  // Creates a stream that reads from the given CopyingInputStream.
+  // If a block_size is given, it specifies the number of bytes that
+  // should be read and returned with each call to Next().  Otherwise,
+  // a reasonable default is used.  The caller retains ownership of
+  // copying_stream unless SetOwnsCopyingStream(true) is called.
+  explicit CopyingInputStreamAdaptor(CopyingInputStream* copying_stream,
+                                     int block_size = -1);
+  ~CopyingInputStreamAdaptor();
+
+  // Call SetOwnsCopyingStream(true) to tell the CopyingInputStreamAdaptor to
+  // delete the underlying CopyingInputStream when it is destroyed.
+  void SetOwnsCopyingStream(bool value) { owns_copying_stream_ = value; }
+
+  // implements ZeroCopyInputStream ----------------------------------
+  bool Next(const void** data, int* size);
+  void BackUp(int count);
+  bool Skip(int count);
+  int64 ByteCount() const;
+
+ private:
+  // Insures that buffer_ is not NULL.
+  void AllocateBufferIfNeeded();
+  // Frees the buffer and resets buffer_used_.
+  void FreeBuffer();
+
+  // The underlying copying stream.
+  CopyingInputStream* copying_stream_;
+  bool owns_copying_stream_;
+
+  // True if we have seen a permenant error from the underlying stream.
+  bool failed_;
+
+  // The current position of copying_stream_, relative to the point where
+  // we started reading.
+  int64 position_;
+
+  // Data is read into this buffer.  It may be NULL if no buffer is currently
+  // in use.  Otherwise, it points to an array of size buffer_size_.
+  scoped_array<uint8> buffer_;
+  const int buffer_size_;
+
+  // Number of valid bytes currently in the buffer (i.e. the size last
+  // returned by Next()).  0 <= buffer_used_ <= buffer_size_.
+  int buffer_used_;
+
+  // Number of bytes in the buffer which were backed up over by a call to
+  // BackUp().  These need to be returned again.
+  // 0 <= backup_bytes_ <= buffer_used_
+  int backup_bytes_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingInputStreamAdaptor);
+};
+
+// ===================================================================
+
+// A generic traditional output stream interface.
+//
+// Lots of traditional output streams (e.g. file descriptors, C stdio
+// streams, and C++ iostreams) expose an interface where every write
+// involves copying bytes from a buffer.  If you want to take such an
+// interface and make a ZeroCopyOutputStream based on it, simply implement
+// CopyingOutputStream and then use CopyingOutputStreamAdaptor.
+//
+// CopyingOutputStream implementations should avoid buffering if possible.
+// CopyingOutputStreamAdaptor does its own buffering and will write data
+// in large blocks.
+class LIBPROTOBUF_EXPORT CopyingOutputStream {
+ public:
+  virtual ~CopyingOutputStream();
+
+  // Writes "size" bytes from the given buffer to the output.  Returns true
+  // if successful, false on a write error.
+  virtual bool Write(const void* buffer, int size) = 0;
+};
+
+// A ZeroCopyOutputStream which writes to a CopyingOutputStream.  This is
+// useful for implementing ZeroCopyOutputStreams that write to traditional
+// streams.  Note that this class is not really zero-copy.
+//
+// If you want to write to file descriptors or C++ ostreams, this is
+// already implemented for you:  use FileOutputStream or OstreamOutputStream
+// respectively.
+class LIBPROTOBUF_EXPORT CopyingOutputStreamAdaptor : public ZeroCopyOutputStream {
+ public:
+  // Creates a stream that writes to the given Unix file descriptor.
+  // If a block_size is given, it specifies the size of the buffers
+  // that should be returned by Next().  Otherwise, a reasonable default
+  // is used.
+  explicit CopyingOutputStreamAdaptor(CopyingOutputStream* copying_stream,
+                                      int block_size = -1);
+  ~CopyingOutputStreamAdaptor();
+
+  // Writes all pending data to the underlying stream.  Returns false if a
+  // write error occurred on the underlying stream.  (The underlying
+  // stream itself is not necessarily flushed.)
+  bool Flush();
+
+  // Call SetOwnsCopyingStream(true) to tell the CopyingOutputStreamAdaptor to
+  // delete the underlying CopyingOutputStream when it is destroyed.
+  void SetOwnsCopyingStream(bool value) { owns_copying_stream_ = value; }
+
+  // implements ZeroCopyOutputStream ---------------------------------
+  bool Next(void** data, int* size);
+  void BackUp(int count);
+  int64 ByteCount() const;
+
+ private:
+  // Write the current buffer, if it is present.
+  bool WriteBuffer();
+  // Insures that buffer_ is not NULL.
+  void AllocateBufferIfNeeded();
+  // Frees the buffer.
+  void FreeBuffer();
+
+  // The underlying copying stream.
+  CopyingOutputStream* copying_stream_;
+  bool owns_copying_stream_;
+
+  // True if we have seen a permenant error from the underlying stream.
+  bool failed_;
+
+  // The current position of copying_stream_, relative to the point where
+  // we started writing.
+  int64 position_;
+
+  // Data is written from this buffer.  It may be NULL if no buffer is
+  // currently in use.  Otherwise, it points to an array of size buffer_size_.
+  scoped_array<uint8> buffer_;
+  const int buffer_size_;
+
+  // Number of valid bytes currently in the buffer (i.e. the size last
+  // returned by Next()).  When BackUp() is called, we just reduce this.
+  // 0 <= buffer_used_ <= buffer_size_.
+  int buffer_used_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingOutputStreamAdaptor);
+};
+
+// ===================================================================
+
+// A ZeroCopyInputStream which reads from a file descriptor.
+//
+// FileInputStream is preferred over using an ifstream with IstreamInputStream.
+// The latter will introduce an extra layer of buffering, harming performance.
+// Also, it's conceivable that FileInputStream could someday be enhanced
+// to use zero-copy file descriptors on OSs which support them.
+class LIBPROTOBUF_EXPORT FileInputStream : public ZeroCopyInputStream {
+ public:
+  // Creates a stream that reads from the given Unix file descriptor.
+  // If a block_size is given, it specifies the number of bytes that
+  // should be read and returned with each call to Next().  Otherwise,
+  // a reasonable default is used.
+  explicit FileInputStream(int file_descriptor, int block_size = -1);
+  ~FileInputStream();
+
+  // Flushes any buffers and closes the underlying file.  Returns false if
+  // an error occurs during the process; use GetErrno() to examine the error.
+  // Even if an error occurs, the file descriptor is closed when this returns.
+  bool Close();
+
+  // By default, the file descriptor is not closed when the stream is
+  // destroyed.  Call SetCloseOnDelete(true) to change that.  WARNING:
+  // This leaves no way for the caller to detect if close() fails.  If
+  // detecting close() errors is important to you, you should arrange
+  // to close the descriptor yourself.
+  void SetCloseOnDelete(bool value) { copying_input_.SetCloseOnDelete(value); }
+
+  // If an I/O error has occurred on this file descriptor, this is the
+  // errno from that error.  Otherwise, this is zero.  Once an error
+  // occurs, the stream is broken and all subsequent operations will
+  // fail.
+  int GetErrno() { return copying_input_.GetErrno(); }
+
+  // implements ZeroCopyInputStream ----------------------------------
+  bool Next(const void** data, int* size);
+  void BackUp(int count);
+  bool Skip(int count);
+  int64 ByteCount() const;
+
+ private:
+  class LIBPROTOBUF_EXPORT CopyingFileInputStream : public CopyingInputStream {
+   public:
+    CopyingFileInputStream(int file_descriptor);
+    ~CopyingFileInputStream();
+
+    bool Close();
+    void SetCloseOnDelete(bool value) { close_on_delete_ = value; }
+    int GetErrno() { return errno_; }
+
+    // implements CopyingInputStream ---------------------------------
+    int Read(void* buffer, int size);
+    int Skip(int count);
+
+   private:
+    // The file descriptor.
+    const int file_;
+    bool close_on_delete_;
+    bool is_closed_;
+
+    // The errno of the I/O error, if one has occurred.  Otherwise, zero.
+    int errno_;
+
+    // Did we try to seek once and fail?  If so, we assume this file descriptor
+    // doesn't support seeking and won't try again.
+    bool previous_seek_failed_;
+
+    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingFileInputStream);
+  };
+
+  CopyingFileInputStream copying_input_;
+  CopyingInputStreamAdaptor impl_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FileInputStream);
+};
+
+// ===================================================================
+
+// A ZeroCopyOutputStream which writes to a file descriptor.
+//
+// FileInputStream is preferred over using an ofstream with OstreamOutputStream.
+// The latter will introduce an extra layer of buffering, harming performance.
+// Also, it's conceivable that FileInputStream could someday be enhanced
+// to use zero-copy file descriptors on OSs which support them.
+class LIBPROTOBUF_EXPORT FileOutputStream : public ZeroCopyOutputStream {
+ public:
+  // Creates a stream that writes to the given Unix file descriptor.
+  // If a block_size is given, it specifies the size of the buffers
+  // that should be returned by Next().  Otherwise, a reasonable default
+  // is used.
+  explicit FileOutputStream(int file_descriptor, int block_size = -1);
+  ~FileOutputStream();
+
+  // Flushes any buffers and closes the underlying file.  Returns false if
+  // an error occurs during the process; use GetErrno() to examine the error.
+  // Even if an error occurs, the file descriptor is closed when this returns.
+  bool Close();
+
+  // By default, the file descriptor is not closed when the stream is
+  // destroyed.  Call SetCloseOnDelete(true) to change that.  WARNING:
+  // This leaves no way for the caller to detect if close() fails.  If
+  // detecting close() errors is important to you, you should arrange
+  // to close the descriptor yourself.
+  void SetCloseOnDelete(bool value) { copying_output_.SetCloseOnDelete(value); }
+
+  // If an I/O error has occurred on this file descriptor, this is the
+  // errno from that error.  Otherwise, this is zero.  Once an error
+  // occurs, the stream is broken and all subsequent operations will
+  // fail.
+  int GetErrno() { return copying_output_.GetErrno(); }
+
+  // implements ZeroCopyOutputStream ---------------------------------
+  bool Next(void** data, int* size);
+  void BackUp(int count);
+  int64 ByteCount() const;
+
+ private:
+  class LIBPROTOBUF_EXPORT CopyingFileOutputStream : public CopyingOutputStream {
+   public:
+    CopyingFileOutputStream(int file_descriptor);
+    ~CopyingFileOutputStream();
+
+    bool Close();
+    void SetCloseOnDelete(bool value) { close_on_delete_ = value; }
+    int GetErrno() { return errno_; }
+
+    // implements CopyingOutputStream --------------------------------
+    bool Write(const void* buffer, int size);
+
+   private:
+    // The file descriptor.
+    const int file_;
+    bool close_on_delete_;
+    bool is_closed_;
+
+    // The errno of the I/O error, if one has occurred.  Otherwise, zero.
+    int errno_;
+
+    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingFileOutputStream);
+  };
+
+  CopyingFileOutputStream copying_output_;
+  CopyingOutputStreamAdaptor impl_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FileOutputStream);
+};
+
+// ===================================================================
+
+// A ZeroCopyInputStream which reads from a C++ istream.
+//
+// Note that for reading files (or anything represented by a file descriptor),
+// FileInputStream is more efficient.
+class LIBPROTOBUF_EXPORT IstreamInputStream : public ZeroCopyInputStream {
+ public:
+  // Creates a stream that reads from the given C++ istream.
+  // If a block_size is given, it specifies the number of bytes that
+  // should be read and returned with each call to Next().  Otherwise,
+  // a reasonable default is used.
+  explicit IstreamInputStream(istream* stream, int block_size = -1);
+  ~IstreamInputStream();
+
+  // implements ZeroCopyInputStream ----------------------------------
+  bool Next(const void** data, int* size);
+  void BackUp(int count);
+  bool Skip(int count);
+  int64 ByteCount() const;
+
+ private:
+  class LIBPROTOBUF_EXPORT CopyingIstreamInputStream : public CopyingInputStream {
+   public:
+    CopyingIstreamInputStream(istream* input);
+    ~CopyingIstreamInputStream();
+
+    // implements CopyingInputStream ---------------------------------
+    int Read(void* buffer, int size);
+    // (We use the default implementation of Skip().)
+
+   private:
+    // The stream.
+    istream* input_;
+
+    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingIstreamInputStream);
+  };
+
+  CopyingIstreamInputStream copying_input_;
+  CopyingInputStreamAdaptor impl_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(IstreamInputStream);
+};
+
+// ===================================================================
+
+// A ZeroCopyOutputStream which writes to a C++ ostream.
+//
+// Note that for writing files (or anything represented by a file descriptor),
+// FileOutputStream is more efficient.
+class LIBPROTOBUF_EXPORT OstreamOutputStream : public ZeroCopyOutputStream {
+ public:
+  // Creates a stream that writes to the given C++ ostream.
+  // If a block_size is given, it specifies the size of the buffers
+  // that should be returned by Next().  Otherwise, a reasonable default
+  // is used.
+  explicit OstreamOutputStream(ostream* stream, int block_size = -1);
+  ~OstreamOutputStream();
+
+  // implements ZeroCopyOutputStream ---------------------------------
+  bool Next(void** data, int* size);
+  void BackUp(int count);
+  int64 ByteCount() const;
+
+ private:
+  class LIBPROTOBUF_EXPORT CopyingOstreamOutputStream : public CopyingOutputStream {
+   public:
+    CopyingOstreamOutputStream(ostream* output);
+    ~CopyingOstreamOutputStream();
+
+    // implements CopyingOutputStream --------------------------------
+    bool Write(const void* buffer, int size);
+
+   private:
+    // The stream.
+    ostream* output_;
+
+    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingOstreamOutputStream);
+  };
+
+  CopyingOstreamOutputStream copying_output_;
+  CopyingOutputStreamAdaptor impl_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(OstreamOutputStream);
+};
+
+// ===================================================================
+
+// A ZeroCopyInputStream which reads from several other streams in sequence.
+// ConcatenatingInputStream is unable to distinguish between end-of-stream
+// and read errors in the underlying streams, so it assumes any errors mean
+// end-of-stream.  So, if the underlying streams fail for any other reason,
+// ConcatenatingInputStream may do odd things.  It is suggested that you do
+// not use ConcatenatingInputStream on streams that might produce read errors
+// other than end-of-stream.
+class LIBPROTOBUF_EXPORT ConcatenatingInputStream : public ZeroCopyInputStream {
+ public:
+  // All streams passed in as well as the array itself must remain valid
+  // until the ConcatenatingInputStream is destroyed.
+  ConcatenatingInputStream(ZeroCopyInputStream* const streams[], int count);
+  ~ConcatenatingInputStream();
+
+  // implements ZeroCopyInputStream ----------------------------------
+  bool Next(const void** data, int* size);
+  void BackUp(int count);
+  bool Skip(int count);
+  int64 ByteCount() const;
+
+
+ private:
+  // As streams are retired, streams_ is incremented and count_ is
+  // decremented.
+  ZeroCopyInputStream* const* streams_;
+  int stream_count_;
+  int64 bytes_retired_;  // Bytes read from previous streams.
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ConcatenatingInputStream);
+};
+
+// ===================================================================
+
+// A ZeroCopyInputStream which wraps some other stream and limits it to
+// a particular byte count.
+class LIBPROTOBUF_EXPORT LimitingInputStream : public ZeroCopyInputStream {
+ public:
+  LimitingInputStream(ZeroCopyInputStream* input, int64 limit);
+  ~LimitingInputStream();
+
+  // implements ZeroCopyInputStream ----------------------------------
+  bool Next(const void** data, int* size);
+  void BackUp(int count);
+  bool Skip(int count);
+  int64 ByteCount() const;
+
+
+ private:
+  ZeroCopyInputStream* input_;
+  int64 limit_;  // Decreases as we go, becomes negative if we overshoot.
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(LimitingInputStream);
+};
+
+// ===================================================================
+
+}  // namespace io
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_IO_ZERO_COPY_STREAM_IMPL_H__