text: // Protocol Buffers - Google's data interchange format
  // Copyright 2008 Google Inc.  All rights reserved.
  // http://code.google.com/p/protobuf/
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //     * Neither the name of Google Inc. nor the names of its
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  // 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 which are only included in the full (non-lite)
  // protobuf library.  These implementations include Unix file descriptors
  // and C++ iostreams.  See also:  zero_copy_stream_impl_lite.h
  
  #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/io/zero_copy_stream_impl_lite.h>
  #include <google/protobuf/stubs/common.h>
  
  
  namespace google_public {
  namespace protobuf {
  namespace io {
  
  
  // ===================================================================
  
  // 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.
  //
  // FileOutputStream is preferred over using an ofstream with
  // OstreamOutputStream.  The latter will introduce an extra layer of buffering,
  // harming performance.  Also, it's conceivable that FileOutputStream 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();
  
    // Flushes FileOutputStream's buffers but does not close the
    // underlying file. No special measures are taken to ensure that
    // underlying operating system file object is synchronized to disk.
    bool Flush();
  
    // 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__
  