328 lines
12 KiB
C++
328 lines
12 KiB
C++
// Protocol Buffers - Google's data interchange format
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// Copyright 2008 Google Inc. All rights reserved.
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// https://developers.google.com/protocol-buffers/
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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// Author: kenton@google.com (Kenton Varda)
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// Based on original Protocol Buffers design by
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// Sanjay Ghemawat, Jeff Dean, and others.
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//
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// This file contains common implementations of the interfaces defined in
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// zero_copy_stream.h which are only included in the full (non-lite)
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// protobuf library. These implementations include Unix file descriptors
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// and C++ iostreams. See also: zero_copy_stream_impl_lite.h
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#ifndef GOOGLE_PROTOBUF_IO_ZERO_COPY_STREAM_IMPL_H__
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#define GOOGLE_PROTOBUF_IO_ZERO_COPY_STREAM_IMPL_H__
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#include <iosfwd>
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#include <string>
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#include <google/protobuf/stubs/common.h>
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#include <google/protobuf/io/zero_copy_stream.h>
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#include <google/protobuf/io/zero_copy_stream_impl_lite.h>
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#include <google/protobuf/port_def.inc>
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namespace google {
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namespace protobuf {
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namespace io {
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// ===================================================================
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// A ZeroCopyInputStream which reads from a file descriptor.
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//
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// FileInputStream is preferred over using an ifstream with IstreamInputStream.
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// The latter will introduce an extra layer of buffering, harming performance.
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// Also, it's conceivable that FileInputStream could someday be enhanced
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// to use zero-copy file descriptors on OSs which support them.
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class PROTOBUF_EXPORT FileInputStream : public ZeroCopyInputStream {
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public:
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// Creates a stream that reads from the given Unix file descriptor.
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// If a block_size is given, it specifies the number of bytes that
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// should be read and returned with each call to Next(). Otherwise,
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// a reasonable default is used.
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explicit FileInputStream(int file_descriptor, int block_size = -1);
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// Flushes any buffers and closes the underlying file. Returns false if
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// an error occurs during the process; use GetErrno() to examine the error.
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// Even if an error occurs, the file descriptor is closed when this returns.
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bool Close();
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// By default, the file descriptor is not closed when the stream is
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// destroyed. Call SetCloseOnDelete(true) to change that. WARNING:
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// This leaves no way for the caller to detect if close() fails. If
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// detecting close() errors is important to you, you should arrange
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// to close the descriptor yourself.
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void SetCloseOnDelete(bool value) { copying_input_.SetCloseOnDelete(value); }
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// If an I/O error has occurred on this file descriptor, this is the
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// errno from that error. Otherwise, this is zero. Once an error
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// occurs, the stream is broken and all subsequent operations will
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// fail.
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int GetErrno() const { return copying_input_.GetErrno(); }
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// implements ZeroCopyInputStream ----------------------------------
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bool Next(const void** data, int* size) override;
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void BackUp(int count) override;
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bool Skip(int count) override;
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int64_t ByteCount() const override;
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private:
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class PROTOBUF_EXPORT CopyingFileInputStream : public CopyingInputStream {
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public:
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CopyingFileInputStream(int file_descriptor);
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~CopyingFileInputStream() override;
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bool Close();
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void SetCloseOnDelete(bool value) { close_on_delete_ = value; }
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int GetErrno() const { return errno_; }
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// implements CopyingInputStream ---------------------------------
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int Read(void* buffer, int size) override;
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int Skip(int count) override;
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private:
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// The file descriptor.
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const int file_;
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bool close_on_delete_;
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bool is_closed_;
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// The errno of the I/O error, if one has occurred. Otherwise, zero.
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int errno_;
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// Did we try to seek once and fail? If so, we assume this file descriptor
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// doesn't support seeking and won't try again.
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bool previous_seek_failed_;
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GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingFileInputStream);
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};
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CopyingFileInputStream copying_input_;
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CopyingInputStreamAdaptor impl_;
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GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FileInputStream);
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};
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// ===================================================================
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// A ZeroCopyOutputStream which writes to a file descriptor.
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//
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// FileOutputStream is preferred over using an ofstream with
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// OstreamOutputStream. The latter will introduce an extra layer of buffering,
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// harming performance. Also, it's conceivable that FileOutputStream could
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// someday be enhanced to use zero-copy file descriptors on OSs which
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// support them.
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class PROTOBUF_EXPORT FileOutputStream : public CopyingOutputStreamAdaptor {
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public:
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// Creates a stream that writes to the given Unix file descriptor.
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// If a block_size is given, it specifies the size of the buffers
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// that should be returned by Next(). Otherwise, a reasonable default
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// is used.
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explicit FileOutputStream(int file_descriptor, int block_size = -1);
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~FileOutputStream() override;
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// Flushes any buffers and closes the underlying file. Returns false if
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// an error occurs during the process; use GetErrno() to examine the error.
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// Even if an error occurs, the file descriptor is closed when this returns.
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bool Close();
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// By default, the file descriptor is not closed when the stream is
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// destroyed. Call SetCloseOnDelete(true) to change that. WARNING:
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// This leaves no way for the caller to detect if close() fails. If
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// detecting close() errors is important to you, you should arrange
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// to close the descriptor yourself.
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void SetCloseOnDelete(bool value) { copying_output_.SetCloseOnDelete(value); }
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// If an I/O error has occurred on this file descriptor, this is the
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// errno from that error. Otherwise, this is zero. Once an error
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// occurs, the stream is broken and all subsequent operations will
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// fail.
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int GetErrno() const { return copying_output_.GetErrno(); }
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private:
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class PROTOBUF_EXPORT CopyingFileOutputStream : public CopyingOutputStream {
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public:
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CopyingFileOutputStream(int file_descriptor);
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~CopyingFileOutputStream() override;
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bool Close();
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void SetCloseOnDelete(bool value) { close_on_delete_ = value; }
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int GetErrno() const { return errno_; }
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// implements CopyingOutputStream --------------------------------
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bool Write(const void* buffer, int size) override;
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private:
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// The file descriptor.
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const int file_;
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bool close_on_delete_;
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bool is_closed_;
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// The errno of the I/O error, if one has occurred. Otherwise, zero.
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int errno_;
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GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingFileOutputStream);
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};
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CopyingFileOutputStream copying_output_;
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GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FileOutputStream);
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};
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// ===================================================================
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// A ZeroCopyInputStream which reads from a C++ istream.
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//
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// Note that for reading files (or anything represented by a file descriptor),
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// FileInputStream is more efficient.
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class PROTOBUF_EXPORT IstreamInputStream : public ZeroCopyInputStream {
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public:
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// Creates a stream that reads from the given C++ istream.
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// If a block_size is given, it specifies the number of bytes that
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// should be read and returned with each call to Next(). Otherwise,
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// a reasonable default is used.
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explicit IstreamInputStream(std::istream* stream, int block_size = -1);
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// implements ZeroCopyInputStream ----------------------------------
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bool Next(const void** data, int* size) override;
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void BackUp(int count) override;
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bool Skip(int count) override;
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int64_t ByteCount() const override;
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private:
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class PROTOBUF_EXPORT CopyingIstreamInputStream : public CopyingInputStream {
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public:
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CopyingIstreamInputStream(std::istream* input);
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~CopyingIstreamInputStream() override;
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// implements CopyingInputStream ---------------------------------
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int Read(void* buffer, int size) override;
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// (We use the default implementation of Skip().)
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private:
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// The stream.
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std::istream* input_;
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GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingIstreamInputStream);
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};
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CopyingIstreamInputStream copying_input_;
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CopyingInputStreamAdaptor impl_;
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GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(IstreamInputStream);
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};
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// ===================================================================
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// A ZeroCopyOutputStream which writes to a C++ ostream.
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//
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// Note that for writing files (or anything represented by a file descriptor),
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// FileOutputStream is more efficient.
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class PROTOBUF_EXPORT OstreamOutputStream : public ZeroCopyOutputStream {
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public:
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// Creates a stream that writes to the given C++ ostream.
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// If a block_size is given, it specifies the size of the buffers
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// that should be returned by Next(). Otherwise, a reasonable default
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// is used.
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explicit OstreamOutputStream(std::ostream* stream, int block_size = -1);
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~OstreamOutputStream() override;
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// implements ZeroCopyOutputStream ---------------------------------
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bool Next(void** data, int* size) override;
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void BackUp(int count) override;
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int64_t ByteCount() const override;
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private:
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class PROTOBUF_EXPORT CopyingOstreamOutputStream
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: public CopyingOutputStream {
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public:
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CopyingOstreamOutputStream(std::ostream* output);
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~CopyingOstreamOutputStream() override;
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// implements CopyingOutputStream --------------------------------
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bool Write(const void* buffer, int size) override;
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private:
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// The stream.
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std::ostream* output_;
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GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingOstreamOutputStream);
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};
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CopyingOstreamOutputStream copying_output_;
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CopyingOutputStreamAdaptor impl_;
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GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(OstreamOutputStream);
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};
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// ===================================================================
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// A ZeroCopyInputStream which reads from several other streams in sequence.
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// ConcatenatingInputStream is unable to distinguish between end-of-stream
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// and read errors in the underlying streams, so it assumes any errors mean
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// end-of-stream. So, if the underlying streams fail for any other reason,
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// ConcatenatingInputStream may do odd things. It is suggested that you do
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// not use ConcatenatingInputStream on streams that might produce read errors
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// other than end-of-stream.
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class PROTOBUF_EXPORT ConcatenatingInputStream : public ZeroCopyInputStream {
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public:
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// All streams passed in as well as the array itself must remain valid
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// until the ConcatenatingInputStream is destroyed.
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ConcatenatingInputStream(ZeroCopyInputStream* const streams[], int count);
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~ConcatenatingInputStream() override = default;
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// implements ZeroCopyInputStream ----------------------------------
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bool Next(const void** data, int* size) override;
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void BackUp(int count) override;
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bool Skip(int count) override;
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int64_t ByteCount() const override;
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private:
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// As streams are retired, streams_ is incremented and count_ is
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// decremented.
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ZeroCopyInputStream* const* streams_;
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int stream_count_;
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int64 bytes_retired_; // Bytes read from previous streams.
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GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ConcatenatingInputStream);
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};
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// ===================================================================
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} // namespace io
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} // namespace protobuf
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} // namespace google
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#include <google/protobuf/port_undef.inc>
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#endif // GOOGLE_PROTOBUF_IO_ZERO_COPY_STREAM_IMPL_H__
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