shared_fd_stream.h

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/*
 * Copyright (C) 2020 The Android Open Source Project
 *
 * 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.
 */
 
// Adapters for using SharedFD as std::istream and std::ostream.
 
#ifndef CUTTLEFISH_COMMON_COMMON_LIBS_FS_SHARED_FD_STREAM_H_
#define CUTTLEFISH_COMMON_COMMON_LIBS_FS_SHARED_FD_STREAM_H_
 
#include <cstdio>
#include <istream>
#include <memory>
#include <ostream>
#include <streambuf>
 
#include "cuttlefish/common/libs/fs/shared_fd.h"
 
namespace cuttlefish {
 
class SharedFDStreambuf : public std::streambuf {
 public:
  SharedFDStreambuf(SharedFD shared_fd);
 
 private:
  // Reading characters from the SharedFD.
  int underflow() override;
  std::streamsize xsgetn(char* dest, std::streamsize count) override;
 
  // Write characters to the SharedFD.
  int overflow(int c) override;
  std::streamsize xsputn(const char* source, std::streamsize count) override;
 
  int pbackfail(int c) override;
 
 private:
  SharedFD shared_fd_;
 
  static constexpr const ptrdiff_t kUngetSize = 128;
  static constexpr const ptrdiff_t kBufferSize = 4096 + kUngetSize;
  std::unique_ptr<char[]> read_buffer_ = nullptr;
};
 
class SharedFDIstream : public std::istream {
 public:
  SharedFDIstream(SharedFD shared_fd);
 
 private:
  SharedFDStreambuf buf_;
};
 
class SharedFDOstream : public std::ostream {
 public:
  SharedFDOstream(SharedFD shared_fd);
 
 private:
  SharedFDStreambuf buf_;
};
 
}  // namespace cuttlefish
 
#endif