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// Copyright 2022 Google LLC
//
// 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 LLC 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.
#ifndef COMMON_LINUX_SCOPED_PIPE_H_
#define COMMON_LINUX_SCOPED_PIPE_H_
#include <stdint.h>
#include <string>
namespace google_breakpad {
// Small RAII wrapper for a pipe pair.
//
// Example (both ends of pipe in same process):
// ScopedPipe tmp;
// std::string line;
// if (tmp.Init() && tmp.Write(bytes, bytes_len)) {
// tmp.CloseWriteFd();
// while (tmp.ReadLine(&line)) {
// std::cerr << line << std::endl;
// }
// }
//
// Example (reading output from a child process):
// ScopedPipe tmp;
// if (fork()) {
// // Parent process, read from the read end of the pipe.
// std::string line;
// while (tmp.ReadLine(line)) {
// // Process output...
// }
// // Close read pipe once done processing the output that we wanted, this
// // should ensure that the child process exits even if we didn't read all
// // of the output.
// tmp.CloseReadFd();
// // Parent process should handle waiting for child to exit here...
// } else {
// // Child process, close the read fd and dup the write fd before exec'ing.
// tmp.CloseReadFd();
// tmp.Dup2WriteFd(STDOUT_FILENO);
// tmp.Dup2WriteFd(STDERR_FILENO);
// execl("some-command", "some-arguments");
// }
class ScopedPipe {
public:
ScopedPipe();
~ScopedPipe();
// Creates the pipe pair - returns false on error.
bool Init();
// Close the read pipe. This only needs to be used when the read pipe needs to
// be closed earlier.
void CloseReadFd();
// Close the write pipe. This only needs to be used when the write pipe needs
// to be closed earlier.
void CloseWriteFd();
// Reads characters until newline or end of pipe. On read failure this will
// close the read pipe, but continue to return true and read buffered lines
// until the internal buffering is exhausted. This will block if there is no
// data available on the read pipe.
bool ReadLine(std::string& line);
// Writes bytes to the write end of the pipe, returns false and closes write
// pipe on failure.
bool WriteForTesting(const void* bytes, size_t bytes_len);
// Calls the dup2 system call to replace any existing open file descriptor
// with number new_fd with a copy of the current write end file descriptor
// for the pipe.
int Dup2WriteFd(int new_fd) const;
private:
int GetReadFd() const {
return fds_[0];
}
int GetWriteFd() const {
return fds_[1];
}
int fds_[2];
std::string read_buffer_;
};
} // namespace google_breakpad
#endif // COMMON_LINUX_SCOPED_PIPE_H_
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