fmt/test/gtest-extra.cc

// Formatting library for C++ - custom Google Test assertions
//
// Copyright (c) 2012 - present, Victor Zverovich
// All rights reserved.
//
// For the license information refer to format.h.

#include "gtest-extra.h"

#if FMT_USE_FILE_DESCRIPTORS

using fmt::file;

void OutputRedirect::flush() {
#if EOF != -1
# error "FMT_RETRY assumes return value of -1 indicating failure"
#endif
  int result = 0;
  FMT_RETRY(result, fflush(file_));
  if (result != 0)
    throw fmt::system_error(errno, "cannot flush stream");
}

void OutputRedirect::restore() {
  if (original_.descriptor() == -1)
    return;  // Already restored.
  flush();
  // Restore the original file.
  original_.dup2(FMT_POSIX(fileno(file_)));
  original_.close();
}

OutputRedirect::OutputRedirect(FILE *f) : file_(f) {
  flush();
  int fd = FMT_POSIX(fileno(f));
  // Create a file object referring to the original file.
  original_ = file::dup(fd);
  // Create a pipe.
  file write_end;
  file::pipe(read_end_, write_end);
  // Connect the passed FILE object to the write end of the pipe.
  write_end.dup2(fd);
}

OutputRedirect::~OutputRedirect() FMT_NOEXCEPT {
  try {
    restore();
  } catch (const std::exception &e) {
    std::fputs(e.what(), stderr);
  }
}

std::string OutputRedirect::restore_and_read() {
  // Restore output.
  restore();

  // Read everything from the pipe.
  std::string content;
  if (read_end_.descriptor() == -1)
    return content;  // Already read.
  enum { BUFFER_SIZE = 4096 };
  char buffer[BUFFER_SIZE];
  std::size_t count = 0;
  do {
    count = read_end_.read(buffer, BUFFER_SIZE);
    content.append(buffer, count);
  } while (count != 0);
  read_end_.close();
  return content;
}

std::string read(file &f, std::size_t count) {
  std::string buffer(count, '\0');
  std::size_t n = 0, offset = 0;
  do {
    n = f.read(&buffer[offset], count - offset);
    // We can't read more than size_t bytes since count has type size_t.
    offset += n;
  } while (offset < count && n != 0);
  buffer.resize(offset);
  return buffer;
}

#endif  // FMT_USE_FILE_DESCRIPTORS

std::string format_system_error(int error_code, fmt::string_view message) {
  fmt::memory_buffer out;
  format_system_error(out, error_code, message);
  return to_string(out);
}