Function FileOpenWritable

cpp/src/arrow/util/io_util.cc:1095–1160

}

Result<FileDescriptor> FileOpenWritable(const PlatformFilename& file_name,
                                        bool write_only, bool truncate, bool append) {
  FileDescriptor fd;

#if defined(_WIN32)
  DWORD desired_access = GENERIC_WRITE;
  DWORD share_mode = FILE_SHARE_READ | FILE_SHARE_WRITE;
  DWORD creation_disposition = OPEN_ALWAYS;

  if (truncate) {
    creation_disposition = CREATE_ALWAYS;
  }

  if (!write_only) {
    desired_access |= GENERIC_READ;
  }

  HANDLE file_handle =
      CreateFileW(file_name.ToNative().c_str(), desired_access, share_mode, NULL,
                  creation_disposition, FILE_ATTRIBUTE_NORMAL, NULL);
  if (file_handle == INVALID_HANDLE_VALUE) {
    return IOErrorFromWinError(GetLastError(), "Failed to open local file '",
                               file_name.ToString(), "'");
  }

  int ret = _open_osfhandle(reinterpret_cast<intptr_t>(file_handle),
                            _O_RDONLY | _O_BINARY | _O_NOINHERIT);
  if (ret == -1) {
    CloseHandle(file_handle);
    return IOErrorFromErrno(errno, "Failed to open local file '", file_name.ToString(),
                            "'");
  }
  fd = FileDescriptor(ret);
#else
  int oflag = O_CREAT;

  if (truncate) {
    oflag |= O_TRUNC;
  }
  if (append) {
    oflag |= O_APPEND;
  }

  if (write_only) {
    oflag |= O_WRONLY;
  } else {
    oflag |= O_RDWR;
  }

  int ret;
  do {
    ret = open(file_name.ToNative().c_str(), oflag, 0666);
  } while (ret == -1 && errno == EINTR);
  if (ret == -1) {
    return IOErrorFromErrno(errno, "Failed to open local file '", file_name.ToString(),
                            "'");
  }
  fd = FileDescriptor(ret);