Method getFile

extensions/sftp/client/SFTPClient.cpp:467–536

}

bool SFTPClient::getFile(const std::string& path, io::BaseStream& output, int64_t expected_size /*= -1*/) {
  /**
   * SFTP servers should not set the mode of an existing file on open
   * (see https://tools.ietf.org/html/draft-ietf-secsh-filexfer-13, Page 33
   * "The 'attrs' field is ignored if an existing file is opened."
   * Unfortunately this is a later SFTP version specification than implemented by most servers.)
   * But because this is the intuitively correct behaviour (especially when opening a file for read only),
   * most servers (OpenSSH for example) implement it this way.
   * mina-sshd, the server we use for testing, however did not until recently,
   * causing all files we read to be set to 0000.
   * The fix to make it behave correctly has been merged back to master, but not yet released:
   * https://github.com/apache/mina-sshd/commit/19adb39e4706929b6e5a1b2df056a2b2a29fac4d
   * If we encounter real servers that behave like this, a workaround would be to stat before opening the file
   * and "re-setting" the mode we read earlier on open.
   * An another option would be to patch libssh2 to not send permissions in attrs when opening a file for read only.
   */
  LIBSSH2_SFTP_HANDLE *file_handle = libssh2_sftp_open(sftp_session_, path.c_str(), LIBSSH2_FXF_READ, 0 /*mode*/);
  if (file_handle == nullptr) {
    int ssh_errno = libssh2_session_last_errno(ssh_session_);
    /* We can only get the sftp error in this case if the ssh error is a protocol error */
    if (ssh_errno == LIBSSH2_ERROR_SFTP_PROTOCOL) {
      last_error_.setLibssh2Error(libssh2_sftp_last_error(sftp_session_));
      logger_->log_error("Failed to open remote file \"%s\", error: %s", path.c_str(), sftp_strerror(last_error_));
    } else {
      last_error_.setSftpError(SFTPError::IoError);
      char *err_msg = nullptr;
      libssh2_session_last_error(ssh_session_, &err_msg, nullptr, 0);
      logger_->log_error("Failed to open remote file \"%s\" due to an underlying SSH error: %s", path.c_str(), err_msg);
    }
    return false;
  }
  const auto guard = gsl::finally([&file_handle]() {
    libssh2_sftp_close(file_handle);
  });

  const size_t buf_size = expected_size < 0 ? MAX_BUFFER_SIZE : std::min<size_t>(expected_size, MAX_BUFFER_SIZE);
  std::vector<uint8_t> buf(buf_size);
  uint64_t total_read = 0U;
  do {
    ssize_t read_ret = libssh2_sftp_read(file_handle, reinterpret_cast<char*>(buf.data()), buf.size());
    if (read_ret < 0) {
      last_error_.setSftpError(SFTPError::IoError);
      logger_->log_error("Failed to read remote file \"%s\"", path.c_str());
      return false;
    } else if (read_ret == 0) {
      logger_->log_trace("EOF while reading remote file \"%s\"", path.c_str());
      break;
    }
    logger_->log_trace("Read %d bytes from remote file \"%s\"", read_ret, path.c_str());
    total_read += read_ret;
    int remaining = read_ret;
    while (remaining > 0) {
      int write_ret = output.write(buf.data() + (read_ret - remaining), remaining);
      if (write_ret < 0) {
        last_error_.setLibssh2Error(LIBSSH2_FX_OK);
        logger_->log_error("Failed to write output");
        return false;
      }