Function pipe

lib/internal/streams/pipeline.js:417–470

(src, dst, finish, finishOnlyHandleError, { end })

}

function pipe(src, dst, finish, finishOnlyHandleError, { end }) {
  let ended = false;
  dst.on('close', () => {
    if (!ended) {
      // Finish if the destination closes before the source has completed.
      finishOnlyHandleError(new ERR_STREAM_PREMATURE_CLOSE());
    }
  });

  src.pipe(dst, { end: false }); // If end is true we already will have a listener to end dst.

  if (end) {
    // Compat. Before node v10.12.0 stdio used to throw an error so
    // pipe() did/does not end() stdio destinations.
    // Now they allow it but "secretly" don't close the underlying fd.

    function endFn() {
      ended = true;
      dst.end();
    }

    if (isReadableFinished(src)) { // End the destination if the source has already ended.
      process.nextTick(endFn);
    } else {
      src.once('end', endFn);
    }
  } else {
    finish();
  }

  eos(src, { readable: true, writable: false }, (err) => {
    const rState = src._readableState;
    if (
      err &&
      err.code === 'ERR_STREAM_PREMATURE_CLOSE' &&
      (rState?.ended && !rState.errored && !rState.errorEmitted)
    ) {
      // Some readable streams will emit 'close' before 'end'. However, since
      // this is on the readable side 'end' should still be emitted if the
      // stream has been ended and no error emitted. This should be allowed in
      // favor of backwards compatibility. Since the stream is piped to a
      // destination this should not result in any observable difference.
      // We don't need to check if this is a writable premature close since
      // eos will only fail with premature close on the reading side for
      // duplex streams.
      src
        .once('end', finish)
        .once('error', finish);
    } else {
      finish(err);
    }
  });
  return eos(dst, { readable: false, writable: true }, finish);
}

module.exports = { pipelineImpl, pipeline };