Function onwrite

lib/internal/streams/writable.js:615–691

(stream, er)

}

function onwrite(stream, er) {
  const state = stream._writableState;

  if ((state[kState] & kExpectWriteCb) === 0) {
    errorOrDestroy(stream, new ERR_MULTIPLE_CALLBACK());
    return;
  }

  const sync = (state[kState] & kSync) !== 0;
  const cb = (state[kState] & kWriteCb) !== 0 ? state[kWriteCbValue] : nop;

  state.writecb = null;
  state[kState] &= ~(kWriting | kExpectWriteCb);
  state.length -= state.writelen;
  state.writelen = 0;

  if (er) {
    // Avoid V8 leak, https://github.com/nodejs/node/pull/34103#issuecomment-652002364
    er.stack; // eslint-disable-line no-unused-expressions

    if ((state[kState] & kErrored) === 0) {
      state[kErroredValue] = er;
      state[kState] |= kErrored;
    }

    // In case of duplex streams we need to notify the readable side of the
    // error.
    if (stream._readableState && !stream._readableState.errored) {
      stream._readableState.errored = er;
    }

    if (sync) {
      process.nextTick(onwriteError, stream, state, er, cb);
    } else {
      onwriteError(stream, state, er, cb);
    }
  } else {
    if ((state[kState] & kBuffered) !== 0) {
      clearBuffer(stream, state);
    }

    if (sync) {
      const needDrain = (state[kState] & kNeedDrain) !== 0 && state.length === 0;
      const needTick = needDrain || (state[kState] & kDestroyed !== 0) || cb !== nop;

      // It is a common case that the callback passed to .write() is always
      // the same. In that case, we do not schedule a new nextTick(), but
      // rather just increase a counter, to improve performance and avoid
      // memory allocations.
      if (cb === nop) {
        if ((state[kState] & kAfterWritePending) === 0 && needTick) {
          process.nextTick(afterWrite, stream, state, 1, cb);
          state[kState] |= kAfterWritePending;
        } else {
          state.pendingcb--;
          if ((state[kState] & kEnding) !== 0) {
            finishMaybe(stream, state, true);
          }