is_main_thread.js

'use strict';

const { ObjectDefineProperty } = primordials;
const rawMethods = internalBinding('process_methods');

// TODO(joyeecheung): deprecate and remove these underscore methods
process._debugProcess = rawMethods._debugProcess;
process._debugEnd = rawMethods._debugEnd;

// See the discussion in https://github.com/nodejs/node/issues/19009 and
// https://github.com/nodejs/node/pull/34010 for why these are no-ops.
// Five word summary: they were broken beyond repair.
process._startProfilerIdleNotifier = () => {};
process._stopProfilerIdleNotifier = () => {};

function defineStream(name, getter) {
  ObjectDefineProperty(process, name, {
    configurable: true,
    enumerable: true,
    get: getter
  });
}

defineStream('stdout', getStdout);
defineStream('stdin', getStdin);
defineStream('stderr', getStderr);

// Worker threads don't receive signals.
const {
  startListeningIfSignal,
  stopListeningIfSignal
} = require('internal/process/signal');
process.on('newListener', startListeningIfSignal);
process.on('removeListener', stopListeningIfSignal);

// ---- keep the attachment of the wrappers above so that it's easier to ----
// ----              compare the setups side-by-side                    -----

const { guessHandleType } = internalBinding('util');

function createWritableStdioStream(fd) {
  let stream;
  // Note stream._type is used for test-module-load-list.js
  switch (guessHandleType(fd)) {
    case 'TTY':
      const tty = require('tty');
      stream = new tty.WriteStream(fd);
      stream._type = 'tty';
      break;

    case 'FILE':
      const SyncWriteStream = require('internal/fs/sync_write_stream');
      stream = new SyncWriteStream(fd, { autoClose: false });
      stream._type = 'fs';
      break;

    case 'PIPE':
    case 'TCP':
      const net = require('net');

      // If fd is already being used for the IPC channel, libuv will return
      // an error when trying to use it again. In that case, create the socket
      // using the existing handle instead of the fd.
      if (process.channel && process.channel.fd === fd) {
        const { kChannelHandle } = require('internal/child_process');
        stream = new net.Socket({
          handle: process[kChannelHandle],
          readable: false,
          writable: true
        });
      } else {
        stream = new net.Socket({
          fd,
          readable: false,
          writable: true
        });
      }

      stream._type = 'pipe';
      break;

    default:
      // Provide a dummy black-hole output for e.g. non-console
      // Windows applications.
      const { Writable } = require('stream');
      stream = new Writable({
        write(buf, enc, cb) {
          cb();
        }
      });
  }

  // For supporting legacy API we put the FD here.
  stream.fd = fd;

  stream._isStdio = true;

  return stream;
}

function dummyDestroy(err, cb) {
  cb(err);

  // We need to emit 'close' anyway so that the closing
  // of the stream is observable. We just make sure we
  // are not going to do it twice.
  // The 'close' event is needed so that finished and
  // pipeline work correctly.
  if (!this._writableState.emitClose) {
    process.nextTick(() => {
      this.emit('close');
    });
  }
}

let stdin;
let stdout;
let stderr;

function getStdout() {
  if (stdout) return stdout;
  stdout = createWritableStdioStream(1);
  stdout.destroySoon = stdout.destroy;
  // Override _destroy so that the fd is never actually closed.
  stdout._destroy = dummyDestroy;
  if (stdout.isTTY) {
    process.on('SIGWINCH', () => stdout._refreshSize());
  }
  return stdout;
}

function getStderr() {
  if (stderr) return stderr;
  stderr = createWritableStdioStream(2);
  stderr.destroySoon = stderr.destroy;
  // Override _destroy so that the fd is never actually closed.
  stderr._destroy = dummyDestroy;
  if (stderr.isTTY) {
    process.on('SIGWINCH', () => stderr._refreshSize());
  }
  return stderr;
}

function getStdin() {
  if (stdin) return stdin;
  const fd = 0;

  switch (guessHandleType(fd)) {
    case 'TTY':
      const tty = require('tty');
      stdin = new tty.ReadStream(fd, {
        highWaterMark: 0,
        readable: true,
        writable: false
      });
      break;

    case 'FILE':
      const fs = require('fs');
      stdin = new fs.ReadStream(null, { fd: fd, autoClose: false });
      break;

    case 'PIPE':
    case 'TCP':
      const net = require('net');

      // It could be that process has been started with an IPC channel
      // sitting on fd=0, in such case the pipe for this fd is already
      // present and creating a new one will lead to the assertion failure
      // in libuv.
      if (process.channel && process.channel.fd === fd) {
        stdin = new net.Socket({
          handle: process.channel,
          readable: true,
          writable: false,
          manualStart: true
        });
      } else {
        stdin = new net.Socket({
          fd: fd,
          readable: true,
          writable: false,
          manualStart: true
        });
      }
      // Make sure the stdin can't be `.end()`-ed
      stdin._writableState.ended = true;
      break;

    default:
      // Provide a dummy contentless input for e.g. non-console
      // Windows applications.
      const { Readable } = require('stream');
      stdin = new Readable({ read() {} });
      stdin.push(null);
  }

  // For supporting legacy API we put the FD here.
  stdin.fd = fd;

  // `stdin` starts out life in a paused state, but node doesn't
  // know yet. Explicitly to readStop() it to put it in the
  // not-reading state.
  if (stdin._handle && stdin._handle.readStop) {
    stdin._handle.reading = false;
    stdin._readableState.reading = false;
    stdin._handle.readStop();
  }

  // If the user calls stdin.pause(), then we need to stop reading
  // once the stream implementation does so (one nextTick later),
  // so that the process can close down.
  stdin.on('pause', () => {
    process.nextTick(onpause);
  });

  function onpause() {
    if (!stdin._handle)
      return;
    if (stdin._handle.reading && !stdin.readableFlowing) {
      stdin._readableState.reading = false;
      stdin._handle.reading = false;
      stdin._handle.readStop();
    }
  }

  return stdin;
}

// Used by internal tests.
rawMethods.resetStdioForTesting = function() {
  stdin = undefined;
  stdout = undefined;
  stderr = undefined;
};