process: use more direct sync I/O for stdio

This avoids routing writes through the full LibuvStreamWrap
write machinery. In particular, it enables the next commit,
because otherwise the callback passed to `_write()`
would not be called synchronously for pipes on Windows
(because the latter does not support `uv_try_write()`,
even for blocking I/O).

PR-URL: #18019
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

lib/internal/net.js

@@ -1,5 +1,8 @@
 'use strict';
 
+const Buffer = require('buffer').Buffer;
+const { writeBuffer } = process.binding('fs');
+
 // Check that the port number is not NaN when coerced to a number,
 // is an integer and that it falls within the legal range of port numbers.
 function isLegalPort(port) {
@@ -9,7 +12,28 @@ function isLegalPort(port) {
   return +port === (+port >>> 0) && port <= 0xFFFF;
 }
 
+function makeSyncWrite(fd) {
+  return function(chunk, enc, cb) {
+    if (enc !== 'buffer')
+      chunk = Buffer.from(chunk, enc);
+
+    this._bytesDispatched += chunk.length;
+
+    try {
+      writeBuffer(fd, chunk, 0, chunk.length, null);
+    } catch (ex) {
+      // Legacy: net writes have .code === .errno, whereas writeBuffer gives the
+      // raw errno number in .errno.
+      if (typeof ex.code === 'string')
+        ex.errno = ex.code;
+      return cb(ex);
+    }
+    cb();
+  };
+}
+
 module.exports = {
   isLegalPort,
+  makeSyncWrite,
   normalizedArgsSymbol: Symbol('normalizedArgs')
 };

lib/net.js

@@ -26,7 +26,11 @@ const stream = require('stream');
 const timers = require('timers');
 const util = require('util');
 const internalUtil = require('internal/util');
-const { isLegalPort, normalizedArgsSymbol } = require('internal/net');
+const {
+  isLegalPort,
+  normalizedArgsSymbol,
+  makeSyncWrite
+} = require('internal/net');
 const assert = require('assert');
 const cares = process.binding('cares_wrap');
 const {
@@ -213,20 +217,24 @@ function Socket(options) {
     this._handle = options.handle; // private
     this[async_id_symbol] = getNewAsyncId(this._handle);
   } else if (options.fd !== undefined) {
-    this._handle = createHandle(options.fd, false);
-    this._handle.open(options.fd);
+    const fd = options.fd;
+    this._handle = createHandle(fd, false);
+    this._handle.open(fd);
     this[async_id_symbol] = this._handle.getAsyncId();
     // options.fd can be string (since it is user-defined),
     // so changing this to === would be semver-major
     // See: https://github.com/nodejs/node/pull/11513
     // eslint-disable-next-line eqeqeq
-    if ((options.fd == 1 || options.fd == 2) &&
+    if ((fd == 1 || fd == 2) &&
         (this._handle instanceof Pipe) &&
         process.platform === 'win32') {
       // Make stdout and stderr blocking on Windows
       var err = this._handle.setBlocking(true);
       if (err)
         throw errnoException(err, 'setBlocking');
+
+      this._writev = null;
+      this._write = makeSyncWrite(fd);
     }
     this.readable = options.readable !== false;
     this.writable = options.writable !== false;

lib/tty.js

@@ -24,6 +24,7 @@
 const util = require('util');
 const net = require('net');
 const { TTY, isTTY } = process.binding('tty_wrap');
+const { makeSyncWrite } = require('internal/net');
 const { inherits } = util;
 const errnoException = util._errnoException;
 const errors = require('internal/errors');
@@ -79,6 +80,8 @@ function WriteStream(fd) {
   // even though it was originally intended to change in v1.0.2 (Libuv 1.2.1).
   // Ref: https://github.com/nodejs/node/pull/1771#issuecomment-119351671
   this._handle.setBlocking(true);
+  this._writev = null;
+  this._write = makeSyncWrite(fd);
 
   var winSize = new Array(2);
   var err = this._handle.getWindowSize(winSize);