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>

Author: addaleax

lib/internal/net.js

@@ -1,5 +1,8 @@
 'use strict';
 
+constBuffer=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.
 functionisLegalPort(port){
@@ -9,7 +12,28 @@ function isLegalPort(port) {
 return+port===(+port>>>0)&&port<=0xFFFF;
 }
 
+functionmakeSyncWrite(fd){
+returnfunction(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(typeofex.code==='string')
+ex.errno=ex.code;
+returncb(ex);
+}
+cb();
+};
+}
+
 module.exports={
  isLegalPort,
+ makeSyncWrite,
 normalizedArgsSymbol: Symbol('normalizedArgs')
 };

lib/net.js

@@ -26,7 +26,11 @@ const stream = require('stream');
 consttimers=require('timers');
 constutil=require('util');
 constinternalUtil=require('internal/util');
-const{ isLegalPort, normalizedArgsSymbol }=require('internal/net');
+const{
+ isLegalPort,
+ normalizedArgsSymbol,
+ makeSyncWrite
+}=require('internal/net');
 constassert=require('assert');
 constcares=process.binding('cares_wrap');
 constuv=process.binding('uv');
@@ -206,20 +210,24 @@ function Socket(options) {
 this._handle=options.handle;// private
 this[async_id_symbol]=getNewAsyncId(this._handle);
 }elseif(options.fd!==undefined){
-this._handle=createHandle(options.fd,false);
-this._handle.open(options.fd);
+constfd=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._handleinstanceofPipe)&&
 process.platform==='win32'){
 // Make stdout and stderr blocking on Windows
 varerr=this._handle.setBlocking(true);
 if(err)
 throwerrnoException(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{ inherits, _extend }=require('util');
 constnet=require('net');
 const{TTY, isTTY }=process.binding('tty_wrap');
+const{ makeSyncWrite }=require('internal/net');
 consterrors=require('internal/errors');
 constreadline=require('readline');
 
@@ -77,6 +78,8 @@ 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);
 
 varwinSize=newArray(2);
 varerr=this._handle.getWindowSize(winSize);