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: https://github.com/nodejs/node/pull/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>

1 files changed, 24 insertions, 0 deletions

diff --git a/lib/internal/net.js b/lib/internal/net.js
index d4558cfca8..847539d576 100644
--- a/lib/internal/net.js
+++ b/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')
 };