child_process: improve ipc write performance

PR-URL: #42931
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Zeyu "Alex" Yang <himself65@outlook.com>

Author: CaramelFur

lib/internal/child_process/serialization.js

@@ -5,7 +5,6 @@ const {
   JSONStringify,
   StringPrototypeSplit,
   ArrayPrototypePush,
-  ReflectApply,
   Symbol,
   TypedArrayPrototypeSubarray,
 } = primordials;
@@ -15,7 +14,6 @@ const v8 = require('v8');
 const { isArrayBufferView } = require('internal/util/types');
 const assert = require('internal/assert');
 const { streamBaseState, kLastWriteWasAsync } = internalBinding('stream_wrap');
-const { readUInt32BE } = require('internal/buffer');
 
 const kMessageBuffer = Symbol('kMessageBuffer');
 const kMessageBufferSize = Symbol('kMessageBufferSize');
@@ -71,7 +69,12 @@ const advanced = {
     while (messageBufferHead.length >= 4) {
       // We call `readUInt32BE` manually here, because this is faster than first converting
       // it to a buffer and using `readUInt32BE` on that.
-      const fullMessageSize = ReflectApply(readUInt32BE, messageBufferHead, [0]) + 4;
+      const fullMessageSize = (
+        messageBufferHead[0] << 24 |
+        messageBufferHead[1] << 16 |
+        messageBufferHead[2] << 8 |
+        messageBufferHead[3]
+      ) + 4;
 
       if (channel[kMessageBufferSize] < fullMessageSize) break;
 
@@ -100,20 +103,27 @@ const advanced = {
 
   writeChannelMessage(channel, req, message, handle) {
     const ser = new ChildProcessSerializer();
+    // Add 4 bytes, to later populate with message length
+    ser.writeRawBytes(Buffer.allocUnsafe(4));
     ser.writeHeader();
     ser.writeValue(message);
+
     const serializedMessage = ser.releaseBuffer();
-    const sizeBuffer = Buffer.allocUnsafe(4);
-    sizeBuffer.writeUInt32BE(serializedMessage.length);
-
-    const buffer = Buffer.concat([
-      sizeBuffer,
-      serializedMessage,
-    ]);
-    const result = channel.writeBuffer(req, buffer, handle);
+    const serializedMessageLength = serializedMessage.length - 4;
+
+    serializedMessage.set([
+      serializedMessageLength >> 24 & 0xFF,
+      serializedMessageLength >> 16 & 0xFF,
+      serializedMessageLength >> 8 & 0xFF,
+      serializedMessageLength & 0xFF,
+    ], 0);
+
+    const result = channel.writeBuffer(req, serializedMessage, handle);
+
     // Mirror what stream_base_commons.js does for Buffer retention.
     if (streamBaseState[kLastWriteWasAsync])
-      req.buffer = buffer;
+      req.buffer = serializedMessage;
+
     return result;
   },
 };