src: improve StreamBase read throughput

Improve performance by providing JS with the raw ingridients
for the read data, i.e. an `ArrayBuffer` + offset + length
fields, instead of creating `Buffer` instances in C++ land.

PR-URL: https://github.com/nodejs/node/pull/23797
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 11 insertions, 4 deletions

diff --git a/lib/internal/child_process.js b/lib/internal/child_process.js
index e6cdde56c1f..74d69de0dcd 100644
--- a/lib/internal/child_process.js
+++ b/lib/internal/child_process.js
@@ -22,7 +22,12 @@ const util = require('util');
 const assert = require('assert');
 
 const { Process } = internalBinding('process_wrap');
-const { WriteWrap } = internalBinding('stream_wrap');
+const {
+  WriteWrap,
+  kReadBytesOrError,
+  kArrayBufferOffset,
+  streamBaseState
+} = internalBinding('stream_wrap');
 const { Pipe, constants: PipeConstants } = internalBinding('pipe_wrap');
 const { TCP } = internalBinding('tcp_wrap');
 const { TTY } = internalBinding('tty_wrap');
@@ -486,11 +491,13 @@ function setupChannel(target, channel) {
   var pendingHandle = null;
   channel.buffering = false;
   channel.pendingHandle = null;
-  channel.onread = function(nread, pool) {
+  channel.onread = function(arrayBuffer) {
     const recvHandle = channel.pendingHandle;
     channel.pendingHandle = null;
-    // TODO(bnoordhuis) Check that nread > 0.
-    if (pool) {
+    if (arrayBuffer) {
+      const nread = streamBaseState[kReadBytesOrError];
+      const offset = streamBaseState[kArrayBufferOffset];
+      const pool = new Uint8Array(arrayBuffer, offset, nread);
       if (recvHandle)
         pendingHandle = recvHandle;