child_process: do not need to count length when maxBuffer is Infinity

PR-URL: nodejs#43822
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>

lib/child_process.js

@@ -458,6 +458,11 @@ function execFile(file, args, options, callback) {
       child.stdout.setEncoding(encoding);
 
     child.stdout.on('data', function onChildStdout(chunk) {
+      // Do not need to count the length
+      if (options.maxBuffer === Infinity) {
+        ArrayPrototypePush(_stdout, chunk);
+        return;
+      }
       const encoding = child.stdout.readableEncoding;
       const length = encoding ?
         Buffer.byteLength(chunk, encoding) :
@@ -483,6 +488,11 @@ function execFile(file, args, options, callback) {
       child.stderr.setEncoding(encoding);
 
     child.stderr.on('data', function onChildStderr(chunk) {
+      // Do not need to count the length
+      if (options.maxBuffer === Infinity) {
+        ArrayPrototypePush(_stderr, chunk);
+        return;
+      }
       const encoding = child.stderr.readableEncoding;
       const length = encoding ?
         Buffer.byteLength(chunk, encoding) :
@@ -497,7 +507,7 @@ function execFile(file, args, options, callback) {
         ex = new ERR_CHILD_PROCESS_STDIO_MAXBUFFER('stderr');
         kill();
       } else {
-        _stderr.push(chunk);
+        ArrayPrototypePush(_stderr, chunk);
       }
     });
   }