Using a less expensive operation to check if the buffer has reached it's limit

Author: WyriHaximus

src/functions.php

@@ -26,7 +26,7 @@ function buffer(ReadableStreamInterface $stream, $maxLength = null)
     $buffer = '';
     $bufferer = function ($data) use (&$buffer, &$bufferer, $stream, $deferred, $maxLength) {
         $buffer .= $data;
-        if ($maxLength !== null && strlen($buffer) > (int)$maxLength) {
+        if ($maxLength !== null && isset($buffer[$maxLength])) {
             $deferred->reject(new \RuntimeException('Buffer exceeded maximum length'));
         }
     };