From 9659e761caaa4a63b9a6996ef89ec877bc716ebc Mon Sep 17 00:00:00 2001
From: Nicos Panayides <nicosp@users.noreply.github.com>
Date: Wed, 14 May 2025 17:21:20 +0300
Subject: [PATCH] GIF detection: Only check the first 6 bytes of the input
 (#1441)

* Only check the first 6 bytes of the input to reduce memory usage and speed up the detection

* Update src/Drivers/AbstractDecoder.php

Co-authored-by: Oliver Vogel <oliver@olivervogel.com>

---------

Co-authored-by: Oliver Vogel <oliver@olivervogel.com>
---
 src/Drivers/AbstractDecoder.php | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/Drivers/AbstractDecoder.php b/src/Drivers/AbstractDecoder.php
index 46567171..029761ba 100644
--- a/src/Drivers/AbstractDecoder.php
+++ b/src/Drivers/AbstractDecoder.php
@@ -22,9 +22,11 @@ abstract class AbstractDecoder implements DecoderInterface
      */
     protected function isGifFormat(string $input): bool
     {
+        $head = substr($input, 0, 6);
+
         return 1 === preg_match(
             "/^47494638(37|39)61/",
-            strtoupper(substr(bin2hex($input), 0, 32))
+            strtoupper(bin2hex($head))
         );
     }