From 253b8e272c85ad5ea2d9c5880ec99d89b4469054 Mon Sep 17 00:00:00 2001
From: Evan Hahn <me@evanhahn.com>
Date: Thu, 9 Nov 2023 09:27:23 -0600
Subject: [PATCH] GIF: clean up reading of trailer block

---
 public/gif/parseGif.js | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/public/gif/parseGif.js b/public/gif/parseGif.js
index d4ae67d..0314c77 100644
--- a/public/gif/parseGif.js
+++ b/public/gif/parseGif.js
@@ -226,6 +226,19 @@ const readExtensionBlock = (bytes, startingOffset) => {
   }
 };
 
+/**
+ * @param {Uint8Array} bytes
+ * @param {number} offset
+ * @returns {{ node: GifNode, newOffset: number }}
+ */
+const readTrailerBlock = (bytes, offset) => ({
+  newOffset: offset + 1,
+  node: {
+    type: GifNodeType.gifTerminator,
+    bytes: bytes.subarray(offset, offset + 1),
+  },
+});
+
 /**
  * @param {Uint8Array} bytes
  * @returns {null | GifNode} The root node of the GIF tree, or null if the GIF is invalid.
@@ -302,8 +315,7 @@ export default (bytes) => {
     offset += sizeOfGlobalColorTableInBytes;
   }
 
-  readingBlocks:
-  while (true) {
+  while (offset < bytes.byteLength) {
     const blockType = bytes[offset];
 
     let readerFn;
@@ -315,11 +327,8 @@ export default (bytes) => {
         readerFn = readExtensionBlock;
         break;
       case BLOCK_TYPE_TRAILER:
-        children.push({
-          type: GifNodeType.gifTerminator,
-          bytes: bytes.subarray(offset, offset + 1),
-        });
-        break readingBlocks;
+        readerFn = readTrailerBlock;
+        break;
       default:
         throw new Error(`Unknown GIF block type: ${blockType}`);
     }