From c2166c47f58735cbf993364f0b0415f481c6b778 Mon Sep 17 00:00:00 2001
From: Borewit <Borewit@users.noreply.github.com>
Date: Sat, 30 Nov 2024 17:01:25 +0100
Subject: [PATCH] Fix random read at position 0

---
 lib/AbstractTokenizer.ts | 21 +++++++--------------
 test/test.ts             | 10 ++++++++++
 2 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/lib/AbstractTokenizer.ts b/lib/AbstractTokenizer.ts
index b65e9cc3..3dbea8fa 100644
--- a/lib/AbstractTokenizer.ts
+++ b/lib/AbstractTokenizer.ts
@@ -133,24 +133,17 @@ export abstract class AbstractTokenizer implements ITokenizer {
 
   protected normalizeOptions(uint8Array: Uint8Array, options?: IReadChunkOptions): INormalizedReadChunkOptions {
 
-    if (options && options.position !== undefined && options.position < this.position) {
+    if (!this.supportsRandomAccess() && options && options.position !== undefined && options.position < this.position) {
       throw new Error('`options.position` must be equal or greater than `tokenizer.position`');
     }
 
-    if (options) {
-      return {
-        mayBeLess: options.mayBeLess === true,
-        offset: options.offset ? options.offset : 0,
-        length: options.length ? options.length : (uint8Array.length - (options.offset ? options.offset : 0)),
-        position: options.position ? options.position : this.position
-      };
-    }
-
     return {
-      mayBeLess: false,
-      offset: 0,
-      length: uint8Array.length,
-      position: this.position
+      ...{
+        mayBeLess: false,
+        offset: 0,
+        length: uint8Array.length,
+        position: this.position
+      }, ...options
     };
   }
 
diff --git a/test/test.ts b/test/test.ts
index f0d78c7e..d96c5534 100644
--- a/test/test.ts
+++ b/test/test.ts
@@ -1012,6 +1012,16 @@ describe('Random-read-acccess', async () => {
     }
   });
 
+  it('Be able to random read from position 0', async () => {
+    const tokenizer = await fromFile(getResourcePath('id3v1.mp3'));
+    // Advance tokenizer.position
+    await tokenizer.ignore(20);
+    const mpegSync = new Uint8Array(2);
+    await tokenizer.readBuffer(mpegSync,{position: 0});
+    assert.strictEqual(mpegSync[0], 255, 'First sync byte');
+    assert.strictEqual(mpegSync[1], 251, 'Second sync byte');
+  });
+
 });