fix(importer): cap chord name read at field width in GP3-5 binary parser

packages/alphatab/src/importer/Gp3To5Importer.ts

@@ -1571,12 +1571,15 @@ export class GpBinaryHelpers {
      * @returns
      */
     public static gpReadStringByteLength(data: IReadable, length: number, encoding: string): string {
+        // Fixed-width string field: 1 length byte + `length` data bytes, decoded
+        // up to min(stringLength, length). Always consumes 1 + length bytes.
         const stringLength: number = data.readByte();
-        const s: string = GpBinaryHelpers.gpReadString(data, stringLength, encoding);
-        if (stringLength < length) {
-            data.skip(length - stringLength);
-        }
-        return s;
+        const fieldBytes: Uint8Array = new Uint8Array(length);
+        data.read(fieldBytes, 0, length);
+        const effectiveLength: number = Math.max(0, Math.min(stringLength, length));
+        const decoded: Uint8Array = new Uint8Array(effectiveLength);
+        decoded.set(fieldBytes.subarray(0, effectiveLength));
+        return IOHelper.toString(decoded, encoding);
     }
 }
 

packages/alphatab/test/importer/Gp5Importer.test.ts

@@ -1,4 +1,6 @@
 import { Settings } from '@coderline/alphatab/Settings';
+import { GpBinaryHelpers } from '@coderline/alphatab/importer/Gp3To5Importer';
+import { ByteBuffer } from '@coderline/alphatab/io/ByteBuffer';
 import { type Beat, BeatBeamingMode } from '@coderline/alphatab/model/Beat';
 import { Direction } from '@coderline/alphatab/model/Direction';
 import { Ottavia } from '@coderline/alphatab/model/Ottavia';
@@ -569,4 +571,28 @@ describe('Gp5ImporterTest', () => {
             }
         }
     });
+
+    it('chord-name-overflow', async () => {
+        // GP5 file with a chord name length byte that exceeds the 21-byte field
+        // (length=32). Pre-fix, gpReadStringByteLength consumed the full 32 bytes,
+        // mis-aligning the stream and triggering an unbounded readBend loop.
+        const score = (
+            await GpImporterTestHelper.prepareImporterWithFile('guitarpro5/chord-name-overflow.gp5')
+        ).readScore();
+        expect(score.tracks.length).to.equal(1);
+        expect(score.masterBars.length).to.equal(193);
+    });
+
+    it('gpReadStringByteLength caps consumption at field width', () => {
+        const sentinelByte = 0xca;
+        const fieldSize = 21;
+        const overlongHint = 32;
+        const buffer = ByteBuffer.fromBuffer(
+            new Uint8Array([overlongHint, ...new Array(fieldSize).fill(0x41), sentinelByte])
+        );
+        const result = GpBinaryHelpers.gpReadStringByteLength(buffer, fieldSize, 'utf-8');
+        expect(result).to.equal('A'.repeat(fieldSize));
+        expect(buffer.position).to.equal(1 + fieldSize);
+        expect(buffer.readByte()).to.equal(sentinelByte);
+    });
 });