feat: updated parser

ts/src/parser.ts

@@ -20,7 +20,7 @@ export class MonoDisplayParser {
 
     // File header (12 bytes)
     const magic = r.readUint32();
-    if (magic !== MONOFORMAT_MAGIC_HEADER) throw new Error(`Bad magic 0x${magic.toString(16)} — expected 0x632B7EAF`);
+    if (magic !== MONOFORMAT_MAGIC_HEADER) throw new Error(`Bad magic 0x${magic.toString(16)} - expected 0x632B7EAF`);
 
     const version = r.readUint32();
     if (version === 0 || version > 1) throw new Error(`Unsupported version ${version}`);
@@ -36,18 +36,19 @@ export class MonoDisplayParser {
       const sectionStart = r.offset;       // start of section DATA
       const dataSize     = sectionSize - 4;
 
+      const sectionEnd = sectionStart + dataSize;
       switch (sectionType) {
         case SectionType.ElementsAlways:
-          sections.push(this.#parseElementsSection(r, SectionType.ElementsAlways, false));
+          sections.push(this.#parseElementsSection(r, SectionType.ElementsAlways, false, sectionEnd));
           break;
         case SectionType.ElementsTimespan:
-          sections.push(this.#parseElementsSection(r, SectionType.ElementsTimespan, true));
+          sections.push(this.#parseElementsSection(r, SectionType.ElementsTimespan, true, sectionEnd));
           break;
         case SectionType.CustomFont:
           sections.push(this.#parseCustomFont(r, dataSize));
           break;
         default:
-          // Unknown — skip
+          // Unknown - skip
           break;
       }
 
@@ -70,6 +71,7 @@ export class MonoDisplayParser {
     r: BinaryReader,
     type: SectionType.ElementsAlways | SectionType.ElementsTimespan,
     hasTimestamp: boolean,
+    sectionEnd: number,
   ): MonoFormatElementsAlways | MonoFormatElementsTimespan {
     const flags       = this.#parseFlags(r.readUint16());
     const numElements = r.readUint16();
@@ -82,8 +84,11 @@ export class MonoDisplayParser {
 
     const elements: MonoFormatElement[] = [];
     for (let i = 0; i < numElements; i++) {
+      // Stop if fewer than 2 bytes remain in section (can't read element type)
+      if (r.offset + 2 > sectionEnd) break;
       const el = this.#parseElement(r);
-      if (el) elements.push(el);
+      if (el === null) break; // unknown type - can't determine size, stop
+      elements.push(el);
     }
 
     if (hasTimestamp) {
@@ -112,7 +117,7 @@ export class MonoDisplayParser {
       case ElementType.ClippedText:      return this.#parseClippedText(r, elementStart);
       case ElementType.HScrollText:      return this.#parseHScrollText(r, elementStart);
       default:
-        // Unknown element type — cannot safely skip without knowing size; stop parsing section elements
+        // Unknown element type - cannot safely skip without knowing size; stop parsing section elements
         return null;
     }
   }