Method lengthResolver

src/parser/document-parser.ts:515–578

(ref: PdfRef)

    // Create length resolver for stream objects with indirect /Length
    const lengthResolver: LengthResolver = (ref: PdfRef) => {
      // Check object cache first
      const cacheKey = `${ref.objectNumber} ${ref.generation}`;
      const cached = cache.get(cacheKey);

      if (cached instanceof PdfNumber) {
        return cached.value;
      }

      const entry = xref.get(ref.objectNumber);

      if (!entry || entry.type === "free") {
        return null;
      }

      // Save scanner position - we must restore it after parsing
      // because we're in the middle of parsing a stream
      const savedPosition = this.scanner.position;

      try {
        let lengthObj: PdfObject | null = null;

        if (entry.type === "uncompressed") {
          const parser = new IndirectObjectParser(this.scanner);
          lengthObj = parser.parseObjectAt(entry.offset).value;
        } else {
          // Compressed: load from object stream
          // Object streams themselves must be uncompressed (per PDF spec 7.5.7)
          const streamEntry = xref.get(entry.streamObjNum);

          if (streamEntry?.type === "uncompressed") {
            // Use cached object stream parser if available
            let objStreamParser = objectStreamCache.get(entry.streamObjNum);

            if (!objStreamParser) {
              const parser = new IndirectObjectParser(this.scanner);
              const streamResult = parser.parseObjectAt(streamEntry.offset);

              if (streamResult.value instanceof PdfStream) {
                objStreamParser = new ObjectStreamParser(streamResult.value);

                objectStreamCache.set(entry.streamObjNum, objStreamParser);
              }
            }

            if (objStreamParser) {
              lengthObj = objStreamParser.getObject(entry.indexInStream);
            }
          }
        }

        this.scanner.moveTo(savedPosition);

        if (lengthObj instanceof PdfNumber) {
          cache.set(cacheKey, lengthObj);

          return lengthObj.value;
        }