Method findStartXRef

src/parser/xref-parser.ts:46–87

* Find the startxref offset by scanning backwards from end of file. * Returns the byte offset where xref starts.

()

   * Returns the byte offset where xref starts.
   */
  findStartXRef(): number {
    const bytes = this.scanner.bytes;
    const len = bytes.length;

    // Skip trailing whitespace/null bytes to find the effective end of file.
    // Some systems pad PDFs with null bytes to block boundaries, which can
    // push the actual %%EOF / startxref beyond the normal 1024-byte window.
    let effectiveEnd = len;

    while (effectiveEnd > 0 && isWhitespace(bytes[effectiveEnd - 1])) {
      effectiveEnd--;
    }

    // Search backwards from effective end, looking for "startxref"
    const searchStart = Math.max(0, effectiveEnd - 1024);

    let startxrefPos = -1;

    for (let i = effectiveEnd - 9; i >= searchStart; i--) {
      if (this.matchesAt(i, "startxref")) {
        startxrefPos = i;
        break;
      }
    }

    if (startxrefPos === -1) {
      throw new XRefParseError("Could not find startxref marker");
    }

    // Skip "startxref" and whitespace to get the offset number
    let pos = startxrefPos + 9;
    pos = this.skipWhitespace(pos);

    // Read the offset number
    const offset = this.readIntegerAt(pos);

    if (offset === null) {
      throw new XRefParseError("Invalid startxref offset");
    }

    return offset;
  }

  /**
   * Parse xref at given byte offset.