Function parsePack

packages/plugins/apps/src/git-client/packfile.ts:426–544

(pack: Uint8Array, options?: ParsePackOptions)

// Parse a full packfile and resolve all deltas. Returns objects keyed by sha.
export async function parsePack(pack: Uint8Array, options?: ParsePackOptions): Promise<ParsedPack> {
  const limits = limitsFor(options);
  requireAvailable(pack, 0, 12, "pack header");
  if (td.decode(pack.subarray(0, 4)) !== "PACK") throw new PackParseError("not a packfile");
  const version = new DataView(pack.buffer, pack.byteOffset + 4, 4).getUint32(0);
  if (version !== 2 && version !== 3) {
    throw new PackParseError(`unsupported pack version: ${version}`);
  }
  const count = new DataView(pack.buffer, pack.byteOffset + 8, 4).getUint32(0);
  let pos = 12;
  let expandedBytes = 0;

  const accountExpanded = (size: number): void => {
    expandedBytes = checkedAdd(expandedBytes, size, "expanded pack size");
    if (expandedBytes > limits.maxExpandedBytes) {
      throw repositoryTooLarge(`expanded objects exceed ${limits.maxExpandedBytes} bytes`);
    }
  };

  const raws: RawObj[] = [];
  for (let i = 0; i < count; i++) {
    const start = pos;
    const { type, size, pos: p1 } = readVarintSize(pack, pos);
    if (size > limits.maxObjectBytes && type !== OBJ_OFS_DELTA && type !== OBJ_REF_DELTA) {
      throw repositoryTooLarge(`object declares ${size} bytes`);
    }
    pos = p1;
    if (type === OBJ_OFS_DELTA) {
      // negative offset varint
      requireAvailable(pack, pos, 1, "ofs-delta base offset");
      let c = pack[pos++]!;
      let ofs = c & 0x7f;
      let bytes = 1;
      while (c & 0x80) {
        if (bytes >= 7) throw new PackParseError("ofs-delta offset varint is too long");
        requireAvailable(pack, pos, 1, "ofs-delta base offset");
        c = pack[pos++]!;
        ofs = checkedAdd(
          checkedMul(ofs + 1, 128, "ofs-delta offset"),
          c & 0x7f,
          "ofs-delta offset",
        );
        bytes += 1;
      }
      const baseOfs = start - ofs;
      if (baseOfs < 12 || baseOfs >= start) {
        throw new PackParseError("ofs-delta base offset is invalid");
      }
      const inf = inflateZlib(pack, pos, limits);
      pos = inf.endPos;
      accountExpanded(inf.out.length);
      raws.push({ type, baseOfs, delta: inf.out, offset: start });
    } else if (type === OBJ_REF_DELTA) {
      requireAvailable(pack, pos, 20, "ref-delta base sha");
      let hex = "";
      for (let j = 0; j < 20; j++) hex += pack[pos + j].toString(16).padStart(2, "0");
      pos += 20;
      const inf = inflateZlib(pack, pos, limits);