const TABLE = buildTable();

function buildTable(): Uint32Array {
  const table = new Uint32Array(256);
  for (let n = 0; n < 256; n++) {
    let c = n;
    for (let k = 0; k < 8; k++) {
      c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
    }
    table[n] = c >>> 0;
  }
  return table;
}

/** CRC32 of `bytes`, as required by the PNG chunk format (ISO 3309 / ITU-T V.42). */
export function crc32(bytes: Uint8Array): number {
  let crc = 0xffffffff;
  for (let i = 0; i < bytes.length; i++) {
    const byte = bytes[i]!;
    crc = TABLE[(crc ^ byte) & 0xff]! ^ (crc >>> 8);
  }
  return (crc ^ 0xffffffff) >>> 0;
}