})();

/** Compute CRC32 checksum for a buffer (used in PNG chunk encoding). */

export function crc32(buf: Buffer): number {

function crc32(buf: Buffer): number {

let crc = 0xffffffff;

for (let i = 0; i < buf.length; i += 1) {

crc = CRC_TABLE[(crc ^ buf[i]) & 0xff] ^ (crc >>> 8);

}

/** Create a PNG chunk with type, data, and CRC. */

export function pngChunk(type: string, data: Buffer): Buffer {

function pngChunk(type: string, data: Buffer): Buffer {

const typeBuf = Buffer.from(type, "ascii");

const len = Buffer.alloc(4);

len.writeUInt32BE(data.length, 0);