archiver-zip-encrypted/lib/zip20/crc.js

AES-256 and legacy Zip 2.0 encryption for Zip files

/**
 * Build CRC table
 */
const CRC_TABLE = [];
for (let i = 0; i < 256; i++) {
    let r = i;
    for (let j = 0; j < 8; j++) {
        if ((r & 1) === 1) {
            r = (r >>> 1) ^ 0xedb88320;
        } else {
            r >>>= 1;
        }
    }
    CRC_TABLE[i] = r;
}

module.exports = function crc32(oldCrc, charAt) {
    return oldCrc >>> 8 ^ CRC_TABLE[(oldCrc ^ charAt) & 0xff];
};