image-in-browser/lib/common/crc32.js

Package for encoding / decoding images, transforming images, applying filters, drawing primitives on images on the client side (no need for server Node.js)

export class Crc32 {
    static makeTable() {
        const table = [];
        let c = 0;
        for (let n = 0; n < 256; n++) {
            c = n;
            for (let k = 0; k < 8; k++) {
                c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
            }
            table[n] = c;
        }
        return table;
    }
    static getChecksum(opt) {
        var _a, _b, _c;
        const t = Crc32._crcTable;
        const len = (_a = opt.length) !== null && _a !== void 0 ? _a : opt.buffer.length;
        const pos = (_b = opt.position) !== null && _b !== void 0 ? _b : 0;
        const end = pos + len;
        let result = ((_c = opt.baseCrc) !== null && _c !== void 0 ? _c : 0) ^ -1;
        for (let i = pos; i < end; i++) {
            result = (result >>> 8) ^ t[(result ^ opt.buffer[i]) & 0xff];
        }
        return (result ^ -1) >>> 0;
    }
}
Crc32._crcTable = new Uint32Array(Crc32.makeTable());
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