adler32

Incremental Adler-32 checksum (RFC 1950). Used in Zlib/Deflate formats.

Module adler32 | Source packages/front/fw/src/io/calc/adler32.js | Deps none | Worker-safe yes

Resolve

const Adler32 = runtime.resolve('adler32');
// Returns: constructor (new Adler32())

API

const adler = new Adler32();

Examples

const Adler32 = runtime.resolve('adler32');

const adler = new Adler32();
adler.append(new Uint8Array([72, 101, 108, 108, 111])); // "Hello"
console.log(adler.get().toString(16)); // "07c801b5"

// Incremental processing
const adler2 = new Adler32();
for (const chunk of dataChunks) {
    adler2.append(chunk);
}
const checksum = adler2.get();

Worker Usage

const worker = fw.createWorker(
    function ({ libs, args }) {
        const Adler32 = libs.adler32;
        const adler = new Adler32();
        adler.append(new Uint8Array(args.data));
        self.postMessage(adler.get());
    },
    { dependencies: ['adler32'], args: { data: Array.from(largeBuffer) } }
);

Notes

• Returned format: (B << 16) | A — big-endian value conforming to RFC 1950.
• Optimized: 2655-byte blocks with fast modular reduction (& 0xFFFF + 15 * (>> 16)).
• Faster than CRC-32 but less robust against corruptions.
• Same API as crc32 (compatible append/get).

See also

• crc32 — CRC-32 checksum (more robust)
• zlib — uses Adler-32 internally