rabin-wasm/src/rabin.js

Rabin fingerprinting implemented in AssemblyScript

/**
 * Rabin fingerprinting
 *
 * @class Rabin
 */
class Rabin {
    /**
     * Creates an instance of Rabin.
     * @param { import("./../dist/rabin-wasm") } asModule
     * @param {number} [bits=12]
     * @param {number} [min=8 * 1024]
     * @param {number} [max=32 * 1024]
     * @param {number} polynomial
     * @memberof Rabin
     */
    constructor(asModule, bits = 12, min = 8 * 1024, max = 32 * 1024, windowSize = 64, polynomial) {
        this.bits = bits
        this.min = min
        this.max = max
        this.asModule = asModule
        this.rabin = new asModule.Rabin(bits, min, max, windowSize, polynomial)
        this.polynomial = polynomial
    }

    /**
     * Fingerprints the buffer
     *
     * @param {Uint8Array} buf
     * @returns {Array<number>}
     * @memberof Rabin
     */
    fingerprint(buf) {
        const {
            __retain,
            __release,
            __allocArray,
            __getInt32Array,
            Int32Array_ID,
            Uint8Array_ID
        } = this.asModule

        const lengths = new Int32Array(Math.ceil(buf.length/this.min))
        const lengthsPtr = __retain(__allocArray(Int32Array_ID, lengths))
        const pointer = __retain(__allocArray(Uint8Array_ID, buf))

        const out = this.rabin.fingerprint(pointer, lengthsPtr)
        const processed = __getInt32Array(out)

        __release(pointer)
        __release(lengthsPtr)

        const end = processed.indexOf(0);
        return end >= 0 ? processed.subarray(0, end) : processed;
    }
}

module.exports = Rabin