@hugoalh/adler32/mod.js

A module to get the checksum of the data with algorithm Adler32.

/**
 * Get the checksum of the data with algorithm Adler32.
 */
export class Adler32 {
    get [Symbol.toStringTag]() {
        return "Adler32";
    }
    #freezed = false;
    #hashHex = null;
    #hashUint8Array = null;
    #a = 1n;
    #b = 0n;
    /**
     * Initialize.
     * @param {Adler32AcceptDataType} [data] Data. Can append later via the method {@linkcode Adler32.update} and {@linkcode Adler32.updateFromStream}.
     */
    constructor(data) {
        if (typeof data !== "undefined") {
            this.update(data);
        }
    }
    /**
     * Whether the instance is freezed.
     * @returns {boolean}
     */
    get freezed() {
        return this.#freezed;
    }
    /**
     * Freeze the instance to prevent any further update.
     * @returns {this}
     */
    freeze() {
        this.#freezed = true;
        return this;
    }
    /**
     * Get the checksum of the data, in Uint8Array.
     * @returns {Uint8Array}
     */
    hash() {
        if (this.#hashUint8Array === null) {
            const hex = this.hashHex();
            const bytes = [];
            for (let index = 0; index < hex.length; index += 2) {
                bytes.push(hex.slice(index, index + 2));
            }
            this.#hashUint8Array = Uint8Array.from(bytes.map((byte) => {
                return Number.parseInt(byte, 16);
            }));
        }
        return Uint8Array.from(this.#hashUint8Array);
    }
    /**
     * Get the checksum of the data, in hexadecimal with padding.
     * @returns {string}
     */
    hashHex() {
        if (this.#hashHex === null) {
            this.#hashHex = (this.#b * 65536n + this.#a).toString(16).toUpperCase().padStart(8, "0");
            if (this.#hashHex.length !== 8) {
                throw new Error(`Unexpected hash hex result \`${this.#hashHex}\`! Please submit a bug report.`);
            }
        }
        return this.#hashHex;
    }
    /**
     * Append data.
     * @param {Adler32AcceptDataType} data Data.
     * @returns {this}
     */
    update(data) {
        if (this.#freezed) {
            throw new Error(`Instance is freezed!`);
        }
        this.#hashHex = null;
        this.#hashUint8Array = null;
        const dataFmt = (typeof data === "string") ? new TextEncoder().encode(data) : data;
        for (const byte of dataFmt) {
            this.#a = (this.#a + BigInt(byte)) % 65521n;
            this.#b = (this.#b + this.#a) % 65521n;
        }
        return this;
    }
    /**
     * Append data from the readable stream.
     * @param {ReadableStream<Adler32AcceptDataType>} stream Data from the readable stream.
     * @returns {Promise<this>}
     */
    async updateFromStream(stream) {
        for await (const chunk of stream) {
            this.update(chunk);
        }
        return this;
    }
}
export default Adler32;