etag-hash/esm/index.js

Es6 class that generates ETag using the same algorithm as S3 via MD5 sum.

import { createHash as createCryptoHash } from 'crypto';
export class ETagHash {
    partSizeInBytes;
    sums;
    part;
    bytes;
    constructor(partSizeInMb = 5) {
        this.partSizeInBytes = partSizeInMb * 1024 * 1024;
        this.sums = [createCryptoHash('md5')];
        this.part = 0;
        this.bytes = 0;
    }
    update(chunk) {
        const len = chunk.length;
        if (this.bytes + len < this.partSizeInBytes) {
            this.sums[this.part].update(chunk);
            this.bytes += len;
        }
        else {
            const bytesNeeded = this.partSizeInBytes - this.bytes;
            this.sums[this.part].update(chunk.subarray(0, bytesNeeded));
            this.part++;
            this.sums.push(createCryptoHash('md5'));
            this.bytes = len - bytesNeeded;
            this.sums[this.part].update(chunk.subarray(bytesNeeded));
        }
        return this;
    }
    digest() {
        if (!this.part) {
            return this.sums[0].digest('hex');
        }
        const checksum = this.sums.map((s) => s.digest('hex')).join('');
        const final = createCryptoHash('md5')
            .update(Buffer.from(checksum, 'hex'))
            .digest('hex');
        return `${final}-${this.part + 1}`;
    }
}
export const createHash = (...args) => {
    return new ETagHash(...args);
};