Fast CRC32 in JavaScript

crc32.js

/**!
 * Fast CRC32 in JavaScript
 * 101arrowz (https://github.com/101arrowz)
 * License: MIT
 */

// If you use this code, please link this gist or attribute it somehow.

// This code uses the Slice-by-16 algorithm to achieve performance
// roughly 2x greater than all other JS CRC32 implementations (e.g.
// crc32-js).

// Per local testing, Slice-by-16 outperforms Slice-by-4 by around 50%
// and Slice-by-8/Slice-by-32/Slice-by-64 by 10-30%

// This CRC implementation can compete with WASM CRC implementations
// as well, and it tends to perform between 30% faster and 10% slower
// than WASM CRC32 (>1MB input chunks is faster on WASM).

// The minified bundle size is under 1kB, about 700B gzipped.

// CRC32 table
// perf: signed integers are 2x more likely to be Smi
// Smi is a V8 datatype in (-2**30, 2**30-1)
// Smi operations are much faster
const crct = new Int32Array(4096);
for (let i = 0; i < 256; ++i) {
  let c = i, k = 9;
  while (--k) c = ((c & 1) && -306674912) ^ (c >>> 1);
  crct[i] = c;
}
for (let i = 0; i < 256; ++i) {
  let lv = crct[i];
  for (let j = 256; j < 4096; j += 256) lv = crct[i | j] = (lv >>> 8) ^ crct[lv & 255];
}

const crcts = [];

for (let i = 0; i < 16;) crcts[i] = crct.subarray(i << 8, ++i << 8);

const [
  t1, t2, t3, t4, t5, t6, t7, t8,
  t9, t10, t11, t12, t13, t14, t15, t16
] = crcts;

// raw CRC function
// stream by passing in previous CRC output as second parameter
const rawCRC = (d, c) => {
  // when second param not specified, defaults to ~0 = -1
  c = ~c;
  let i = 0;
  const max = d.length - 16;
  for (; i < max;) {
    c =
        t16[d[i++] ^ (c & 255)] ^
        t15[d[i++] ^ ((c >> 8) & 255)] ^
        t14[d[i++] ^ ((c >> 16) & 255)] ^
        t13[d[i++] ^ (c >>> 24)] ^
        t12[d[i++]] ^
        t11[d[i++]] ^
        t10[d[i++]] ^
        t9[d[i++]] ^
        t8[d[i++]] ^
        t7[d[i++]] ^
        t6[d[i++]] ^
        t5[d[i++]] ^
        t4[d[i++]] ^
        t3[d[i++]] ^
        t2[d[i++]] ^
        t1[d[i++]];
  }
  for (; i < d.length; ++i) c = t1[(c & 255) ^ d[i]] ^ (c >>> 8);
  return ~c;
}

// Nicer API here
// Remove this for smaller bundle
class CRC {
  /**
   * Updates the CRC value by processing the buffer provided
   * @param {Uint8Array} buf The buffer of data to process
   * @returns {CRC} The current CRC
   */
  update(buf) {
    if (!(buf instanceof Uint8Array)) {
      throw new TypeError(
        'need a Uint8Array, not' + 
        Object.prototype.toString.call(buf).slice(8, -1)
      );
    }
    this.value = rawCRC(buf, this.value);
    return this;
  }
  /**
   * Returns the current value of the CRC
   * @param {('hex'|'raw')} type The method with which to digest, default hex
   * @returns The CRC value as hex or binary
   */
  digest(type) {
    const value = this.value < 0
      ? 0x1_0000_0000 + this.value
      : this.value;
    if (type == 'raw') {
      return value;
    } else if (type == 'hex' || type == undefined) {
      return value.toString(16);
    } else {
      throw new TypeError(`cannot digest in form ${type}`)
    }
  }
}

// License: MIT (use freely, but please attribute/link this gist)

crc32.min.js

/**!
 * Fast CRC32 in JavaScript
 * 101arrowz (https://github.com/101arrowz)
 * License: MIT
 */
!function(e){"undefined"!=typeof module&&"object"==typeof exports?module.exports=e():"undefined"!=typeof define&&define.amd?define(["CRC",e]):("undefined"!=typeof self?self:this).CRC=e()}((function(){for(var e=new Int32Array(4096),t=0;t<256;++t){for(var r=t,n=9;--n;)r=(1&r&&-306674912)^r>>>1;e[t]=r}for(t=0;t<256;++t)for(var o=e[t],i=256;i<4096;i+=256)o=e[t|i]=o>>>8^e[255&o];var f=[];for(t=0;t<16;)f[t]=e.subarray(t<<8,++t<<8);var a=f[0],u=f[1],d=f[2],l=f[3],s=f[4],p=f[5],c=f[6],y=f[7],h=f[8],v=f[9],g=f[10],w=f[11],m=f[12],C=f[13],b=f[14],x=f[15],A=function(){};return A.prototype.update=function(e){if(!(e instanceof Uint8Array))throw new TypeError("need a Uint8Array, not"+Object.prototype.toString.call(e).slice(8,-1));return this.value=function(e,t){t=~t;for(var r=0,n=e.length-16;r<n;)t=x[e[r++]^255&t]^b[e[r++]^t>>8&255]^C[e[r++]^t>>16&255]^m[e[r++]^t>>>24]^w[e[r++]]^g[e[r++]]^v[e[r++]]^h[e[r++]]^y[e[r++]]^c[e[r++]]^p[e[r++]]^s[e[r++]]^l[e[r++]]^d[e[r++]]^u[e[r++]]^a[e[r++]];for(;r<e.length;++r)t=a[255&t^e[r]]^t>>>8;return~t}(e,this.value),this},A.prototype.digest=function(e){var t=this.value<0?4294967296+this.value:this.value;if("raw"==e)return t;if("hex"==e||null==e)return t.toString(16);throw new TypeError("cannot digest in form "+e)},A}))