sha1.ts

import { HashAlgorithm } from "./hash.ts";

/*
 * Calculate the SHA-1 of an array of big-endian words, and a bit length
 */
function binb_sha1(x: number[], len: number): number[] {
  /* append padding */
  x[len >> 5] |= 0x80 << (24 - (len % 32));
  x[(((len + 64) >> 9) << 4) + 15] = len;

  const w: number[] = [];
  let a = 1732584193;
  let b = -271733879;
  let c = -1732584194;
  let d = 271733878;
  let e = -1009589776;

  for (let i = 0; i < x.length; i += 16) {
    const olda = a;
    const oldb = b;
    const oldc = c;
    const oldd = d;
    const olde = e;

    for (let j = 0; j < 80; j++) {
      if (j < 16) w[j] = x[i + j];
      else w[j] = bit_rol(w[j - 3] ^ w[j - 8] ^ w[j - 14] ^ w[j - 16], 1);
      var t = safe_add(
        safe_add(bit_rol(a, 5), sha1_ft(j, b, c, d)),
        safe_add(safe_add(e, w[j]), sha1_kt(j)),
      );
      e = d;
      d = c;
      c = bit_rol(b, 30);
      b = a;
      a = t;
    }

    a = safe_add(a, olda);
    b = safe_add(b, oldb);
    c = safe_add(c, oldc);
    d = safe_add(d, oldd);
    e = safe_add(e, olde);
  }
  return [a, b, c, d, e];
}

/*
 * Perform the appropriate triplet combination function for the current
 * iteration
 */
function sha1_ft(t: number, b: number, c: number, d: number): number {
  if (t < 20) return (b & c) | (~b & d);
  if (t < 40) return b ^ c ^ d;
  if (t < 60) return (b & c) | (b & d) | (c & d);
  return b ^ c ^ d;
}

/*
 * Determine the appropriate additive constant for the current iteration
 */
function sha1_kt(t: number): number {
  return t < 20
    ? 1518500249
    : t < 40
    ? 1859775393
    : t < 60
    ? -1894007588
    : -899497514;
}

/*
 * Add integers, wrapping at 2^32. This uses 16-bit operations internally
 * to work around bugs in some JS interpreters.
 */
function safe_add(x: number, y: number): number {
  const lsw = (x & 0xffff) + (y & 0xffff);
  const msw = (x >> 16) + (y >> 16) + (lsw >> 16);
  return (msw << 16) | (lsw & 0xffff);
}

/*
 * Bitwise rotate a 32-bit number to the left.
 */
function bit_rol(num: number, cnt: number): number {
  return (num << cnt) | (num >>> (32 - cnt));
}

export class Sha1Hash implements HashAlgorithm {
  digest(bytes: Uint8Array): Uint8Array {
    let data: number[] = [];
    for (var i = 0; i < bytes.length * 8; i += 8) {
      data[i >> 5] |= (bytes[i / 8] & 0xff) << (24 - (i % 32));
    }
    data = binb_sha1(data, bytes.length * 8);
    return this.toStrBytes(data);
  }

  /*
   * Convert an array of big-endian words to a string
   */
  private toStrBytes(input: number[]): Uint8Array {
    let pos = 0;
    const data = new Uint8Array(input.length * 4);
    for (let i = 0; i < input.length * 32; i += 8) {
      data[pos++] = (input[i >> 5] >> (24 - (i % 32))) & 0xff;
    }
    return data;
  }
}