text: // Adapted from Chris Veness' SHA1 code at
  // http://www.movable-type.co.uk/scripts/sha1.html
  'use strict';
  
  function f(s, x, y, z) {
    switch (s) {
      case 0: return (x & y) ^ (~x & z);
      case 1: return x ^ y ^ z;
      case 2: return (x & y) ^ (x & z) ^ (y & z);
      case 3: return x ^ y ^ z;
    }
  }
  
  function ROTL(x, n) {
    return (x << n) | (x>>> (32 - n));
  }
  
  function sha1(bytes) {
    var K = [0x5a827999, 0x6ed9eba1, 0x8f1bbcdc, 0xca62c1d6];
    var H = [0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476, 0xc3d2e1f0];
  
    if (typeof(bytes) == 'string') {
      var msg = unescape(encodeURIComponent(bytes)); // UTF8 escape
      bytes = new Array(msg.length);
      for (var i = 0; i < msg.length; i++) bytes[i] = msg.charCodeAt(i);
    }
  
    bytes.push(0x80);
  
    var l = bytes.length/4 + 2;
    var N = Math.ceil(l/16);
    var M = new Array(N);
  
    for (var i=0; i<N; i++) {
      M[i] = new Array(16);
      for (var j=0; j<16; j++) {
        M[i][j] =
          bytes[i * 64 + j * 4] << 24 |
          bytes[i * 64 + j * 4 + 1] << 16 |
          bytes[i * 64 + j * 4 + 2] << 8 |
          bytes[i * 64 + j * 4 + 3];
      }
    }
  
    M[N - 1][14] = ((bytes.length - 1) * 8) /
      Math.pow(2, 32); M[N - 1][14] = Math.floor(M[N - 1][14]);
    M[N - 1][15] = ((bytes.length - 1) * 8) & 0xffffffff;
  
    for (var i=0; i<N; i++) {
      var W = new Array(80);
  
      for (var t=0; t<16; t++) W[t] = M[i][t];
      for (var t=16; t<80; t++) {
        W[t] = ROTL(W[t - 3] ^ W[t - 8] ^ W[t - 14] ^ W[t - 16], 1);
      }
  
      var a = H[0], b = H[1], c = H[2], d = H[3], e = H[4];
  
      for (var t=0; t<80; t++) {
        var s = Math.floor(t/20);
        var T = ROTL(a, 5) + f(s, b, c, d) + e + K[s] + W[t] >>> 0;
        e = d;
        d = c;
        c = ROTL(b, 30) >>> 0;
        b = a;
        a = T;
      }
  
      H[0] = (H[0] + a) >>> 0;
      H[1] = (H[1] + b) >>> 0;
      H[2] = (H[2] + c) >>> 0;
      H[3] = (H[3] + d) >>> 0;
      H[4] = (H[4] + e) >>> 0;
    }
  
    return [
      H[0] >> 24 & 0xff, H[0] >> 16 & 0xff, H[0] >> 8 & 0xff, H[0] & 0xff,
      H[1] >> 24 & 0xff, H[1] >> 16 & 0xff, H[1] >> 8 & 0xff, H[1] & 0xff,
      H[2] >> 24 & 0xff, H[2] >> 16 & 0xff, H[2] >> 8 & 0xff, H[2] & 0xff,
      H[3] >> 24 & 0xff, H[3] >> 16 & 0xff, H[3] >> 8 & 0xff, H[3] & 0xff,
      H[4] >> 24 & 0xff, H[4] >> 16 & 0xff, H[4] >> 8 & 0xff, H[4] & 0xff
    ];
  }
  
  module.exports = sha1;
  