function sha1 (str) {
  //  discuss at: http://locutus.io/php/sha1/
  // original by: Webtoolkit.info (http://www.webtoolkit.info/)
  // improved by: Michael White (http://getsprink.com)
  // improved by: Kevin van Zonneveld (http://kvz.io)
  //    input by: Brett Zamir (http://brett-zamir.me)
  //      note 1: Keep in mind that in accordance with PHP, the whole string is buffered and then
  //      note 1: hashed. If available, we'd recommend using Node's native crypto modules directly
  //      note 1: in a steaming fashion for faster and more efficient hashing
  //   example 1: sha1('Kevin van Zonneveld')
  //   returns 1: '54916d2e62f65b3afa6e192e6a601cdbe5cb5897'
  var hash
  try {
    var crypto = require('crypto')
    var sha1sum = crypto.createHash('sha1')
    sha1sum.update(str)
    hash = sha1sum.digest('hex')
  } catch (e) {
    hash = undefined
  }
  if (hash !== undefined) {
    return hash
  }
  var _rotLeft = function (n, s) {
    var t4 = (n << s) | (n >>> (32 - s))
    return t4
  }
  var _cvtHex = function (val) {
    var str = ''
    var i
    var v
    for (i = 7; i >= 0; i--) {
      v = (val >>> (i * 4)) & 0x0f
      str += v.toString(16)
    }
    return str
  }
  var blockstart
  var i, j
  var W = new Array(80)
  var H0 = 0x67452301
  var H1 = 0xEFCDAB89
  var H2 = 0x98BADCFE
  var H3 = 0x10325476
  var H4 = 0xC3D2E1F0
  var A, B, C, D, E
  var temp
  // utf8_encode
  str = unescape(encodeURIComponent(str))
  var strLen = str.length
  var wordArray = []
  for (i = 0; i < strLen - 3; i += 4) {
    j = str.charCodeAt(i) << 24 |
      str.charCodeAt(i + 1) << 16 |
      str.charCodeAt(i + 2) << 8 |
      str.charCodeAt(i + 3)
    wordArray.push(j)
  }
  switch (strLen % 4) {
    case 0:
      i = 0x080000000
      break
    case 1:
      i = str.charCodeAt(strLen - 1) << 24 | 0x0800000
      break
    case 2:
      i = str.charCodeAt(strLen - 2) << 24 | str.charCodeAt(strLen - 1) << 16 | 0x08000
      break
    case 3:
      i = str.charCodeAt(strLen - 3) << 24 |
        str.charCodeAt(strLen - 2) << 16 |
        str.charCodeAt(strLen - 1) <<
      8 | 0x80
      break
  }
  wordArray.push(i)
  while ((wordArray.length % 16) !== 14) {
    wordArray.push(0)
  }
  wordArray.push(strLen >>> 29)
  wordArray.push((strLen << 3) & 0x0ffffffff)
  for (blockstart = 0; blockstart < wordArray.length; blockstart += 16) {
    for (i = 0; i < 16; i++) {
      W[i] = wordArray[blockstart + i]
    }
    for (i = 16; i <= 79; i++) {
      W[i] = _rotLeft(W[i - 3] ^ W[i - 8] ^ W[i - 14] ^ W[i - 16], 1)
    }
    A = H0
    B = H1
    C = H2
    D = H3
    E = H4
    for (i = 0; i <= 19; i++) {
      temp = (_rotLeft(A, 5) + ((B & C) | (~B & D)) + E + W[i] + 0x5A827999) & 0x0ffffffff
      E = D
      D = C
      C = _rotLeft(B, 30)
      B = A
      A = temp
    }
    for (i = 20; i <= 39; i++) {
      temp = (_rotLeft(A, 5) + (B ^ C ^ D) + E + W[i] + 0x6ED9EBA1) & 0x0ffffffff
      E = D
      D = C
      C = _rotLeft(B, 30)
      B = A
      A = temp
    }
    for (i = 40; i <= 59; i++) {
      temp = (_rotLeft(A, 5) + ((B & C) | (B & D) | (C & D)) + E + W[i] + 0x8F1BBCDC) & 0x0ffffffff
      E = D
      D = C
      C = _rotLeft(B, 30)
      B = A
      A = temp
    }
    for (i = 60; i <= 79; i++) {
      temp = (_rotLeft(A, 5) + (B ^ C ^ D) + E + W[i] + 0xCA62C1D6) & 0x0ffffffff
      E = D
      D = C
      C = _rotLeft(B, 30)
      B = A
      A = temp
    }
    H0 = (H0 + A) & 0x0ffffffff
    H1 = (H1 + B) & 0x0ffffffff
    H2 = (H2 + C) & 0x0ffffffff
    H3 = (H3 + D) & 0x0ffffffff
    H4 = (H4 + E) & 0x0ffffffff
  }
  temp = _cvtHex(H0) + _cvtHex(H1) + _cvtHex(H2) + _cvtHex(H3) + _cvtHex(H4)
  return temp.toLowerCase()
}