md5加密文件

function safe_add(x, y) {
  var lsw = (x & 0xFFFF) + (y & 0xFFFF)
  var msw = (x >> 16) + (y >> 16) + (lsw >> 16)
  return (msw << 16) | (lsw & 0xFFFF)
}

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

/* 
 * These functions implement the four basic operations the algorithm uses. 
 */
function cmn(q, a, b, x, s, t) {
  return safe_add(rol(safe_add(safe_add(a, q), safe_add(x, t)), s), b)
}
function ff(a, b, c, d, x, s, t) {
  return cmn((b & c) | ((~b) & d), a, b, x, s, t)
}
function gg(a, b, c, d, x, s, t) {
  return cmn((b & d) | (c & (~d)), a, b, x, s, t)
}
function hh(a, b, c, d, x, s, t) {
  return cmn(b ^ c ^ d, a, b, x, s, t)
}
function ii(a, b, c, d, x, s, t) {
  return cmn(c ^ (b | (~d)), a, b, x, s, t)
}

/* 
 * Calculate the MD5 of an array of little-endian words, producing an array 
 * of little-endian words. 
 */
function coreMD5(x) {
  var a = 1732584193
  var b = -271733879
  var c = -1732584194
  var d = 271733878

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

    a = ff(a, b, c, d, x[i + 0], 7, -680876936)
    d = ff(d, a, b, c, x[i + 1], 12, -389564586)
    c = ff(c, d, a, b, x[i + 2], 17, 606105819)
    b = ff(b, c, d, a, x[i + 3], 22, -1044525330)
    a = ff(a, b, c, d, x[i + 4], 7, -176418897)
    d = ff(d, a, b, c, x[i + 5], 12, 1200080426)
    c = ff(c, d, a, b, x[i + 6], 17, -1473231341)
    b = ff(b, c, d, a, x[i + 7], 22, -45705983)
    a = ff(a, b, c, d, x[i + 8], 7, 1770035416)
    d = ff(d, a, b, c, x[i + 9], 12, -1958414417)
    c = ff(c, d, a, b, x[i + 10], 17, -42063)
    b = ff(b, c, d, a, x[i + 11], 22, -1990404162)
    a = ff(a, b, c, d, x[i + 12], 7, 1804603682)
    d = ff(d, a, b, c, x[i + 13], 12, -40341101)
    c = ff(c, d, a, b, x[i + 14], 17, -1502002290)
    b = ff(b, c, d, a, x[i + 15], 22, 1236535329)

    a = gg(a, b, c, d, x[i + 1], 5, -165796510)
    d = gg(d, a, b, c, x[i + 6], 9, -1069501632)
    c = gg(c, d, a, b, x[i + 11], 14, 643717713)
    b = gg(b, c, d, a, x[i + 0], 20, -373897302)
    a = gg(a, b, c, d, x[i + 5], 5, -701558691)
    d = gg(d, a, b, c, x[i + 10], 9, 38016083)
    c = gg(c, d, a, b, x[i + 15], 14, -660478335)
    b = gg(b, c, d, a, x[i + 4], 20, -405537848)
    a = gg(a, b, c, d, x[i + 9], 5, 568446438)
    d = gg(d, a, b, c, x[i + 14], 9, -1019803690)
    c = gg(c, d, a, b, x[i + 3], 14, -187363961)
    b = gg(b, c, d, a, x[i + 8], 20, 1163531501)
    a = gg(a, b, c, d, x[i + 13], 5, -1444681467)
    d = gg(d, a, b, c, x[i + 2], 9, -51403784)
    c = gg(c, d, a, b, x[i + 7], 14, 1735328473)
    b = gg(b, c, d, a, x[i + 12], 20, -1926607734)

    a = hh(a, b, c, d, x[i + 5], 4, -378558)
    d = hh(d, a, b, c, x[i + 8], 11, -2022574463)
    c = hh(c, d, a, b, x[i + 11], 16, 1839030562)
    b = hh(b, c, d, a, x[i + 14], 23, -35309556)
    a = hh(a, b, c, d, x[i + 1], 4, -1530992060)
    d = hh(d, a, b, c, x[i + 4], 11, 1272893353)
    c = hh(c, d, a, b, x[i + 7], 16, -155497632)
    b = hh(b, c, d, a, x[i + 10], 23, -1094730640)
    a = hh(a, b, c, d, x[i + 13], 4, 681279174)
    d = hh(d, a, b, c, x[i + 0], 11, -358537222)
    c = hh(c, d, a, b, x[i + 3], 16, -722521979)
    b = hh(b, c, d, a, x[i + 6], 23, 76029189)
    a = hh(a, b, c, d, x[i + 9], 4, -640364487)
    d = hh(d, a, b, c, x[i + 12], 11, -421815835)
    c = hh(c, d, a, b, x[i + 15], 16, 530742520)
    b = hh(b, c, d, a, x[i + 2], 23, -995338651)

    a = ii(a, b, c, d, x[i + 0], 6, -198630844)
    d = ii(d, a, b, c, x[i + 7], 10, 1126891415)
    c = ii(c, d, a, b, x[i + 14], 15, -1416354905)
    b = ii(b, c, d, a, x[i + 5], 21, -57434055)
    a = ii(a, b, c, d, x[i + 12], 6, 1700485571)
    d = ii(d, a, b, c, x[i + 3], 10, -1894986606)
    c = ii(c, d, a, b, x[i + 10], 15, -1051523)
    b = ii(b, c, d, a, x[i + 1], 21, -2054922799)
    a = ii(a, b, c, d, x[i + 8], 6, 1873313359)
    d = ii(d, a, b, c, x[i + 15], 10, -30611744)
    c = ii(c, d, a, b, x[i + 6], 15, -1560198380)
    b = ii(b, c, d, a, x[i + 13], 21, 1309151649)
    a = ii(a, b, c, d, x[i + 4], 6, -145523070)
    d = ii(d, a, b, c, x[i + 11], 10, -1120210379)
    c = ii(c, d, a, b, x[i + 2], 15, 718787259)
    b = ii(b, c, d, a, x[i + 9], 21, -343485551)

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

/* 
 * Convert an array of little-endian words to a hex string. 
 */
function binl2hex(binarray) {
  var hex_tab = "0123456789abcdef"
  var str = ""
  for (var i = 0; i < binarray.length * 4; i++) {
    str += hex_tab.charAt((binarray[i >> 2] >> ((i % 4) * 8 + 4)) & 0xF) +
      hex_tab.charAt((binarray[i >> 2] >> ((i % 4) * 8)) & 0xF)
  }
  return str
}

/* 
 * Convert an array of little-endian words to a base64 encoded string. 
 */
function binl2b64(binarray) {
  var tab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
  var str = ""
  for (var i = 0; i < binarray.length * 32; i += 6) {
    str += tab.charAt(((binarray[i >> 5] << (i % 32)) & 0x3F) |
      ((binarray[i >> 5 + 1] >> (32 - i % 32)) & 0x3F))
  }
  return str
}

/* 
 * Convert an 8-bit character string to a sequence of 16-word blocks, stored 
 * as an array, and append appropriate padding for MD4/5 calculation. 
 * If any of the characters are >255, the high byte is silently ignored. 
 */
function str2binl(str) {
  var nblk = ((str.length + 8) >> 6) + 1 // number of 16-word blocks  
  var blks = new Array(nblk * 16)
  for (var i = 0; i < nblk * 16; i++) blks[i] = 0
  for (var i = 0; i < str.length; i++)
    blks[i >> 2] |= (str.charCodeAt(i) & 0xFF) << ((i % 4) * 8)
  blks[i >> 2] |= 0x80 << ((i % 4) * 8)
  blks[nblk * 16 - 2] = str.length * 8
  return blks
}

/* 
 * Convert a wide-character string to a sequence of 16-word blocks, stored as 
 * an array, and append appropriate padding for MD4/5 calculation. 
 */
function strw2binl(str) {
  var nblk = ((str.length + 4) >> 5) + 1 // number of 16-word blocks  
  var blks = new Array(nblk * 16)
  for (var i = 0; i < nblk * 16; i++) blks[i] = 0
  for (var i = 0; i < str.length; i++)
    blks[i >> 1] |= str.charCodeAt(i) << ((i % 2) * 16)
  blks[i >> 1] |= 0x80 << ((i % 2) * 16)
  blks[nblk * 16 - 2] = str.length * 16
  return blks
}

/* 
 * External interface 
 */
function hexMD5(str) { return binl2hex(coreMD5(str2binl(str))) }
function hexMD5w(str) { return binl2hex(coreMD5(strw2binl(str))) }
function b64MD5(str) { return binl2b64(coreMD5(str2binl(str))) }
function b64MD5w(str) { return binl2b64(coreMD5(strw2binl(str))) }
/* Backward compatibility */
function calcMD5(str) { return binl2hex(coreMD5(str2binl(str))) }
module.exports = {
  hexMD5: hexMD5
}