/**//*

 * A JavaScript implementation of the Secure Hash Algorithm, SHA-1, as defined in FIPS PUB 180-1

 * By lizq

 * 2006-11-11

 */

/**//*

 * Configurable variables.

 */

var hexcase = 0;  /**//* hex output format. 0 - lowercase; 1 - uppercase        */

var chrsz   = 8;  /**//* bits per input character. 8 - ASCII; 16 - Unicode      */

 

/**//*

 * The main function to calculate message digest

 */

function hex_sha1(s)

{

       return binb2hex(core_sha1(AlignSHA1(s)));

}

 

 

/**//*

 * Perform a simple self-test to see if the VM is working

 */

function sha1_vm_test()

{

  return hex_sha1("abc") == "a9993e364706816aba3e25717850c26c9cd0d89d";

}

 

 

/**//*

 * Calculate the SHA-1 of an array of big-endian words, and a bit length

 */

function core_sha1(blockArray)

{

  var x = blockArray;  //append padding

 

  var w = Array(80);

  var a =  1732584193;

  var b = -271733879;

  var c = -1732584194;

  var d =  271733878;

  var e = -1009589776;

 

  for(var i = 0; i < x.length; i += 16)  //每次处理512位 16*32

  {

    var olda = a;

    var oldb = b;

    var oldc = c;

    var oldd = d;

    var olde = e;

 

    for(var j = 0; j < 80; j++)  //对每个512位进行80步操作

    {

      if(j < 16) w[j] = x[i + j];

      else w[j] = rol(w[j-3] ^ w[j-8] ^ w[j-14] ^ w[j-16], 1);

      

      var t = safe_add(safe_add(rol(a, 5), sha1_ft(j, b, c, d)),

                       safe_add(safe_add(e, w[j]), sha1_kt(j)));

      e = d;

      d = c;

      c = 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 new Array(a, b, c, d, e);

 

}

 

 

/**//*

 * Perform the appropriate triplet combination function for the current iteration

 * 返回对应F函数的值

 */

function sha1_ft(t, b, c, d)

{

  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;  //t<80

}

 

 

/**//*

 * Determine the appropriate additive constant for the current iteration

 * 返回对应的Kt值

 */

function sha1_kt(t)

{

  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.

 * 将32位数拆成高16位和低16位分别进行相加，从而实现 MOD 2^32 的加法

 */

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.

 * 32位二进制数循环左移

 */

function rol(num, cnt)

{

  return (num << cnt) | (num >>> (32 - cnt));

}

 

 

/**//*

 * The standard SHA1 needs the input string to fit into a block

 * This function align the input string to meet the requirement

 */

function AlignSHA1(str){

  var nblk=((str.length+8)>>6)+1, blks=new Array(nblk*16);

  for(var i=0;i<nblk*16;i++)blks[i]=0;

  for(i=0;i<str.length;i++)

    blks[i>>2]|=str.charCodeAt(i)<<(24-(i&3)*8);

  blks[i>>2]|=0x80<<(24-(i&3)*8);

  blks[nblk*16-1]=str.length*8;

  return blks;

}

 

 

/**//*

 * Convert an array of big-endian words to a hex string.

 */

function binb2hex(binarray)

{

  var hex_tab = hexcase ? "0123456789ABCDEF" : "0123456789abcdef";

  var str = "";

  for(var i = 0; i < binarray.length * 4; i++)

  {

    str += hex_tab.charAt((binarray[i>>2] >> ((3 - i%4)*8+4)) & 0xF) +

           hex_tab.charAt((binarray[i>>2] >> ((3 - i%4)*8  )) & 0xF);

  }

  return str;

}

 

/**//*

 * calculate MessageDigest accord to source message that inputted

 */