<?php
  /*
  * Copyright (C) 2006 Hieu Tran Dang (lt2hieu2004)
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
  * Free Software Foundation; either version 2 of the License, or (at your option)
  * any later version.
  *
  * This program is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License along with
  * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
  * Place, Suite 330, Boston, MA 02111-1307 USA
  */
  
  class Hash
  {
    function sha256($msg)
    {
      $msg = Hash::utf8Encode($msg);
      $msg.= chr(128);
      
      $l = ceil(strlen($msg) / 4) + 2;
      $N = ceil($l / 16);
      $M = array();
      
      for ($i = 0; $i < $N; $i++)
      {
        $M[] = array();
        for ($j = 0; $j < 16; $j ++)
        {
          $M[$i][] = (ord(substr($msg, $i * 64 + $j * 4, 1)) << 24) |
                     (ord(substr($msg, $i * 64 + $j * 4 + 1, 1)) << 16) |
                     (ord(substr($msg, $i * 64 + $j * 4 + 2, 1)) << 8) |
                     (ord(substr($msg, $i * 64 + $j * 4 + 3, 1)));
        }
      }
      
      $M[$N-1][14] = Hash::SHR((strlen($msg) - 1) * 8, 32);
      $M[$N-1][15] = ((strlen($msg) - 1) * 8) & 0xffffffff;

      $H = array(
              0x6a09e667, 0xbb67ae85,
              0x3c6ef372, 0xa54ff53a,
              0x510e527f, 0x9b05688c,
              0x1f83d9ab, 0x5be0cd19
   );

      $K = array(
              0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
              0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
              0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
              0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
              0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
              0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
              0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
              0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
   );
      
      $W = array();
      
      for ($i = 0; $i < $N; $i++)
      {
        for ($t = 0; $t < 16; $t++) $W[$t] = $M[$i][$t];
        for ($t = 16; $t < 64; $t++)
          $W[$t] = Hash::sum(Hash::gamma1($W[$t - 2]), $W[$t - 7], Hash::gamma0($W[$t - 15]), $W[$t - 16]);

        $a = $H[0];
        $b = $H[1];
        $c = $H[2];
        $d = $H[3];
        $e = $H[4];
        $f = $H[5];
        $g = $H[6];
        $h = $H[7];

        for ($t = 0; $t < 64; $t++)
        {
          $T1 = Hash::sum($h, Hash::sigma1($e), Hash::Ch($e, $f, $g), $K[$t], $W[$t]);
          $T2 = Hash::sum(Hash::sigma0($a), Hash::Maj($a, $b, $c));
          $h = $g;
          $g = $f;
          $f = $e;
          $e = Hash::sum($d, $T1);
          $d = $c;
          $c = $b;
          $b = $a;
          $a = Hash::sum($T1, $T2);
        }
        
        $H[0] = Hash::sum($a, $H[0]);
        $H[1] = Hash::sum($b, $H[1]);
        $H[2] = Hash::sum($c, $H[2]);
        $H[3] = Hash::sum($d, $H[3]);
        $H[4] = Hash::sum($e, $H[4]);
        $H[5] = Hash::sum($f, $H[5]);
        $H[6] = Hash::sum($g, $H[6]);
        $H[7] = Hash::sum($h, $H[7]);
      }
      
      $hash = "";
      for ($i = 0; $i < 8; $i++)
      {
        $H[$i] = dechex($H[$i]);
        while (strlen($H[$i]) < 8) $H[$i] = '0'.$H[$i];
        $hash.= $H[$i];
      }
      
      return $hash;
    }
    
    function gamma0($x)
    {
      return (Hash::ROTR($x, 7) ^ Hash::ROTR($x, 18) ^ (Hash::SHR($x, 3)));
    }
    
    function gamma1($x)
    {
      return (Hash::ROTR($x, 17) ^ Hash::ROTR($x, 19) ^ (Hash::SHR($x, 10)));
    }

    function sigma0($x)
    {
      return (Hash::ROTR($x, 2) ^ Hash::ROTR($x, 13) ^ Hash::ROTR($x, 22));
    }

    function sigma1($x)
    {
      return (Hash::ROTR($x, 6) ^ Hash::ROTR($x, 11) ^ Hash::ROTR($x, 25));
    }
    
    function Ch($x, $y, $z)
    {
      return (($x & $y) ^ (~$x & $z));
    }
    
    function Maj($x, $y, $z)
    {
      return (($x & $y) ^ ($x & $z) ^ ($y & $z));
    }
    
    function ROTR($x, $n)
    {
      return (Hash::SHR($x, $n) | ($x << (32 - $n)));
    }
    
    function SHR($a, $b)
    {
      return ($a >> $b) & (pow(2, 32 - $b) - 1);
    }
    
    // Hàm được viết bởi Fyed
    function sum()
    {
      $T = 0;
      
      for($x = 0, $y = func_num_args(); $x < $y; $x++)
      {
        $a = func_get_arg($x);
        $c = 0;

        for($i = 0; $i < 32; $i++)
        {
          $j = (($T >> $i) & 1) + (($a >> $i) & 1) + $c;
          $c = ($j >> 1) & 1;
          $j &= 1;
          $T &= ~(1 << $i);
          $T |= $j << $i;
        }
      }

      return $T;
    }
    
    // Dựa trên đoạn code viết bởi Angel Martin & Paul Johnston
    function utf8Encode($msg)
    {
      $utfText = "";
      
      for ($n = 0; $n < strlen($msg); $n++)
      {
        $c = ord(substr($msg, $n, 1));
        
        if ($c < 128)
        {
          $utfText.= chr($c);
        }
        else if (($c > 127) && ($c < 2048))
        {
          $utfText.= chr(($c >> 6) | 192);
          $utfText.= chr(($c & 63) | 128);
        }
        else
        {
          $utfText.= chr(($c >> 12) | 224);
          $utfText.= chr((($c >> 6) & 63) | 128);
          $utfText.= chr(($c & 63) | 128);
        }
      }
      
      return $utfText;
    }
  }
?>