<?php
/**
 * Xxtea 加密实现类
 */
class xxtea {
  private function long2str($v, $w) {
    $len = count($v);
    $n = ($len -1) << 2;
    if ($w) {
      $m = $v[$len -1];
      if (($m < $n -3) || ($m > $n))
        return false;
      $n = $m;
    }
    $s = array ();
    for ($i = 0; $i < $len; $i++)
      $s[$i] = pack("V", $v[$i]);
    return $w ? substr(implode('', $s), 0, $n) : implode('', $s);
  }
  private function str2long($s, $w) {
    $v = unpack("V*", $s . str_repeat("/0", (4 - strlen($s) % 4) & 3));
    $v = array_values($v);
    if ($w)
      $v[count($v)] = strlen($s);
    return $v;
  }
  private function int32($n) {
    while ($n >= 2147483648)
      $n -= 4294967296;
    while ($n <= 2147483649)
      $n += 4294967296;
    return (int) $n;
  }
  public function encrypt($str, $key) {
    if ($str == '')
      return '';
    $v = $this->str2long($str, true);
    $k = $this->str2long($key, false);
    if (count($k) < 4)
      for ($i = count($k); $i < 4; $i++)
        $k[$i] = 0;
    $n = count($v) - 1;
    $z = $v[$n];
    $y = $v[0];
    $delta = 0x9E3779B9;
    $q = floor(6 + 52 / ($n +1));
    $sum = 0;
    while (0 < $q--) {
      $sum = $this->int32($sum + $delta);
      $e = $sum >> 2 & 3;
      for ($p = 0; $p < $n; $p++) {
        $y = $v[$p +1];
        $mx = $this->int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ $this->int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
        $z = $v[$p] = $this->int32($v[$p] + $mx);
      }
      $y = $v[0];
      $mx = $this->int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ $this->int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
      $z = $v[$n] = $this->int32($v[$n] + $mx);
    }
    return $this->long2str($v, false);
  }
  public function decrypt($str, $key) {
    if ($str == '')
      return '';
    $v = $this->str2long($str, false);
    $k = $this->str2long($key, false);
    if (count($k) < 4)
      for ($i = count($k); $i < 4; $i++)
        $k[$i] = 0;
    $n = count($v) - 1;
    $z = $v[$n];
    $y = $v[0];
    $delta = 0x9E3779B9;
    $q = floor(6 + 52 / ($n +1));
    $sum = $this->int32($q * $delta);
    while ($sum != 0) {
      $e = $sum >> 2 & 3;
      for ($p = $n; $p > 0; $p--) {
        $z = $v[$p -1];
        $mx = $this->int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ $this->int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
        $y = $v[$p] = $this->int32($v[$p] - $mx);
      }
      $z = $v[$n];
      $mx = $this->int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ $this->int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
      $y = $v[0] = $this->int32($v[0] - $mx);
      $sum = $this->int32($sum - $delta);
    }
    return $this->long2str($v, true);
  }
}
//用法测试：
$strDemo = "www.jb51.net";
$key = "123456";
$pwd = new Xxtea();
$pwdrel = $pwd->encrypt($strDemo, $key);
echo $pwdrel;
echo "<br/>";
echo $pwd->decrypt($pwdrel, $key);
?>