<?php  
/** 
 * XXTEA encryption arithmetic library. 
 * 
 * Copyright (C) 2006 Ma Bingyao <andot@ujn.edu.cn> 
 * Version:      1.5 
 * LastModified: Dec 5, 2006
 */  
  
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]);  
    }  
    if ($w) {  
        return substr(join('', $s), 0, $n);  
    } else {  
        return join('', $s);  
    }  
}  
  
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;  
}  
  
function int32($n) {  
    while ($n >= 2147483648) $n -= 4294967296;  
    while ($n <= -2147483649) $n += 4294967296;  
    return (int)$n;  
}  
  
function xxtea_encrypt($str, $key) {  
    if ($str == "") {  
        return "";  
    }  
    $v = str2long($str, true);  
    $k = str2long($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--) {  
        $sum = int32($sum + $delta);  
        $e = $sum >> 2 & 3;  
        for ($p = 0; $p < $n; $p++) {  
            $y = $v[$p + 1];  
            $mx = int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));  
            $z = $v[$p] = int32($v[$p] + $mx);  
        }  
        $y = $v[0];  
        $mx = int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));  
        $z = $v[$n] = int32($v[$n] + $mx);  
    }  
    return long2str($v, false);  
}  
  
function xxtea_decrypt($str, $key) {  
    if ($str == "") {  
        return "";  
    }  
    $v = str2long($str, false);  
    $k = str2long($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));  
    $sum = int32($q * $delta);  
    while ($sum != 0) {  
        $e = $sum >> 2 & 3;  
        for ($p = $n; $p > 0; $p--) {  
            $z = $v[$p - 1];  
            $mx = int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));  
            $y = $v[$p] = int32($v[$p] - $mx);  
        }  
        $z = $v[$n];  
        $mx = int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));  
        $y = $v[0] = int32($v[0] - $mx);  
        $sum = int32($sum - $delta);  
    }  
    return long2str($v, true);  
}  