工作需要，想弄一个加密的串，就想仿照base64的编码方式，写一个加密的方法，所以就有了下面这个用php实现的base64的代码
<?php
/**
* Base64 编码/解码
* @author liruixing
*/
class Base64{
private $_base64hash = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'; /*这是Base64编码使用的标准字典*/
private $_DecodeTable = array( /* 这是php源码中使用的解码表,包含了256个字符对应的编码 */
-2, -2, -2, -2, -2, -2, -2, -2, -2, -1, -1, -2, -2, -1, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-1, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, 62, -2, -2, -2, 63,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -2, -2, -2, -2, -2, -2,
-2, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -2, -2, -2, -2, -2,
-2, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2
);
private $_encode_data = 0xfc0000;
private $_debug = false;
private $_encode_result = '';
public function encode($str) {
$len = strlen($str);
$num = 0;
$bin = 0;
$arr = array();
if($len >= 3) {
for($i=0;$i<$len;$i++) {
$bin = $bin << 8;
if($this->_debug) {
echo '$bin = ',decbin($bin),"\n";
echo 'binary = ', decbin(ord($str[$i])),"\n";
}
$bin = $bin | ord($str{$i});
if(($i+1)%3 == 0) {
$this->_encode_func($bin,3);
$bin = 0;
}
}
}
if($len%3 == 1) {
$bin = ord($str[$len-1]);
$bin = $bin << 4;
$this->_encode_func($bin,1);
$this->_encode_result .= '==';
} else if($len%3 == 2) {
$bin = ord($str[$len-2]);
$bin = $bin << 8;
$bin = $bin | ord($str[$len-1]);
$bin = $bin << 2;
$this->_encode_func($bin,2);
$this->_encode_result .= '=';
}
return $this->_encode_result;
}
private function _encode_func($bin,$bytes = 3) {
$num = 3;
$matches = 0;
$bits1 = ($num - $bytes) * 6;
$bits2 = $bytes * 6;
$matches = $this->_encode_data >> $bits1;
while( $matches ) {
$result = $bin & $matches;
$result = $result >> $bits2;
$bytes--;
$bits1 = ($num - $bytes) * 6;
$bits2 = $bytes * 6;
$matches = $this->_encode_data >> $bits1;
if($this->_debug) {
echo '$result = ',$result,' binary = ',decbin($result),"\n";
}
$this->_encode_result .= $this->_base64hash[$result];
}
}
public function decode($str) {
$bin = 0;
$length = strlen($str)-1;
$_decode_result = '';
$len = 0;
$i = 0;
while( ($len <= $length) ) {
$ch = $str[$len++];
if ($ch == '=') { // 当前一个字符是“=”号
/*
先说明一个概念：在解码时，4个字符为一组进行一轮字符匹配。
如果某一轮匹配的第二个是“=”且第三个字符不是“=”，说明这个带解析字符串不合法，直接返回空
*/
if ($str[$len] != '=' && (($i % 4) == 1)) {
return NULL;
}
continue;
}
$ch = $this->_DecodeTable[ord($ch)];
// 下面这连个条件，只有 ch < 0 会起作用，ch == -2 永远不会起作用，即所有不合法的字符均跳过。
if ($ch < 0 || $ch == -1) { /* a space or some other separator character, we simply skip over */
continue;
} else if ($ch == -2) {
return NULL;
}
switch($i % 4) {
case 0:
$bin = intval($ch) << 2;
break;
case 1:
$bin = intval($bin) | intval($ch) >> 4;
$_decode_result .= chr($bin);
$bin = ( intval($ch) & 0x0f ) << 4;
break;
case 2:
$bin = intval($bin) | intval($ch) >> 2;
$_decode_result .= chr($bin);
$bin = ( intval($ch) & 0x03 ) << 6;
break;
case 3:
$bin = intval($bin) | intval($ch);
$_decode_result .= chr($bin);
break;
}
$i++;
}
return $_decode_result;
}
public function debug($open = true) {
$this->_debug = $open;
}
}
上面有一个简单的debug开关，是刚开始写代码时自己调试用的，感觉还不错，就当是做个记录吧。
参考：