php的encode64編碼類

encode64可以獲得最短的由26個英文大小寫字母數字加上"-_"兩個符號編碼的數據, 這個個字串可以在網絡自由傳輸, 無需考慮被自動轉碼引起的混亂. 缺點: 對于大字串太慢了, 原因不明, 可能PHP腳本本身就是慢, 所以它內置 很多函數, 這些函數如果用腳本來實現是不可忍受的. 而JavaScript就沒這個問題, 腳本的速度快的多.

<?PHP
//encode64編碼可以同時取代encodeURI,encodeURIComponent,endode函數, 因為選取的這些字符都不會被編碼.
class Encode64{
    function code($str) {
        $KEY = 'PaAwO65goUf7IK2vi9-xq8cFTEXLCDY1Hd3tV0ryzjbpN_BlnSs4mGRkQWMZJeuh';
        $a = StrToBytes($str);
        $len = count($a);
        $res = $len % 3;
        $s = "";$i = 2;$v = 0;
        for (; $i < $len; $i += 3) {
            $v = $a[$i - 2] + ($a[$i - 1] << 8) + ($a[$i] << 16);
            $s .= $KEY[$v & 0x3f];
            $s .= $KEY[($v >> 6) & 0x3f];
            $s .= $KEY[($v >> 12) & 0x3f];
            $s .= $KEY[($v >> 18)];
        }
        if ($res == 1) {
            $v = $a[$i - 2];
            $s .= $KEY[$v & 0x3f];
            $s .= $KEY[($v >> 6) & 0x3f];
        } else if ($res == 2) {
            $v = $a[$i - 2] + ($a[$i - 1] << 8);
            $s .= $KEY[$v & 0x3f];
            $s .= $KEY[($v >> 6) & 0x3f];
            $s .= $KEY[($v >> 12) & 0x3f];
        }
        return $s;
    }
    function decode($codeStr) {
        $KEY = 'PaAwO65goUf7IK2vi9-xq8cFTEXLCDY1Hd3tV0ryzjbpN_BlnSs4mGRkQWMZJeuh';
        $dic = array();
        for ($i = 0; $i < 64; $i++) {
            $dic[$KEY[$i]] = $i;
        }
        $len = strlen($codeStr);
        $res = $len % 4;
        $cLen = floor($len/4)*3;
        if($res==2) $clen += 1;
        elseif($res==3) $clen += 2;
        $code = range(0,$clen);
        $i = 3;$v = 0; $j = 0;
        for (; $i < $len; $i += 4) {
            $v = $dic[$codeStr[$i - 3]];
            $v += $dic[$codeStr[$i - 2]] << 6;
            $v += $dic[$codeStr[$i - 1]] << 12;
            $v += $dic[$codeStr[$i]] << 18;
            $code[$j] = $v & 0xff;
            $code[$j+1] = ($v >> 8) & 0xff;
            $code[$j+2] = ($v >> 16) & 0xff;
            $j += 3;
        }
        if ($res == 2) {//正確的字節數肯定是余2或3, 沒有1的情況, 如果出現, 舍棄.
            $v = $dic[$codeStr[$i - 3]];
            $v += $dic[$codeStr[$i - 2]] << 6;
            $code[$j] = $v & 0xff;
        } else if ($res == 3) {
            $v = $dic[$codeStr[$i - 3]];
            $v += $dic[$codeStr[$i - 2]] << 6;
            $v += $dic[$codeStr[$i - 1]] << 12;
            $code[$j] = $v & 0xff;
            $code[$j+1] = ($v >> 8) & 0xff;
        }
        return BytesToStr($code);
    }
}
function BytesToStr($bytes) {
    $str = '';
    foreach($bytes as $ch) {
        $str .= chr($ch);
    }
    return iconv('UTF-16BE','utf-8',$str);
}
function StrToBytes($str) {
    $str = iconv('utf-8','UTF-16BE',$str);
    $len = strlen($str);
    $bytes = array();
    for($i=0;$i<$len;$i++) {
        $bytes[] =  ord($str[$i]) ;
    }
    return $bytes;
}
?>