在编码转错的情况下,如何恢复
编码问题的确非常的棘手。很多时候,你一不小心,在某个阶段没有正确的转码,结果造成存储下来的文件 或者 保存进入数据库的字段是乱码。如果这个字段是非常重要的信息,你可能认为,你已经无法恢复这些信息了,其实,在大多数情况下面这个是能够恢复的,你要分析你转码的每个过程,确定出差错的位置,然后进行这个编码的逆转。
这里我只举一个我实际中遇到的一个例子。这个例子的情况是这样的,我在cookie里面保存了一个username字段,写cookie是通过PHP程序写的,这个PHP程序的编码是gbk的。另外一个统计系统,这个统计系统,通过Javascript 读取cookie信息,然后通过url编码这些信息,发送到服务器端。这个统计的服务器的编码是utf-8的。
我在设计这个系统的时候,username是英文或者数字,但是运行了一段时间以后,那个PHP网站变了,允许中文字符了,但是我这边的统计系统并不知道,这样可想而知,保存进入数据库的是一堆乱码。
因为用户名是一个用户的唯一标志,这个字段要是丢失,后果非常的严重。 如何把这段乱码恢复过来呢?
首先你要分析整个过程:
1. PHP写cookie,不会进行转换编码,但是会对字符进行urlencode。
2. Javascript 读取cookie的内容,进行urldecode,保存进入一个字符串
3. 调用Javascript urlencode函数,这个函数有问题,他默认认为Javascript 的 编码是本地Unicode的。
并转换成utf-8 。顺便提一句,比如你的页面是gbk的,但是 a = "变量值" a内部保存是Unicode的,不再是gbk。浏览器会进行编码转换。
4. 服务器端把这个字符串转码,然后保存进入数据库。
可以发现,实际上出错的地方就是Javascript 认为cookie读到的字符串是本地Unicode的。而实际上是一个gbk编码的字符串。
这样只要倒过来就可以了:读出数据库字符串的内容,把utf-8的代码转成Unicode,这个转过后的Unicode 就是原来的 gbk编码的序列。
下面附上一段源代码。为了查看字符串内部字节的排列,我把序列都用urlencode过。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
$name = "王志文"; //著名电影明星
$urlencode_name = "%CD%F5%D6%BE%CE%C4";
//存在数据库中的字节序列
$db_name = "脥玫脰戮脦脛";
$urlencode_dnname = "%C3%8D%C3%B5%C3%96%C2%BE%C3%8E%C3%84";
$unicode = utf8_to_unicode(urldecode($urlencode_dnname));
$decodename = "";
foreach ($unicode as $code)
{
$decodename .= chr($code);
}
echo $decodename;
function utf8_to_unicode($str)
{
$mState = 0; // cached expected number of octets after the current octet
// until the beginning of the next UTF8 character sequence
$mUcs4 = 0; // cached Unicode character
$mBytes = 1; // cached expected number of octets in the current sequence
$out = array();
$len = strlen($str);
for($i = 0; $i < $len; $i++) {
$in = ord($str{$i});
if ( $mState == 0) {
// When mState is zero we expect either a US-ASCII character or a
// multi-octet sequence.
if (0 == (0x80 & ($in))) {
// US-ASCII, pass straight through.
$out[] = $in;
$mBytes = 1;
} else if (0xC0 == (0xE0 & ($in))) {
// First octet of 2 octet sequence
$mUcs4 = ($in);
$mUcs4 = ($mUcs4 & 0x1F) << 6;
$mState = 1;
$mBytes = 2;
} else if (0xE0 == (0xF0 & ($in))) {
// First octet of 3 octet sequence
$mUcs4 = ($in);
$mUcs4 = ($mUcs4 & 0x0F) << 12;
$mState = 2;
$mBytes = 3;
} else if (0xF0 == (0xF8 & ($in))) {
// First octet of 4 octet sequence
$mUcs4 = ($in);
$mUcs4 = ($mUcs4 & 0x07) << 18;
$mState = 3;
$mBytes = 4;
} else if (0xF8 == (0xFC & ($in))) {
/* First octet of 5 octet sequence.
*
* This is illegal because the encoded codepoint must be either
* (a) not the shortest form or
* (b) outside the Unicode range of 0-0x10FFFF.
* Rather than trying to resynchronize, we will carry on until the end
* of the sequence and let the later error handling code catch it.
*/
$mUcs4 = ($in);
$mUcs4 = ($mUcs4 & 0x03) << 24;
$mState = 4;
$mBytes = 5;
} else if (0xFC == (0xFE & ($in))) {
// First octet of 6 octet sequence, see comments for 5 octet sequence.
$mUcs4 = ($in);
$mUcs4 = ($mUcs4 & 1) << 30;
$mState = 5;
$mBytes = 6;
} else {
/* Current octet is neither in the US-ASCII range nor a legal first
* octet of a multi-octet sequence.
*/
trigger_error(
'utf8_to_unicode: Illegal sequence identifier '.
'in UTF-8 at byte '.$i,
E_USER_WARNING
);
return FALSE;
}
} else {
// When mState is non-zero, we expect a continuation of the multi-octet
// sequence
if (0x80 == (0xC0 & ($in))) {
// Legal continuation.
$shift = ($mState - 1) * 6;
$tmp = $in;
$tmp = ($tmp & 0x0000003F) << $shift;
$mUcs4 |= $tmp;
/**
* End of the multi-octet sequence. mUcs4 now contains the final
* Unicode codepoint to be output
*/
if (0 == --$mState) {
/*
* Check for illegal sequences and codepoints.
*/
// From Unicode 3.1, non-shortest form is illegal
if (((2 == $mBytes) && ($mUcs4 < 0x0080)) ||
((3 == $mBytes) && ($mUcs4 < 0x0800)) ||
((4 == $mBytes) && ($mUcs4 < 0x10000)) ||
(4 < $mBytes) ||
// From Unicode 3.2, surrogate characters are illegal
(($mUcs4 & 0xFFFFF800) == 0xD800) ||
// Codepoints outside the Unicode range are illegal
($mUcs4 > 0x10FFFF)) {
trigger_error(
'utf8_to_unicode: Illegal sequence or codepoint '.
'in UTF-8 at byte '.$i,
E_USER_WARNING
);
return FALSE;
}
if (0xFEFF != $mUcs4) {
// BOM is legal but we don't want to output it
$out[] = $mUcs4;
}
//initialize UTF8 cache
$mState = 0;
$mUcs4 = 0;
$mBytes = 1;
}
} else {
/**
*((0xC0 & (*in) != 0x80) && (mState != 0))
* Incomplete multi-octet sequence.
*/
trigger_error(
'utf8_to_unicode: Incomplete multi-octet '.
' sequence in UTF-8 at byte '.$i,
E_USER_WARNING
);
return FALSE;
}
}
}
return $out;
}
关于 utf8 和 Unicode 序列转换规则 你可以google。PHP里面不支持本地Unicode。也没有提供相关的函数。