识别无BOM的UTF8文本得方法

识别无BOM的UTF8文本得方法

/* IsTextUTF8
*
* UTF-8 is the encoding of Unicode based on Internet Society RFC2279
* ( See http://www.cis.ohio-state.edu/htbin/rfc/rfc2279.html )
*
* Basicly:
* 0000 0000-0000 007F - 0xxxxxxx (ascii converts to 1 octet!)
* 0000 0080-0000 07FF - 110xxxxx 10xxxxxx ( 2 octet format)
* 0000 0800-0000 FFFF - 1110xxxx 10xxxxxx 10xxxxxx (3 octet format)
* (this keeps going for 32 bit unicode)
*
*
* Return value: TRUE, if the text is in UTF-8 format.
* FALSE, if the text is not in UTF-8 format.
* We will also return FALSE is it is only 7-bit ascii, so the right code page
* will be used.
*
* Actually for 7 bit ascii, it doesn't matter which code page we use, but
* notepad will remember that it is utf-8 and "save" or "save as" will store
* the file with a UTF-8 BOM. Not cool.
*/

INT IsTextUTF8( LPSTR lpstrInputStream, INT iLen )
{
INT i;
DWORD cOctets; // octets to go in this UTF-8 encoded character
UCHAR chr;
BOOL bAllAscii= TRUE;

cOctets= 0;
for( i=0; i < iLen; i++ ) {
chr= *(lpstrInputStream+i);

if( (chr&0x80) != 0 ) bAllAscii= FALSE;

if( cOctets == 0 ) {
//
// 7 bit ascii after 7 bit ascii is just fine. Handle start of encoding case.
//
if( chr >= 0x80 ) {
//
// count of the leading 1 bits is the number of characters encoded
//
do {
chr <<= 1;
cOctets++;
}
while( (chr&0x80) != 0 );

cOctets--; // count includes this character
if( cOctets == 0 ) return FALSE; // must start with 11xxxxxx
}
}
else {
// non-leading bytes must start as 10xxxxxx
if( (chr&0xC0) != 0x80 ) {
return FALSE;
}
cOctets--; // processed another octet in encoding
}
}

//
// End of text. Check for consistency.
//

if( cOctets > 0 ) { // anything left over at the end is an error
return FALSE;
}

if( bAllAscii ) { // Not utf-8 if all ascii. Forces caller to use code pages for conversion
return FALSE;
}

return TRUE;
}

不过这段代码是有bug的，微软记事本很著名的“联通”的bug也是这段代码引起的，暂时还没找到更好的识别无BOM的UTF8文本的更好的办法