Unicode與UTF-8編碼轉(zhuǎn)換（一）
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Unicode是一個符號集合，規(guī)定了符號的二進制代碼，而UTF-8是Unicode的一種實現(xiàn)，具體Unicode和UTF-8的聯(lián)系如下所示：
Unicode符號范圍 UTF-8編碼規(guī)則 1 | 0000 0000 - 0000 007F | 0xxxxxxx 2 | 0000 0080 - 0000 07FF | 110xxxxx 10xxxxxx 3 | 0000 0800 - 0000 FFFF | 1110xxxx 10xxxxxx 10xxxxxx 4 | 0001 0000 - 0010 FFFF | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx 5 | 0020 0000 - 03FF FFFF | 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 6 | 0400 0000 - 7FFF FFFF | 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
由圖可清晰的知道Unicode和UTF－8間的聯(lián)系。其中UTF-8編碼規(guī)則中的x就是讓你編碼的地方。接下來逐一舉例說明各段的編碼：
1，范圍0x00-0x7F：給定的用例Unicode碼為0x41，對應的二進制位：0100 0001，而UTF-8編碼規(guī)則為：0xxxxxxx。故有：
0xxx xxxx
+ 100 0001
0100 0001
所以Unicode編碼0x41轉(zhuǎn)換為UTF-8后為：0x41。
所以對于區(qū)間段0x00-0x7F之間的Unicode和UTF-8編碼是一致的。即與ASCII碼一致（ASCII共規(guī)定了128個字符的編碼）
2，范圍0x80-0x7FF：給定的用例Unicode碼為0x123，對應的二進制為：0001 0010 0011，而UTF-8編碼規(guī)則為：110xxxxx 10xxxxxx。故有：
110x xxxx 10xx xxxx
+ 0 0100 10 0011
1100 0100 1010 0011
所以Unicode編碼0x123轉(zhuǎn)換為UTF-8后為：0xC4A3
3，范圍0x800-0xFFFF：給定的用例Unicode碼為0x4E25，對應的二進制為：0100 1110 0010 0101，而UTF－8編碼規(guī)則為：1110xxxx 10xxxxxx 10xxxxxx，故有：
1110 xxxx 10xx xxxx 10xx xxxx
+ 0100 11 1000 10 0101
1110 0100 1011 1000 1010 0101
所以Unicode編碼為0x4E25轉(zhuǎn)換為UTF－8后為：0xE4B8A5
4，范圍0x10000-0x10FFFF：給定的Unicode碼為0x23456，對應的二進制為：0010 0011 0100 0101 0110，而UTF-8編碼規(guī)則為：111100xx 10xxxxxx 10xxxxxx 10xxxxxx。故有：
1111 00xx 10xx xxxx 10xx xxxx 10xx xxxx
＋ 00 10 0011 01 0001 01 0110
1111 0000 1010 0011 1001 0001 1001 0110
所以Unicode編碼為0x23456轉(zhuǎn)換UTF－8后為：0xF0A39196
5，范圍0x200000-0x3FFFFFF：給定的Unicode碼為0x234567，對應的二進制為：0010 0011 0100 0101 0110 0111，UTF-8編碼規(guī)則為：111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx。故有：
1111 10xx 10xx xxxx 10xx xxxx 10xx xxxx 10xx xxxx
+ 00 1000 11 0100 01 0101 10 0111
1111 1000 1000 1000 1011 0100 1001 0101 1010 0111
所以Unicode編碼為0x234567轉(zhuǎn)換UTF－8后為：0xF888B495A7
6，范圍0x4000000-0x7FFFFFFF：給定的Unicode碼為0x34561234，對應的二進制為：0011 0100 0101 0110 0001 0010 0011 0100，UTF－8編碼規(guī)則為：1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx。故有：
1111 110x 10xx xxxx 10xx xxxx 10xx xxxx 10xx xxxx 10xx xxxx
+ 0 11 0100 01 0101 10 0001 00 1000 11 0100
1111 1100 1011 0100 1001 0101 1010 0001 1000 1000 1011 0100
所以Unicode編碼為0x34561234轉(zhuǎn)換UTF－8后為：0xFCB495A188B4
1，通過以上案例分析可得如下單字符Unicode編碼轉(zhuǎn)UTF-8程序為：
1）由于本系統(tǒng)采用大頭方式（Big endian），所以先打出來的是高位的值。
2）實現(xiàn)思路：移動指定的位數(shù)是該字節(jié)處于易于操作的位置或使操作完的值達到指定位置，使用與運算取得指定位上的值，使用或運算實現(xiàn)相加效果。
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int
unicode_to_utf( unsigned long unicode, unsigned char *utf )
{
assert( utf );
int size = 0;
if ( unicode <= 0x7F )
{
*( utf + size++ ) = unicode & 0x7F;
}
else if ( unicode >= 0x80 && unicode <= 0x7FF )
{
*( utf + size++ ) = ( ( unicode >> 6 ) & 0x1F ) | 0xC0;
*( utf + size++ ) = ( unicode & 0x3F ) | 0x80;
}
else if ( unicode >= 0x800 && unicode <= 0xFFFF )
{
*( utf + size++ ) = ( ( unicode >> 12 ) & 0x0F ) | 0xE0;
*( utf + size++ ) = ( ( unicode >> 6 ) & 0x3F ) | 0x80;
*( utf + size++ ) = ( unicode & 0x3F ) | 0x80;
}
else if ( unicode >= 0x10000 && unicode <= 0x10FFFF )
{
*( utf + size++ ) = ( (unicode >> 18 ) & 0x7 ) | 0xF0;
*( utf + size++ ) = ( (unicode >> 12 ) & 0x3F ) | 0x80;
*( utf + size++ ) = ( (unicode >> 6 ) & 0x3F ) | 0x80;
*( utf + size++ ) = ( unicode & 0x3F ) | 0x80;
}
else if ( unicode >= 0x200000 && unicode <= 0x3FFFFFF )
{
*( utf + size++ ) = ( (unicode >> 24 ) & 0x3 ) | 0xF8;
*( utf + size++ ) = ( (unicode >> 18 ) & 0x3F ) | 0x80;
*( utf + size++ ) = ( (unicode >> 12 ) & 0x3F ) | 0x80;
*( utf + size++ ) = ( (unicode >> 6 ) & 0x3F ) | 0x80;
*( utf + size++ ) = ( unicode & 0x3F ) | 0x80;
}
else if ( unicode >= 0x4000000 && unicode <= 0x7FFFFFFF )
{
*( utf + size++ ) = ( (unicode >> 30 ) & 0x1 ) | 0xFC;
*( utf + size++ ) = ( (unicode >> 24 ) & 0x3F ) | 0x80;
*( utf + size++ ) = ( (unicode >> 18 ) & 0x3F ) | 0x80;
*( utf + size++ ) = ( (unicode >> 12 ) & 0x3F ) | 0x80;
*( utf + size++ ) = ( (unicode >> 6 ) & 0x3F ) | 0x80;
*( utf + size++ ) = ( unicode & 0x3F ) | 0x80;
}
else
{
printf( "Error : unknow scope\n" );
return -1;
}
*( utf + size ) = '\0';
return size;
}測試用例如下：
int
main( int argc, char *argv[] )
{
unsigned long unicode1 = 0x55;
unsigned char utf[7] = { 0 };
int size = unicode_to_utf( unicode1, utf );
utf_print( utf, size );
unsigned long unicode2 = 0x123;
size = unicode_to_utf( unicode2, utf );
utf_print( utf, size );
memset( utf, 0x00, sizeof( utf ) );
unsigned long unicode3 = 0x4E25;
size = unicode_to_utf( unicode3, utf );
utf_print( utf, size );
memset( utf, 0x00, sizeof( utf ) );
unsigned long unicode4 = 0x23456;
size = unicode_to_utf( unicode4, utf );
utf_print( utf, size );
memset( utf, 0x00, sizeof( utf ) );
unsigned long unicode5 = 0x234567;
size = unicode_to_utf( unicode5, utf );
utf_print( utf, size );
memset( utf, 0x00, sizeof( utf ) );
unsigned long unicode6 = 0x34561234;
size = unicode_to_utf( unicode6, utf );
utf_print( utf, size );
/* error */
memset( utf, 0x00, sizeof( utf ) );
unsigned long unicode7 = 0x8FFFFFFF;
size = unicode_to_utf( unicode7, utf );
utf_print( utf, size );
return 0;
}打印函數(shù)如下：
void
utf_print( unsigned char *utf, int size )
{
if ( size == -1 )
{
printf( "unknow scope\n" );
return;
}
int index = 0;
for ( ; index < size; index += 1 )
{
printf( "%X", *( utf + index) );
}
printf( "\n" );
}2，單字符UTF-8編碼轉(zhuǎn)Unicode編碼：
int
utf_to_unicode( unsigned long utf, unsigned char *unicode )
{
int size = 0;
if ( utf <= 0x7F )
{
*( unicode + size++ ) = utf & 0x7F;
}
else if ( utf >= 0xC080 && utf <= 0xCFBF )
{
*( unicode + size++ ) = ( ( utf >> 10 ) & 0x07 );
*( unicode + size++ ) = ( utf & 0x3F ) | ( ( ( utf >> 8 ) & 0x03 ) << 6);
}
else if ( utf >= 0xE08080 && utf <= 0xEFBFBF )
{
*( unicode + size++ ) = ( ( utf >> 10 ) & 0x0F ) | (( utf >> 16 ) & 0x0F ) << 4;
*( unicode + size++ ) = ( utf & 0x3F ) | ((( utf >> 8 ) & 0x03 ) << 6 );
}
else if ( utf >= 0xF0808080 && utf <= 0xF7BFBFBF )
{
*( unicode + size++ ) = ( (utf >> 20 ) & 0x03 ) | ((( utf >> 24 ) & 0x07 ) << 2 );
*( unicode + size++ ) = (( utf >> 10 ) & 0x0F ) | ( ( ( utf >> 16 ) & 0x0F ) << 4 );
*( unicode + size++ ) = ( utf & 0x3F ) | ( ( utf >> 8 ) & 0x03 ) << 6;
}
else if ( utf >= 0xF880808080 && utf <= 0xFBBFBFBFBF )
{
*( unicode + size++ ) = ( utf >> 32 ) & 0x03;
*( unicode + size++ ) = ( ( utf >> 20 ) & 0x03 ) | ( ( ( utf >> 24 ) & 0x3F ) << 2 );
*( unicode + size++ ) = ( ( utf >> 10 ) & 0x0F ) | ( ( ( utf >> 16 ) & 0x0F ) << 4 );
*( unicode + size++ ) = ( utf & 0x3F ) | ( ( (utf >> 8) & 0x03 ) << 6 );
}
else if ( utf >= 0xFC8080808080 && utf <= 0xFDBFBFBFBFBF )
{
*( unicode + size++ ) = ( ( utf >> 32 ) & 0x3F ) | ( ( ( utf >> 40 ) & 0x01 ) << 6 );
*( unicode + size++ ) = ( ( utf >> 20 ) & 0x03 ) | ( ( ( utf >> 24 ) & 0x3F ) << 2 );
*( unicode + size++ ) = ( ( utf >> 10 ) & 0x0F ) | ( ( ( utf >> 16 ) & 0x0F ) << 4 );
*( unicode + size++ ) = ( utf & 0x3F ) | ( ( ( utf >> 8 ) & 0x03 ) << 6 );
}
else
{
printf( "Error : unknow scope\n" );
return -1;
}
*( unicode + size ) = '\0';
return size;
}測試用例：
int
main( int argc, char *argv[] )
{
unsigned char unicode[9];
int size = 0;
memset( unicode, 0x00, sizeof( unicode ) );
unsigned long utf1 = 0x55;
size = utf_to_unicode( utf1, unicode );
unicode_print( unicode, size );
memset( unicode, 0x00, sizeof( unicode ) );
unsigned long utf2 = 0xC480;
size = utf_to_unicode( utf2, unicode );
unicode_print( unicode, size );
memset( unicode, 0x00, sizeof( unicode ) );
unsigned long utf3 = 0xE4B8A5;
size = utf_to_unicode( utf3, unicode );
unicode_print( unicode, size);
memset( unicode, 0x00, sizeof( unicode ) );
unsigned long utf4 = 0xF0A39196;
size = utf_to_unicode( utf4, unicode );
unicode_print( unicode, size);
memset( unicode, 0x00, sizeof( unicode ) );
unsigned long utf5 = 0xF888B495A7;
size = utf_to_unicode( utf5, unicode );
unicode_print( unicode, size);
memset( unicode, 0x00, sizeof( unicode ) );
unsigned long utf6 = 0xFCB495A188B4;
size = utf_to_unicode( utf6, unicode );
unicode_print( unicode, size);
memset( unicode, 0x00, sizeof( unicode ) );
unsigned long utf7 = 0xFEBFBFBFBFBF;
size = utf_to_unicode( utf7, unicode );
unicode_print( unicode, size);
return 0;
}打印函數(shù)如下：
void
unicode_print( unsigned char *unicode, int size )
{
if ( size == -1 )
{
printf("Error : unknow scope\n");
return;
}
int index = 0;
for ( ; index < size; index += 1 )
{
printf( "%02X", *( unicode + index ) );
}
printf("\n");
}本文參考文獻：http://www.ruanyifeng.com/blog/2007/10/ascii_unicode_and_utf-8.html
