代码片段: Unicode与UTF-8互转

#include <stdint.h>

// Unicode 转 UTF-8
int unicode_to_utf8(uint8_t *utf8Buffer, uint16_t *unicodeBuffer, int unicodeNum, uint8_t flag){
    int utf8Length = 0;
    uint16_t unicode;
    while(unicodeNum-- > 0){
        unicode = *(unicodeBuffer++);
        if(unicode <= 0x007f){
            utf8Buffer[0] = unicode & 0x007f;
            utf8Buffer += 1;
            utf8Length += 1;
        }else if(unicode <= 0x07ff){
            utf8Buffer[0] = 0xc0 | ((unicode>>6) & 0x001f);   //6-10位
            utf8Buffer[1] = 0x80 | (unicode & 0x003f);        //0-5位
            utf8Buffer += 2;
            utf8Length += 2;
        }else{
            utf8Buffer[0] = 0xe0 | ((unicode>>12) & 0x000f);  //12-15位
            utf8Buffer[1] = 0x80 | ((unicode>>6)  & 0x003f);  //6-11位
            utf8Buffer[2] = 0x80 | (unicode & 0x003f);        //0-5位
            utf8Buffer += 3;
            utf8Length += 3;
        }
    }
    if(flag){
        utf8Buffer[0] = 0;
        return utf8Length + 1;
    }else{
        return utf8Length;
    }
}

// UTF-8 转 Unicode
int utf8_to_unicode(uint16_t *unicodeBuffer, uint8_t *utf8Buffer, int utf8Length, uint8_t flag){
    int unicodeNum = 0;
    while(utf8Length > 0){
        if(utf8Buffer[0] < 0xc0){
            unicodeBuffer[unicodeNum++] = utf8Buffer[0];
            utf8Buffer += 1;
            utf8Length -= 1;
        }else if(utf8Buffer[0] < 0xe0){
            unicodeBuffer[unicodeNum++] = ((uint16_t)(utf8Buffer[0] & 0x1f) << 6) | (utf8Buffer[1] & 0x3f);
            utf8Buffer += 2;
            utf8Length -= 2;
        }else if(utf8Buffer[0] < 0xf0){
            unicodeBuffer[unicodeNum++] = ((uint16_t)(utf8Buffer[0] & 0x0f) << 12) | ((utf8Buffer[1] & 0x3f) << 6) | (utf8Buffer[2] & 0x3f);
            utf8Buffer += 3;
            utf8Length -= 3;
        }else{
            utf8Buffer += 1;
            utf8Length -= 1;
        }
    }
    if(flag){
        unicodeBuffer[unicodeNum++] = 0;
    }
    return unicodeNum + unicodeNum;
}