void utf_8(char *str)
{
    int i = 0;
    while(str[i]!='\0')
    {
        if( (str[i]&0xc0)==0x00)
        {
            i+=1;
        }
        if( (str[i]&0xe0)==0xc0)
        {
            i+=2;
        }
        if( (str[i]&0xf0)==0xe0)
        {
            i+=3;
        }
        if( (str[i]&0xf8)==0xf0)
        {
            i+=4;
        }
        if( (str[i]&0xfc)==0xf8)
        {
            i+=5;
        }
        if( (str[i]&0xfe)==0xfc)
        {
            i+=6;
        }
    }
    int j = i;
    i = 0;
    char *tmp =  (char*)malloc(j+1);
    memset(tmp,j+1,0);
    tmp[j]='\0';
    while(str[i]!='\0')
    {
        if( (str[i]&0xc0)==0x00)
        {
            tmp[j-1] = str[i];
            j-=1;
            i+=1;
        }
        if( (str[i]&0xe0)==0xc0)
        {
            tmp[j-1] = str[i];
            j-=2;
            i+=2;
        }
        if( (str[i]&0xf0)==0xe0)
        {
            tmp[j-1] = str[i];
            j-=3;
            i+=3;
        }
        if( (str[i]&0xf8)==0xf0)
        {
            tmp[j-1] = str[i];
            j-=4;
            i+=4;
        }
        if( (str[i]&0xfc)==0xf8)
        {
            tmp[j-1] = str[i];
            j-=5;
            i+=5;
        }
        if( (str[i]&0xfe)==0xfc)
        {
            tmp[j-1] = str[i];
            j-=6;
            i+=6;
        }
    }

    *str = *tmp; // tmp=321,而str=323；
    free tmp;

}
为什么 在我输入123的时候  已经反过来了，可在赋值的时候 str=323