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16进制字符串转字节

#include 
   
    #include 
    
     #include 
     
      void hex_str_to_byte(char *in, int len, unsigned char *out){
       char *str = (char *)malloc(len);    memset(str, 0, len);    memcpy(str, in, len);    for (int i = 0; i < len; i += 2)    {
           //小写转大写        if (str[i] >= 'a' && str[i] <= 'f')            str[i] = str[i] - 0x20;        if (str[i + 1] >= 'a' && str[i] <= 'f')            str[i + 1] = str[i + 1] - 0x20;        //处理第前4位        if (str[i] >= 'A' && str[i] <= 'F')            out[i / 2] = (str[i] - 'A' + 10) << 4;        else            out[i / 2] = (str[i] & ~0x30) << 4;        //处理后4位, 并组合起来        if (str[i + 1] >= 'A' && str[i + 1] <= 'F')            out[i / 2] |= (str[i + 1] - 'A' + 10);        else            out[i / 2] |= (str[i + 1] & ~0x30);    }    free(str);}int main(){
       char *str = "FF32333435363738393a3b3c3d3e3f40";    unsigned char temp[16] = {
   0};    hex_str_to_byte(str, strlen("ff32333435363738393a3b3c3d3e3f40"), temp);    for (int i = 0; i < 16; i++)    {
           printf("%02x ", temp[i]);    }    printf("\n");    return 0;}
     
    
   

演示

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