get_hex_value_if_hex_string, C (clang)

Language: Layout:

//clang 3.8.0

#include  <stdio.h>
#include  <string.h> #И нахрена оно тут?..

static int get_hex_value(char string[]){

//	char *x = "0123456789ABCDEFabcdef";	//string with all possible hexadecimal symbols

/*
        //show char codes of this
        for(int i=0;i<strlen(x);i++){
            printf("%d\n", x[i]);
        }
    */	
        //sort char codes by ranges
        //48 49 50 51 52 53 54 55 56 57 
        //65 66 67 68 69 70
        //97 98 99 100 101 102
	
    /*
        //lookup table	
        static const char xvalue[] = {
            //shifting char code +48			codes range - digits range
            0, 1, 2, 3, 4, 5, 6, 7, 8, 9,	//	(48-57)			(0-9)
            -1, -1, -1, -1, -1, -1, -1,
            10, 11, 12, 13, 14, 15,	 		//	(65-7-1)		(A-F)
            -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1,
            10, 11, 12, 13, 14, 15			//	(97-102)		(a-f)
        };//this not returning -1 for another symbols
    */
    
        //using switch
        int code;										//decimal value of hex character if this is hex
        
        printf("test string %s\n", string);
        for(int j=0;j<strlen(string);j++){				//read string
            const int o = 48; 							//start offset for charcodes
            switch (string[j]) {//compare charcode
                case o+0 ... o+9:  code = string[j]-o; break;			//0-9
                case o+17 ... o+22: code = string[j]-o-7; break;		//A-F
                case o+49 ... o+54: code = string[j]-o-39; break;		//a-f
                default: code = -1; break;								//else -1
            }
            if(code == -1) break;										//break from cycle, if invalid char
            
            //else...
            //show this for each symbol
            printf(	"index = %d, "
                    "char = %c, charcode = %d, "
                    "offset = %d, value = %d, \n",
                    j,
					string[j], string[j],
					string[j]-48, code
            );
            //each number contains 4 bit [0000-1111].
            //With this values can be used shift bitwise rotate functions.
            //code<<4(left)
            //code>>4(right)
        }
        
        if(code!=-1){
            printf("code = %d, (string is hexadecimal.)\n\n", code); 			//show this at last
        }else{
            printf("code = %d, (if -1 string not hexadecimal.)\n\n", code); //show this at last
        }
        return code;
    }
    
int main(void)
{
    char *test1 = "AfbC19073"; //hex string
    char *test2 = "ABcD1-9073"; //not a hex string
    
    get_hex_value(test1); //hex string
    get_hex_value(test2); //not a hex string
}

Show compiler warnings [ + ] Compiler args [ + ] Show input
Compilation time: 0.25 sec, absolute running time: 0.2 sec, cpu time: 0.09 sec, memory peak: 3 Mb, absolute service time: 0,57 sec