I can't understand how to convert hex string to unsigned char in C?

Question

I have input

unsigned char hex[64] =  9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a0"

and I want output like this:

unsigned char tmpInHash[32] = { 0x9f, 0x86, 0xd0, 0x81, 0x88, 0x4c, 0x7d, 0x65, 0x9a, 0x2f, 0xea, 0xa0, 0xc5, 0x5a, 0xd0, 0x15, 0xa3, 0xbf, 0x4f, 0x1b, 0x2b, 0x0b, 0x82, 0x2c, 0xd1, 0x5d, 0x6c, 0x15, 0xb0, 0xf0, 0x0a, 0x08 }

I searched for the answer everywhere, but the answers , which I found, do not fit.

EDIT

I want that when I write:

for(i=0; i< strlen(tmpInHash); i++ {
    printf("%c ", tmpInHash);
}

I get this:

0x9f 0x86 0xd0 0x81 0x88 0x4c 0x7d 0x65 0x9a ...

Is it possible?

Answer 1

One way to convert this is the following way:

• Iterate through every item of the string, where every 2 characters represent a number.
• Break out each such character pair and store them in a temporary string: char tmp {str[i], str[i+1], '\0'};.
• Call strtol(tmp, NULL, 16) on this string to get the integer number.

Answer 2

Without "high level" functions

#include <stdio.h>
#include <string.h>

int main(void)
{
    unsigned char hex[] = "9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08";

    size_t stringLength = (sizeof(hex)/sizeof(hex[0]))-1;

    unsigned char tmpInHash[stringLength/2];

    int j=0;

    // reset the char to 0. This grants that next or operation works on reset buffer
    tmpInHash[0] = 0;

    // loop that parse the whole string
    for (size_t i = 0; i < stringLength; i++)
    {
        // check if the char is a to f
        if ((hex[i] >= 'a') && (hex[i] <= 'f'))
        {
            tmpInHash[j] |= hex[i] -'a' + 10;
        }
        // che if is a digit
        else if ((hex[i] >= '0') && (hex[i] <= '9'))
        {
            tmpInHash[j] |= hex[i] -'0';
        }
        // character not allowed
        else
        {
            fprintf(stderr, "Character not allowed: %c position: %zu\n", hex[i], i);
            return 1;
        }

        // even index chars are hig 4 bits of unsigned char
        if ((i%2) == 0)
        {
            tmpInHash[j]<<=4;
        }
        else
        {
            // nex unsigned char
            j++;

            // reset the char to 0. This grants that next or operation works on reset buffer
            if (j < stringLength/2)
               tmpInHash[j] = 0;
        }

    }

    for (size_t i = 0; i < stringLength/2; i++)
    {
        printf("0x%02X ", tmpInHash[i]);
    }

    printf("\n");


    return 0;
}

OUTPUT

0x9F 0x86 0xD0 0x81 0x88 0x4C 0x7D 0x65 0x9A 0x2F 0xEA 0xA0 0xC5 0x5A 0xD0 0x15 0xA3 0xBF 0x4F 0x1B 0x2B 0x0B 0x82 0x2C 0xD1 0x5D 0x6C 0x15 0xB0 0xF0 0x0A 0x08

EDIT Another example can be

#include <stdio.h>
#include <string.h>

unsigned char hex[] = "9f86d081884g7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08";

#define HEX_LEN (sizeof(hex)-1)

unsigned char tmpInHash[HEX_LEN/2]={0};

int main(void)
{
    size_t i = 0;
    size_t j = 0;

    // parse all charcaters of hex
    while(hex[i] != '\0')
    {
        // check if the char is a to f
        if ((hex[i] >= 'a') && (hex[i] <= 'f'))
        {
            tmpInHash[j] |= hex[i] -'a' + 10;
        }
        // che if is a digit
        else if ((hex[i] >= '0') && (hex[i] <= '9'))
        {
            tmpInHash[j] |= hex[i] -'0';
        }
        // character not allowed
        else
        {
            fprintf(stderr, "Character not allowed: %c position: %zu\n", hex[i], i);
            return 1;
        }

        // even index chars are hig 4 bits of unsigned char
        if ((i%2) == 0)
        {
            tmpInHash[j]<<=4;
        }
        else
        {
            // nex unsigned char
            j++;
        }

        // next hex char
        i++;
    }

    // print loop
    for (i = 0; i < (HEX_LEN/2); i++)
    {
        printf("0x%02X ", tmpInHash[i]);
    }

    printf("\n");

    return 0;
}

Answer 3

unsigned char hex[64] =  "9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a0";
 unsigned char *ptrHex =hex;
    unsigned char tmpInHash[32];
    int i ,tmp ;
    for(i=0 ; i < 32 ; i++)
    {
         if((*ptrHex)<=9 && (*ptrHex) >=0)
                  tmp=(*ptrHex)-'0';
         else tmp=(*ptrHex)-'a'+10;
         tmpInHash[i]=(tmp<<4);
         ptrHex++;

       if((*ptrHex)<=9 && (*ptrHex) >=0)
                  tmp=(*ptrHex)-'0';
         else tmp=(*ptrHex)-'a'+10;

         tmpInHash[i]|=tmp ;
         ptrHex++;
    }