Question

Referring second answer to question: How to convert from ASCII to Hex and vice versa?

I want to save the char hex[3] equivalent of different characters as follows:

char *str ="abcd";

// I want to get hex[3] of each character in above string and save into the following:

char str2[4]; // should contain hex values as : \x61 for a,\x62 for b,\x63 for c,\x64 for d

How can I do this ?

I tried the following so far:

int i;
char ch;
char hex[3];
for(i=0; i<strlen(str);i++) {
    ch = charToHex(*(str+i), hex);
    // now hex contains the first and second hex characters in hex[0] & hex[1]
    // I need to save them in the first index of str2 
    // e.g. if hex[0] = 7 and hex[1] = f, then str2[0] should be "\x7f"

    // -> how do I do this part ?

}

Thanks.

Answer 1

You can use a for loop to iterate over all characters of a string, and then apply the conversion for each character. Bear in mind that C strings are null-terminated.

Also note that 4 characters will not be enough if you want to store \x61\x62\x63\x64 – you’ll need 4 * strlen(str) + 1, i.e. 17.

---

In response to the code:

You don’t actually need ch. The function charToHex return void, i.e. nothing.

Simply copy the characters to the output string, like this:

str2[2*i] = hex[0];
str2[2*i+1] = hex[1];

Again, don’t forget to set the null terminator in the result string.

Also, since you call strlen in each iteration, you’re writing a Schlemiel the Painter algorithm.