[SOLVED] Convert Base 16 (Hexadecimal) to Base 36 String in C

Convert Base 16 (Hexadecimal) to Base 36 String in C

In C, what's an efficient way to convert a 64 character hexadecimal number (as a string) into a base 36 string?

I mean, is it as easy as combining a few GLIB2 functions (on Linux), or Standard Library functions? Or, do I have to do it all custom?

Solution

This is easy with a library like GMP:

mpz_t nr;
mpz_init(nr);
mpz_set_str(nr, hexstr, 16);
printf("%s\n", mpz_get_str(NULL, 36, nr));

On debian-based systems you can install the GMP-library with:

apt-get install libgmp-dev

Full example:

#include <stdio.h>
#include <gmp.h>

int main(int argc, char **argv) {   
    mpz_t nr;
    mpz_init(nr);
    mpz_set_str(nr, argv[1], 16);
    printf("%s\n", mpz_get_str(NULL, 36, nr));

    return 0;
}

Compiled with:

gcc -O2 conv.c -o conv -lgmp

Performs quite well:

$ time ./conv 2eb1a3e346933962bdfbb7b118404b68b967d44006986d4b1e88ec23e433de12
15wa17qx942cddy4n5q5px1fw6yi9llw0lzxjg2ahh2q0w9amq

real    0m0.001s
user    0m0.000s
sys     0m0.000s