🚀 go-pugleaf

jB wrote:
> 
> Could anyone please help me with a couple of small routines to convert a
> base10 number into a base32 string and a routine to convert base32 string
> into a base10 number.
> 

The C standard library has the strtol() function which will convert a 
string to a long using a base between 2 and 36. There is no standard 
function to do the complementary conversion, at least that I am aware of.

I have written a small function to do that long to string conversion 
using a base between 2 and 36. It is copied below. There is also a small 
command line test program that converts its first argument using the 
second argument as a base.

These functions should let you do your conversions to and from base 32.

HTH
Dennis Cote



#include <stdlib.h>
#include <stdio.h>

static char digit_symbols[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVXYZ";

bool ltostr(long n, char* str, int base)
{
     char buf[33];
     char* p = buf;

     if (!str || base < 2 || base > 36)
         return false;

     if (n < 0) {
         *str++ = '-';
         n = -n;
     }

     do {
         *p++ = digit_symbols[n % base];
         n /= base;
     } while (n > 0);

     do {
         *str++ = *(--p);
     } while (p > buf);

     *str = 0;
     return true;
}


#pragma argsused
int main(int argc, char* argv[])
{
     char str[33];
     long m;
     long n = atol(argv[1]);
     int base = atoi(argv[2]);

     printf("n = %ld base 10\n", n);

     if (ltostr(n, str, base))
         printf("n = %s base %d\n", str, base);
     else
         printf("error converting n\n");

     m = strtol(str, NULL, base);

     printf("m = %ld base 10\n", m);

     return 0;
}