/*
 * uint64_to_string.c
 *
 * Converts a unsigned 64-bit integer to a printable string.
 *
 *    $ gcc -g -Wall -pedantic -o foo foo.c
 *    $ ./foo
 *    1234 is 1234
 *    4321 is 4321
 *    0 is 0
 *    2147483646 is 2147483646
 *
 */

#include <stdio.h>
#include <limits.h>
#include <unistd.h>
#include <stdint.h>     // <-- this is the only header uint64_to_string needs
#include <string.h>     // <-- this is needed for strlen(3)

char *uint64_to_string(uint64_t n);

int
main(int argc, char *argv[])
{
    int ints[] = { 1234, 4321, 0, INT_MAX-1, 1234576890 };
    char *s;

    int i;
    for(i=0; i<5; i++) {
        s = uint64_to_string(ints[i]);
        printf("%d is ", ints[i]);
        fflush(stdout);
        write(1, s, strlen(s)); 
        write(1, "\n", 1);
    }
}

char *
uint64_to_string(uint64_t n)
{
    static char s[32] = "0000000000000000000000000000000\0";
    int i;

    for(i=30; i>0; i--) {
        s[i] = (n % 10) + '0';
        n = n / 10;
        if(n == 0)
            break;
    }

    return &s[i];
}