/*
 * pointer_to_hex_le.c
 *
 * Converts a pointer (little-endian) to a printable string.
 *
 *   $ gcc -g -Wall -pedantic -o pointer_to_hex_le pointer_to_hex_le.c
 *   $ ./pointer_to_hex_le
 *   pointer_to_hex_le says: 0x000055c0fe64a2a0
 *   printf says:            0x000055c0fe64a2a0
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdint.h>     // <-- this is the only header pointer_to_hex_le needs

char *pointer_to_hex_le(void *);

int
main(int argc, char *argv[])
{
    int *p = malloc(sizeof(int));

    write(1, "pointer_to_hex_le says: 0x", 26);
    write(1, pointer_to_hex_le(p), sizeof(p) * 2);
    write(1, "\n", 1);

    printf("printf says:            0x%016lx\n", (uint64_t) p);
}

char *
pointer_to_hex_le(void *ptr)
{
    static char hex[sizeof(ptr) * 2 + 1];
    char hex_chars[] = "0123456789abcdef";
    int i;
    uint8_t nibble;

    uint64_t mask = 0xf;
    uint64_t shift = 0;

    for(i=sizeof(ptr) * 2 - 1; i>=0; i-=1) {
        nibble = ((uint64_t) ptr & mask) >> shift;
        hex[i] = hex_chars[nibble];

        mask = mask << 4;
        shift += 4;
    }
    hex[sizeof(ptr) * 2] = '\0';

    return hex;
}