num.c

/*
 * Copyright (c) 2015-2016, Fred Morcos <fred.morcos@gmail.com>
 *
 * Permission to  use, copy,  modify, and/or distribute  this software
 * for any  purpose with  or without fee  is hereby  granted, provided
 * that the above  copyright notice and this  permission notice appear
 * in all copies.
 *
 * THE  SOFTWARE IS  PROVIDED "AS  IS"  AND THE  AUTHOR DISCLAIMS  ALL
 * WARRANTIES  WITH  REGARD TO  THIS  SOFTWARE  INCLUDING ALL  IMPLIED
 * WARRANTIES OF  MERCHANTABILITY AND FITNESS.  IN NO EVENT  SHALL THE
 * AUTHOR   BE  LIABLE   FOR   ANY  SPECIAL,   DIRECT,  INDIRECT,   OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
 * OF  USE,  DATA  OR  PROFITS,  WHETHER IN  AN  ACTION  OF  CONTRACT,
 * NEGLIGENCE  OR  OTHER  TORTIOUS  ACTION,   ARISING  OUT  OF  OR  IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <assert.h>
#include <limits.h>
#include <math.h>
#include <stdlib.h>
#include "num.h"

unsigned int ndigits(unsigned long long val) {
  unsigned int len = 0;

  do {
    val /= 10;
    len++;
  } while (val);

  return len;
}

void ulltoa(char *str, unsigned long long val, const unsigned int len) {
  assert(str != NULL);
  assert(len > 0);

  double res = pow(10, len - 1);

  assert(res > 0);
  assert(res <= LLONG_MAX);

  unsigned long long div = (unsigned long long) llround(res);

  for (unsigned long long digit = 0; div > 0; div /= 10) {
    digit = val / div;
    *(str++) = (char) ('0' + digit);
    val -= digit * div;
  }
}