tests/test-ffs.c

   1 /*
   2  * Copyright (C) 2011-2017 Free Software Foundation, Inc.
   3  *
   4  * This program is free software: you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 3 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Eric Blake.  */
  18 #include <config.h>
  19
  20 #include <strings.h>
  21
  22 #include "signature.h"
  23 SIGNATURE_CHECK (ffs, int, (int));
  24
  25 #include <limits.h>
  26
  27 #include "macros.h"
  28
  29 #define NBITS (sizeof (int) * CHAR_BIT)
  30
  31 static int
  32 naive (int i)
  33 {
  34   unsigned int j;
  35   for (j = 0; j < NBITS; j++)
  36     if (i & (1U << j))
  37       return j + 1;
  38   return 0;
  39 }
  40
  41 int
  42 main (int argc, char *argv[])
  43 {
  44   int x;
  45   int i;
  46
  47   for (x = -128; x <= 128; x++)
  48     ASSERT (ffs (x) == naive (x));
  49   for (i = 0; i < NBITS; i++)
  50     {
  51       ASSERT (ffs (1U << i) == naive (1U << i));
  52       ASSERT (ffs (1U << i) == i + 1);
  53       ASSERT (ffs (-1U << i) == i + 1);
  54     }
  55   for (i = 0; i < NBITS - 1; i++)
  56     {
  57       ASSERT (ffs (3U << i) == i + 1);
  58       ASSERT (ffs (-3U << i) == i + 1);
  59     }
  60   for (i = 0; i < NBITS - 2; i++)
  61     {
  62       ASSERT (ffs (5U << i) == i + 1);
  63       ASSERT (ffs (-5U << i) == i + 1);
  64       ASSERT (ffs (7U << i) == i + 1);
  65       ASSERT (ffs (-7U << i) == i + 1);
  66     }
  67   return 0;
  68 }