bit.c

a very popular packet of cryptography tools,it encloses the most common used algorithm and protocols

/* Test mpz_setbit, mpz_clrbit, mpz_tstbit.

Copyright 1997, 2000, 2001, 2002 Free Software Foundation, Inc.

This file is part of the GNU MP Library.

The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or (at your
option) any later version.

The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
License for more details.

You should have received a copy of the GNU Lesser General Public License
along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */

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

#include "gmp.h"
#include "gmp-impl.h"
#include "tests.h"

#ifndef SIZE
#define SIZE 4
#endif


void
debug_mp (mpz_srcptr x, int base)
{
  mpz_out_str (stdout, base, x); fputc ('\n', stdout);
}


/* See that mpz_tstbit matches a twos complement calculated explicitly, for
   various low zeros.  */
void
check_tstbit (void)
{
#define MAX_ZEROS  3
#define NUM_LIMBS  3

  mp_limb_t      pos[1+NUM_LIMBS+MAX_ZEROS];
  mp_limb_t      neg[1+NUM_LIMBS+MAX_ZEROS];
  mpz_t          z;
  unsigned long  i;
  int            zeros, low1;
  int            got, want;

  mpz_init (z);
  for (zeros = 0; zeros <= MAX_ZEROS; zeros++)
    {
      MPN_ZERO (pos, numberof(pos));
      mpn_random2 (pos+zeros, NUM_LIMBS);

      for (low1 = 0; low1 <= 1; low1++)
        {
          if (low1)
            pos[0] |= 1;

          refmpn_neg_n (neg, pos, numberof(neg));
          mpz_set_n (z, neg, numberof(neg));
          mpz_neg (z, z);

          for (i = 0; i < numberof(pos)*GMP_NUMB_BITS; i++)
            {
              got = mpz_tstbit (z, i);
              want = refmpn_tstbit (pos, i);
              if (got != want)
                {
                  printf ("wrong at bit %lu, with %d zeros\n", i, zeros);
                  printf ("z neg "); debug_mp (z, -16);
                  mpz_set_n (z, pos, numberof(pos));
                  printf ("pos   "); debug_mp (z, -16);
                  mpz_set_n (z, neg, numberof(neg));
                  printf ("neg   "); debug_mp (z, -16);
                  exit (1);
                }
            }
        }
    }
  mpz_clear (z);
}


void
check_single (void)
{
  mpz_t  x;
  int    limb, offset, initial;
  unsigned long  bit;

  mpz_init (x);

  for (limb = 0; limb < 4; limb++)
    {
      for (offset = (limb==0 ? 0 : -2); offset <= 2; offset++)
        {
          for (initial = 0; initial >= -1; initial--)
            {
              mpz_set_si (x, (long) initial);

              bit = (unsigned long) limb*BITS_PER_MP_LIMB + offset;

              mpz_clrbit (x, bit);
              MPZ_CHECK_FORMAT (x);
              if (mpz_tstbit (x, bit) != 0)
                {
                  printf ("check_single(): expected 0\n");
                  abort ();
                }
          
              mpz_setbit (x, bit);
              MPZ_CHECK_FORMAT (x);
              if (mpz_tstbit (x, bit) != 1)
                {
                  printf ("check_single(): expected 0\n");
                  abort ();
                }
          
              mpz_clrbit (x, bit);
              MPZ_CHECK_FORMAT (x);
              if (mpz_tstbit (x, bit) != 0)
                {
                  printf ("check_single(): expected 0\n");
                  abort ();
                }
            }
        }
    }          

  mpz_clear (x);
}


void
check_random (int argc, char *argv[])
{
  mpz_t x, s0, s1, s2, s3, m;
  mp_size_t xsize;
  int i;
  int reps = 100000;
  int bit0, bit1, bit2, bit3;
  unsigned long int bitindex;
  const char  *s = "";

  if (argc == 2)
    reps = atoi (argv[1]);

  mpz_init (x);
  mpz_init (s0);
  mpz_init (s1);
  mpz_init (s2);
  mpz_init (s3);
  mpz_init (m);

  for (i = 0; i < reps; i++)
    {
      xsize = urandom () % (2 * SIZE) - SIZE;
      mpz_random2 (x, xsize);
      bitindex = urandom () % SIZE;

      mpz_set (s0, x);
      bit0 = mpz_tstbit (x, bitindex);
      mpz_setbit (x, bitindex);
      MPZ_CHECK_FORMAT (x);

      mpz_set (s1, x);
      bit1 = mpz_tstbit (x, bitindex);
      mpz_clrbit (x, bitindex);
      MPZ_CHECK_FORMAT (x);

      mpz_set (s2, x);
      bit2 = mpz_tstbit (x, bitindex);
      mpz_setbit (x, bitindex);
      MPZ_CHECK_FORMAT (x);

      mpz_set (s3, x);
      bit3 = mpz_tstbit (x, bitindex);

#define FAIL(str) do { s = str; goto fail; } while (0)

      if (bit1 != 1)  FAIL ("bit1 != 1");
      if (bit2 != 0)  FAIL ("bit2 != 0");
      if (bit3 != 1)  FAIL ("bit3 != 1");

      if (bit0 == 0)
	{
	  if (mpz_cmp (s0, s1) == 0 || mpz_cmp (s0, s2) != 0 || mpz_cmp (s0, s3) == 0)
	    abort ();
	}
      else
	{
	  if (mpz_cmp (s0, s1) != 0 || mpz_cmp (s0, s2) == 0 || mpz_cmp (s0, s3) != 0)
	    abort ();
	}

      if (mpz_cmp (s1, s2) == 0 || mpz_cmp (s1, s3) != 0)
	abort ();
      if (mpz_cmp (s2, s3) == 0)
	abort ();

      mpz_ui_pow_ui (m, 2L, bitindex);
      MPZ_CHECK_FORMAT (m);
      mpz_ior (x, s2, m);
      MPZ_CHECK_FORMAT (x);
      if (mpz_cmp (x, s3) != 0)
	abort ();

      mpz_com (m, m);
      MPZ_CHECK_FORMAT (m);
      mpz_and (x, s1, m);
      MPZ_CHECK_FORMAT (x);
      if (mpz_cmp (x, s2) != 0)
	abort ();
    }

  mpz_clear (x);
  mpz_clear (s0);
  mpz_clear (s1);
  mpz_clear (s2);
  mpz_clear (s3);
  mpz_clear (m);
  return;


 fail:
  printf ("%s\n", s);
  printf ("bitindex = %lu\n", bitindex);
  printf ("x = "); mpz_out_str (stdout, -16, x); printf (" hex\n");
  exit (1);
}



int
main (int argc, char *argv[])
{
  tests_start ();

  check_tstbit ();
  check_random (argc, argv);
  check_single ();

  tests_end ();
  exit (0);
}