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mpi-bit.c
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/* mpi-bit.c - MPI bit level fucntions
* Copyright (C) 1998, 1999, 2001, 2002, 2005 Free Software Foundation, Inc.
*
* This file is part of Libgcrypt.
*
* Libgcrypt 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.
*
* Libgcrypt 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 this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#include <gcrypt-mpi-internal.h>
#include <stdlib.h>
#include <assert.h>
#include <stdio.h>
#include "longlong.h"
#ifdef MPI_INTERNAL_NEED_CLZ_TAB
#ifdef __STDC__
const
#endif
unsigned char _gcry_clz_tab[] = {
0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5,
5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8,
};
#endif
#define A_LIMB_1 ((mpi_limb_t)1)
/****************
* Sometimes we have MSL (most significant limbs) which are 0;
* this is for some reasons not good, so this function removes them.
*/
void
_gcry_mpi_normalize (gcry_core_mpi_t a)
{
if (mpi_is_opaque (a))
return;
for (; a->nlimbs && !a->d[a->nlimbs - 1]; a->nlimbs--)
;
}
/****************
* Return the number of bits in A.
*/
unsigned int
_gcry_mpi_get_nbits (gcry_core_context_t ctx, gcry_core_mpi_t a)
{
unsigned n;
if (mpi_is_opaque (a))
{
return a->sign; /* which holds the number of bits */
}
_gcry_mpi_normalize (a);
if (a->nlimbs)
{
mpi_limb_t alimb = a->d[a->nlimbs - 1];
if (alimb)
count_leading_zeros (n, alimb);
else
n = BITS_PER_MPI_LIMB;
n = BITS_PER_MPI_LIMB - n + (a->nlimbs - 1) * BITS_PER_MPI_LIMB;
}
else
n = 0;
return n;
}
/****************
* Test whether bit N is set.
*/
int
_gcry_mpi_test_bit (gcry_core_context_t ctx, gcry_core_mpi_t a,
unsigned int n)
{
unsigned int limbno, bitno;
mpi_limb_t limb;
limbno = n / BITS_PER_MPI_LIMB;
bitno = n % BITS_PER_MPI_LIMB;
if (limbno >= a->nlimbs)
return 0; /* too far left: this is a 0 */
limb = a->d[limbno];
return (limb & (A_LIMB_1 << bitno)) ? 1 : 0;
}
/****************
* Set bit N of A.
*/
void
_gcry_mpi_set_bit (gcry_core_context_t ctx, gcry_core_mpi_t a,
unsigned int n)
{
unsigned int limbno, bitno;
limbno = n / BITS_PER_MPI_LIMB;
bitno = n % BITS_PER_MPI_LIMB;
if (limbno >= a->nlimbs)
{ /* resize */
if (a->alloced >= limbno)
_gcry_mpi_resize (ctx, a, limbno + 1);
a->nlimbs = limbno + 1;
}
a->d[limbno] |= (A_LIMB_1 << bitno);
}
/****************
* Set bit N of A. and clear all bits above
*/
void
_gcry_mpi_set_highbit (gcry_core_context_t ctx, gcry_core_mpi_t a,
unsigned int n)
{
unsigned int limbno, bitno;
limbno = n / BITS_PER_MPI_LIMB;
bitno = n % BITS_PER_MPI_LIMB;
if (limbno >= a->nlimbs)
{ /* resize */
if (a->alloced >= limbno)
_gcry_mpi_resize (ctx, a, limbno + 1);
a->nlimbs = limbno + 1;
}
a->d[limbno] |= (A_LIMB_1 << bitno);
for (bitno++; bitno < BITS_PER_MPI_LIMB; bitno++)
a->d[limbno] &= ~(A_LIMB_1 << bitno);
a->nlimbs = limbno + 1;
}
/****************
* clear bit N of A and all bits above
*/
void
_gcry_mpi_clear_highbit (gcry_core_context_t context, gcry_core_mpi_t a,
unsigned int n)
{
unsigned int limbno, bitno;
limbno = n / BITS_PER_MPI_LIMB;
bitno = n % BITS_PER_MPI_LIMB;
if (limbno >= a->nlimbs)
return; /* not allocated, so need to clear bits :-) */
for (; bitno < BITS_PER_MPI_LIMB; bitno++)
a->d[limbno] &= ~(A_LIMB_1 << bitno);
a->nlimbs = limbno + 1;
}
/****************
* Clear bit N of A.
*/
void
_gcry_mpi_clear_bit (gcry_core_context_t context, gcry_core_mpi_t a,
unsigned int n)
{
unsigned int limbno, bitno;
limbno = n / BITS_PER_MPI_LIMB;
bitno = n % BITS_PER_MPI_LIMB;
if (limbno >= a->nlimbs)
return; /* don't need to clear this bit, it's to far to left */
a->d[limbno] &= ~(A_LIMB_1 << bitno);
}
/****************
* Shift A by N bits to the right
* FIXME: should use alloc_limb if X and A are same.
*/
void
_gcry_mpi_rshift (gcry_core_context_t context, gcry_core_mpi_t x,
gcry_core_mpi_t a, unsigned n)
{
mpi_ptr_t xp;
mpi_size_t xsize;
xsize = a->nlimbs;
x->sign = a->sign;
RESIZE_IF_NEEDED (context, x, xsize);
xp = x->d;
if (xsize)
{
_gcry_mpih_rshift (xp, a->d, xsize, n);
MPN_NORMALIZE (xp, xsize);
}
x->nlimbs = xsize;
}
/****************
* Shift A by COUNT limbs to the left
* This is used only within the MPI library
*/
void
_gcry_mpi_lshift_limbs (gcry_core_context_t context, gcry_core_mpi_t a,
unsigned int count)
{
mpi_ptr_t ap = a->d;
int n = a->nlimbs;
int i;
if (!count || !n)
return;
RESIZE_IF_NEEDED (context, a, n + count);
for (i = n - 1; i >= 0; i--)
ap[i + count] = ap[i];
for (i = 0; i < count; i++)
ap[i] = 0;
a->nlimbs += count;
}
/****************
* Shift A by COUNT limbs to the right
* This is used only within the MPI library
*/
void
_gcry_mpi_rshift_limbs (gcry_core_context_t context, gcry_core_mpi_t a,
unsigned int count)
{
mpi_ptr_t ap = a->d;
mpi_size_t n = a->nlimbs;
unsigned int i;
if (count >= n)
{
a->nlimbs = 0;
return;
}
for (i = 0; i < n - count; i++)
ap[i] = ap[i + count];
ap[i] = 0;
a->nlimbs -= count;
}
/* END. */

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