/* mpi-bit.c - MPI bit level functions
* Copyright (C) 1998, 1999, 2001, 2002, 2006 Free Software Foundation, Inc.
* Copyright (C) 2013 g10 Code GmbH
*
* 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, see .
* SPDX-License-Identifier: LGPL-2.1-or-later
*/
#include
#include
#include
#include "mpi-internal.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_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_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_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_mpi_t a, unsigned int n )
{
unsigned int i, limbno, bitno;
if (mpi_is_immutable (a))
{
mpi_immutable_failed ();
return;
}
limbno = n / BITS_PER_MPI_LIMB;
bitno = n % BITS_PER_MPI_LIMB;
if ( limbno >= a->nlimbs )
{
for (i=a->nlimbs; i < a->alloced; i++)
a->d[i] = 0;
mpi_resize (a, limbno+1 );
a->nlimbs = limbno+1;
}
a->d[limbno] |= (A_LIMB_1<= a->nlimbs )
{
for (i=a->nlimbs; i < a->alloced; i++)
a->d[i] = 0;
mpi_resize (a, limbno+1 );
a->nlimbs = limbno+1;
}
a->d[limbno] |= (A_LIMB_1<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_mpi_t a, unsigned int n )
{
unsigned int limbno, bitno;
if (mpi_is_immutable (a))
{
mpi_immutable_failed ();
return;
}
limbno = n / BITS_PER_MPI_LIMB;
bitno = n % BITS_PER_MPI_LIMB;
if( limbno >= a->nlimbs )
return; /* not allocated, therefore no 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_mpi_t a, unsigned int n )
{
unsigned int limbno, bitno;
if (mpi_is_immutable (a))
{
mpi_immutable_failed ();
return;
}
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 far too left. */
a->d[limbno] &= ~(A_LIMB_1 << bitno);
}
/****************
* Shift A by COUNT limbs to the right
* This is used only within the MPI library
*/
void
_gcry_mpi_rshift_limbs( gcry_mpi_t a, unsigned int count )
{
mpi_ptr_t ap = a->d;
mpi_size_t n = a->nlimbs;
unsigned int i;
if (mpi_is_immutable (a))
{
mpi_immutable_failed ();
return;
}
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;
}
/*
* Shift A by N bits to the right.
*/
void
_gcry_mpi_rshift ( gcry_mpi_t x, gcry_mpi_t a, unsigned int n )
{
unsigned int nlimbs = (n/BITS_PER_MPI_LIMB);
unsigned int nbits = (n%BITS_PER_MPI_LIMB);
unsigned int i;
mpi_size_t alimbs;
mpi_ptr_t xp, ap;
if (mpi_is_immutable (x))
{
mpi_immutable_failed ();
return;
}
alimbs = a->nlimbs;
if (x != a)
{
RESIZE_IF_NEEDED (x, alimbs);
x->nlimbs = alimbs;
x->flags = a->flags;
x->sign = a->sign;
}
/* In-place operation. */
if (nlimbs >= alimbs)
{
x->nlimbs = 0;
return;
}
xp = x->d;
ap = a->d;
if (alimbs && nbits)
{
_gcry_mpih_rshift (xp, ap + nlimbs, alimbs - nlimbs, nbits);
if (nlimbs)
xp[alimbs - nlimbs] = 0;
x->nlimbs -= nlimbs;
}
else if (nlimbs || (x != a))
{
for (i = 0; i < alimbs - nlimbs; i++ )
xp[i] = ap[i + nlimbs];
if (nlimbs)
xp[i] = 0;
x->nlimbs -= nlimbs;
}
MPN_NORMALIZE (x->d, x->nlimbs);
}
/****************
* Shift A by COUNT limbs to the left
* This is used only within the MPI library
*/
void
_gcry_mpi_lshift_limbs (gcry_mpi_t a, unsigned int count)
{
mpi_ptr_t ap;
int n = a->nlimbs;
int i;
if (!count || !n)
return;
RESIZE_IF_NEEDED (a, n+count);
ap = a->d;
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 N bits to the left.
*/
void
_gcry_mpi_lshift ( gcry_mpi_t x, gcry_mpi_t a, unsigned int n )
{
unsigned int nlimbs = (n/BITS_PER_MPI_LIMB);
unsigned int nbits = (n%BITS_PER_MPI_LIMB);
mpi_size_t alimbs;
mpi_ptr_t xp, ap;
int i;
if (mpi_is_immutable (x))
{
mpi_immutable_failed ();
return;
}
if (x == a && !n)
return; /* In-place shift with an amount of zero. */
/* Note: might be in-place operation, so a==x or a!=x. */
alimbs = a->nlimbs;
RESIZE_IF_NEEDED (x, alimbs + nlimbs + 1);
xp = x->d;
ap = a->d;
if (nbits && alimbs)
{
x->nlimbs = alimbs + nlimbs + 1;
xp[alimbs + nlimbs] = _gcry_mpih_lshift (xp + nlimbs, ap, alimbs, nbits);
}
else
{
x->nlimbs = alimbs + nlimbs;
for (i = alimbs - 1; i >= 0; i--)
xp[i + nlimbs] = ap[i];
}
for (i = 0; i < nlimbs; i++)
xp[i] = 0;
x->flags = a->flags;
x->sign = a->sign;
MPN_NORMALIZE (x->d, x->nlimbs);
}