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/* mpi-bit.c - MPI bit level fucntions
* Copyright (c) 1997 by Werner Koch (dd9jn)
*
* This file is part of G10.
*
* G10 is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* G10 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 General Public License for more details.
*
* You should have received a copy of the GNU 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 <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "mpi-internal.h"
/****************
* Return the number of bits in A.
* fixme: we should not count leading zero bits
*/
unsigned
mpi_get_nbits( MPI a )
{
return a->nlimbs * BITS_PER_MPI_LIMB;
}
/****************
* Test wether bit N is set.
*/
int
mpi_test_bit( MPI a, unsigned n )
{
unsigned 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 & (1 << bitno))? 1: 0;
}
/****************
* Set bit N of A.
*/
void
mpi_set_bit( MPI a, unsigned n )
{
unsigned limbno, bitno;
limbno = n / BITS_PER_MPI_LIMB;
bitno = n % BITS_PER_MPI_LIMB;
if( limbno >= a->nlimbs ) { /* resize */
if( a->alloced >= limbno )
mpi_resize(a, limbno+1 );
a->nlimbs = limbno+1;
}
a->d[limbno] |= (1<<bitno);
}
/****************
* Clear bit N of A.
*/
void
mpi_clear_bit( MPI a, unsigned n )
{
unsigned 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] &= ~(1 << bitno);
}
void
mpi_set_bytes( MPI a, unsigned nbits, byte (*fnc)(int), int opaque )
{
byte *p;
unsigned nlimbs, nlimbs2, xbits, xbytes;
unsigned n;
int i;
nlimbs = nbits / BITS_PER_MPI_LIMB;
xbits = nbits % BITS_PER_MPI_LIMB;
nlimbs2 = xbits? (nlimbs+1):nlimbs;
xbytes = xbits / 8;
xbits = xbits % 8;
if( a->alloced < nlimbs2 )
mpi_resize(a, nlimbs2 );
a->nlimbs = nlimbs2;
for(n=0; n < nlimbs; n++ ) {
p = (byte*)(a->d+n);
#ifdef HAVE_LITTLE_ENDIAN
for(i=0; i < BYTES_PER_MPI_LIMB; i++ )
p[i] = fnc(opaque);
#else
for(i=BYTES_PER_MPI_LIMB-1; i>=0; i-- )
p[i] = fnc(opaque);
#endif
}
if( xbytes ) {
p = (byte*)(a->d+n);
#ifdef HAVE_LITTLE_ENDIAN
for(i=0; i < xbytes; i++ )
p[i] = fnc(opaque);
#else
for(i=xbytes-1; i>=0; i-- )
p[i] = fnc(opaque);
#endif
}
assert(!xbits);
}
/****************
* Shift A by N bits to the right
* FIXME: should use alloc_limb if X and A are same.
*/
void
mpi_rshift( MPI x, MPI a, unsigned n )
{
mpi_ptr_t xp;
mpi_size_t xsize;
xsize = a->nlimbs;
x->sign = a->sign;
RESIZE_IF_NEEDED(x, xsize);
xp = x->d;
if( xsize ) {
mpihelp_rshift( xp, a->d, xsize, n);
MPN_NORMALIZE( xp, xsize);
}
x->nlimbs = xsize;
}
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