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155 lines
3.4 KiB
C
155 lines
3.4 KiB
C
/* mpi-bit.c - MPI bit level fucntions
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* Copyright (c) 1997 by Werner Koch (dd9jn)
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*
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* This file is part of G10.
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*
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* G10 is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* G10 is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#include <config.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <assert.h>
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#include "mpi-internal.h"
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/****************
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* Return the number of bits in A.
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* fixme: we should not count leading zero bits
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*/
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unsigned
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mpi_get_nbits( MPI a )
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{
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return a->nlimbs * BITS_PER_MPI_LIMB;
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}
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/****************
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* Test wether bit N is set.
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*/
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int
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mpi_test_bit( MPI a, unsigned n )
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{
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unsigned limbno, bitno;
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mpi_limb_t limb;
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limbno = n / BITS_PER_MPI_LIMB;
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bitno = n % BITS_PER_MPI_LIMB;
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if( limbno >= a->nlimbs )
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return 0; /* too far left: this is a 0 */
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limb = a->d[limbno];
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return (limb & (1 << bitno))? 1: 0;
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}
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/****************
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* Set bit N of A.
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*/
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void
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mpi_set_bit( MPI a, unsigned n )
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{
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unsigned limbno, bitno;
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limbno = n / BITS_PER_MPI_LIMB;
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bitno = n % BITS_PER_MPI_LIMB;
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if( limbno >= a->nlimbs ) { /* resize */
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if( a->alloced >= limbno )
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mpi_resize(a, limbno+1 );
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a->nlimbs = limbno+1;
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}
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a->d[limbno] |= (1<<bitno);
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}
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/****************
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* Clear bit N of A.
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*/
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void
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mpi_clear_bit( MPI a, unsigned n )
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{
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unsigned limbno, bitno;
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limbno = n / BITS_PER_MPI_LIMB;
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bitno = n % BITS_PER_MPI_LIMB;
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if( limbno >= a->nlimbs )
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return; /* don't need to clear this bit, it's to far to left */
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a->d[limbno] &= ~(1 << bitno);
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}
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void
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mpi_set_bytes( MPI a, unsigned nbits, byte (*fnc)(int), int opaque )
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{
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byte *p;
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unsigned nlimbs, nlimbs2, xbits, xbytes;
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unsigned n;
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int i;
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nlimbs = nbits / BITS_PER_MPI_LIMB;
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xbits = nbits % BITS_PER_MPI_LIMB;
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nlimbs2 = xbits? (nlimbs+1):nlimbs;
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xbytes = xbits / 8;
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xbits = xbits % 8;
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if( a->alloced < nlimbs2 )
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mpi_resize(a, nlimbs2 );
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a->nlimbs = nlimbs2;
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for(n=0; n < nlimbs; n++ ) {
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p = (byte*)(a->d+n);
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#ifdef HAVE_LITTLE_ENDIAN
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for(i=0; i < BYTES_PER_MPI_LIMB; i++ )
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p[i] = fnc(opaque);
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#else
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for(i=BYTES_PER_MPI_LIMB-1; i>=0; i-- )
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p[i] = fnc(opaque);
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#endif
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}
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if( xbytes ) {
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p = (byte*)(a->d+n);
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#ifdef HAVE_LITTLE_ENDIAN
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for(i=0; i < xbytes; i++ )
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p[i] = fnc(opaque);
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#else
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for(i=xbytes-1; i>=0; i-- )
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p[i] = fnc(opaque);
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#endif
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}
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assert(!xbits);
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}
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/****************
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* Shift A by N bits to the right
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* FIXME: should use alloc_limb if X and A are same.
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*/
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void
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mpi_rshift( MPI x, MPI a, unsigned n )
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{
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mpi_ptr_t xp;
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mpi_size_t xsize;
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xsize = a->nlimbs;
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x->sign = a->sign;
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RESIZE_IF_NEEDED(x, xsize);
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xp = x->d;
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if( xsize ) {
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mpihelp_rshift( xp, a->d, xsize, n);
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MPN_NORMALIZE( xp, xsize);
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}
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x->nlimbs = xsize;
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}
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