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202 lines
4.4 KiB
C
202 lines
4.4 KiB
C
/* mpi-bit.c - MPI bit level fucntions
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* Copyright (C) 1998 Free Software Foundation, Inc.
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*
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* This file is part of GnuPG.
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*
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* GnuPG 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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* GnuPG 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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#include "longlong.h"
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#ifdef MPI_INTERNAL_NEED_CLZ_TAB
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#ifdef __STDC__
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const
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#endif
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unsigned char
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__clz_tab[] =
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{
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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};
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#endif
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#define A_LIMB_1 ((mpi_limb_t)1)
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/****************
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* Return the number of bits in A.
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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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unsigned n;
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if( mpi_is_protected(a) ) {
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n = mpi_get_nbit_info(a);
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if( !n )
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n = a->nlimbs * BITS_PER_MPI_LIMB;
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return n;
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}
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if( a->nlimbs ) {
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mpi_limb_t alimb = a->d[a->nlimbs-1];
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if( alimb )
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count_leading_zeros( n, alimb );
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else
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n = BITS_PER_MPI_LIMB;
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n = BITS_PER_MPI_LIMB - n + (a->nlimbs-1) * BITS_PER_MPI_LIMB;
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}
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else
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n = 0;
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return n;
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}
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/****************
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* Test whether 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 & (A_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] |= (A_LIMB_1<<bitno);
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}
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/****************
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* Set bit N of A. and clear all bits above
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*/
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void
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mpi_set_highbit( 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] |= (A_LIMB_1<<bitno);
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for( bitno++; bitno < BITS_PER_MPI_LIMB; bitno++ )
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a->d[limbno] &= ~(A_LIMB_1 << bitno);
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a->nlimbs = limbno+1;
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}
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/****************
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* clear bit N of A and all bits above
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*/
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void
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mpi_clear_highbit( 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; /* not allocated, so need to clear bits :-) */
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for( ; bitno < BITS_PER_MPI_LIMB; bitno++ )
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a->d[limbno] &= ~(A_LIMB_1 << bitno);
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a->nlimbs = limbno+1;
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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] &= ~(A_LIMB_1 << bitno);
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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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