mirror of
git://git.gnupg.org/gnupg.git
synced 2024-11-13 22:08:52 +01:00
133 lines
3.2 KiB
C
133 lines
3.2 KiB
C
/* mpi-scan.c - MPI functions
|
|
* Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
|
|
*
|
|
* This file is part of GnuPG.
|
|
*
|
|
* GnuPG 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.
|
|
*
|
|
* GnuPG 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 "mpi-internal.h"
|
|
#include "longlong.h"
|
|
|
|
/****************
|
|
* Scan through an mpi and return byte for byte. a -1 is returned to indicate
|
|
* the end of the mpi. Scanning is done from the lsb to the msb, returned
|
|
* values are in the range of 0 .. 255.
|
|
*
|
|
* FIXME: This code is VERY ugly!
|
|
*/
|
|
int
|
|
mpi_getbyte( MPI a, unsigned idx )
|
|
{
|
|
int i, j;
|
|
unsigned n;
|
|
mpi_ptr_t ap;
|
|
mpi_limb_t limb;
|
|
|
|
ap = a->d;
|
|
for(n=0,i=0; i < a->nlimbs; i++ ) {
|
|
limb = ap[i];
|
|
for( j=0; j < BYTES_PER_MPI_LIMB; j++, n++ )
|
|
if( n == idx )
|
|
return (limb >> j*8) & 0xff;
|
|
}
|
|
return -1;
|
|
}
|
|
|
|
|
|
/****************
|
|
* Put a value at position IDX into A. idx counts from lsb to msb
|
|
*/
|
|
void
|
|
mpi_putbyte( MPI a, unsigned idx, int xc )
|
|
{
|
|
int i, j;
|
|
unsigned n;
|
|
mpi_ptr_t ap;
|
|
mpi_limb_t limb, c;
|
|
|
|
c = xc & 0xff;
|
|
ap = a->d;
|
|
for(n=0,i=0; i < a->alloced; i++ ) {
|
|
limb = ap[i];
|
|
for( j=0; j < BYTES_PER_MPI_LIMB; j++, n++ )
|
|
if( n == idx ) {
|
|
#if BYTES_PER_MPI_LIMB == 4
|
|
if( j == 0 )
|
|
limb = (limb & 0xffffff00) | c;
|
|
else if( j == 1 )
|
|
limb = (limb & 0xffff00ff) | (c<<8);
|
|
else if( j == 2 )
|
|
limb = (limb & 0xff00ffff) | (c<<16);
|
|
else
|
|
limb = (limb & 0x00ffffff) | (c<<24);
|
|
#elif BYTES_PER_MPI_LIMB == 8
|
|
if( j == 0 )
|
|
limb = (limb & 0xffffffffffffff00) | c;
|
|
else if( j == 1 )
|
|
limb = (limb & 0xffffffffffff00ff) | (c<<8);
|
|
else if( j == 2 )
|
|
limb = (limb & 0xffffffffff00ffff) | (c<<16);
|
|
else if( j == 3 )
|
|
limb = (limb & 0xffffffff00ffffff) | (c<<24);
|
|
else if( j == 4 )
|
|
limb = (limb & 0xffffff00ffffffff) | (c<<32);
|
|
else if( j == 5 )
|
|
limb = (limb & 0xffff00ffffffffff) | (c<<40);
|
|
else if( j == 6 )
|
|
limb = (limb & 0xff00ffffffffffff) | (c<<48);
|
|
else
|
|
limb = (limb & 0x00ffffffffffffff) | (c<<56);
|
|
#else
|
|
#error please enhance this function, its ugly - i know.
|
|
#endif
|
|
if( a->nlimbs <= i )
|
|
a->nlimbs = i+1;
|
|
ap[i] = limb;
|
|
return;
|
|
}
|
|
}
|
|
abort(); /* index out of range */
|
|
}
|
|
|
|
|
|
/****************
|
|
* Count the number of zerobits at the low end of A
|
|
*/
|
|
unsigned
|
|
mpi_trailing_zeros( MPI a )
|
|
{
|
|
unsigned n, count = 0;
|
|
|
|
for(n=0; n < a->nlimbs; n++ ) {
|
|
if( a->d[n] ) {
|
|
unsigned nn;
|
|
mpi_limb_t alimb = a->d[n];
|
|
|
|
count_trailing_zeros( nn, alimb );
|
|
count += nn;
|
|
break;
|
|
}
|
|
count += BITS_PER_MPI_LIMB;
|
|
}
|
|
return count;
|
|
|
|
}
|
|
|
|
|