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/* mpi-scan.c - MPI functions
* Copyright (C) 1998, 2001, 2002, 2003 Free Software Foundation, Inc.
*
* 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, 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 */
/* _gcry_mpi_getbyte( gcry_mpi_t 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 */
/* _gcry_mpi_putbyte( gcry_mpi_t 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
_gcry_mpi_trailing_zeros( gcry_mpi_t 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;
}
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