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/* mpihelp-sub.c - MPI helper functions
* Copyright (c) 1997 by Werner Koch (dd9jn)
* Copyright (C) 1994, 1996 Free Software Foundation, Inc.
*
* 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
*
* Note: This code is heavily based on the GNU MP Library.
* Actually it's the same code with only minor changes in the
* way the data is stored; this is to support the abstraction
* of an optional secure memory allocation which may be used
* to avoid revealing of sensitive data due to paging etc.
* The GNU MP Library itself is published under the LGPL;
* however I decided to publish this code under the plain GPL.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include "mpi-internal.h"
#ifndef __GNUC__
mpi_limb_t
mpihelp_sub_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
mpi_size_t s1_size, mpi_limb_t s2_limb )
{
mpi_limb_t x;
x = *s1_ptr++;
s2_limb = x - s2_limb;
*res_ptr++ = s2_limb;
if( s2_limb > x ) {
while( --s1_size ) {
x = *s1_ptr++;
*res_ptr++ = x - 1;
if( x )
goto leave;
}
return 1;
}
leave:
if( res_ptr != s1_ptr ) {
mpi_size_t i;
for( i=0; i < s1_size-1; i++ )
res_ptr[i] = s1_ptr[i];
}
return 0;
}
mpi_limb_t
mpihelp_sub( mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
mpi_ptr_t s2_ptr, mpi_size_t s2_size)
{
mpi_limb_t cy = 0;
if( s2_size )
cy = mpihelp_sub_n(res_ptr, s1_ptr, s2_ptr, s2_size);
if( s1_size - s2_size )
cy = mpihelp_sub_1(res_ptr + s2_size, s1_ptr + s2_size,
s1_size - s2_size, cy);
return cy;
}
#endif
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