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/* mpihelp-add.c - MPI helper functions
* Copyright (C) 1998 Free Software Foundation, Inc.
* Copyright (C) 1994, 1996 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
*
* 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"
/****************
* Add to S1_PTR with size S1_SIZE the limb S2_LIMB and
* store the result in RES_PTR. Return the carry
* S1_SIZE must be > 0.
*/
#ifndef __GNUC__
/*_EXTERN_INLINE */
mpi_limb_t
mpihelp_add_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;
*res_ptr++ = s2_limb;
if( s2_limb < x ) { /* sum is less than the left operand: handle carry */
while( --s1_size ) {
x = *s1_ptr++ + 1; /* add carry */
*res_ptr++ = x; /* and store */
if( x ) /* not 0 (no overflow): we can stop */
goto leave;
}
return 1; /* return carry (size of s1 to small) */
}
leave:
if( res_ptr != s1_ptr ) { /* not the same variable */
mpi_size_t i; /* copy the rest */
for( i=0; i < s1_size-1; i++ )
res_ptr[i] = s1_ptr[i];
}
return 0; /* no carry */
}
/*_EXTERN_INLINE*/
mpi_limb_t
mpihelp_add(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_add_n( res_ptr, s1_ptr, s2_ptr, s2_size );
if( s1_size - s2_size )
cy = mpihelp_add_1( res_ptr + s2_size, s1_ptr + s2_size,
s1_size - s2_size, cy);
return cy;
}
#endif
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