1 /* mpihelp-sub.c  -  MPI helper functions
2  *	Copyright (C) 1994, 1996 Free Software Foundation, Inc.
3  *	Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
4  *
5  * This file is part of GnuPG.
6  *
7  * GnuPG is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License as published by
9  * the Free Software Foundation; either version 2 of the License, or
10  * (at your option) any later version.
11  *
12  * GnuPG is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with this program; if not, write to the Free Software
19  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
20  *
21  * Note: This code is heavily based on the GNU MP Library.
22  *	 Actually it's the same code with only minor changes in the
23  *	 way the data is stored; this is to support the abstraction
24  *	 of an optional secure memory allocation which may be used
25  *	 to avoid revealing of sensitive data due to paging etc.
26  *	 The GNU MP Library itself is published under the LGPL;
27  *	 however I decided to publish this code under the plain GPL.
28  */
29 
30 #include "mpi-internal.h"
31 
32 /****************
33  * Compare OP1_PTR/OP1_SIZE with OP2_PTR/OP2_SIZE.
34  * There are no restrictions on the relative sizes of
35  * the two arguments.
36  * Return 1 if OP1 > OP2, 0 if they are equal, and -1 if OP1 < OP2.
37  */
mpihelp_cmp(mpi_ptr_t op1_ptr,mpi_ptr_t op2_ptr,mpi_size_t size)38 int mpihelp_cmp(mpi_ptr_t op1_ptr, mpi_ptr_t op2_ptr, mpi_size_t size)
39 {
40 	mpi_size_t i;
41 	mpi_limb_t op1_word, op2_word;
42 
43 	for (i = size - 1; i >= 0; i--) {
44 		op1_word = op1_ptr[i];
45 		op2_word = op2_ptr[i];
46 		if (op1_word != op2_word)
47 			goto diff;
48 	}
49 	return 0;
50 
51 diff:
52 	/* This can *not* be simplified to
53 	 *   op2_word - op2_word
54 	 * since that expression might give signed overflow.  */
55 	return (op1_word > op2_word) ? 1 : -1;
56 }
57