1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* mpihelp-sub.c  -  MPI helper functions
3  *	Copyright (C) 1994, 1996 Free Software Foundation, Inc.
4  *	Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
5  *
6  * This file is part of GnuPG.
7  *
8  * Note: This code is heavily based on the GNU MP Library.
9  *	 Actually it's the same code with only minor changes in the
10  *	 way the data is stored; this is to support the abstraction
11  *	 of an optional secure memory allocation which may be used
12  *	 to avoid revealing of sensitive data due to paging etc.
13  *	 The GNU MP Library itself is published under the LGPL;
14  *	 however I decided to publish this code under the plain GPL.
15  */
16 
17 #include "mpi-internal.h"
18 
19 /****************
20  * Compare OP1_PTR/OP1_SIZE with OP2_PTR/OP2_SIZE.
21  * There are no restrictions on the relative sizes of
22  * the two arguments.
23  * Return 1 if OP1 > OP2, 0 if they are equal, and -1 if OP1 < OP2.
24  */
mpihelp_cmp(mpi_ptr_t op1_ptr,mpi_ptr_t op2_ptr,mpi_size_t size)25 int mpihelp_cmp(mpi_ptr_t op1_ptr, mpi_ptr_t op2_ptr, mpi_size_t size)
26 {
27 	mpi_size_t i;
28 	mpi_limb_t op1_word, op2_word;
29 
30 	for (i = size - 1; i >= 0; i--) {
31 		op1_word = op1_ptr[i];
32 		op2_word = op2_ptr[i];
33 		if (op1_word != op2_word)
34 			goto diff;
35 	}
36 	return 0;
37 
38 diff:
39 	/* This can *not* be simplified to
40 	 *   op2_word - op2_word
41 	 * since that expression might give signed overflow.  */
42 	return (op1_word > op2_word) ? 1 : -1;
43 }
44