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 */
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 }