Root/lib/mpi/mpih-cmp.c

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 */
38int 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
51diff:
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

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