LXR linux/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