stdlib/cmp.c

   1 /* mpn_cmp -- Compare two low-level natural-number integers.
   2
   3 Copyright (C) 1991-2017 Free Software Foundation, Inc.
   4
   5 This file is part of the GNU MP Library.
   6
   7 The GNU MP Library is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU Lesser General Public License as published by
   9 the Free Software Foundation; either version 2.1 of the License, or (at your
  10 option) any later version.
  11
  12 The GNU MP Library is distributed in the hope that it will be useful, but
  13 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  14 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  15 License for more details.
  16
  17 You should have received a copy of the GNU Lesser General Public License
  18 along with the GNU MP Library; see the file COPYING.LIB.  If not, see
  19 <http://www.gnu.org/licenses/>.  */
  20
  21 #include <gmp.h>
  22 #include "gmp-impl.h"
  23
  24 /* Compare OP1_PTR/OP1_SIZE with OP2_PTR/OP2_SIZE.
  25    There are no restrictions on the relative sizes of
  26    the two arguments.
  27    Return 1 if OP1 > OP2, 0 if they are equal, and -1 if OP1 < OP2.  */
  28
  29 int
  30 mpn_cmp (mp_srcptr op1_ptr, mp_srcptr op2_ptr, mp_size_t size)
  31 {
  32   mp_size_t i;
  33   mp_limb_t op1_word, op2_word;
  34
  35   for (i = size - 1; i >= 0; i--)
  36     {
  37       op1_word = op1_ptr[i];
  38       op2_word = op2_ptr[i];
  39       if (op1_word != op2_word)
  40         goto diff;
  41     }
  42   return 0;
  43  diff:
  44   /* This can *not* be simplified to
  45         op2_word - op2_word
  46      since that expression might give signed overflow.  */
  47   return (op1_word > op2_word) ? 1 : -1;
  48 }