File : s-memcom.adb


   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                  S Y S T E M .  M E M O R Y _ C O M P A R E              --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --            Copyright (C) 2006-2014, Free Software Foundation, Inc.       --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  17 --                                                                          --
  18 --                                                                          --
  19 --                                                                          --
  20 --                                                                          --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31 
  32 with Ada.Unchecked_Conversion;
  33 with Interfaces.C; use Interfaces.C;
  34 
  35 package body System.Memory_Compare is
  36 
  37    subtype mem is char_array (size_t);
  38    type memptr is access mem;
  39 
  40    function to_memptr is new Ada.Unchecked_Conversion (Address, memptr);
  41 
  42    ------------
  43    -- memcmp --
  44    ------------
  45 
  46    function memcmp (S1 : Address; S2 : Address; N : size_t) return int is
  47       s1_p : constant memptr := to_memptr (S1);
  48       s2_p : constant memptr := to_memptr (S2);
  49 
  50    begin
  51       if N = 0 then
  52          return 0;
  53       end if;
  54 
  55       for J in 0 .. N - 1 loop
  56          if s1_p (J) < s2_p (J) then
  57             return -1;
  58          elsif s1_p (J) > s2_p (J) then
  59             return 1;
  60          end if;
  61       end loop;
  62 
  63       return 0;
  64    end memcmp;
  65 
  66 end System.Memory_Compare;