gcc/ada/s-carsi8.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                    GNAT RUN-TIME LIBRARY COMPONENTS                      --
   4 --                                                                          --
   5 --         S Y S T E M . C O M P A R E _ A R R A Y _ S I G N E D _ 8        --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 2002-2009, 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 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  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 System.Address_Operations; use System.Address_Operations;
  33
  34 with Ada.Unchecked_Conversion;
  35
  36 package body System.Compare_Array_Signed_8 is
  37
  38    type Word is mod 2 ** 32;
  39    --  Used to process operands by words
  40
  41    type Big_Words is array (Natural) of Word;
  42    type Big_Words_Ptr is access Big_Words;
  43    for Big_Words_Ptr'Storage_Size use 0;
  44    --  Array type used to access by words
  45
  46    type Byte is range -128 .. +127;
  47    for Byte'Size use 8;
  48    --  Used to process operands by bytes
  49
  50    type Big_Bytes is array (Natural) of Byte;
  51    type Big_Bytes_Ptr is access Big_Bytes;
  52    for Big_Bytes_Ptr'Storage_Size use 0;
  53    --  Array type used to access by bytes
  54
  55    function To_Big_Words is new
  56      Ada.Unchecked_Conversion (System.Address, Big_Words_Ptr);
  57
  58    function To_Big_Bytes is new
  59      Ada.Unchecked_Conversion (System.Address, Big_Bytes_Ptr);
  60
  61    ----------------------
  62    -- Compare_Array_S8 --
  63    ----------------------
  64
  65    function Compare_Array_S8
  66      (Left      : System.Address;
  67       Right     : System.Address;
  68       Left_Len  : Natural;
  69       Right_Len : Natural) return Integer
  70    is
  71       Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
  72
  73    begin
  74       --  If operands are non-aligned, or length is too short, go by bytes
  75
  76       if ModA (OrA (Left, Right), 4) /= 0 or else Compare_Len < 4 then
  77          return Compare_Array_S8_Unaligned (Left, Right, Left_Len, Right_Len);
  78       end if;
  79
  80       --  Here we can go by words
  81
  82       declare
  83          LeftP                   : constant Big_Words_Ptr :=
  84                                      To_Big_Words (Left);
  85          RightP                  : constant Big_Words_Ptr :=
  86                                      To_Big_Words (Right);
  87          Words_To_Compare        : constant Natural := Compare_Len / 4;
  88          Bytes_Compared_As_Words : constant Natural := Words_To_Compare * 4;
  89
  90       begin
  91          for J in 0 .. Words_To_Compare - 1 loop
  92             if LeftP (J) /= RightP (J) then
  93                return Compare_Array_S8_Unaligned
  94                         (AddA (Left,  Address (4 * J)),
  95                          AddA (Right, Address (4 * J)),
  96                          4, 4);
  97             end if;
  98          end loop;
  99
 100          return Compare_Array_S8_Unaligned
 101                   (AddA (Left,  Address (Bytes_Compared_As_Words)),
 102                    AddA (Right, Address (Bytes_Compared_As_Words)),
 103                    Left_Len  - Bytes_Compared_As_Words,
 104                    Right_Len - Bytes_Compared_As_Words);
 105       end;
 106    end Compare_Array_S8;
 107
 108    --------------------------------
 109    -- Compare_Array_S8_Unaligned --
 110    --------------------------------
 111
 112    function Compare_Array_S8_Unaligned
 113      (Left      : System.Address;
 114       Right     : System.Address;
 115       Left_Len  : Natural;
 116       Right_Len : Natural) return Integer
 117    is
 118       Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
 119
 120       LeftP  : constant Big_Bytes_Ptr := To_Big_Bytes (Left);
 121       RightP : constant Big_Bytes_Ptr := To_Big_Bytes (Right);
 122
 123    begin
 124       for J in 0 .. Compare_Len - 1 loop
 125          if LeftP (J) /= RightP (J) then
 126             if LeftP (J) > RightP (J) then
 127                return +1;
 128             else
 129                return -1;
 130             end if;
 131          end if;
 132       end loop;
 133
 134       if Left_Len = Right_Len then
 135          return 0;
 136       elsif Left_Len > Right_Len then
 137          return +1;
 138       else
 139          return -1;
 140       end if;
 141    end Compare_Array_S8_Unaligned;
 142
 143 end System.Compare_Array_Signed_8;