1------------------------------------------------------------------------------
2--                                                                          --
3--                   GNU ADA RUNTIME 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--                                 S p e c                                  --
8--                                                                          --
9--             Copyright (C) 2002 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 2,  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.  See the GNU General Public License --
17-- for  more details.  You should have  received  a copy of the GNU General --
18-- Public License  distributed with GNAT;  see file COPYING.  If not, write --
19-- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
20-- MA 02111-1307, USA.                                                      --
21--                                                                          --
22-- As a special exception,  if other files  instantiate  generics from this --
23-- unit, or you link  this unit with other files  to produce an executable, --
24-- this  unit  does not  by itself cause  the resulting  executable  to  be --
25-- covered  by the  GNU  General  Public  License.  This exception does not --
26-- however invalidate  any other reasons why  the executable file  might be --
27-- covered by the  GNU Public License.                                      --
28--                                                                          --
29-- GNAT was originally developed  by the GNAT team at  New York University. --
30-- Extensive contributions were provided by Ada Core Technologies Inc.      --
31--                                                                          --
32------------------------------------------------------------------------------
33
34with Unchecked_Conversion;
35
36package 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   --  Array type used to access by words
44
45   type Byte is range -128 .. +127;
46   for Byte'Size use 8;
47   --  Used to process operands by bytes
48
49   type Big_Bytes is array (Natural) of Byte;
50   type Big_Bytes_Ptr is access Big_Bytes;
51   --  Array type used to access by bytes
52
53   function To_Big_Words is new
54     Unchecked_Conversion (System.Address, Big_Words_Ptr);
55
56   function To_Big_Bytes is new
57     Unchecked_Conversion (System.Address, Big_Bytes_Ptr);
58
59   ----------------------
60   -- Compare_Array_S8 --
61   ----------------------
62
63   function Compare_Array_S8
64     (Left      : System.Address;
65      Right     : System.Address;
66      Left_Len  : Natural;
67      Right_Len : Natural)
68      return      Integer
69   is
70      Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
71
72   begin
73      --  If operands are non-aligned, or length is too short, go by bytes
74
75      if (((Left or Right) and 2#11#) /= 0) or else Compare_Len < 4 then
76         return Compare_Array_S8_Unaligned (Left, Right, Left_Len, Right_Len);
77      end if;
78
79      --  Here we can go by words
80
81      declare
82         LeftP  : constant Big_Words_Ptr := To_Big_Words (Left);
83         RightP : constant Big_Words_Ptr := To_Big_Words (Right);
84         Clen4  : constant Natural       := Compare_Len / 4 - 1;
85         Clen4F : constant Natural       := Clen4 * 4;
86
87      begin
88         for J in 0 .. Clen4 loop
89            if LeftP (J) /= RightP (J) then
90               return Compare_Array_S8_Unaligned
91                        (Left  + Address (4 * J),
92                         Right + Address (4 * J),
93                         4, 4);
94            end if;
95         end loop;
96
97         return Compare_Array_S8_Unaligned
98                  (Left      + Address (Clen4F),
99                   Right     + Address (Clen4F),
100                   Left_Len  - Clen4F,
101                   Right_Len - Clen4F);
102      end;
103   end Compare_Array_S8;
104
105   --------------------------------
106   -- Compare_Array_S8_Unaligned --
107   --------------------------------
108
109   function Compare_Array_S8_Unaligned
110     (Left      : System.Address;
111      Right     : System.Address;
112      Left_Len  : Natural;
113      Right_Len : Natural)
114      return      Integer
115   is
116      Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
117
118      LeftP  : constant Big_Bytes_Ptr := To_Big_Bytes (Left);
119      RightP : constant Big_Bytes_Ptr := To_Big_Bytes (Right);
120
121   begin
122      for J in 0 .. Compare_Len - 1 loop
123         if LeftP (J) /= RightP (J) then
124            if LeftP (J) > RightP (J) then
125               return +1;
126            else
127               return -1;
128            end if;
129         end if;
130      end loop;
131
132      if Left_Len = Right_Len then
133         return 0;
134      elsif Left_Len > Right_Len then
135         return +1;
136      else
137         return -1;
138      end if;
139   end Compare_Array_S8_Unaligned;
140
141end System.Compare_Array_Signed_8;
142