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) 2002-2020, 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
32with System.Address_Operations; use System.Address_Operations;
33
34with Ada.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   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         pragma Assert (Left_Len >= Bytes_Compared_As_Words);
101         pragma Assert (Right_Len >= Bytes_Compared_As_Words);
102         --  Left_Len and Right_Len are always greater or equal to
103         --  Bytes_Compared_As_Words because:
104         --    * Compare_Len is min (Left_Len, Right_Len)
105         --    * Words_To_Compare = Compare_Len / 4
106         --    * Bytes_Compared_As_Words = Words_To_Compare * 4
107         return Compare_Array_S8_Unaligned
108                  (AddA (Left,  Address (Bytes_Compared_As_Words)),
109                   AddA (Right, Address (Bytes_Compared_As_Words)),
110                   Left_Len  - Bytes_Compared_As_Words,
111                   Right_Len - Bytes_Compared_As_Words);
112      end;
113   end Compare_Array_S8;
114
115   --------------------------------
116   -- Compare_Array_S8_Unaligned --
117   --------------------------------
118
119   function Compare_Array_S8_Unaligned
120     (Left      : System.Address;
121      Right     : System.Address;
122      Left_Len  : Natural;
123      Right_Len : Natural) return Integer
124   is
125      Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
126
127      LeftP  : constant Big_Bytes_Ptr := To_Big_Bytes (Left);
128      RightP : constant Big_Bytes_Ptr := To_Big_Bytes (Right);
129
130   begin
131      for J in 0 .. Compare_Len - 1 loop
132         if LeftP (J) /= RightP (J) then
133            if LeftP (J) > RightP (J) then
134               return +1;
135            else
136               return -1;
137            end if;
138         end if;
139      end loop;
140
141      if Left_Len = Right_Len then
142         return 0;
143      elsif Left_Len > Right_Len then
144         return +1;
145      else
146         return -1;
147      end if;
148   end Compare_Array_S8_Unaligned;
149
150end System.Compare_Array_Signed_8;
151