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 _ U N S I G N E D _ 8      --
6--                                                                          --
7--                                 B o d y                                  --
8--                                                                          --
9--          Copyright (C) 2002-2021, 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
32pragma Compiler_Unit_Warning;
33
34with System.Address_Operations; use System.Address_Operations;
35
36with Ada.Unchecked_Conversion;
37
38package body System.Compare_Array_Unsigned_8 is
39
40   type Word is mod 2 ** 32;
41   --  Used to process operands by words
42
43   type Big_Words is array (Natural) of Word;
44   type Big_Words_Ptr is access Big_Words;
45   for Big_Words_Ptr'Storage_Size use 0;
46   --  Array type used to access by words
47
48   type Byte is mod 2 ** 8;
49   --  Used to process operands by bytes
50
51   type Big_Bytes is array (Natural) of Byte;
52   type Big_Bytes_Ptr is access Big_Bytes;
53   for Big_Bytes_Ptr'Storage_Size use 0;
54   --  Array type used to access by bytes
55
56   function To_Big_Words is new
57     Ada.Unchecked_Conversion (System.Address, Big_Words_Ptr);
58
59   function To_Big_Bytes is new
60     Ada.Unchecked_Conversion (System.Address, Big_Bytes_Ptr);
61
62   ----------------------
63   -- Compare_Array_U8 --
64   ----------------------
65
66   function Compare_Array_U8
67     (Left      : System.Address;
68      Right     : System.Address;
69      Left_Len  : Natural;
70      Right_Len : Natural) return Integer
71   is
72      Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
73
74   begin
75      --  If operands are non-aligned, or length is too short, go by bytes
76
77      if (ModA (OrA (Left, Right), 4) /= 0) or else Compare_Len < 4 then
78         return Compare_Array_U8_Unaligned (Left, Right, Left_Len, Right_Len);
79      end if;
80
81      --  Here we can go by words
82
83      declare
84         LeftP                   : constant Big_Words_Ptr :=
85                                     To_Big_Words (Left);
86         RightP                  : constant Big_Words_Ptr :=
87                                     To_Big_Words (Right);
88         Words_To_Compare        : constant Natural := Compare_Len / 4;
89         Bytes_Compared_As_Words : constant Natural := Words_To_Compare * 4;
90
91      begin
92         for J in 0 .. Words_To_Compare - 1 loop
93            if LeftP (J) /= RightP (J) then
94               return Compare_Array_U8_Unaligned
95                        (AddA (Left,  Address (4 * J)),
96                         AddA (Right, Address (4 * J)),
97                         4, 4);
98            end if;
99         end loop;
100
101         pragma Assert (Left_Len >= Bytes_Compared_As_Words);
102         pragma Assert (Right_Len >= Bytes_Compared_As_Words);
103         --  Left_Len and Right_Len are always greater or equal to
104         --  Bytes_Compared_As_Words because:
105         --    * Compare_Len is min (Left_Len, Right_Len)
106         --    * Words_To_Compare = Compare_Len / 4
107         --    * Bytes_Compared_As_Words = Words_To_Compare * 4
108         return Compare_Array_U8_Unaligned
109                  (AddA (Left,  Address (Bytes_Compared_As_Words)),
110                   AddA (Right, Address (Bytes_Compared_As_Words)),
111                   Left_Len  - Bytes_Compared_As_Words,
112                   Right_Len - Bytes_Compared_As_Words);
113      end;
114   end Compare_Array_U8;
115
116   --------------------------------
117   -- Compare_Array_U8_Unaligned --
118   --------------------------------
119
120   function Compare_Array_U8_Unaligned
121     (Left      : System.Address;
122      Right     : System.Address;
123      Left_Len  : Natural;
124      Right_Len : Natural) return Integer
125   is
126      Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
127
128      LeftP  : constant Big_Bytes_Ptr := To_Big_Bytes (Left);
129      RightP : constant Big_Bytes_Ptr := To_Big_Bytes (Right);
130
131   begin
132      for J in 0 .. Compare_Len - 1 loop
133         if LeftP (J) /= RightP (J) then
134            if LeftP (J) > RightP (J) then
135               return +1;
136            else
137               return -1;
138            end if;
139         end if;
140      end loop;
141
142      if Left_Len = Right_Len then
143         return 0;
144      elsif Left_Len > Right_Len then
145         return +1;
146      else
147         return -1;
148      end if;
149   end Compare_Array_U8_Unaligned;
150
151end System.Compare_Array_Unsigned_8;
152