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) 2002-2013, 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         return Compare_Array_U8_Unaligned
102                  (AddA (Left,  Address (Bytes_Compared_As_Words)),
103                   AddA (Right, Address (Bytes_Compared_As_Words)),
104                   Left_Len  - Bytes_Compared_As_Words,
105                   Right_Len - Bytes_Compared_As_Words);
106      end;
107   end Compare_Array_U8;
108
109   --------------------------------
110   -- Compare_Array_U8_Unaligned --
111   --------------------------------
112
113   function Compare_Array_U8_Unaligned
114     (Left      : System.Address;
115      Right     : System.Address;
116      Left_Len  : Natural;
117      Right_Len : Natural) return Integer
118   is
119      Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
120
121      LeftP  : constant Big_Bytes_Ptr := To_Big_Bytes (Left);
122      RightP : constant Big_Bytes_Ptr := To_Big_Bytes (Right);
123
124   begin
125      for J in 0 .. Compare_Len - 1 loop
126         if LeftP (J) /= RightP (J) then
127            if LeftP (J) > RightP (J) then
128               return +1;
129            else
130               return -1;
131            end if;
132         end if;
133      end loop;
134
135      if Left_Len = Right_Len then
136         return 0;
137      elsif Left_Len > Right_Len then
138         return +1;
139      else
140         return -1;
141      end if;
142   end Compare_Array_U8_Unaligned;
143
144end System.Compare_Array_Unsigned_8;
145