1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
|
------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME LIBRARY COMPONENTS --
-- --
-- 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 --
-- --
-- B o d y --
-- --
-- Copyright (C) 2002-2024, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
with System.Storage_Elements; use System.Storage_Elements;
with Ada.Unchecked_Conversion;
package body System.Compare_Array_Unsigned_8 is
type Word is mod 2 ** 32;
-- Used to process operands by words
type Big_Words is array (Natural) of Word;
type Big_Words_Ptr is access Big_Words;
for Big_Words_Ptr'Storage_Size use 0;
-- Array type used to access by words
type Byte is mod 2 ** 8;
-- Used to process operands by bytes
type Big_Bytes is array (Natural) of Byte;
type Big_Bytes_Ptr is access Big_Bytes;
for Big_Bytes_Ptr'Storage_Size use 0;
-- Array type used to access by bytes
function To_Big_Words is new
Ada.Unchecked_Conversion (System.Address, Big_Words_Ptr);
function To_Big_Bytes is new
Ada.Unchecked_Conversion (System.Address, Big_Bytes_Ptr);
pragma Annotate (Gnatcheck, Exempt_On, "Improper_Returns",
"early returns for performance");
----------------------
-- Compare_Array_U8 --
----------------------
function Compare_Array_U8
(Left : System.Address;
Right : System.Address;
Left_Len : Natural;
Right_Len : Natural) return Integer
is
Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
begin
-- If operands are non-aligned, or length is too short, go by bytes
if Left mod Storage_Offset (4) /= 0
or else Right mod Storage_Offset (4) /= 0
or else Compare_Len < 4
then
return Compare_Array_U8_Unaligned (Left, Right, Left_Len, Right_Len);
end if;
-- Here we can go by words
declare
LeftP : constant Big_Words_Ptr :=
To_Big_Words (Left);
RightP : constant Big_Words_Ptr :=
To_Big_Words (Right);
Words_To_Compare : constant Natural := Compare_Len / 4;
Bytes_Compared_As_Words : constant Natural := Words_To_Compare * 4;
begin
for J in 0 .. Words_To_Compare - 1 loop
if LeftP (J) /= RightP (J) then
return Compare_Array_U8_Unaligned
(Left + Storage_Offset (4 * J),
Right + Storage_Offset (4 * J),
4, 4);
end if;
end loop;
pragma Assert (Left_Len >= Bytes_Compared_As_Words);
pragma Assert (Right_Len >= Bytes_Compared_As_Words);
-- Left_Len and Right_Len are always greater or equal to
-- Bytes_Compared_As_Words because:
-- * Compare_Len is min (Left_Len, Right_Len)
-- * Words_To_Compare = Compare_Len / 4
-- * Bytes_Compared_As_Words = Words_To_Compare * 4
return Compare_Array_U8_Unaligned
(Left + Storage_Offset (Bytes_Compared_As_Words),
Right + Storage_Offset (Bytes_Compared_As_Words),
Left_Len - Bytes_Compared_As_Words,
Right_Len - Bytes_Compared_As_Words);
end;
end Compare_Array_U8;
--------------------------------
-- Compare_Array_U8_Unaligned --
--------------------------------
function Compare_Array_U8_Unaligned
(Left : System.Address;
Right : System.Address;
Left_Len : Natural;
Right_Len : Natural) return Integer
is
Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
LeftP : constant Big_Bytes_Ptr := To_Big_Bytes (Left);
RightP : constant Big_Bytes_Ptr := To_Big_Bytes (Right);
begin
for J in 0 .. Compare_Len - 1 loop
if LeftP (J) /= RightP (J) then
if LeftP (J) > RightP (J) then
return +1;
else
return -1;
end if;
end if;
end loop;
if Left_Len = Right_Len then
return 0;
elsif Left_Len > Right_Len then
return +1;
else
return -1;
end if;
end Compare_Array_U8_Unaligned;
pragma Annotate (Gnatcheck, Exempt_Off, "Improper_Returns");
end System.Compare_Array_Unsigned_8;
|
