1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME LIBRARY COMPONENTS --
5 -- S Y S T E M . S T R I N G _ C O M P A R E --
9 -- Copyright (C) 2002-2007, Free Software Foundation, Inc. --
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, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
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. --
29 -- GNAT was originally developed by the GNAT team at New York University. --
30 -- Extensive contributions were provided by Ada Core Technologies Inc. --
32 ------------------------------------------------------------------------------
34 pragma Warnings (Off);
38 with Ada.Unchecked_Conversion;
40 package body System.String_Compare is
42 type Word is mod 2 ** 32;
43 -- Used to process operands by words
45 type Big_Words is array (Natural) of Word;
46 type Big_Words_Ptr is access Big_Words;
47 -- Array type used to access by words
49 type Byte is mod 2 ** 8;
50 -- Used to process operands by bytes
52 type Big_Bytes is array (Natural) of Byte;
53 type Big_Bytes_Ptr is access Big_Bytes;
54 -- Array type used to access by bytes
56 function To_Big_Words is new
57 Ada.Unchecked_Conversion (System.Address, Big_Words_Ptr);
59 function To_Big_Bytes is new
60 Ada.Unchecked_Conversion (System.Address, Big_Bytes_Ptr);
67 (Left : System.Address;
68 Right : System.Address;
70 Right_Len : Natural) return Integer
72 Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
75 -- If operands are non-aligned, or length is too short, go by bytes
77 if (((Left or Right) and 2#11#) /= 0) or else Compare_Len < 4 then
78 return Str_Compare_Bytes (Left, Right, Left_Len, Right_Len);
81 -- Here we can go by words
84 LeftP : constant Big_Words_Ptr := To_Big_Words (Left);
85 RightP : constant Big_Words_Ptr := To_Big_Words (Right);
86 Clen4 : constant Natural := Compare_Len / 4 - 1;
87 Clen4F : constant Natural := Clen4 * 4;
90 for J in 0 .. Clen4 loop
91 if LeftP (J) /= RightP (J) then
92 return Str_Compare_Bytes
93 (Left + Address (4 * J),
94 Right + Address (4 * J),
99 return Str_Compare_Bytes
100 (Left + Address (Clen4F),
101 Right + Address (Clen4F),
107 -----------------------
108 -- Str_Compare_Bytes --
109 -----------------------
111 function Str_Compare_Bytes
112 (Left : System.Address;
113 Right : System.Address;
115 Right_Len : Natural) return Integer
117 Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
119 LeftP : constant Big_Bytes_Ptr := To_Big_Bytes (Left);
120 RightP : constant Big_Bytes_Ptr := To_Big_Bytes (Right);
123 for J in 0 .. Compare_Len - 1 loop
124 if LeftP (J) /= RightP (J) then
125 if LeftP (J) > RightP (J) then
133 if Left_Len = Right_Len then
135 elsif Left_Len > Right_Len then
140 end Str_Compare_Bytes;
142 end System.String_Compare;