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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME LIBRARY COMPONENTS --
-- --
-- S Y S T E M . S T R I N G _ C O M P A R E --
-- --
-- B o d y --
-- --
-- Copyright (C) 2002-2009, 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. --
-- --
------------------------------------------------------------------------------
pragma Compiler_Unit;
with Ada.Unchecked_Conversion;
package body System.String_Compare 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);
-----------------
-- Str_Compare --
-----------------
function Str_Compare
(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 or Right) and 2#11#) /= 0) or else Compare_Len < 4 then
return Str_Compare_Bytes (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);
Clen4 : constant Natural := Compare_Len / 4 - 1;
Clen4F : constant Natural := Clen4 * 4;
begin
for J in 0 .. Clen4 loop
if LeftP (J) /= RightP (J) then
return Str_Compare_Bytes
(Left + Address (4 * J),
Right + Address (4 * J),
4, 4);
end if;
end loop;
return Str_Compare_Bytes
(Left + Address (Clen4F),
Right + Address (Clen4F),
Left_Len - Clen4F,
Right_Len - Clen4F);
end;
end Str_Compare;
-----------------------
-- Str_Compare_Bytes --
-----------------------
function Str_Compare_Bytes
(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 Str_Compare_Bytes;
end System.String_Compare;
|
