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[/] [openrisc/] [trunk/] [gnu-src/] [gcc-4.5.1/] [gcc/] [ada/] [s-strcom.adb] - Blame information for rev 410

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1 281 jeremybenn
------------------------------------------------------------------------------
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--                                                                          --
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--                    GNAT RUN-TIME LIBRARY COMPONENTS                      --
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--                                                                          --
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--                S Y S T E M . S T R I N G _ C O M P A R E                 --
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--                                                                          --
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--                                 B o d y                                  --
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--                                                                          --
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--          Copyright (C) 2002-2009, Free Software Foundation, Inc.         --
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--                                                                          --
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-- GNAT is free software;  you can  redistribute it  and/or modify it under --
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-- terms of the  GNU General Public License as published  by the Free Soft- --
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-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
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-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
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--                                                                          --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception,   --
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-- version 3.1, as published by the Free Software Foundation.               --
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--                                                                          --
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-- You should have received a copy of the GNU General Public License and    --
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-- a copy of the GCC Runtime Library Exception along with this program;     --
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-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
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-- <http://www.gnu.org/licenses/>.                                          --
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--                                                                          --
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-- GNAT was originally developed  by the GNAT team at  New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc.      --
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--                                                                          --
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------------------------------------------------------------------------------
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pragma Compiler_Unit;
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with Ada.Unchecked_Conversion;
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package body System.String_Compare is
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   type Word is mod 2 ** 32;
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   --  Used to process operands by words
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   type Big_Words is array (Natural) of Word;
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   type Big_Words_Ptr is access Big_Words;
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   for Big_Words_Ptr'Storage_Size use 0;
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   --  Array type used to access by words
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   type Byte is mod 2 ** 8;
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   --  Used to process operands by bytes
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   type Big_Bytes is array (Natural) of Byte;
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   type Big_Bytes_Ptr is access Big_Bytes;
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   for Big_Bytes_Ptr'Storage_Size use 0;
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   --  Array type used to access by bytes
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   function To_Big_Words is new
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     Ada.Unchecked_Conversion (System.Address, Big_Words_Ptr);
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   function To_Big_Bytes is new
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     Ada.Unchecked_Conversion (System.Address, Big_Bytes_Ptr);
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   -----------------
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   -- Str_Compare --
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   -----------------
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   function Str_Compare
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     (Left      : System.Address;
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      Right     : System.Address;
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      Left_Len  : Natural;
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      Right_Len : Natural) return Integer
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   is
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      Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
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   begin
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      --  If operands are non-aligned, or length is too short, go by bytes
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      if (((Left or Right) and 2#11#) /= 0) or else Compare_Len < 4 then
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         return Str_Compare_Bytes (Left, Right, Left_Len, Right_Len);
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      end if;
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      --  Here we can go by words
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      declare
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         LeftP  : constant Big_Words_Ptr := To_Big_Words (Left);
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         RightP : constant Big_Words_Ptr := To_Big_Words (Right);
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         Clen4  : constant Natural       := Compare_Len / 4 - 1;
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         Clen4F : constant Natural       := Clen4 * 4;
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      begin
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         for J in 0 .. Clen4 loop
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            if LeftP (J) /= RightP (J) then
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               return Str_Compare_Bytes
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                        (Left  + Address (4 * J),
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                         Right + Address (4 * J),
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                         4, 4);
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            end if;
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         end loop;
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         return Str_Compare_Bytes
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                  (Left      + Address (Clen4F),
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                   Right     + Address (Clen4F),
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                   Left_Len  - Clen4F,
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                   Right_Len - Clen4F);
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      end;
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   end Str_Compare;
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   -----------------------
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   -- Str_Compare_Bytes --
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   -----------------------
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   function Str_Compare_Bytes
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     (Left      : System.Address;
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      Right     : System.Address;
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      Left_Len  : Natural;
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      Right_Len : Natural) return Integer
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   is
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      Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
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      LeftP  : constant Big_Bytes_Ptr := To_Big_Bytes (Left);
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      RightP : constant Big_Bytes_Ptr := To_Big_Bytes (Right);
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   begin
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      for J in 0 .. Compare_Len - 1 loop
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         if LeftP (J) /= RightP (J) then
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            if LeftP (J) > RightP (J) then
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               return +1;
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            else
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               return -1;
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            end if;
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         end if;
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      end loop;
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      if Left_Len = Right_Len then
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         return 0;
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      elsif Left_Len > Right_Len then
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         return +1;
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      else
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         return -1;
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      end if;
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   end Str_Compare_Bytes;
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end System.String_Compare;

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