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1 12 jlechner
------------------------------------------------------------------------------
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--                                                                          --
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--                         GNAT RUN-TIME COMPONENTS                         --
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--                                                                          --
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--                       S Y S T E M . W C H _ J I S                        --
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--                                                                          --
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--                                 B o d y                                  --
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--                                                                          --
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--          Copyright (C) 1992-2005, 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 2,  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.  See the GNU General Public License --
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-- for  more details.  You should have  received  a copy of the GNU General --
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-- Public License  distributed with GNAT;  see file COPYING.  If not, write --
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-- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
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-- Boston, MA 02110-1301, USA.                                              --
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--                                                                          --
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-- As a special exception,  if other files  instantiate  generics from this --
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-- unit, or you link  this unit with other files  to produce an executable, --
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-- this  unit  does not  by itself cause  the resulting  executable  to  be --
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-- covered  by the  GNU  General  Public  License.  This exception does not --
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-- however invalidate  any other reasons why  the executable file  might be --
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-- covered by the  GNU Public License.                                      --
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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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package body System.WCh_JIS is
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   type Byte is mod 256;
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   EUC_Hankaku_Kana : constant Byte := 16#8E#;
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   --  Prefix byte in EUC for Hankaku Kana (small Katakana). Such characters
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   --  in EUC are represented by a prefix byte followed by the code, which
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   --  is in the upper half (the corresponding JIS internal code is in the
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   --  range 16#0080# - 16#00FF#).
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   function EUC_To_JIS (EUC1, EUC2 : Character) return Wide_Character is
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      EUC1B  : constant Byte := Character'Pos (EUC1);
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      EUC2B  : constant Byte := Character'Pos (EUC2);
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   begin
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      if EUC2B not in 16#A0# .. 16#FE# then
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         raise Constraint_Error;
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      end if;
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      if EUC1B = EUC_Hankaku_Kana then
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         return Wide_Character'Val (EUC2B);
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      else
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         if EUC1B not in 16#A0# .. 16#FE# then
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            raise Constraint_Error;
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         else
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            return Wide_Character'Val
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              (256 * Natural (EUC1B and 16#7F#) + Natural (EUC2B and 16#7F#));
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         end if;
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      end if;
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   end EUC_To_JIS;
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   ----------------
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   -- JIS_To_EUC --
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   ----------------
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   procedure JIS_To_EUC
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     (J    : in Wide_Character;
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      EUC1 : out Character;
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      EUC2 : out Character)
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   is
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      JIS1 : constant Natural := Wide_Character'Pos (J) / 256;
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      JIS2 : constant Natural := Wide_Character'Pos (J) rem 256;
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   begin
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      if JIS1 = 0 then
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         EUC1 := Character'Val (EUC_Hankaku_Kana);
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         EUC2 := Character'Val (JIS2);
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      else
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         EUC1 := Character'Val (JIS1 + 16#80#);
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         EUC2 := Character'Val (JIS2 + 16#80#);
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      end if;
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   end JIS_To_EUC;
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   ----------------------
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   -- JIS_To_Shift_JIS --
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   ----------------------
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   procedure JIS_To_Shift_JIS
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     (J   : in Wide_Character;
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      SJ1 : out Character;
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      SJ2 : out Character)
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   is
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      JIS1 : Byte;
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      JIS2 : Byte;
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   begin
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      --  The following is the required algorithm, it's hard to make any
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      --  more intelligent comments! This was copied from a public domain
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      --  C program called etos.c (author unknown).
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      JIS1 := Byte (Natural (Wide_Character'Pos (J) / 256));
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      JIS2 := Byte (Natural (Wide_Character'Pos (J) rem 256));
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      if JIS1 > 16#5F# then
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         JIS1 := JIS1 + 16#80#;
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      end if;
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      if (JIS1 mod 2) = 0 then
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         SJ1 := Character'Val ((JIS1 - 16#30#) / 2 + 16#88#);
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         SJ2 := Character'Val (JIS2 + 16#7E#);
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      else
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         if JIS2 >= 16#60# then
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            JIS2 := JIS2 + 16#01#;
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         end if;
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         SJ1 := Character'Val ((JIS1 - 16#31#) / 2 + 16#89#);
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         SJ2 := Character'Val (JIS2 + 16#1F#);
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      end if;
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   end JIS_To_Shift_JIS;
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   ----------------------
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   -- Shift_JIS_To_JIS --
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   ----------------------
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   function Shift_JIS_To_JIS (SJ1, SJ2 : Character) return Wide_Character is
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      SJIS1 : Byte;
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      SJIS2 : Byte;
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      JIS1  : Byte;
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      JIS2  : Byte;
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   begin
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      --  The following is the required algorithm, it's hard to make any
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      --  more intelligent comments! This was copied from a public domain
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      --  C program called stoj.c written by shige@csk.JUNET.
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      SJIS1 := Character'Pos (SJ1);
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      SJIS2 := Character'Pos (SJ2);
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      if SJIS1 >= 16#E0# then
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         SJIS1 := SJIS1 - 16#40#;
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      end if;
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      if SJIS2 >= 16#9F# then
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         JIS1 := (SJIS1 - 16#88#) * 2 + 16#30#;
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         JIS2 := SJIS2 - 16#7E#;
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      else
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         if SJIS2 >= 16#7F# then
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            SJIS2 := SJIS2 - 16#01#;
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         end if;
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         JIS1 := (SJIS1 - 16#89#) * 2 + 16#31#;
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         JIS2 := SJIS2 - 16#1F#;
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      end if;
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      if JIS1 not in 16#20# .. 16#7E#
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        or else JIS2 not in 16#20# .. 16#7E#
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      then
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         raise Constraint_Error;
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      else
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         return Wide_Character'Val (256 * Natural (JIS1) + Natural (JIS2));
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      end if;
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   end Shift_JIS_To_JIS;
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end System.WCh_JIS;

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