gcc/ada/libgnat/s-wchjis.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                       S Y S T E M . W C H _ J I S                        --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2024, Free Software Foundation, Inc.         --
  10 --                                                                          --
  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 3,  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.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 package body System.WCh_JIS is
  33
  34    type Byte is mod 256;
  35
  36    EUC_Hankaku_Kana : constant Byte := 16#8E#;
  37    --  Prefix byte in EUC for Hankaku Kana (small Katakana). Such characters
  38    --  in EUC are represented by a prefix byte followed by the code, which
  39    --  is in the upper half (the corresponding JIS internal code is in the
  40    --  range 16#0080# - 16#00FF#).
  41
  42    function EUC_To_JIS (EUC1, EUC2 : Character) return Wide_Character is
  43       EUC1B  : constant Byte := Character'Pos (EUC1);
  44       EUC2B  : constant Byte := Character'Pos (EUC2);
  45
  46    begin
  47       if EUC2B not in 16#A0# .. 16#FE# then
  48          raise Constraint_Error;
  49       end if;
  50
  51       if EUC1B = EUC_Hankaku_Kana then
  52          return Wide_Character'Val (EUC2B);
  53
  54       else
  55          if EUC1B not in 16#A0# .. 16#FE# then
  56             raise Constraint_Error;
  57          else
  58             return Wide_Character'Val
  59               (256 * Natural (EUC1B and 16#7F#) + Natural (EUC2B and 16#7F#));
  60          end if;
  61       end if;
  62    end EUC_To_JIS;
  63
  64    ----------------
  65    -- JIS_To_EUC --
  66    ----------------
  67
  68    procedure JIS_To_EUC
  69      (J    : Wide_Character;
  70       EUC1 : out Character;
  71       EUC2 : out Character)
  72    is
  73       JIS1 : constant Natural := Wide_Character'Pos (J) / 256;
  74       JIS2 : constant Natural := Wide_Character'Pos (J) rem 256;
  75
  76    begin
  77       --  Special case of small Katakana
  78
  79       if JIS1 = 0 then
  80
  81          --  The value must be in the range 16#80# to 16#FF# so that the upper
  82          --  bit is set in both bytes.
  83
  84          if JIS2 < 16#80# then
  85             raise Constraint_Error;
  86          end if;
  87
  88          EUC1 := Character'Val (EUC_Hankaku_Kana);
  89          EUC2 := Character'Val (JIS2);
  90
  91       --  The upper bit of both characters must be clear, or this is not
  92       --  a valid character for representation in EUC form.
  93
  94       elsif JIS1 > 16#7F# or else JIS2 > 16#7F# then
  95          raise Constraint_Error;
  96
  97       --  Result is just the two characters with upper bits set
  98
  99       else
 100          EUC1 := Character'Val (JIS1 + 16#80#);
 101          EUC2 := Character'Val (JIS2 + 16#80#);
 102       end if;
 103    end JIS_To_EUC;
 104
 105    ----------------------
 106    -- JIS_To_Shift_JIS --
 107    ----------------------
 108
 109    procedure JIS_To_Shift_JIS
 110      (J   : Wide_Character;
 111       SJ1 : out Character;
 112       SJ2 : out Character)
 113    is
 114       JIS1 : Byte;
 115       JIS2 : Byte;
 116
 117    begin
 118       --  The following is the required algorithm, it's hard to make any
 119       --  more intelligent comments. This was copied from a public domain
 120       --  C program called etos.c (author unknown).
 121
 122       JIS1 := Byte (Natural (Wide_Character'Pos (J) / 256));
 123       JIS2 := Byte (Natural (Wide_Character'Pos (J) rem 256));
 124
 125       if JIS1 > 16#5F# then
 126          JIS1 := JIS1 + 16#80#;
 127       end if;
 128
 129       if (JIS1 mod 2) = 0 then
 130          SJ1 := Character'Val ((JIS1 - 16#30#) / 2 + 16#88#);
 131          SJ2 := Character'Val (JIS2 + 16#7E#);
 132
 133       else
 134          if JIS2 >= 16#60# then
 135             JIS2 := JIS2 + 16#01#;
 136          end if;
 137
 138          SJ1 := Character'Val ((JIS1 - 16#31#) / 2 + 16#89#);
 139          SJ2 := Character'Val (JIS2 + 16#1F#);
 140       end if;
 141    end JIS_To_Shift_JIS;
 142
 143    ----------------------
 144    -- Shift_JIS_To_JIS --
 145    ----------------------
 146
 147    function Shift_JIS_To_JIS (SJ1, SJ2 : Character) return Wide_Character is
 148       SJIS1 : Byte;
 149       SJIS2 : Byte;
 150       JIS1  : Byte;
 151       JIS2  : Byte;
 152
 153    begin
 154       --  The following is the required algorithm, it's hard to make any
 155       --  more intelligent comments. This was copied from a public domain
 156       --  C program called stoj.c written by shige@csk.JUNET.
 157
 158       SJIS1 := Character'Pos (SJ1);
 159       SJIS2 := Character'Pos (SJ2);
 160
 161       if SJIS1 >= 16#E0# then
 162          SJIS1 := SJIS1 - 16#40#;
 163       end if;
 164
 165       if SJIS2 >= 16#9F# then
 166          JIS1 := (SJIS1 - 16#88#) * 2 + 16#30#;
 167          JIS2 := SJIS2 - 16#7E#;
 168
 169       else
 170          if SJIS2 >= 16#7F# then
 171             SJIS2 := SJIS2 - 16#01#;
 172          end if;
 173
 174          JIS1 := (SJIS1 - 16#89#) * 2 + 16#31#;
 175          JIS2 := SJIS2 - 16#1F#;
 176       end if;
 177
 178       if JIS1 not in 16#20# .. 16#7E#
 179         or else JIS2 not in 16#20# .. 16#7E#
 180       then
 181          raise Constraint_Error;
 182       else
 183          return Wide_Character'Val (256 * Natural (JIS1) + Natural (JIS2));
 184       end if;
 185    end Shift_JIS_To_JIS;
 186
 187 end System.WCh_JIS;