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) 1992-2020, 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 pragma Compiler_Unit_Warning;
  33
  34 package body System.WCh_JIS is
  35
  36    type Byte is mod 256;
  37
  38    EUC_Hankaku_Kana : constant Byte := 16#8E#;
  39    --  Prefix byte in EUC for Hankaku Kana (small Katakana). Such characters
  40    --  in EUC are represented by a prefix byte followed by the code, which
  41    --  is in the upper half (the corresponding JIS internal code is in the
  42    --  range 16#0080# - 16#00FF#).
  43
  44    function EUC_To_JIS (EUC1, EUC2 : Character) return Wide_Character is
  45       EUC1B  : constant Byte := Character'Pos (EUC1);
  46       EUC2B  : constant Byte := Character'Pos (EUC2);
  47
  48    begin
  49       if EUC2B not in 16#A0# .. 16#FE# then
  50          raise Constraint_Error;
  51       end if;
  52
  53       if EUC1B = EUC_Hankaku_Kana then
  54          return Wide_Character'Val (EUC2B);
  55
  56       else
  57          if EUC1B not in 16#A0# .. 16#FE# then
  58             raise Constraint_Error;
  59          else
  60             return Wide_Character'Val
  61               (256 * Natural (EUC1B and 16#7F#) + Natural (EUC2B and 16#7F#));
  62          end if;
  63       end if;
  64    end EUC_To_JIS;
  65
  66    ----------------
  67    -- JIS_To_EUC --
  68    ----------------
  69
  70    procedure JIS_To_EUC
  71      (J    : Wide_Character;
  72       EUC1 : out Character;
  73       EUC2 : out Character)
  74    is
  75       JIS1 : constant Natural := Wide_Character'Pos (J) / 256;
  76       JIS2 : constant Natural := Wide_Character'Pos (J) rem 256;
  77
  78    begin
  79       --  Special case of small Katakana
  80
  81       if JIS1 = 0 then
  82
  83          --  The value must be in the range 16#80# to 16#FF# so that the upper
  84          --  bit is set in both bytes.
  85
  86          if JIS2 < 16#80# then
  87             raise Constraint_Error;
  88          end if;
  89
  90          EUC1 := Character'Val (EUC_Hankaku_Kana);
  91          EUC2 := Character'Val (JIS2);
  92
  93       --  The upper bit of both characters must be clear, or this is not
  94       --  a valid character for representation in EUC form.
  95
  96       elsif JIS1 > 16#7F# or else JIS2 > 16#7F# then
  97          raise Constraint_Error;
  98
  99       --  Result is just the two characters with upper bits set
 100
 101       else
 102          EUC1 := Character'Val (JIS1 + 16#80#);
 103          EUC2 := Character'Val (JIS2 + 16#80#);
 104       end if;
 105    end JIS_To_EUC;
 106
 107    ----------------------
 108    -- JIS_To_Shift_JIS --
 109    ----------------------
 110
 111    procedure JIS_To_Shift_JIS
 112      (J   : Wide_Character;
 113       SJ1 : out Character;
 114       SJ2 : out Character)
 115    is
 116       JIS1 : Byte;
 117       JIS2 : Byte;
 118
 119    begin
 120       --  The following is the required algorithm, it's hard to make any
 121       --  more intelligent comments. This was copied from a public domain
 122       --  C program called etos.c (author unknown).
 123
 124       JIS1 := Byte (Natural (Wide_Character'Pos (J) / 256));
 125       JIS2 := Byte (Natural (Wide_Character'Pos (J) rem 256));
 126
 127       if JIS1 > 16#5F# then
 128          JIS1 := JIS1 + 16#80#;
 129       end if;
 130
 131       if (JIS1 mod 2) = 0 then
 132          SJ1 := Character'Val ((JIS1 - 16#30#) / 2 + 16#88#);
 133          SJ2 := Character'Val (JIS2 + 16#7E#);
 134
 135       else
 136          if JIS2 >= 16#60# then
 137             JIS2 := JIS2 + 16#01#;
 138          end if;
 139
 140          SJ1 := Character'Val ((JIS1 - 16#31#) / 2 + 16#89#);
 141          SJ2 := Character'Val (JIS2 + 16#1F#);
 142       end if;
 143    end JIS_To_Shift_JIS;
 144
 145    ----------------------
 146    -- Shift_JIS_To_JIS --
 147    ----------------------
 148
 149    function Shift_JIS_To_JIS (SJ1, SJ2 : Character) return Wide_Character is
 150       SJIS1 : Byte;
 151       SJIS2 : Byte;
 152       JIS1  : Byte;
 153       JIS2  : Byte;
 154
 155    begin
 156       --  The following is the required algorithm, it's hard to make any
 157       --  more intelligent comments. This was copied from a public domain
 158       --  C program called stoj.c written by shige@csk.JUNET.
 159
 160       SJIS1 := Character'Pos (SJ1);
 161       SJIS2 := Character'Pos (SJ2);
 162
 163       if SJIS1 >= 16#E0# then
 164          SJIS1 := SJIS1 - 16#40#;
 165       end if;
 166
 167       if SJIS2 >= 16#9F# then
 168          JIS1 := (SJIS1 - 16#88#) * 2 + 16#30#;
 169          JIS2 := SJIS2 - 16#7E#;
 170
 171       else
 172          if SJIS2 >= 16#7F# then
 173             SJIS2 := SJIS2 - 16#01#;
 174          end if;
 175
 176          JIS1 := (SJIS1 - 16#89#) * 2 + 16#31#;
 177          JIS2 := SJIS2 - 16#1F#;
 178       end if;
 179
 180       if JIS1 not in 16#20# .. 16#7E#
 181         or else JIS2 not in 16#20# .. 16#7E#
 182       then
 183          raise Constraint_Error;
 184       else
 185          return Wide_Character'Val (256 * Natural (JIS1) + Natural (JIS2));
 186       end if;
 187    end Shift_JIS_To_JIS;
 188
 189 end System.WCh_JIS;