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) 1992-2009, 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
32pragma Compiler_Unit;
33
34package 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
189end System.WCh_JIS;
190