1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
|
------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- ADA.STRINGS.UTF_ENCODING.STRINGS --
-- --
-- B o d y --
-- --
-- Copyright (C) 2010, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
package body Ada.Strings.UTF_Encoding.Strings is
use Interfaces;
------------
-- Decode --
------------
-- Decode UTF-8/UTF-16BE/UTF-16LE input to String
function Decode
(Item : UTF_String;
Input_Scheme : Encoding_Scheme) return String
is
begin
if Input_Scheme = UTF_8 then
return Decode (Item);
else
return Decode (To_UTF_16 (Item, Input_Scheme));
end if;
end Decode;
-- Decode UTF-8 input to String
function Decode (Item : UTF_8_String) return String is
Result : String (1 .. Item'Length);
-- Result string (worst case is same length as input)
Len : Natural := 0;
-- Length of result stored so far
Iptr : Natural;
-- Input Item pointer
C : Unsigned_8;
R : Unsigned_16;
procedure Get_Continuation;
-- Reads a continuation byte of the form 10xxxxxx, shifts R left
-- by 6 bits, and or's in the xxxxxx to the low order 6 bits. On
-- return Ptr is incremented. Raises exceptioon if continuation
-- byte does not exist or is invalid.
----------------------
-- Get_Continuation --
----------------------
procedure Get_Continuation is
begin
if Iptr > Item'Last then
Raise_Encoding_Error (Iptr - 1);
else
C := To_Unsigned_8 (Item (Iptr));
Iptr := Iptr + 1;
if C not in 2#10_000000# .. 2#10_111111# then
Raise_Encoding_Error (Iptr - 1);
else
R := Shift_Left (R, 6) or Unsigned_16 (C and 2#00_111111#);
end if;
end if;
end Get_Continuation;
-- Start of processing for Decode
begin
Iptr := Item'First;
-- Skip BOM at start
if Item'Length >= 3
and then Item (Iptr .. Iptr + 2) = BOM_8
then
Iptr := Iptr + 3;
-- Error if bad BOM
elsif Item'Length >= 2
and then (Item (Iptr .. Iptr + 1) = BOM_16BE
or else
Item (Iptr .. Iptr + 1) = BOM_16LE)
then
Raise_Encoding_Error (Iptr);
end if;
while Iptr <= Item'Last loop
C := To_Unsigned_8 (Item (Iptr));
Iptr := Iptr + 1;
-- Codes in the range 16#00# - 16#7F# are represented as
-- 0xxxxxxx
if C <= 16#7F# then
R := Unsigned_16 (C);
-- No initial code can be of the form 10xxxxxx. Such codes are used
-- only for continuations.
elsif C <= 2#10_111111# then
Raise_Encoding_Error (Iptr - 1);
-- Codes in the range 16#80# - 16#7FF# are represented as
-- 110yyyxx 10xxxxxx
elsif C <= 2#110_11111# then
R := Unsigned_16 (C and 2#000_11111#);
Get_Continuation;
-- Codes in the range 16#800# - 16#FFFF# are represented as
-- 1110yyyy 10yyyyxx 10xxxxxx
-- Such codes are out of range for type Character
-- Codes in the range 16#10000# - 16#10FFFF# are represented as
-- 11110zzz 10zzyyyy 10yyyyxx 10xxxxxx
-- Such codes are out of range for Wide_String output
-- Thus all remaining cases raise Encoding_Error
else
Raise_Encoding_Error (Iptr - 1);
end if;
Len := Len + 1;
Result (Len) := Character'Val (R);
end loop;
return Result (1 .. Len);
end Decode;
-- Decode UTF-16 input to String
function Decode (Item : UTF_16_Wide_String) return String is
Result : String (1 .. Item'Length);
-- Result is same length as input (possibly minus 1 if BOM present)
Len : Natural := 0;
-- Length of result
Iptr : Natural;
-- Index of next Item element
C : Unsigned_16;
begin
-- Skip UTF-16 BOM at start
Iptr := Item'First;
if Item'Length > 0 and then Item (Iptr) = BOM_16 (1) then
Iptr := Iptr + 1;
end if;
-- Loop through input characters
while Iptr <= Item'Last loop
C := To_Unsigned_16 (Item (Iptr));
Iptr := Iptr + 1;
-- Codes in the range 16#0000#..16#00FF# represent their own value
if C <= 16#00FF# then
Len := Len + 1;
Result (Len) := Character'Val (C);
-- All other codes are invalid, either they are invalid UTF-16
-- encoding sequences, or they represent values that are out of
-- range for type Character.
else
Raise_Encoding_Error (Iptr - 1);
end if;
end loop;
return Result (1 .. Len);
end Decode;
------------
-- Encode --
------------
-- Encode String in UTF-8, UTF-16BE or UTF-16LE
function Encode
(Item : String;
Output_Scheme : Encoding_Scheme;
Output_BOM : Boolean := False) return UTF_String
is
begin
-- Case of UTF_8
if Output_Scheme = UTF_8 then
return Encode (Item, Output_BOM);
-- Case of UTF_16LE or UTF_16BE, use UTF-16 intermediary
else
return From_UTF_16 (UTF_16_Wide_String'(Encode (Item)),
Output_Scheme, Output_BOM);
end if;
end Encode;
-- Encode String in UTF-8
function Encode
(Item : String;
Output_BOM : Boolean := False) return UTF_8_String
is
Result : UTF_8_String (1 .. 3 * Item'Length + 3);
-- Worst case is three bytes per input byte + space for BOM
Len : Natural;
-- Number of output codes stored in Result
C : Unsigned_8;
-- Single input character
procedure Store (C : Unsigned_8);
pragma Inline (Store);
-- Store one output code, C is in the range 0 .. 255
-----------
-- Store --
-----------
procedure Store (C : Unsigned_8) is
begin
Len := Len + 1;
Result (Len) := Character'Val (C);
end Store;
-- Start of processing for UTF8_Encode
begin
-- Output BOM if required
if Output_BOM then
Result (1 .. 3) := BOM_8;
Len := 3;
else
Len := 0;
end if;
-- Loop through characters of input
for J in Item'Range loop
C := To_Unsigned_8 (Item (J));
-- Codes in the range 16#00# - 16#7F# are represented as
-- 0xxxxxxx
if C <= 16#7F# then
Store (C);
-- Codes in the range 16#80# - 16#7FF# are represented as
-- 110yyyxx 10xxxxxx
-- For type character of course, the limit is 16#FF# in any case
else
Store (2#110_00000# or Shift_Right (C, 6));
Store (2#10_000000# or (C and 2#00_111111#));
end if;
end loop;
return Result (1 .. Len);
end Encode;
-- Encode String in UTF-16
function Encode
(Item : String;
Output_BOM : Boolean := False) return UTF_16_Wide_String
is
Result : UTF_16_Wide_String
(1 .. Item'Length + Boolean'Pos (Output_BOM));
-- Output is same length as input + possible BOM
Len : Integer;
-- Length of output string
C : Unsigned_8;
begin
-- Output BOM if required
if Output_BOM then
Result (1) := BOM_16 (1);
Len := 1;
else
Len := 0;
end if;
-- Loop through input characters encoding them
for Iptr in Item'Range loop
C := To_Unsigned_8 (Item (Iptr));
-- Codes in the range 16#0000#..16#00FF# are output unchanged. This
-- includes all possible cases of Character values.
Len := Len + 1;
Result (Len) := Wide_Character'Val (C);
end loop;
return Result;
end Encode;
end Ada.Strings.UTF_Encoding.Strings;
|
