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
|
/*
* utf16.c - routines to handle UTF-16 (RFC 2781).
*/
#ifndef ENUM_CHARSETS
#include "charset.h"
#include "internal.h"
struct utf16 {
int s0; /* initial value of state->s0 */
};
static void read_utf16(charset_spec const *charset, long int input_chr,
charset_state *state,
void (*emit)(void *ctx, long int output),
void *emitctx)
{
struct utf16 const *utf = (struct utf16 *)charset->data;
long int hw;
/*
* State variable s1 handles the combining of bytes into
* transport-endianness halfwords. It contains:
*
* - 0 if we're between halfwords
* - 0x100 plus the first byte if we're in mid-halfword
*
* State variable s0 handles everything from there upwards. It
* contains:
*
* - Bottom 16 bits are set to a surrogate value if we've just
* seen one.
* - Next two bits (17:16) indicate possible endiannesses. Bit
* 17 is set if we might be BE; bit 16 if we might be LE. If
* they're both zero, it has to be because this is right at
* the start, so the first thing we do is set them to the
* correct initial state.
* - The bit after that (18) is 1 iff we have already seen at
* least one halfword (meaning we should pass any further
* BOMs straight through).
*/
/* Set up s0 if this is the start. */
if (state->s0 == 0)
state->s0 = utf->s0;
/* Accumulate a transport-endianness halfword. */
if (state->s1 == 0) {
state->s1 = 0x100 | input_chr;
return;
}
hw = ((state->s1 & 0xFF) << 8) + input_chr;
state->s1 = 0;
/* Process BOM and determine byte order. */
if (!(state->s0 & 0x40000)) {
state->s0 |= 0x40000;
if (hw == 0xFEFF && (state->s0 & 0x20000)) {
/*
* Text starts with a big-endian BOM, and big-
* endianness is a possibility. So clear the
* little-endian bit (the BOM confirms our endianness),
* and return without emitting the BOM in Unicode.
*/
state->s0 &= ~0x10000;
return;
} else if (hw == 0xFFFE && (state->s0 & 0x10000)) {
/*
* Text starts with a little-endian BOM, and little-
* endianness is a possibility. So clear the big-endian
* bit (the BOM confirms our endianness), and return
* without emitting the BOM in Unicode.
*/
state->s0 &= ~0x20000;
return;
} else {
/*
* Text does not begin with a BOM. RFC 2781 states that
* in this case we must assume big-endianness if we
* haven't been told otherwise by the content type.
*/
if ((state->s0 & 0x30000) == 0x30000)
state->s0 &= ~0x10000; /* clear LE bit */
}
}
/*
* Byte-swap transport-endianness halfword if necessary. We may
* now test individual endianness bits, since we can be sure
* exactly one is set.
*/
if (state->s0 & 0x10000)
hw = ((hw >> 8) | (hw << 8)) & 0xFFFF;
/*
* Now that the endianness issue has been dealt with, what
* reaches this point should be a stream of halfwords in
* sensible numeric form. So now we process surrogates.
*/
if (state->s0 & 0xFFFF) {
/*
* We have already seen a high surrogate, so we expect a
* low surrogate. Whinge if we didn't get it.
*/
if (hw < 0xDC00 || hw >= 0xE000) {
emit(emitctx, ERROR);
} else {
hw &= 0x3FF;
hw |= (state->s0 & 0x3FF) << 10;
emit(emitctx, hw + 0x10000);
}
state->s0 &= 0xFFFF0000;
} else {
/*
* Any low surrogate is an error.
*/
if (hw >= 0xDC00 && hw < 0xE000) {
emit(emitctx, ERROR);
return;
}
/*
* Any high surrogate is simply stored until we see the
* next halfword.
*/
if (hw >= 0xD800 && hw < 0xDC00) {
state->s0 |= hw;
return;
}
/*
* Anything else we simply output.
*/
emit(emitctx, hw);
}
}
/*
* Repeated code in write_utf16 abstracted out for sanity.
*/
static void emithl(void (*emit)(void *ctx, long int output), void *emitctx,
unsigned long s0, long int hw)
{
int h = (hw >> 8) & 0xFF, l = hw & 0xFF;
if (s0 & 0x20000) {
/* Big-endian takes priority over little, if both are allowed. */
emit(emitctx, h);
emit(emitctx, l);
} else {
emit(emitctx, l);
emit(emitctx, h);
}
}
static int write_utf16(charset_spec const *charset, long int input_chr,
charset_state *state,
void (*emit)(void *ctx, long int output),
void *emitctx)
{
struct utf16 const *utf = (struct utf16 *)charset->data;
/*
* state->s0 == 0 means we have not output anything yet (and so
* must output a BOM before we do anything else). state->s0 ==
* 1 means we are off and running.
*/
if (input_chr < 0)
return TRUE; /* no cleanup required */
if ((input_chr >= 0xD800 && input_chr < 0xE000) ||
input_chr >= 0x110000) {
/*
* We can't output surrogates, or anything above 0x10FFFF.
*/
return FALSE;
}
if (!state->s0) {
state->s0 = 1;
emithl(emit, emitctx, utf->s0, 0xFEFF);
}
if (input_chr < 0x10000) {
emithl(emit, emitctx, utf->s0, input_chr);
} else {
input_chr -= 0x10000;
/* now input_chr is between 0 and 0xFFFFF inclusive */
emithl(emit, emitctx, utf->s0, 0xD800 | ((input_chr >> 10) & 0x3FF));
emithl(emit, emitctx, utf->s0, 0xDC00 | (input_chr & 0x3FF));
}
return TRUE;
}
static const struct utf16 utf16_bigendian = { 0x20000 };
static const struct utf16 utf16_littleendian = { 0x10000 };
static const struct utf16 utf16_variable_endianness = { 0x30000 };
const charset_spec charset_CS_UTF16BE = {
CS_UTF16BE, read_utf16, write_utf16, &utf16_bigendian
};
const charset_spec charset_CS_UTF16LE = {
CS_UTF16LE, read_utf16, write_utf16, &utf16_littleendian
};
const charset_spec charset_CS_UTF16 = {
CS_UTF16, read_utf16, write_utf16, &utf16_variable_endianness
};
#else /* ENUM_CHARSETS */
ENUM_CHARSET(CS_UTF16)
ENUM_CHARSET(CS_UTF16BE)
ENUM_CHARSET(CS_UTF16LE)
#endif /* ENUM_CHARSETS */
|
