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
|
#include "mupdf/fitz.h"
/* TODO: error checking */
#define LZW_CLEAR(lzw) (1 << ((lzw)->min_bits - 1))
#define LZW_EOD(lzw) (LZW_CLEAR(lzw) + 1)
#define LZW_FIRST(lzw) (LZW_CLEAR(lzw) + 2)
enum
{
MAX_BITS = 12,
NUM_CODES = (1 << MAX_BITS),
MAX_LENGTH = 4097
};
typedef struct lzw_code_s lzw_code;
struct lzw_code_s
{
int prev; /* prev code (in string) */
unsigned short length; /* string len, including this token */
unsigned char value; /* data value */
unsigned char first_char; /* first token of string */
};
typedef struct fz_lzwd_s fz_lzwd;
struct fz_lzwd_s
{
fz_stream *chain;
int eod;
int early_change;
int reverse_bits;
int old_tiff;
int min_bits; /* minimum num bits/code */
int code_bits; /* num bits/code */
int code; /* current code */
int old_code; /* previously recognized code */
int next_code; /* next free entry */
lzw_code table[NUM_CODES];
unsigned char bp[MAX_LENGTH];
unsigned char *rp, *wp;
unsigned char buffer[4096];
};
static int
next_lzwd(fz_context *ctx, fz_stream *stm, size_t len)
{
fz_lzwd *lzw = stm->state;
lzw_code *table = lzw->table;
unsigned char *buf = lzw->buffer;
unsigned char *p = buf;
unsigned char *ep;
unsigned char *s;
int codelen;
int code_bits = lzw->code_bits;
int code = lzw->code;
int old_code = lzw->old_code;
int next_code = lzw->next_code;
if (len > sizeof(lzw->buffer))
len = sizeof(lzw->buffer);
ep = buf + len;
while (lzw->rp < lzw->wp && p < ep)
*p++ = *lzw->rp++;
while (p < ep)
{
if (lzw->eod)
return EOF;
if (lzw->reverse_bits)
code = fz_read_rbits(ctx, lzw->chain, code_bits);
else
code = fz_read_bits(ctx, lzw->chain, code_bits);
if (fz_is_eof_bits(ctx, lzw->chain))
{
lzw->eod = 1;
break;
}
if (code == LZW_EOD(lzw))
{
lzw->eod = 1;
break;
}
/* Old Tiffs are allowed to NOT send the clear code, and to
* overrun at the end. */
if (!lzw->old_tiff && next_code > NUM_CODES && code != LZW_CLEAR(lzw))
{
fz_warn(ctx, "missing clear code in lzw decode");
code = LZW_CLEAR(lzw);
}
if (code == LZW_CLEAR(lzw))
{
code_bits = lzw->min_bits;
next_code = LZW_FIRST(lzw);
old_code = -1;
continue;
}
/* if stream starts without a clear code, old_code is undefined... */
if (old_code == -1)
{
old_code = code;
}
else if (!lzw->old_tiff && next_code == NUM_CODES)
{
/* TODO: Ghostscript checks for a following clear code before tolerating */
fz_warn(ctx, "tolerating a single out of range code in lzw decode");
next_code++;
}
else if (code > next_code || (!lzw->old_tiff && next_code >= NUM_CODES))
{
fz_warn(ctx, "out of range code encountered in lzw decode");
}
else if (next_code < NUM_CODES)
{
/* add new entry to the code table */
table[next_code].prev = old_code;
table[next_code].first_char = table[old_code].first_char;
table[next_code].length = table[old_code].length + 1;
if (code < next_code)
table[next_code].value = table[code].first_char;
else if (code == next_code)
table[next_code].value = table[next_code].first_char;
else
fz_warn(ctx, "out of range code encountered in lzw decode");
next_code ++;
if (next_code > (1 << code_bits) - lzw->early_change - 1)
{
code_bits ++;
if (code_bits > MAX_BITS)
code_bits = MAX_BITS;
}
old_code = code;
}
/* code maps to a string, copy to output (in reverse...) */
if (code >= LZW_CLEAR(lzw))
{
codelen = table[code].length;
lzw->rp = lzw->bp;
lzw->wp = lzw->bp + codelen;
assert(codelen < MAX_LENGTH);
s = lzw->wp;
do {
*(--s) = table[code].value;
code = table[code].prev;
} while (code >= 0 && s > lzw->bp);
}
/* ... or just a single character */
else
{
lzw->bp[0] = code;
lzw->rp = lzw->bp;
lzw->wp = lzw->bp + 1;
}
/* copy to output */
while (lzw->rp < lzw->wp && p < ep)
*p++ = *lzw->rp++;
}
lzw->code_bits = code_bits;
lzw->code = code;
lzw->old_code = old_code;
lzw->next_code = next_code;
stm->rp = buf;
stm->wp = p;
if (buf == p)
return EOF;
stm->pos += p - buf;
return *stm->rp++;
}
static void
close_lzwd(fz_context *ctx, void *state_)
{
fz_lzwd *lzw = (fz_lzwd *)state_;
fz_sync_bits(ctx, lzw->chain);
fz_drop_stream(ctx, lzw->chain);
fz_free(ctx, lzw);
}
/* Default: early_change = 1 */
fz_stream *
fz_open_lzwd(fz_context *ctx, fz_stream *chain, int early_change, int min_bits, int reverse_bits, int old_tiff)
{
fz_lzwd *lzw = NULL;
int i;
fz_var(lzw);
fz_try(ctx)
{
if (min_bits > MAX_BITS)
{
fz_warn(ctx, "out of range initial lzw code size");
min_bits = MAX_BITS;
}
lzw = fz_malloc_struct(ctx, fz_lzwd);
lzw->chain = chain;
lzw->eod = 0;
lzw->early_change = early_change;
lzw->reverse_bits = reverse_bits;
lzw->old_tiff = old_tiff;
lzw->min_bits = min_bits;
lzw->code_bits = lzw->min_bits;
lzw->code = -1;
lzw->next_code = LZW_FIRST(lzw);
lzw->old_code = -1;
lzw->rp = lzw->bp;
lzw->wp = lzw->bp;
for (i = 0; i < LZW_CLEAR(lzw); i++)
{
lzw->table[i].value = i;
lzw->table[i].first_char = i;
lzw->table[i].length = 1;
lzw->table[i].prev = -1;
}
for (i = LZW_CLEAR(lzw); i < NUM_CODES; i++)
{
lzw->table[i].value = 0;
lzw->table[i].first_char = 0;
lzw->table[i].length = 0;
lzw->table[i].prev = -1;
}
}
fz_catch(ctx)
{
fz_free(ctx, lzw);
fz_drop_stream(ctx, chain);
fz_rethrow(ctx);
}
return fz_new_stream(ctx, lzw, next_lzwd, close_lzwd);
}
|
