1/****************************************************************************
2 *
3 * ftzopen.c
4 *
5 * FreeType support for .Z compressed files.
6 *
7 * This optional component relies on NetBSD's zopen(). It should mainly
8 * be used to parse compressed PCF fonts, as found with many X11 server
9 * distributions.
10 *
11 * Copyright (C) 2005-2023 by
12 * David Turner.
13 *
14 * This file is part of the FreeType project, and may only be used,
15 * modified, and distributed under the terms of the FreeType project
16 * license, LICENSE.TXT. By continuing to use, modify, or distribute
17 * this file you indicate that you have read the license and
18 * understand and accept it fully.
19 *
20 */
21
22#include "ftzopen.h"
23#include <freetype/internal/ftmemory.h>
24#include <freetype/internal/ftstream.h>
25#include <freetype/internal/ftdebug.h>
26
27
28 static int
29 ft_lzwstate_refill( FT_LzwState state )
30 {
31 FT_ULong count;
32
33
34 if ( state->in_eof )
35 return -1;
36
37 count = FT_Stream_TryRead( state->source,
38 state->buf_tab,
39 state->num_bits ); /* WHY? */
40
41 state->buf_size = (FT_UInt)count;
42 state->buf_total += count;
43 state->in_eof = FT_BOOL( count < state->num_bits );
44 state->buf_offset = 0;
45
46 state->buf_size <<= 3;
47 if ( state->buf_size > state->num_bits )
48 state->buf_size -= state->num_bits - 1;
49 else
50 return -1; /* not enough data */
51
52 if ( count == 0 ) /* end of file */
53 return -1;
54
55 return 0;
56 }
57
58
59 static FT_Int32
60 ft_lzwstate_get_code( FT_LzwState state )
61 {
62 FT_UInt num_bits = state->num_bits;
63 FT_UInt offset = state->buf_offset;
64 FT_Byte* p;
65 FT_Int result;
66
67
68 if ( state->buf_clear ||
69 offset >= state->buf_size ||
70 state->free_ent >= state->free_bits )
71 {
72 if ( state->free_ent >= state->free_bits )
73 {
74 state->num_bits = ++num_bits;
75 if ( num_bits > LZW_MAX_BITS )
76 return -1;
77
78 state->free_bits = state->num_bits < state->max_bits
79 ? (FT_UInt)( ( 1UL << num_bits ) - 256 )
80 : state->max_free + 1;
81 }
82
83 if ( state->buf_clear )
84 {
85 state->num_bits = num_bits = LZW_INIT_BITS;
86 state->free_bits = (FT_UInt)( ( 1UL << num_bits ) - 256 );
87 state->buf_clear = 0;
88 }
89
90 if ( ft_lzwstate_refill( state ) < 0 )
91 return -1;
92
93 offset = 0;
94 }
95
96 state->buf_offset = offset + num_bits;
97
98 p = &state->buf_tab[offset >> 3];
99 offset &= 7;
100 result = *p++ >> offset;
101 offset = 8 - offset;
102 num_bits -= offset;
103
104 if ( num_bits >= 8 )
105 {
106 result |= *p++ << offset;
107 offset += 8;
108 num_bits -= 8;
109 }
110 if ( num_bits > 0 )
111 result |= ( *p & LZW_MASK( num_bits ) ) << offset;
112
113 return result;
114 }
115
116
117 /* grow the character stack */
118 static int
119 ft_lzwstate_stack_grow( FT_LzwState state )
120 {
121 if ( state->stack_top >= state->stack_size )
122 {
123 FT_Memory memory = state->memory;
124 FT_Error error;
125 FT_Offset old_size = state->stack_size;
126 FT_Offset new_size = old_size;
127
128 new_size = new_size + ( new_size >> 1 ) + 4;
129
130 /* if relocating to heap */
131 if ( state->stack == state->stack_0 )
132 {
133 state->stack = NULL;
134 old_size = 0;
135 }
136
137 /* requirement of the character stack larger than 1<<LZW_MAX_BITS */
138 /* implies bug in the decompression code */
139 if ( new_size > ( 1 << LZW_MAX_BITS ) )
140 {
141 new_size = 1 << LZW_MAX_BITS;
142 if ( new_size == old_size )
143 return -1;
144 }
145
146 if ( FT_QREALLOC( state->stack, old_size, new_size ) )
147 return -1;
148
149 /* if relocating to heap */
150 if ( old_size == 0 )
151 FT_MEM_COPY( state->stack, state->stack_0, FT_LZW_DEFAULT_STACK_SIZE );
152
153 state->stack_size = new_size;
154 }
155 return 0;
156 }
157
158
159 /* grow the prefix/suffix arrays */
160 static int
161 ft_lzwstate_prefix_grow( FT_LzwState state )
162 {
163 FT_UInt old_size = state->prefix_size;
164 FT_UInt new_size = old_size;
165 FT_Memory memory = state->memory;
166 FT_Error error;
167
168
169 if ( new_size == 0 ) /* first allocation -> 9 bits */
170 new_size = 512;
171 else
172 new_size += new_size >> 2; /* don't grow too fast */
173
174 /*
175 * Note that the `suffix' array is located in the same memory block
176 * pointed to by `prefix'.
177 *
178 * I know that sizeof(FT_Byte) == 1 by definition, but it is clearer
179 * to write it literally.
180 *
181 */
182 if ( FT_REALLOC_MULT( state->prefix, old_size, new_size,
183 sizeof ( FT_UShort ) + sizeof ( FT_Byte ) ) )
184 return -1;
185
186 /* now adjust `suffix' and move the data accordingly */
187 state->suffix = (FT_Byte*)( state->prefix + new_size );
188
189 FT_MEM_MOVE( state->suffix,
190 state->prefix + old_size,
191 old_size * sizeof ( FT_Byte ) );
192
193 state->prefix_size = new_size;
194 return 0;
195 }
196
197
198 FT_LOCAL_DEF( void )
199 ft_lzwstate_reset( FT_LzwState state )
200 {
201 state->in_eof = 0;
202 state->buf_offset = 0;
203 state->buf_size = 0;
204 state->buf_clear = 0;
205 state->buf_total = 0;
206 state->stack_top = 0;
207 state->num_bits = LZW_INIT_BITS;
208 state->phase = FT_LZW_PHASE_START;
209 }
210
211
212 FT_LOCAL_DEF( void )
213 ft_lzwstate_init( FT_LzwState state,
214 FT_Stream source )
215 {
216 FT_ZERO( state );
217
218 state->source = source;
219 state->memory = source->memory;
220
221 state->prefix = NULL;
222 state->suffix = NULL;
223 state->prefix_size = 0;
224
225 state->stack = state->stack_0;
226 state->stack_size = sizeof ( state->stack_0 );
227
228 ft_lzwstate_reset( state );
229 }
230
231
232 FT_LOCAL_DEF( void )
233 ft_lzwstate_done( FT_LzwState state )
234 {
235 FT_Memory memory = state->memory;
236
237
238 ft_lzwstate_reset( state );
239
240 if ( state->stack != state->stack_0 )
241 FT_FREE( state->stack );
242
243 FT_FREE( state->prefix );
244 state->suffix = NULL;
245
246 FT_ZERO( state );
247 }
248
249
250#define FTLZW_STACK_PUSH( c ) \
251 FT_BEGIN_STMNT \
252 if ( state->stack_top >= state->stack_size && \
253 ft_lzwstate_stack_grow( state ) < 0 ) \
254 goto Eof; \
255 \
256 state->stack[state->stack_top++] = (FT_Byte)(c); \
257 FT_END_STMNT
258
259
260 FT_LOCAL_DEF( FT_ULong )
261 ft_lzwstate_io( FT_LzwState state,
262 FT_Byte* buffer,
263 FT_ULong out_size )
264 {
265 FT_ULong result = 0;
266
267 FT_UInt old_char = state->old_char;
268 FT_UInt old_code = state->old_code;
269 FT_UInt in_code = state->in_code;
270
271
272 if ( out_size == 0 )
273 goto Exit;
274
275 switch ( state->phase )
276 {
277 case FT_LZW_PHASE_START:
278 {
279 FT_Byte max_bits;
280 FT_Int32 c;
281
282
283 /* skip magic bytes, and read max_bits + block_flag */
284 if ( FT_Stream_Seek( state->source, 2 ) != 0 ||
285 FT_Stream_TryRead( state->source, &max_bits, 1 ) != 1 )
286 goto Eof;
287
288 state->max_bits = max_bits & LZW_BIT_MASK;
289 state->block_mode = max_bits & LZW_BLOCK_MASK;
290 state->max_free = (FT_UInt)( ( 1UL << state->max_bits ) - 256 );
291
292 if ( state->max_bits > LZW_MAX_BITS )
293 goto Eof;
294
295 state->num_bits = LZW_INIT_BITS;
296 state->free_ent = ( state->block_mode ? LZW_FIRST
297 : LZW_CLEAR ) - 256;
298 in_code = 0;
299
300 state->free_bits = state->num_bits < state->max_bits
301 ? (FT_UInt)( ( 1UL << state->num_bits ) - 256 )
302 : state->max_free + 1;
303
304 c = ft_lzwstate_get_code( state );
305 if ( c < 0 || c > 255 )
306 goto Eof;
307
308 old_code = old_char = (FT_UInt)c;
309
310 if ( buffer )
311 buffer[result] = (FT_Byte)old_char;
312
313 if ( ++result >= out_size )
314 goto Exit;
315
316 state->phase = FT_LZW_PHASE_CODE;
317 }
318 FALL_THROUGH;
319
320 case FT_LZW_PHASE_CODE:
321 {
322 FT_Int32 c;
323 FT_UInt code;
324
325
326 NextCode:
327 c = ft_lzwstate_get_code( state );
328 if ( c < 0 )
329 goto Eof;
330
331 code = (FT_UInt)c;
332
333 if ( code == LZW_CLEAR && state->block_mode )
334 {
335 /* why not LZW_FIRST-256 ? */
336 state->free_ent = ( LZW_FIRST - 1 ) - 256;
337 state->buf_clear = 1;
338
339 /* not quite right, but at least more predictable */
340 old_code = 0;
341 old_char = 0;
342
343 goto NextCode;
344 }
345
346 in_code = code; /* save code for later */
347
348 if ( code >= 256U )
349 {
350 /* special case for KwKwKwK */
351 if ( code - 256U >= state->free_ent )
352 {
353 /* corrupted LZW stream */
354 if ( code - 256U > state->free_ent )
355 goto Eof;
356
357 FTLZW_STACK_PUSH( old_char );
358 code = old_code;
359 }
360
361 while ( code >= 256U )
362 {
363 if ( !state->prefix )
364 goto Eof;
365
366 FTLZW_STACK_PUSH( state->suffix[code - 256] );
367 code = state->prefix[code - 256];
368 }
369 }
370
371 old_char = code;
372 FTLZW_STACK_PUSH( old_char );
373
374 state->phase = FT_LZW_PHASE_STACK;
375 }
376 FALL_THROUGH;
377
378 case FT_LZW_PHASE_STACK:
379 {
380 while ( state->stack_top > 0 )
381 {
382 state->stack_top--;
383
384 if ( buffer )
385 buffer[result] = state->stack[state->stack_top];
386
387 if ( ++result == out_size )
388 goto Exit;
389 }
390
391 /* now create new entry */
392 if ( state->free_ent < state->max_free )
393 {
394 if ( state->free_ent >= state->prefix_size &&
395 ft_lzwstate_prefix_grow( state ) < 0 )
396 goto Eof;
397
398 FT_ASSERT( state->free_ent < state->prefix_size );
399
400 state->prefix[state->free_ent] = (FT_UShort)old_code;
401 state->suffix[state->free_ent] = (FT_Byte) old_char;
402
403 state->free_ent += 1;
404 }
405
406 old_code = in_code;
407
408 state->phase = FT_LZW_PHASE_CODE;
409 goto NextCode;
410 }
411
412 default: /* state == EOF */
413 ;
414 }
415
416 Exit:
417 state->old_code = old_code;
418 state->old_char = old_char;
419 state->in_code = in_code;
420
421 return result;
422
423 Eof:
424 state->phase = FT_LZW_PHASE_EOF;
425 goto Exit;
426 }
427
428
429/* END */
430