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1 /*-------------------------------------------------------------------------
2 * Filename: mini_inflate.c
3 * Version: $Id: mini_inflate.c,v 1.3 2002/01/24 22:58:42 rfeany Exp $
4 * Copyright: Copyright (C) 2001, Russ Dill
5 * Author: Russ Dill <Russ.Dill@asu.edu>
6 * Description: Mini inflate implementation (RFC 1951)
7 *-----------------------------------------------------------------------*/
9 * SPDX-License-Identifier: GPL-2.0+
13 #include <jffs2/mini_inflate.h>
15 /* The order that the code lengths in section 3.2.7 are in */
16 static unsigned char huffman_order
[] = {16, 17, 18, 0, 8, 7, 9, 6, 10, 5,
17 11, 4, 12, 3, 13, 2, 14, 1, 15};
19 inline void cramfs_memset(int *s
, const int c
, size n
)
22 for (;n
> 0; n
--) s
[n
] = c
;
26 /* associate a stream with a block of data and reset the stream */
27 static void init_stream(struct bitstream
*stream
, unsigned char *data
,
28 void *(*inflate_memcpy
)(void *, const void *, size
))
30 stream
->error
= NO_ERROR
;
31 stream
->memcpy
= inflate_memcpy
;
34 stream
->bit
= 0; /* The first bit of the stream is the lsb of the
37 /* really sorry about all this initialization, think of a better way,
38 * let me know and it will get cleaned up */
39 stream
->codes
.bits
= 8;
40 stream
->codes
.num_symbols
= 19;
41 stream
->codes
.lengths
= stream
->code_lengths
;
42 stream
->codes
.symbols
= stream
->code_symbols
;
43 stream
->codes
.count
= stream
->code_count
;
44 stream
->codes
.first
= stream
->code_first
;
45 stream
->codes
.pos
= stream
->code_pos
;
47 stream
->lengths
.bits
= 16;
48 stream
->lengths
.num_symbols
= 288;
49 stream
->lengths
.lengths
= stream
->length_lengths
;
50 stream
->lengths
.symbols
= stream
->length_symbols
;
51 stream
->lengths
.count
= stream
->length_count
;
52 stream
->lengths
.first
= stream
->length_first
;
53 stream
->lengths
.pos
= stream
->length_pos
;
55 stream
->distance
.bits
= 16;
56 stream
->distance
.num_symbols
= 32;
57 stream
->distance
.lengths
= stream
->distance_lengths
;
58 stream
->distance
.symbols
= stream
->distance_symbols
;
59 stream
->distance
.count
= stream
->distance_count
;
60 stream
->distance
.first
= stream
->distance_first
;
61 stream
->distance
.pos
= stream
->distance_pos
;
65 /* pull 'bits' bits out of the stream. The last bit pulled it returned as the
66 * msb. (section 3.1.1)
68 inline unsigned long pull_bits(struct bitstream
*stream
,
69 const unsigned int bits
)
75 for (i
= 0; i
< bits
; i
++) {
76 ret
+= ((*(stream
->data
) >> stream
->bit
) & 1) << i
;
78 /* if, before incrementing, we are on bit 7,
79 * go to the lsb of the next byte */
80 if (stream
->bit
++ == 7) {
88 inline int pull_bit(struct bitstream
*stream
)
90 int ret
= ((*(stream
->data
) >> stream
->bit
) & 1);
91 if (stream
->bit
++ == 7) {
98 /* discard bits up to the next whole byte */
99 static void discard_bits(struct bitstream
*stream
)
101 if (stream
->bit
!= 0) {
107 /* No decompression, the data is all literals (section 3.2.4) */
108 static void decompress_none(struct bitstream
*stream
, unsigned char *dest
)
112 discard_bits(stream
);
113 length
= *(stream
->data
++);
114 length
+= *(stream
->data
++) << 8;
115 pull_bits(stream
, 16); /* throw away the inverse of the size */
117 stream
->decoded
+= length
;
118 stream
->memcpy(dest
, stream
->data
, length
);
119 stream
->data
+= length
;
122 /* Read in a symbol from the stream (section 3.2.2) */
123 static int read_symbol(struct bitstream
*stream
, struct huffman_set
*set
)
127 while (!(set
->count
[bits
] && code
< set
->first
[bits
] +
129 code
= (code
<< 1) + pull_bit(stream
);
130 if (++bits
> set
->bits
) {
131 /* error decoding (corrupted data?) */
132 stream
->error
= CODE_NOT_FOUND
;
136 return set
->symbols
[set
->pos
[bits
] + code
- set
->first
[bits
]];
139 /* decompress a stream of data encoded with the passed length and distance
141 static void decompress_huffman(struct bitstream
*stream
, unsigned char *dest
)
143 struct huffman_set
*lengths
= &(stream
->lengths
);
144 struct huffman_set
*distance
= &(stream
->distance
);
146 int symbol
, length
, dist
, i
;
149 if ((symbol
= read_symbol(stream
, lengths
)) < 0) return;
151 *(dest
++) = symbol
; /* symbol is a literal */
153 } else if (symbol
> 256) {
154 /* Determine the length of the repitition
156 if (symbol
< 265) length
= symbol
- 254;
157 else if (symbol
== 285) length
= 258;
159 length
= pull_bits(stream
, (symbol
- 261) >> 2);
160 length
+= (4 << ((symbol
- 261) >> 2)) + 3;
161 length
+= ((symbol
- 1) % 4) <<
162 ((symbol
- 261) >> 2);
165 /* Determine how far back to go */
166 if ((symbol
= read_symbol(stream
, distance
)) < 0)
168 if (symbol
< 4) dist
= symbol
+ 1;
170 dist
= pull_bits(stream
, (symbol
- 2) >> 1);
171 dist
+= (2 << ((symbol
- 2) >> 1)) + 1;
172 dist
+= (symbol
% 2) << ((symbol
- 2) >> 1);
174 stream
->decoded
+= length
;
175 for (i
= 0; i
< length
; i
++) {
180 } while (symbol
!= 256); /* 256 is the end of the data block */
183 /* Fill the lookup tables (section 3.2.2) */
184 static void fill_code_tables(struct huffman_set
*set
)
186 int code
= 0, i
, length
;
188 /* fill in the first code of each bit length, and the pos pointer */
190 for (i
= 1; i
< set
->bits
; i
++) {
191 code
= (code
+ set
->count
[i
- 1]) << 1;
192 set
->first
[i
] = code
;
193 set
->pos
[i
] = set
->pos
[i
- 1] + set
->count
[i
- 1];
196 /* Fill in the table of symbols in order of their huffman code */
197 for (i
= 0; i
< set
->num_symbols
; i
++) {
198 if ((length
= set
->lengths
[i
]))
199 set
->symbols
[set
->pos
[length
]++] = i
;
202 /* reset the pos pointer */
203 for (i
= 1; i
< set
->bits
; i
++) set
->pos
[i
] -= set
->count
[i
];
206 static void init_code_tables(struct huffman_set
*set
)
208 cramfs_memset(set
->lengths
, 0, set
->num_symbols
);
209 cramfs_memset(set
->count
, 0, set
->bits
);
210 cramfs_memset(set
->first
, 0, set
->bits
);
213 /* read in the huffman codes for dynamic decoding (section 3.2.7) */
214 static void decompress_dynamic(struct bitstream
*stream
, unsigned char *dest
)
216 /* I tried my best to minimize the memory footprint here, while still
217 * keeping up performance. I really dislike the _lengths[] tables, but
218 * I see no way of eliminating them without a sizable performance
219 * impact. The first struct table keeps track of stats on each bit
220 * length. The _length table keeps a record of the bit length of each
221 * symbol. The _symbols table is for looking up symbols by the huffman
222 * code (the pos element points to the first place in the symbol table
223 * where that bit length occurs). I also hate the initization of these
224 * structs, if someone knows how to compact these, lemme know. */
226 struct huffman_set
*codes
= &(stream
->codes
);
227 struct huffman_set
*lengths
= &(stream
->lengths
);
228 struct huffman_set
*distance
= &(stream
->distance
);
230 int hlit
= pull_bits(stream
, 5) + 257;
231 int hdist
= pull_bits(stream
, 5) + 1;
232 int hclen
= pull_bits(stream
, 4) + 4;
233 int length
, curr_code
, symbol
, i
, last_code
;
237 init_code_tables(codes
);
238 init_code_tables(lengths
);
239 init_code_tables(distance
);
241 /* fill in the count of each bit length' as well as the lengths
243 for (i
= 0; i
< hclen
; i
++) {
244 length
= pull_bits(stream
, 3);
245 codes
->lengths
[huffman_order
[i
]] = length
;
246 if (length
) codes
->count
[length
]++;
249 fill_code_tables(codes
);
251 /* Do the same for the length codes, being carefull of wrap through
252 * to the distance table */
254 while (curr_code
< hlit
) {
255 if ((symbol
= read_symbol(stream
, codes
)) < 0) return;
259 } else if (symbol
< 16) { /* Literal length */
260 lengths
->lengths
[curr_code
] = last_code
= symbol
;
261 lengths
->count
[symbol
]++;
263 } else if (symbol
== 16) { /* repeat the last symbol 3 - 6
265 length
= 3 + pull_bits(stream
, 2);
266 for (;length
; length
--, curr_code
++)
267 if (curr_code
< hlit
) {
268 lengths
->lengths
[curr_code
] =
270 lengths
->count
[last_code
]++;
271 } else { /* wrap to the distance table */
272 distance
->lengths
[curr_code
- hlit
] =
274 distance
->count
[last_code
]++;
276 } else if (symbol
== 17) { /* repeat a bit length 0 */
277 curr_code
+= 3 + pull_bits(stream
, 3);
279 } else { /* same, but more times */
280 curr_code
+= 11 + pull_bits(stream
, 7);
284 fill_code_tables(lengths
);
286 /* Fill the distance table, don't need to worry about wrapthrough
289 while (curr_code
< hdist
) {
290 if ((symbol
= read_symbol(stream
, codes
)) < 0) return;
294 } else if (symbol
< 16) {
295 distance
->lengths
[curr_code
] = last_code
= symbol
;
296 distance
->count
[symbol
]++;
298 } else if (symbol
== 16) {
299 length
= 3 + pull_bits(stream
, 2);
300 for (;length
; length
--, curr_code
++) {
301 distance
->lengths
[curr_code
] =
303 distance
->count
[last_code
]++;
305 } else if (symbol
== 17) {
306 curr_code
+= 3 + pull_bits(stream
, 3);
309 curr_code
+= 11 + pull_bits(stream
, 7);
313 fill_code_tables(distance
);
315 decompress_huffman(stream
, dest
);
318 /* fill in the length and distance huffman codes for fixed encoding
320 static void decompress_fixed(struct bitstream
*stream
, unsigned char *dest
)
322 /* let gcc fill in the initial values */
323 struct huffman_set
*lengths
= &(stream
->lengths
);
324 struct huffman_set
*distance
= &(stream
->distance
);
326 cramfs_memset(lengths
->count
, 0, 16);
327 cramfs_memset(lengths
->first
, 0, 16);
328 cramfs_memset(lengths
->lengths
, 8, 144);
329 cramfs_memset(lengths
->lengths
+ 144, 9, 112);
330 cramfs_memset(lengths
->lengths
+ 256, 7, 24);
331 cramfs_memset(lengths
->lengths
+ 280, 8, 8);
332 lengths
->count
[7] = 24;
333 lengths
->count
[8] = 152;
334 lengths
->count
[9] = 112;
336 cramfs_memset(distance
->count
, 0, 16);
337 cramfs_memset(distance
->first
, 0, 16);
338 cramfs_memset(distance
->lengths
, 5, 32);
339 distance
->count
[5] = 32;
342 fill_code_tables(lengths
);
343 fill_code_tables(distance
);
346 decompress_huffman(stream
, dest
);
349 /* returns the number of bytes decoded, < 0 if there was an error. Note that
350 * this function assumes that the block starts on a byte boundry
351 * (non-compliant, but I don't see where this would happen). section 3.2.3 */
352 long decompress_block(unsigned char *dest
, unsigned char *source
,
353 void *(*inflate_memcpy
)(void *, const void *, size
))
356 struct bitstream stream
;
358 init_stream(&stream
, source
, inflate_memcpy
);
360 bfinal
= pull_bit(&stream
);
361 btype
= pull_bits(&stream
, 2);
362 if (btype
== NO_COMP
) decompress_none(&stream
, dest
+ stream
.decoded
);
363 else if (btype
== DYNAMIC_COMP
)
364 decompress_dynamic(&stream
, dest
+ stream
.decoded
);
365 else if (btype
== FIXED_COMP
) decompress_fixed(&stream
, dest
+ stream
.decoded
);
366 else stream
.error
= COMP_UNKNOWN
;
367 } while (!bfinal
&& !stream
.error
);
370 putstr("decompress_block start\r\n");
371 putLabeledWord("stream.error = ",stream
.error
);
372 putLabeledWord("stream.decoded = ",stream
.decoded
);
373 putLabeledWord("dest = ",dest
);
374 putstr("decompress_block end\r\n");
376 return stream
.error
? -stream
.error
: stream
.decoded
;