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1 | /* |
2 | * JFFS2 -- Journalling Flash File System, Version 2. |
3 | * |
4 | * Copyright © 2001-2007 Red Hat, Inc. |
5 | * Copyright © 2004-2010 David Woodhouse <dwmw2@infradead.org> |
6 | * |
7 | * Created by Arjan van de Ven <arjanv@redhat.com> |
8 | * |
9 | * For licensing information, see the file 'LICENCE' in this directory. |
10 | * |
11 | */ |
12 | |
13 | #include <linux/string.h> |
14 | #include <linux/types.h> |
15 | #include <linux/jffs2.h> |
16 | #include <linux/errno.h> |
17 | #include "compr.h" |
18 | |
19 | |
20 | #define RUBIN_REG_SIZE 16 |
21 | #define UPPER_BIT_RUBIN (((long) 1)<<(RUBIN_REG_SIZE-1)) |
22 | #define LOWER_BITS_RUBIN ((((long) 1)<<(RUBIN_REG_SIZE-1))-1) |
23 | |
24 | |
25 | #define BIT_DIVIDER_MIPS 1043 |
26 | static int bits_mips[8] = { 277, 249, 290, 267, 229, 341, 212, 241}; |
27 | |
28 | struct pushpull { |
29 | unsigned char *buf; |
30 | unsigned int buflen; |
31 | unsigned int ofs; |
32 | unsigned int reserve; |
33 | }; |
34 | |
35 | struct rubin_state { |
36 | unsigned long p; |
37 | unsigned long q; |
38 | unsigned long rec_q; |
39 | long bit_number; |
40 | struct pushpull pp; |
41 | int bit_divider; |
42 | int bits[8]; |
43 | }; |
44 | |
45 | static inline void init_pushpull(struct pushpull *pp, char *buf, |
46 | unsigned buflen, unsigned ofs, |
47 | unsigned reserve) |
48 | { |
49 | pp->buf = buf; |
50 | pp->buflen = buflen; |
51 | pp->ofs = ofs; |
52 | pp->reserve = reserve; |
53 | } |
54 | |
55 | static inline int pushbit(struct pushpull *pp, int bit, int use_reserved) |
56 | { |
57 | if (pp->ofs >= pp->buflen - (use_reserved?0:pp->reserve)) |
58 | return -ENOSPC; |
59 | |
60 | if (bit) |
61 | pp->buf[pp->ofs >> 3] |= (1<<(7-(pp->ofs & 7))); |
62 | else |
63 | pp->buf[pp->ofs >> 3] &= ~(1<<(7-(pp->ofs & 7))); |
64 | |
65 | pp->ofs++; |
66 | |
67 | return 0; |
68 | } |
69 | |
70 | static inline int pushedbits(struct pushpull *pp) |
71 | { |
72 | return pp->ofs; |
73 | } |
74 | |
75 | static inline int pullbit(struct pushpull *pp) |
76 | { |
77 | int bit; |
78 | |
79 | bit = (pp->buf[pp->ofs >> 3] >> (7-(pp->ofs & 7))) & 1; |
80 | |
81 | pp->ofs++; |
82 | return bit; |
83 | } |
84 | |
85 | static inline int pulledbits(struct pushpull *pp) |
86 | { |
87 | return pp->ofs; |
88 | } |
89 | |
90 | |
91 | static void init_rubin(struct rubin_state *rs, int div, int *bits) |
92 | { |
93 | int c; |
94 | |
95 | rs->q = 0; |
96 | rs->p = (long) (2 * UPPER_BIT_RUBIN); |
97 | rs->bit_number = (long) 0; |
98 | rs->bit_divider = div; |
99 | |
100 | for (c=0; c<8; c++) |
101 | rs->bits[c] = bits[c]; |
102 | } |
103 | |
104 | |
105 | static int encode(struct rubin_state *rs, long A, long B, int symbol) |
106 | { |
107 | |
108 | long i0, i1; |
109 | int ret; |
110 | |
111 | while ((rs->q >= UPPER_BIT_RUBIN) || |
112 | ((rs->p + rs->q) <= UPPER_BIT_RUBIN)) { |
113 | rs->bit_number++; |
114 | |
115 | ret = pushbit(&rs->pp, (rs->q & UPPER_BIT_RUBIN) ? 1 : 0, 0); |
116 | if (ret) |
117 | return ret; |
118 | rs->q &= LOWER_BITS_RUBIN; |
119 | rs->q <<= 1; |
120 | rs->p <<= 1; |
121 | } |
122 | i0 = A * rs->p / (A + B); |
123 | if (i0 <= 0) |
124 | i0 = 1; |
125 | |
126 | if (i0 >= rs->p) |
127 | i0 = rs->p - 1; |
128 | |
129 | i1 = rs->p - i0; |
130 | |
131 | if (symbol == 0) |
132 | rs->p = i0; |
133 | else { |
134 | rs->p = i1; |
135 | rs->q += i0; |
136 | } |
137 | return 0; |
138 | } |
139 | |
140 | |
141 | static void end_rubin(struct rubin_state *rs) |
142 | { |
143 | |
144 | int i; |
145 | |
146 | for (i = 0; i < RUBIN_REG_SIZE; i++) { |
147 | pushbit(&rs->pp, (UPPER_BIT_RUBIN & rs->q) ? 1 : 0, 1); |
148 | rs->q &= LOWER_BITS_RUBIN; |
149 | rs->q <<= 1; |
150 | } |
151 | } |
152 | |
153 | |
154 | static void init_decode(struct rubin_state *rs, int div, int *bits) |
155 | { |
156 | init_rubin(rs, div, bits); |
157 | |
158 | /* behalve lower */ |
159 | rs->rec_q = 0; |
160 | |
161 | for (rs->bit_number = 0; rs->bit_number++ < RUBIN_REG_SIZE; |
162 | rs->rec_q = rs->rec_q * 2 + (long) (pullbit(&rs->pp))) |
163 | ; |
164 | } |
165 | |
166 | static void __do_decode(struct rubin_state *rs, unsigned long p, |
167 | unsigned long q) |
168 | { |
169 | register unsigned long lower_bits_rubin = LOWER_BITS_RUBIN; |
170 | unsigned long rec_q; |
171 | int c, bits = 0; |
172 | |
173 | /* |
174 | * First, work out how many bits we need from the input stream. |
175 | * Note that we have already done the initial check on this |
176 | * loop prior to calling this function. |
177 | */ |
178 | do { |
179 | bits++; |
180 | q &= lower_bits_rubin; |
181 | q <<= 1; |
182 | p <<= 1; |
183 | } while ((q >= UPPER_BIT_RUBIN) || ((p + q) <= UPPER_BIT_RUBIN)); |
184 | |
185 | rs->p = p; |
186 | rs->q = q; |
187 | |
188 | rs->bit_number += bits; |
189 | |
190 | /* |
191 | * Now get the bits. We really want this to be "get n bits". |
192 | */ |
193 | rec_q = rs->rec_q; |
194 | do { |
195 | c = pullbit(&rs->pp); |
196 | rec_q &= lower_bits_rubin; |
197 | rec_q <<= 1; |
198 | rec_q += c; |
199 | } while (--bits); |
200 | rs->rec_q = rec_q; |
201 | } |
202 | |
203 | static int decode(struct rubin_state *rs, long A, long B) |
204 | { |
205 | unsigned long p = rs->p, q = rs->q; |
206 | long i0, threshold; |
207 | int symbol; |
208 | |
209 | if (q >= UPPER_BIT_RUBIN || ((p + q) <= UPPER_BIT_RUBIN)) |
210 | __do_decode(rs, p, q); |
211 | |
212 | i0 = A * rs->p / (A + B); |
213 | if (i0 <= 0) |
214 | i0 = 1; |
215 | |
216 | if (i0 >= rs->p) |
217 | i0 = rs->p - 1; |
218 | |
219 | threshold = rs->q + i0; |
220 | symbol = rs->rec_q >= threshold; |
221 | if (rs->rec_q >= threshold) { |
222 | rs->q += i0; |
223 | i0 = rs->p - i0; |
224 | } |
225 | |
226 | rs->p = i0; |
227 | |
228 | return symbol; |
229 | } |
230 | |
231 | |
232 | |
233 | static int out_byte(struct rubin_state *rs, unsigned char byte) |
234 | { |
235 | int i, ret; |
236 | struct rubin_state rs_copy; |
237 | rs_copy = *rs; |
238 | |
239 | for (i=0; i<8; i++) { |
240 | ret = encode(rs, rs->bit_divider-rs->bits[i], |
241 | rs->bits[i], byte & 1); |
242 | if (ret) { |
243 | /* Failed. Restore old state */ |
244 | *rs = rs_copy; |
245 | return ret; |
246 | } |
247 | byte >>= 1 ; |
248 | } |
249 | return 0; |
250 | } |
251 | |
252 | static int in_byte(struct rubin_state *rs) |
253 | { |
254 | int i, result = 0, bit_divider = rs->bit_divider; |
255 | |
256 | for (i = 0; i < 8; i++) |
257 | result |= decode(rs, bit_divider - rs->bits[i], |
258 | rs->bits[i]) << i; |
259 | |
260 | return result; |
261 | } |
262 | |
263 | |
264 | |
265 | static int rubin_do_compress(int bit_divider, int *bits, unsigned char *data_in, |
266 | unsigned char *cpage_out, uint32_t *sourcelen, |
267 | uint32_t *dstlen) |
268 | { |
269 | int outpos = 0; |
270 | int pos=0; |
271 | struct rubin_state rs; |
272 | |
273 | init_pushpull(&rs.pp, cpage_out, *dstlen * 8, 0, 32); |
274 | |
275 | init_rubin(&rs, bit_divider, bits); |
276 | |
277 | while (pos < (*sourcelen) && !out_byte(&rs, data_in[pos])) |
278 | pos++; |
279 | |
280 | end_rubin(&rs); |
281 | |
282 | if (outpos > pos) { |
283 | /* We failed */ |
284 | return -1; |
285 | } |
286 | |
287 | /* Tell the caller how much we managed to compress, |
288 | * and how much space it took */ |
289 | |
290 | outpos = (pushedbits(&rs.pp)+7)/8; |
291 | |
292 | if (outpos >= pos) |
293 | return -1; /* We didn't actually compress */ |
294 | *sourcelen = pos; |
295 | *dstlen = outpos; |
296 | return 0; |
297 | } |
298 | #if 0 |
299 | /* _compress returns the compressed size, -1 if bigger */ |
300 | int jffs2_rubinmips_compress(unsigned char *data_in, unsigned char *cpage_out, |
301 | uint32_t *sourcelen, uint32_t *dstlen) |
302 | { |
303 | return rubin_do_compress(BIT_DIVIDER_MIPS, bits_mips, data_in, |
304 | cpage_out, sourcelen, dstlen); |
305 | } |
306 | #endif |
307 | static int jffs2_dynrubin_compress(unsigned char *data_in, |
308 | unsigned char *cpage_out, |
309 | uint32_t *sourcelen, uint32_t *dstlen) |
310 | { |
311 | int bits[8]; |
312 | unsigned char histo[256]; |
313 | int i; |
314 | int ret; |
315 | uint32_t mysrclen, mydstlen; |
316 | |
317 | mysrclen = *sourcelen; |
318 | mydstlen = *dstlen - 8; |
319 | |
320 | if (*dstlen <= 12) |
321 | return -1; |
322 | |
323 | memset(histo, 0, 256); |
324 | for (i=0; i<mysrclen; i++) |
325 | histo[data_in[i]]++; |
326 | memset(bits, 0, sizeof(int)*8); |
327 | for (i=0; i<256; i++) { |
328 | if (i&128) |
329 | bits[7] += histo[i]; |
330 | if (i&64) |
331 | bits[6] += histo[i]; |
332 | if (i&32) |
333 | bits[5] += histo[i]; |
334 | if (i&16) |
335 | bits[4] += histo[i]; |
336 | if (i&8) |
337 | bits[3] += histo[i]; |
338 | if (i&4) |
339 | bits[2] += histo[i]; |
340 | if (i&2) |
341 | bits[1] += histo[i]; |
342 | if (i&1) |
343 | bits[0] += histo[i]; |
344 | } |
345 | |
346 | for (i=0; i<8; i++) { |
347 | bits[i] = (bits[i] * 256) / mysrclen; |
348 | if (!bits[i]) bits[i] = 1; |
349 | if (bits[i] > 255) bits[i] = 255; |
350 | cpage_out[i] = bits[i]; |
351 | } |
352 | |
353 | ret = rubin_do_compress(256, bits, data_in, cpage_out+8, &mysrclen, |
354 | &mydstlen); |
355 | if (ret) |
356 | return ret; |
357 | |
358 | /* Add back the 8 bytes we took for the probabilities */ |
359 | mydstlen += 8; |
360 | |
361 | if (mysrclen <= mydstlen) { |
362 | /* We compressed */ |
363 | return -1; |
364 | } |
365 | |
366 | *sourcelen = mysrclen; |
367 | *dstlen = mydstlen; |
368 | return 0; |
369 | } |
370 | |
371 | static void rubin_do_decompress(int bit_divider, int *bits, |
372 | unsigned char *cdata_in, |
373 | unsigned char *page_out, uint32_t srclen, |
374 | uint32_t destlen) |
375 | { |
376 | int outpos = 0; |
377 | struct rubin_state rs; |
378 | |
379 | init_pushpull(&rs.pp, cdata_in, srclen, 0, 0); |
380 | init_decode(&rs, bit_divider, bits); |
381 | |
382 | while (outpos < destlen) |
383 | page_out[outpos++] = in_byte(&rs); |
384 | } |
385 | |
386 | |
387 | static int jffs2_rubinmips_decompress(unsigned char *data_in, |
388 | unsigned char *cpage_out, |
389 | uint32_t sourcelen, uint32_t dstlen) |
390 | { |
391 | rubin_do_decompress(BIT_DIVIDER_MIPS, bits_mips, data_in, |
392 | cpage_out, sourcelen, dstlen); |
393 | return 0; |
394 | } |
395 | |
396 | static int jffs2_dynrubin_decompress(unsigned char *data_in, |
397 | unsigned char *cpage_out, |
398 | uint32_t sourcelen, uint32_t dstlen) |
399 | { |
400 | int bits[8]; |
401 | int c; |
402 | |
403 | for (c=0; c<8; c++) |
404 | bits[c] = data_in[c]; |
405 | |
406 | rubin_do_decompress(256, bits, data_in+8, cpage_out, sourcelen-8, |
407 | dstlen); |
408 | return 0; |
409 | } |
410 | |
411 | static struct jffs2_compressor jffs2_rubinmips_comp = { |
412 | .priority = JFFS2_RUBINMIPS_PRIORITY, |
413 | .name = "rubinmips", |
414 | .compr = JFFS2_COMPR_DYNRUBIN, |
415 | .compress = NULL, /*&jffs2_rubinmips_compress,*/ |
416 | .decompress = &jffs2_rubinmips_decompress, |
417 | #ifdef JFFS2_RUBINMIPS_DISABLED |
418 | .disabled = 1, |
419 | #else |
420 | .disabled = 0, |
421 | #endif |
422 | }; |
423 | |
424 | int jffs2_rubinmips_init(void) |
425 | { |
426 | return jffs2_register_compressor(&jffs2_rubinmips_comp); |
427 | } |
428 | |
429 | void jffs2_rubinmips_exit(void) |
430 | { |
431 | jffs2_unregister_compressor(&jffs2_rubinmips_comp); |
432 | } |
433 | |
434 | static struct jffs2_compressor jffs2_dynrubin_comp = { |
435 | .priority = JFFS2_DYNRUBIN_PRIORITY, |
436 | .name = "dynrubin", |
437 | .compr = JFFS2_COMPR_RUBINMIPS, |
438 | .compress = jffs2_dynrubin_compress, |
439 | .decompress = &jffs2_dynrubin_decompress, |
440 | #ifdef JFFS2_DYNRUBIN_DISABLED |
441 | .disabled = 1, |
442 | #else |
443 | .disabled = 0, |
444 | #endif |
445 | }; |
446 | |
447 | int jffs2_dynrubin_init(void) |
448 | { |
449 | return jffs2_register_compressor(&jffs2_dynrubin_comp); |
450 | } |
451 | |
452 | void jffs2_dynrubin_exit(void) |
453 | { |
454 | jffs2_unregister_compressor(&jffs2_dynrubin_comp); |
455 | } |
456 |
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