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