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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14
15 #include <linux/string.h>
16 #include <linux/types.h>
17 #include <linux/jffs2.h>
18 #include <linux/errno.h>
19 #include "compr.h"
20
21
22 #define RUBIN_REG_SIZE 16
23 #define UPPER_BIT_RUBIN (((long) 1)<<(RUBIN_REG_SIZE-1))
24 #define LOWER_BITS_RUBIN ((((long) 1)<<(RUBIN_REG_SIZE-1))-1)
25
26
27 #define BIT_DIVIDER_MIPS 1043
28 static int bits_mips[8] = { 277, 249, 290, 267, 229, 341, 212, 241};
29
30 struct pushpull {
31 unsigned char *buf;
32 unsigned int buflen;
33 unsigned int ofs;
34 unsigned int reserve;
35 };
36
37 struct rubin_state {
38 unsigned long p;
39 unsigned long q;
40 unsigned long rec_q;
41 long bit_number;
42 struct pushpull pp;
43 int bit_divider;
44 int bits[8];
45 };
46
init_pushpull(struct pushpull * pp,char * buf,unsigned buflen,unsigned ofs,unsigned reserve)47 static inline void init_pushpull(struct pushpull *pp, char *buf,
48 unsigned buflen, unsigned ofs,
49 unsigned reserve)
50 {
51 pp->buf = buf;
52 pp->buflen = buflen;
53 pp->ofs = ofs;
54 pp->reserve = reserve;
55 }
56
pushbit(struct pushpull * pp,int bit,int use_reserved)57 static inline int pushbit(struct pushpull *pp, int bit, int use_reserved)
58 {
59 if (pp->ofs >= pp->buflen - (use_reserved?0:pp->reserve))
60 return -ENOSPC;
61
62 if (bit)
63 pp->buf[pp->ofs >> 3] |= (1<<(7-(pp->ofs & 7)));
64 else
65 pp->buf[pp->ofs >> 3] &= ~(1<<(7-(pp->ofs & 7)));
66
67 pp->ofs++;
68
69 return 0;
70 }
71
pushedbits(struct pushpull * pp)72 static inline int pushedbits(struct pushpull *pp)
73 {
74 return pp->ofs;
75 }
76
pullbit(struct pushpull * pp)77 static inline int pullbit(struct pushpull *pp)
78 {
79 int bit;
80
81 bit = (pp->buf[pp->ofs >> 3] >> (7-(pp->ofs & 7))) & 1;
82
83 pp->ofs++;
84 return bit;
85 }
86
pulledbits(struct pushpull * pp)87 static inline int pulledbits(struct pushpull *pp)
88 {
89 return pp->ofs;
90 }
91
92
init_rubin(struct rubin_state * rs,int div,int * bits)93 static void init_rubin(struct rubin_state *rs, int div, int *bits)
94 {
95 int c;
96
97 rs->q = 0;
98 rs->p = (long) (2 * UPPER_BIT_RUBIN);
99 rs->bit_number = (long) 0;
100 rs->bit_divider = div;
101
102 for (c=0; c<8; c++)
103 rs->bits[c] = bits[c];
104 }
105
106
encode(struct rubin_state * rs,long A,long B,int symbol)107 static int encode(struct rubin_state *rs, long A, long B, int symbol)
108 {
109
110 long i0, i1;
111 int ret;
112
113 while ((rs->q >= UPPER_BIT_RUBIN) ||
114 ((rs->p + rs->q) <= UPPER_BIT_RUBIN)) {
115 rs->bit_number++;
116
117 ret = pushbit(&rs->pp, (rs->q & UPPER_BIT_RUBIN) ? 1 : 0, 0);
118 if (ret)
119 return ret;
120 rs->q &= LOWER_BITS_RUBIN;
121 rs->q <<= 1;
122 rs->p <<= 1;
123 }
124 i0 = A * rs->p / (A + B);
125 if (i0 <= 0)
126 i0 = 1;
127
128 if (i0 >= rs->p)
129 i0 = rs->p - 1;
130
131 i1 = rs->p - i0;
132
133 if (symbol == 0)
134 rs->p = i0;
135 else {
136 rs->p = i1;
137 rs->q += i0;
138 }
139 return 0;
140 }
141
142
end_rubin(struct rubin_state * rs)143 static void end_rubin(struct rubin_state *rs)
144 {
145
146 int i;
147
148 for (i = 0; i < RUBIN_REG_SIZE; i++) {
149 pushbit(&rs->pp, (UPPER_BIT_RUBIN & rs->q) ? 1 : 0, 1);
150 rs->q &= LOWER_BITS_RUBIN;
151 rs->q <<= 1;
152 }
153 }
154
155
init_decode(struct rubin_state * rs,int div,int * bits)156 static void init_decode(struct rubin_state *rs, int div, int *bits)
157 {
158 init_rubin(rs, div, bits);
159
160 /* behalve lower */
161 rs->rec_q = 0;
162
163 for (rs->bit_number = 0; rs->bit_number++ < RUBIN_REG_SIZE;
164 rs->rec_q = rs->rec_q * 2 + (long) (pullbit(&rs->pp)))
165 ;
166 }
167
__do_decode(struct rubin_state * rs,unsigned long p,unsigned long q)168 static void __do_decode(struct rubin_state *rs, unsigned long p,
169 unsigned long q)
170 {
171 register unsigned long lower_bits_rubin = LOWER_BITS_RUBIN;
172 unsigned long rec_q;
173 int c, bits = 0;
174
175 /*
176 * First, work out how many bits we need from the input stream.
177 * Note that we have already done the initial check on this
178 * loop prior to calling this function.
179 */
180 do {
181 bits++;
182 q &= lower_bits_rubin;
183 q <<= 1;
184 p <<= 1;
185 } while ((q >= UPPER_BIT_RUBIN) || ((p + q) <= UPPER_BIT_RUBIN));
186
187 rs->p = p;
188 rs->q = q;
189
190 rs->bit_number += bits;
191
192 /*
193 * Now get the bits. We really want this to be "get n bits".
194 */
195 rec_q = rs->rec_q;
196 do {
197 c = pullbit(&rs->pp);
198 rec_q &= lower_bits_rubin;
199 rec_q <<= 1;
200 rec_q += c;
201 } while (--bits);
202 rs->rec_q = rec_q;
203 }
204
decode(struct rubin_state * rs,long A,long B)205 static int decode(struct rubin_state *rs, long A, long B)
206 {
207 unsigned long p = rs->p, q = rs->q;
208 long i0, threshold;
209 int symbol;
210
211 if (q >= UPPER_BIT_RUBIN || ((p + q) <= UPPER_BIT_RUBIN))
212 __do_decode(rs, p, q);
213
214 i0 = A * rs->p / (A + B);
215 if (i0 <= 0)
216 i0 = 1;
217
218 if (i0 >= rs->p)
219 i0 = rs->p - 1;
220
221 threshold = rs->q + i0;
222 symbol = rs->rec_q >= threshold;
223 if (rs->rec_q >= threshold) {
224 rs->q += i0;
225 i0 = rs->p - i0;
226 }
227
228 rs->p = i0;
229
230 return symbol;
231 }
232
233
234
out_byte(struct rubin_state * rs,unsigned char byte)235 static int out_byte(struct rubin_state *rs, unsigned char byte)
236 {
237 int i, ret;
238 struct rubin_state rs_copy;
239 rs_copy = *rs;
240
241 for (i=0; i<8; i++) {
242 ret = encode(rs, rs->bit_divider-rs->bits[i],
243 rs->bits[i], byte & 1);
244 if (ret) {
245 /* Failed. Restore old state */
246 *rs = rs_copy;
247 return ret;
248 }
249 byte >>= 1 ;
250 }
251 return 0;
252 }
253
in_byte(struct rubin_state * rs)254 static int in_byte(struct rubin_state *rs)
255 {
256 int i, result = 0, bit_divider = rs->bit_divider;
257
258 for (i = 0; i < 8; i++)
259 result |= decode(rs, bit_divider - rs->bits[i],
260 rs->bits[i]) << i;
261
262 return result;
263 }
264
265
266
rubin_do_compress(int bit_divider,int * bits,unsigned char * data_in,unsigned char * cpage_out,uint32_t * sourcelen,uint32_t * dstlen)267 static int rubin_do_compress(int bit_divider, int *bits, unsigned char *data_in,
268 unsigned char *cpage_out, uint32_t *sourcelen,
269 uint32_t *dstlen)
270 {
271 int outpos = 0;
272 int pos=0;
273 struct rubin_state rs;
274
275 init_pushpull(&rs.pp, cpage_out, *dstlen * 8, 0, 32);
276
277 init_rubin(&rs, bit_divider, bits);
278
279 while (pos < (*sourcelen) && !out_byte(&rs, data_in[pos]))
280 pos++;
281
282 end_rubin(&rs);
283
284 if (outpos > pos) {
285 /* We failed */
286 return -1;
287 }
288
289 /* Tell the caller how much we managed to compress,
290 * and how much space it took */
291
292 outpos = (pushedbits(&rs.pp)+7)/8;
293
294 if (outpos >= pos)
295 return -1; /* We didn't actually compress */
296 *sourcelen = pos;
297 *dstlen = outpos;
298 return 0;
299 }
300 #if 0
301 /* _compress returns the compressed size, -1 if bigger */
302 int jffs2_rubinmips_compress(unsigned char *data_in, unsigned char *cpage_out,
303 uint32_t *sourcelen, uint32_t *dstlen)
304 {
305 return rubin_do_compress(BIT_DIVIDER_MIPS, bits_mips, data_in,
306 cpage_out, sourcelen, dstlen);
307 }
308 #endif
jffs2_dynrubin_compress(unsigned char * data_in,unsigned char * cpage_out,uint32_t * sourcelen,uint32_t * dstlen)309 static int jffs2_dynrubin_compress(unsigned char *data_in,
310 unsigned char *cpage_out,
311 uint32_t *sourcelen, uint32_t *dstlen)
312 {
313 int bits[8];
314 unsigned char histo[256];
315 int i;
316 int ret;
317 uint32_t mysrclen, mydstlen;
318
319 mysrclen = *sourcelen;
320 mydstlen = *dstlen - 8;
321
322 if (*dstlen <= 12)
323 return -1;
324
325 memset(histo, 0, 256);
326 for (i=0; i<mysrclen; i++)
327 histo[data_in[i]]++;
328 memset(bits, 0, sizeof(int)*8);
329 for (i=0; i<256; i++) {
330 if (i&128)
331 bits[7] += histo[i];
332 if (i&64)
333 bits[6] += histo[i];
334 if (i&32)
335 bits[5] += histo[i];
336 if (i&16)
337 bits[4] += histo[i];
338 if (i&8)
339 bits[3] += histo[i];
340 if (i&4)
341 bits[2] += histo[i];
342 if (i&2)
343 bits[1] += histo[i];
344 if (i&1)
345 bits[0] += histo[i];
346 }
347
348 for (i=0; i<8; i++) {
349 bits[i] = (bits[i] * 256) / mysrclen;
350 if (!bits[i]) bits[i] = 1;
351 if (bits[i] > 255) bits[i] = 255;
352 cpage_out[i] = bits[i];
353 }
354
355 ret = rubin_do_compress(256, bits, data_in, cpage_out+8, &mysrclen,
356 &mydstlen);
357 if (ret)
358 return ret;
359
360 /* Add back the 8 bytes we took for the probabilities */
361 mydstlen += 8;
362
363 if (mysrclen <= mydstlen) {
364 /* We compressed */
365 return -1;
366 }
367
368 *sourcelen = mysrclen;
369 *dstlen = mydstlen;
370 return 0;
371 }
372
rubin_do_decompress(int bit_divider,int * bits,unsigned char * cdata_in,unsigned char * page_out,uint32_t srclen,uint32_t destlen)373 static void rubin_do_decompress(int bit_divider, int *bits,
374 unsigned char *cdata_in,
375 unsigned char *page_out, uint32_t srclen,
376 uint32_t destlen)
377 {
378 int outpos = 0;
379 struct rubin_state rs;
380
381 init_pushpull(&rs.pp, cdata_in, srclen, 0, 0);
382 init_decode(&rs, bit_divider, bits);
383
384 while (outpos < destlen)
385 page_out[outpos++] = in_byte(&rs);
386 }
387
388
jffs2_rubinmips_decompress(unsigned char * data_in,unsigned char * cpage_out,uint32_t sourcelen,uint32_t dstlen)389 static int jffs2_rubinmips_decompress(unsigned char *data_in,
390 unsigned char *cpage_out,
391 uint32_t sourcelen, uint32_t dstlen)
392 {
393 rubin_do_decompress(BIT_DIVIDER_MIPS, bits_mips, data_in,
394 cpage_out, sourcelen, dstlen);
395 return 0;
396 }
397
jffs2_dynrubin_decompress(unsigned char * data_in,unsigned char * cpage_out,uint32_t sourcelen,uint32_t dstlen)398 static int jffs2_dynrubin_decompress(unsigned char *data_in,
399 unsigned char *cpage_out,
400 uint32_t sourcelen, uint32_t dstlen)
401 {
402 int bits[8];
403 int c;
404
405 for (c=0; c<8; c++)
406 bits[c] = data_in[c];
407
408 rubin_do_decompress(256, bits, data_in+8, cpage_out, sourcelen-8,
409 dstlen);
410 return 0;
411 }
412
413 static struct jffs2_compressor jffs2_rubinmips_comp = {
414 .priority = JFFS2_RUBINMIPS_PRIORITY,
415 .name = "rubinmips",
416 .compr = JFFS2_COMPR_DYNRUBIN,
417 .compress = NULL, /*&jffs2_rubinmips_compress,*/
418 .decompress = &jffs2_rubinmips_decompress,
419 #ifdef JFFS2_RUBINMIPS_DISABLED
420 .disabled = 1,
421 #else
422 .disabled = 0,
423 #endif
424 };
425
jffs2_rubinmips_init(void)426 int jffs2_rubinmips_init(void)
427 {
428 return jffs2_register_compressor(&jffs2_rubinmips_comp);
429 }
430
jffs2_rubinmips_exit(void)431 void jffs2_rubinmips_exit(void)
432 {
433 jffs2_unregister_compressor(&jffs2_rubinmips_comp);
434 }
435
436 static struct jffs2_compressor jffs2_dynrubin_comp = {
437 .priority = JFFS2_DYNRUBIN_PRIORITY,
438 .name = "dynrubin",
439 .compr = JFFS2_COMPR_RUBINMIPS,
440 .compress = jffs2_dynrubin_compress,
441 .decompress = &jffs2_dynrubin_decompress,
442 #ifdef JFFS2_DYNRUBIN_DISABLED
443 .disabled = 1,
444 #else
445 .disabled = 0,
446 #endif
447 };
448
jffs2_dynrubin_init(void)449 int jffs2_dynrubin_init(void)
450 {
451 return jffs2_register_compressor(&jffs2_dynrubin_comp);
452 }
453
jffs2_dynrubin_exit(void)454 void jffs2_dynrubin_exit(void)
455 {
456 jffs2_unregister_compressor(&jffs2_dynrubin_comp);
457 }
458