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

source code of linux/fs/jffs2/compr_rubin.c