Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
[linux-2.6] / fs / jffs2 / compr_rubin.c
1 /*
2  * JFFS2 -- Journalling Flash File System, Version 2.
3  *
4  * Copyright © 2001-2007 Red Hat, Inc.
5  *
6  * Created by Arjan van de Ven <arjanv@redhat.com>
7  *
8  * For licensing information, see the file 'LICENCE' in this directory.
9  *
10  */
11
12 #include <linux/string.h>
13 #include <linux/types.h>
14 #include <linux/jffs2.h>
15 #include <linux/errno.h>
16 #include "compr.h"
17
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
44 static inline void init_pushpull(struct pushpull *pp, char *buf,
45                                  unsigned buflen, unsigned ofs,
46                                  unsigned reserve)
47 {
48         pp->buf = buf;
49         pp->buflen = buflen;
50         pp->ofs = ofs;
51         pp->reserve = reserve;
52 }
53
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
69 static inline int pushedbits(struct pushpull *pp)
70 {
71         return pp->ofs;
72 }
73
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 static inline int pulledbits(struct pushpull *pp)
85 {
86         return pp->ofs;
87 }
88
89
90 static void init_rubin(struct rubin_state *rs, int div, int *bits)
91 {
92         int c;
93
94         rs->q = 0;
95         rs->p = (long) (2 * UPPER_BIT_RUBIN);
96         rs->bit_number = (long) 0;
97         rs->bit_divider = div;
98
99         for (c=0; c<8; c++)
100                 rs->bits[c] = bits[c];
101 }
102
103
104 static int encode(struct rubin_state *rs, long A, long B, int symbol)
105 {
106
107         long i0, i1;
108         int ret;
109
110         while ((rs->q >= UPPER_BIT_RUBIN) ||
111                ((rs->p + rs->q) <= UPPER_BIT_RUBIN)) {
112                 rs->bit_number++;
113
114                 ret = pushbit(&rs->pp, (rs->q & UPPER_BIT_RUBIN) ? 1 : 0, 0);
115                 if (ret)
116                         return ret;
117                 rs->q &= LOWER_BITS_RUBIN;
118                 rs->q <<= 1;
119                 rs->p <<= 1;
120         }
121         i0 = A * rs->p / (A + B);
122         if (i0 <= 0)
123                 i0 = 1;
124
125         if (i0 >= rs->p)
126                 i0 = rs->p - 1;
127
128         i1 = rs->p - i0;
129
130         if (symbol == 0)
131                 rs->p = i0;
132         else {
133                 rs->p = i1;
134                 rs->q += i0;
135         }
136         return 0;
137 }
138
139
140 static void end_rubin(struct rubin_state *rs)
141 {
142
143         int i;
144
145         for (i = 0; i < RUBIN_REG_SIZE; i++) {
146                 pushbit(&rs->pp, (UPPER_BIT_RUBIN & rs->q) ? 1 : 0, 1);
147                 rs->q &= LOWER_BITS_RUBIN;
148                 rs->q <<= 1;
149         }
150 }
151
152
153 static void init_decode(struct rubin_state *rs, int div, int *bits)
154 {
155         init_rubin(rs, div, bits);
156
157         /* behalve lower */
158         rs->rec_q = 0;
159
160         for (rs->bit_number = 0; rs->bit_number++ < RUBIN_REG_SIZE;
161              rs->rec_q = rs->rec_q * 2 + (long) (pullbit(&rs->pp)))
162                 ;
163 }
164
165 static void __do_decode(struct rubin_state *rs, unsigned long p,
166                         unsigned long q)
167 {
168         register unsigned long lower_bits_rubin = LOWER_BITS_RUBIN;
169         unsigned long rec_q;
170         int c, bits = 0;
171
172         /*
173          * First, work out how many bits we need from the input stream.
174          * Note that we have already done the initial check on this
175          * loop prior to calling this function.
176          */
177         do {
178                 bits++;
179                 q &= lower_bits_rubin;
180                 q <<= 1;
181                 p <<= 1;
182         } while ((q >= UPPER_BIT_RUBIN) || ((p + q) <= UPPER_BIT_RUBIN));
183
184         rs->p = p;
185         rs->q = q;
186
187         rs->bit_number += bits;
188
189         /*
190          * Now get the bits.  We really want this to be "get n bits".
191          */
192         rec_q = rs->rec_q;
193         do {
194                 c = pullbit(&rs->pp);
195                 rec_q &= lower_bits_rubin;
196                 rec_q <<= 1;
197                 rec_q += c;
198         } while (--bits);
199         rs->rec_q = rec_q;
200 }
201
202 static int decode(struct rubin_state *rs, long A, long B)
203 {
204         unsigned long p = rs->p, q = rs->q;
205         long i0, threshold;
206         int symbol;
207
208         if (q >= UPPER_BIT_RUBIN || ((p + q) <= UPPER_BIT_RUBIN))
209                 __do_decode(rs, p, q);
210
211         i0 = A * rs->p / (A + B);
212         if (i0 <= 0)
213                 i0 = 1;
214
215         if (i0 >= rs->p)
216                 i0 = rs->p - 1;
217
218         threshold = rs->q + i0;
219         symbol = rs->rec_q >= threshold;
220         if (rs->rec_q >= threshold) {
221                 rs->q += i0;
222                 i0 = rs->p - i0;
223         }
224
225         rs->p = i0;
226
227         return symbol;
228 }
229
230
231
232 static int out_byte(struct rubin_state *rs, unsigned char byte)
233 {
234         int i, ret;
235         struct rubin_state rs_copy;
236         rs_copy = *rs;
237
238         for (i=0; i<8; i++) {
239                 ret = encode(rs, rs->bit_divider-rs->bits[i],
240                              rs->bits[i], byte & 1);
241                 if (ret) {
242                         /* Failed. Restore old state */
243                         *rs = rs_copy;
244                         return ret;
245                 }
246                 byte >>= 1 ;
247         }
248         return 0;
249 }
250
251 static int in_byte(struct rubin_state *rs)
252 {
253         int i, result = 0, bit_divider = rs->bit_divider;
254
255         for (i = 0; i < 8; i++)
256                 result |= decode(rs, bit_divider - rs->bits[i],
257                                  rs->bits[i]) << i;
258
259         return result;
260 }
261
262
263
264 static int rubin_do_compress(int bit_divider, int *bits, unsigned char *data_in,
265                              unsigned char *cpage_out, uint32_t *sourcelen,
266                              uint32_t *dstlen)
267         {
268         int outpos = 0;
269         int pos=0;
270         struct rubin_state rs;
271
272         init_pushpull(&rs.pp, cpage_out, *dstlen * 8, 0, 32);
273
274         init_rubin(&rs, bit_divider, bits);
275
276         while (pos < (*sourcelen) && !out_byte(&rs, data_in[pos]))
277                 pos++;
278
279         end_rubin(&rs);
280
281         if (outpos > pos) {
282                 /* We failed */
283                 return -1;
284         }
285
286         /* Tell the caller how much we managed to compress,
287          * and how much space it took */
288
289         outpos = (pushedbits(&rs.pp)+7)/8;
290
291         if (outpos >= pos)
292                 return -1; /* We didn't actually compress */
293         *sourcelen = pos;
294         *dstlen = outpos;
295         return 0;
296 }
297 #if 0
298 /* _compress returns the compressed size, -1 if bigger */
299 int jffs2_rubinmips_compress(unsigned char *data_in, unsigned char *cpage_out,
300                    uint32_t *sourcelen, uint32_t *dstlen, void *model)
301 {
302         return rubin_do_compress(BIT_DIVIDER_MIPS, bits_mips, data_in,
303                                  cpage_out, sourcelen, dstlen);
304 }
305 #endif
306 static int jffs2_dynrubin_compress(unsigned char *data_in,
307                                    unsigned char *cpage_out,
308                                    uint32_t *sourcelen, uint32_t *dstlen,
309                                    void *model)
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                                       void *model)
391 {
392         rubin_do_decompress(BIT_DIVIDER_MIPS, bits_mips, data_in,
393                             cpage_out, sourcelen, dstlen);
394         return 0;
395 }
396
397 static int jffs2_dynrubin_decompress(unsigned char *data_in,
398                                      unsigned char *cpage_out,
399                                      uint32_t sourcelen, uint32_t dstlen,
400                                      void *model)
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
426 int jffs2_rubinmips_init(void)
427 {
428         return jffs2_register_compressor(&jffs2_rubinmips_comp);
429 }
430
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
449 int jffs2_dynrubin_init(void)
450 {
451         return jffs2_register_compressor(&jffs2_dynrubin_comp);
452 }
453
454 void jffs2_dynrubin_exit(void)
455 {
456         jffs2_unregister_compressor(&jffs2_dynrubin_comp);
457 }