Root/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
25static int bits_mips[8] = { 277, 249, 290, 267, 229, 341, 212, 241};
26
27struct pushpull {
28    unsigned char *buf;
29    unsigned int buflen;
30    unsigned int ofs;
31    unsigned int reserve;
32};
33
34struct 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
44static 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
54static 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
69static inline int pushedbits(struct pushpull *pp)
70{
71    return pp->ofs;
72}
73
74static 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
84static inline int pulledbits(struct pushpull *pp)
85{
86    return pp->ofs;
87}
88
89
90static 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
104static 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
140static 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
153static 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
165static 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
202static 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
232static 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
251static 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
264static 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 */
299int 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
306static 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
371static 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
387static 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
397static 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
413static 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
426int jffs2_rubinmips_init(void)
427{
428    return jffs2_register_compressor(&jffs2_rubinmips_comp);
429}
430
431void jffs2_rubinmips_exit(void)
432{
433    jffs2_unregister_compressor(&jffs2_rubinmips_comp);
434}
435
436static 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
449int jffs2_dynrubin_init(void)
450{
451    return jffs2_register_compressor(&jffs2_dynrubin_comp);
452}
453
454void jffs2_dynrubin_exit(void)
455{
456    jffs2_unregister_compressor(&jffs2_dynrubin_comp);
457}
458

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