[JFFS2] Check for all-zero node headers
[linux-2.6] / fs / jffs2 / compr_rubin.c
1 /*
2  * JFFS2 -- Journalling Flash File System, Version 2.
3  *
4  * Copyright (C) 2001, 2002 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  * $Id: compr_rubin.c,v 1.20 2004/06/23 16:34:40 havasi Exp $
11  *
12  */
13
14 #include <linux/string.h>
15 #include <linux/types.h>
16 #include <linux/jffs2.h>
17 #include "compr_rubin.h"
18 #include "histo_mips.h"
19 #include "compr.h"
20
21 static void init_rubin(struct rubin_state *rs, int div, int *bits)
22 {
23         int c;
24
25         rs->q = 0;
26         rs->p = (long) (2 * UPPER_BIT_RUBIN);
27         rs->bit_number = (long) 0;
28         rs->bit_divider = div;
29         for (c=0; c<8; c++)
30                 rs->bits[c] = bits[c];
31 }
32
33
34 static int encode(struct rubin_state *rs, long A, long B, int symbol)
35 {
36
37         long i0, i1;
38         int ret;
39
40         while ((rs->q >= UPPER_BIT_RUBIN) || ((rs->p + rs->q) <= UPPER_BIT_RUBIN)) {
41                 rs->bit_number++;
42
43                 ret = pushbit(&rs->pp, (rs->q & UPPER_BIT_RUBIN) ? 1 : 0, 0);
44                 if (ret)
45                         return ret;
46                 rs->q &= LOWER_BITS_RUBIN;
47                 rs->q <<= 1;
48                 rs->p <<= 1;
49         }
50         i0 = A * rs->p / (A + B);
51         if (i0 <= 0) {
52                 i0 = 1;
53         }
54         if (i0 >= rs->p) {
55                 i0 = rs->p - 1;
56         }
57         i1 = rs->p - i0;
58
59         if (symbol == 0)
60                 rs->p = i0;
61         else {
62                 rs->p = i1;
63                 rs->q += i0;
64         }
65         return 0;
66 }
67
68
69 static void end_rubin(struct rubin_state *rs)
70 {
71
72         int i;
73
74         for (i = 0; i < RUBIN_REG_SIZE; i++) {
75                 pushbit(&rs->pp, (UPPER_BIT_RUBIN & rs->q) ? 1 : 0, 1);
76                 rs->q &= LOWER_BITS_RUBIN;
77                 rs->q <<= 1;
78         }
79 }
80
81
82 static void init_decode(struct rubin_state *rs, int div, int *bits)
83 {
84         init_rubin(rs, div, bits);
85
86         /* behalve lower */
87         rs->rec_q = 0;
88
89         for (rs->bit_number = 0; rs->bit_number++ < RUBIN_REG_SIZE; rs->rec_q = rs->rec_q * 2 + (long) (pullbit(&rs->pp)))
90                 ;
91 }
92
93 static void __do_decode(struct rubin_state *rs, unsigned long p, unsigned long q)
94 {
95         register unsigned long lower_bits_rubin = LOWER_BITS_RUBIN;
96         unsigned long rec_q;
97         int c, bits = 0;
98
99         /*
100          * First, work out how many bits we need from the input stream.
101          * Note that we have already done the initial check on this
102          * loop prior to calling this function.
103          */
104         do {
105                 bits++;
106                 q &= lower_bits_rubin;
107                 q <<= 1;
108                 p <<= 1;
109         } while ((q >= UPPER_BIT_RUBIN) || ((p + q) <= UPPER_BIT_RUBIN));
110
111         rs->p = p;
112         rs->q = q;
113
114         rs->bit_number += bits;
115
116         /*
117          * Now get the bits.  We really want this to be "get n bits".
118          */
119         rec_q = rs->rec_q;
120         do {
121                 c = pullbit(&rs->pp);
122                 rec_q &= lower_bits_rubin;
123                 rec_q <<= 1;
124                 rec_q += c;
125         } while (--bits);
126         rs->rec_q = rec_q;
127 }
128
129 static int decode(struct rubin_state *rs, long A, long B)
130 {
131         unsigned long p = rs->p, q = rs->q;
132         long i0, threshold;
133         int symbol;
134
135         if (q >= UPPER_BIT_RUBIN || ((p + q) <= UPPER_BIT_RUBIN))
136                 __do_decode(rs, p, q);
137
138         i0 = A * rs->p / (A + B);
139         if (i0 <= 0) {
140                 i0 = 1;
141         }
142         if (i0 >= rs->p) {
143                 i0 = rs->p - 1;
144         }
145
146         threshold = rs->q + i0;
147         symbol = rs->rec_q >= threshold;
148         if (rs->rec_q >= threshold) {
149                 rs->q += i0;
150                 i0 = rs->p - i0;
151         }
152
153         rs->p = i0;
154
155         return symbol;
156 }
157
158
159
160 static int out_byte(struct rubin_state *rs, unsigned char byte)
161 {
162         int i, ret;
163         struct rubin_state rs_copy;
164         rs_copy = *rs;
165
166         for (i=0;i<8;i++) {
167                 ret = encode(rs, rs->bit_divider-rs->bits[i],rs->bits[i],byte&1);
168                 if (ret) {
169                         /* Failed. Restore old state */
170                         *rs = rs_copy;
171                         return ret;
172                 }
173                 byte=byte>>1;
174         }
175         return 0;
176 }
177
178 static int in_byte(struct rubin_state *rs)
179 {
180         int i, result = 0, bit_divider = rs->bit_divider;
181
182         for (i = 0; i < 8; i++)
183                 result |= decode(rs, bit_divider - rs->bits[i], rs->bits[i]) << i;
184
185         return result;
186 }
187
188
189
190 static int rubin_do_compress(int bit_divider, int *bits, unsigned char *data_in,
191                       unsigned char *cpage_out, uint32_t *sourcelen, uint32_t *dstlen)
192         {
193         int outpos = 0;
194         int pos=0;
195         struct rubin_state rs;
196
197         init_pushpull(&rs.pp, cpage_out, *dstlen * 8, 0, 32);
198
199         init_rubin(&rs, bit_divider, bits);
200
201         while (pos < (*sourcelen) && !out_byte(&rs, data_in[pos]))
202                 pos++;
203
204         end_rubin(&rs);
205
206         if (outpos > pos) {
207                 /* We failed */
208                 return -1;
209         }
210
211         /* Tell the caller how much we managed to compress,
212          * and how much space it took */
213
214         outpos = (pushedbits(&rs.pp)+7)/8;
215
216         if (outpos >= pos)
217                 return -1; /* We didn't actually compress */
218         *sourcelen = pos;
219         *dstlen = outpos;
220         return 0;
221 }
222 #if 0
223 /* _compress returns the compressed size, -1 if bigger */
224 int jffs2_rubinmips_compress(unsigned char *data_in, unsigned char *cpage_out,
225                    uint32_t *sourcelen, uint32_t *dstlen, void *model)
226 {
227         return rubin_do_compress(BIT_DIVIDER_MIPS, bits_mips, data_in, cpage_out, sourcelen, dstlen);
228 }
229 #endif
230 static int jffs2_dynrubin_compress(unsigned char *data_in,
231                                    unsigned char *cpage_out,
232                                    uint32_t *sourcelen, uint32_t *dstlen,
233                                    void *model)
234 {
235         int bits[8];
236         unsigned char histo[256];
237         int i;
238         int ret;
239         uint32_t mysrclen, mydstlen;
240
241         mysrclen = *sourcelen;
242         mydstlen = *dstlen - 8;
243
244         if (*dstlen <= 12)
245                 return -1;
246
247         memset(histo, 0, 256);
248         for (i=0; i<mysrclen; i++) {
249                 histo[data_in[i]]++;
250         }
251         memset(bits, 0, sizeof(int)*8);
252         for (i=0; i<256; i++) {
253                 if (i&128)
254                         bits[7] += histo[i];
255                 if (i&64)
256                         bits[6] += histo[i];
257                 if (i&32)
258                         bits[5] += histo[i];
259                 if (i&16)
260                         bits[4] += histo[i];
261                 if (i&8)
262                         bits[3] += histo[i];
263                 if (i&4)
264                         bits[2] += histo[i];
265                 if (i&2)
266                         bits[1] += histo[i];
267                 if (i&1)
268                         bits[0] += histo[i];
269         }
270
271         for (i=0; i<8; i++) {
272                 bits[i] = (bits[i] * 256) / mysrclen;
273                 if (!bits[i]) bits[i] = 1;
274                 if (bits[i] > 255) bits[i] = 255;
275                 cpage_out[i] = bits[i];
276         }
277
278         ret = rubin_do_compress(256, bits, data_in, cpage_out+8, &mysrclen, &mydstlen);
279         if (ret)
280                 return ret;
281
282         /* Add back the 8 bytes we took for the probabilities */
283         mydstlen += 8;
284
285         if (mysrclen <= mydstlen) {
286                 /* We compressed */
287                 return -1;
288         }
289
290         *sourcelen = mysrclen;
291         *dstlen = mydstlen;
292         return 0;
293 }
294
295 static void rubin_do_decompress(int bit_divider, int *bits, unsigned char *cdata_in,
296                          unsigned char *page_out, uint32_t srclen, uint32_t destlen)
297 {
298         int outpos = 0;
299         struct rubin_state rs;
300
301         init_pushpull(&rs.pp, cdata_in, srclen, 0, 0);
302         init_decode(&rs, bit_divider, bits);
303
304         while (outpos < destlen) {
305                 page_out[outpos++] = in_byte(&rs);
306         }
307 }
308
309
310 static int jffs2_rubinmips_decompress(unsigned char *data_in,
311                                       unsigned char *cpage_out,
312                                       uint32_t sourcelen, uint32_t dstlen,
313                                       void *model)
314 {
315         rubin_do_decompress(BIT_DIVIDER_MIPS, bits_mips, data_in, cpage_out, sourcelen, dstlen);
316         return 0;
317 }
318
319 static int jffs2_dynrubin_decompress(unsigned char *data_in,
320                                      unsigned char *cpage_out,
321                                      uint32_t sourcelen, uint32_t dstlen,
322                                      void *model)
323 {
324         int bits[8];
325         int c;
326
327         for (c=0; c<8; c++)
328                 bits[c] = data_in[c];
329
330         rubin_do_decompress(256, bits, data_in+8, cpage_out, sourcelen-8, dstlen);
331         return 0;
332 }
333
334 static struct jffs2_compressor jffs2_rubinmips_comp = {
335     .priority = JFFS2_RUBINMIPS_PRIORITY,
336     .name = "rubinmips",
337     .compr = JFFS2_COMPR_DYNRUBIN,
338     .compress = NULL, /*&jffs2_rubinmips_compress,*/
339     .decompress = &jffs2_rubinmips_decompress,
340 #ifdef JFFS2_RUBINMIPS_DISABLED
341     .disabled = 1,
342 #else
343     .disabled = 0,
344 #endif
345 };
346
347 int jffs2_rubinmips_init(void)
348 {
349     return jffs2_register_compressor(&jffs2_rubinmips_comp);
350 }
351
352 void jffs2_rubinmips_exit(void)
353 {
354     jffs2_unregister_compressor(&jffs2_rubinmips_comp);
355 }
356
357 static struct jffs2_compressor jffs2_dynrubin_comp = {
358     .priority = JFFS2_DYNRUBIN_PRIORITY,
359     .name = "dynrubin",
360     .compr = JFFS2_COMPR_RUBINMIPS,
361     .compress = jffs2_dynrubin_compress,
362     .decompress = &jffs2_dynrubin_decompress,
363 #ifdef JFFS2_DYNRUBIN_DISABLED
364     .disabled = 1,
365 #else
366     .disabled = 0,
367 #endif
368 };
369
370 int jffs2_dynrubin_init(void)
371 {
372     return jffs2_register_compressor(&jffs2_dynrubin_comp);
373 }
374
375 void jffs2_dynrubin_exit(void)
376 {
377     jffs2_unregister_compressor(&jffs2_dynrubin_comp);
378 }