xref: /linux/fs/jffs2/compr_rubin.c (revision 04b43ea325d21c4c98e831383a1b7d540721898a)
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 
87 
init_rubin(struct rubin_state * rs,int div,int * bits)88 static 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 
encode(struct rubin_state * rs,long A,long B,int symbol)102 static 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(&rs->pp, (rs->q & UPPER_BIT_RUBIN) ? 1 : 0, 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 
end_rubin(struct rubin_state * rs)138 static void end_rubin(struct rubin_state *rs)
139 {
140 
141 	int i;
142 
143 	for (i = 0; i < RUBIN_REG_SIZE; i++) {
144 		pushbit(&rs->pp, (UPPER_BIT_RUBIN & rs->q) ? 1 : 0, 1);
145 		rs->q &= LOWER_BITS_RUBIN;
146 		rs->q <<= 1;
147 	}
148 }
149 
150 
init_decode(struct rubin_state * rs,int div,int * bits)151 static 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(&rs->pp)))
160 		;
161 }
162 
__do_decode(struct rubin_state * rs,unsigned long p,unsigned long q)163 static 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(&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 
decode(struct rubin_state * rs,long A,long B)200 static 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 
out_byte(struct rubin_state * rs,unsigned char byte)230 static 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, rs->bit_divider-rs->bits[i],
238 			     rs->bits[i], 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 
in_byte(struct rubin_state * rs)249 static 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, bit_divider - rs->bits[i],
255 				 rs->bits[i]) << i;
256 
257 	return result;
258 }
259 
260 
261 
rubin_do_compress(int bit_divider,int * bits,unsigned char * data_in,unsigned char * cpage_out,uint32_t * sourcelen,uint32_t * dstlen)262 static 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(&rs.pp, cpage_out, *dstlen * 8, 0, 32);
271 
272 	init_rubin(&rs, bit_divider, bits);
273 
274 	while (pos < (*sourcelen) && !out_byte(&rs, data_in[pos]))
275 		pos++;
276 
277 	end_rubin(&rs);
278 
279 	/* Tell the caller how much we managed to compress,
280 	 * and how much space it took */
281 
282 	outpos = (pushedbits(&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 */
292 int 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
jffs2_dynrubin_compress(unsigned char * data_in,unsigned char * cpage_out,uint32_t * sourcelen,uint32_t * dstlen)299 static 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(256, bits, data_in, cpage_out+8, &mysrclen,
346 				&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 
rubin_do_decompress(int bit_divider,int * bits,unsigned char * cdata_in,unsigned char * page_out,uint32_t srclen,uint32_t destlen)363 static 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(&rs.pp, cdata_in, srclen, 0, 0);
372 	init_decode(&rs, bit_divider, bits);
373 
374 	while (outpos < destlen)
375 		page_out[outpos++] = in_byte(&rs);
376 }
377 
378 
jffs2_rubinmips_decompress(unsigned char * data_in,unsigned char * cpage_out,uint32_t sourcelen,uint32_t dstlen)379 static 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_mips, data_in,
384 			    cpage_out, sourcelen, dstlen);
385 	return 0;
386 }
387 
jffs2_dynrubin_decompress(unsigned char * data_in,unsigned char * cpage_out,uint32_t sourcelen,uint32_t dstlen)388 static 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(256, bits, data_in+8, cpage_out, sourcelen-8,
399 			    dstlen);
400 	return 0;
401 }
402 
403 static 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 
jffs2_rubinmips_init(void)416 int jffs2_rubinmips_init(void)
417 {
418 	return jffs2_register_compressor(&jffs2_rubinmips_comp);
419 }
420 
jffs2_rubinmips_exit(void)421 void jffs2_rubinmips_exit(void)
422 {
423 	jffs2_unregister_compressor(&jffs2_rubinmips_comp);
424 }
425 
426 static 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 
jffs2_dynrubin_init(void)439 int jffs2_dynrubin_init(void)
440 {
441 	return jffs2_register_compressor(&jffs2_dynrubin_comp);
442 }
443 
jffs2_dynrubin_exit(void)444 void jffs2_dynrubin_exit(void)
445 {
446 	jffs2_unregister_compressor(&jffs2_dynrubin_comp);
447 }
448