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 
pulledbits(struct pushpull * pp)87 static inline int pulledbits(struct pushpull *pp)
88 {
89 	return pp->ofs;
90 }
91 
92 
init_rubin(struct rubin_state * rs,int div,int * bits)93 static void init_rubin(struct rubin_state *rs, int div, int *bits)
94 {
95 	int c;
96 
97 	rs->q = 0;
98 	rs->p = (long) (2 * UPPER_BIT_RUBIN);
99 	rs->bit_number = (long) 0;
100 	rs->bit_divider = div;
101 
102 	for (c=0; c<8; c++)
103 		rs->bits[c] = bits[c];
104 }
105 
106 
encode(struct rubin_state * rs,long A,long B,int symbol)107 static int encode(struct rubin_state *rs, long A, long B, int symbol)
108 {
109 
110 	long i0, i1;
111 	int ret;
112 
113 	while ((rs->q >= UPPER_BIT_RUBIN) ||
114 	       ((rs->p + rs->q) <= UPPER_BIT_RUBIN)) {
115 		rs->bit_number++;
116 
117 		ret = pushbit(&rs->pp, (rs->q & UPPER_BIT_RUBIN) ? 1 : 0, 0);
118 		if (ret)
119 			return ret;
120 		rs->q &= LOWER_BITS_RUBIN;
121 		rs->q <<= 1;
122 		rs->p <<= 1;
123 	}
124 	i0 = A * rs->p / (A + B);
125 	if (i0 <= 0)
126 		i0 = 1;
127 
128 	if (i0 >= rs->p)
129 		i0 = rs->p - 1;
130 
131 	i1 = rs->p - i0;
132 
133 	if (symbol == 0)
134 		rs->p = i0;
135 	else {
136 		rs->p = i1;
137 		rs->q += i0;
138 	}
139 	return 0;
140 }
141 
142 
end_rubin(struct rubin_state * rs)143 static void end_rubin(struct rubin_state *rs)
144 {
145 
146 	int i;
147 
148 	for (i = 0; i < RUBIN_REG_SIZE; i++) {
149 		pushbit(&rs->pp, (UPPER_BIT_RUBIN & rs->q) ? 1 : 0, 1);
150 		rs->q &= LOWER_BITS_RUBIN;
151 		rs->q <<= 1;
152 	}
153 }
154 
155 
init_decode(struct rubin_state * rs,int div,int * bits)156 static void init_decode(struct rubin_state *rs, int div, int *bits)
157 {
158 	init_rubin(rs, div, bits);
159 
160 	/* behalve lower */
161 	rs->rec_q = 0;
162 
163 	for (rs->bit_number = 0; rs->bit_number++ < RUBIN_REG_SIZE;
164 	     rs->rec_q = rs->rec_q * 2 + (long) (pullbit(&rs->pp)))
165 		;
166 }
167 
__do_decode(struct rubin_state * rs,unsigned long p,unsigned long q)168 static void __do_decode(struct rubin_state *rs, unsigned long p,
169 			unsigned long q)
170 {
171 	register unsigned long lower_bits_rubin = LOWER_BITS_RUBIN;
172 	unsigned long rec_q;
173 	int c, bits = 0;
174 
175 	/*
176 	 * First, work out how many bits we need from the input stream.
177 	 * Note that we have already done the initial check on this
178 	 * loop prior to calling this function.
179 	 */
180 	do {
181 		bits++;
182 		q &= lower_bits_rubin;
183 		q <<= 1;
184 		p <<= 1;
185 	} while ((q >= UPPER_BIT_RUBIN) || ((p + q) <= UPPER_BIT_RUBIN));
186 
187 	rs->p = p;
188 	rs->q = q;
189 
190 	rs->bit_number += bits;
191 
192 	/*
193 	 * Now get the bits.  We really want this to be "get n bits".
194 	 */
195 	rec_q = rs->rec_q;
196 	do {
197 		c = pullbit(&rs->pp);
198 		rec_q &= lower_bits_rubin;
199 		rec_q <<= 1;
200 		rec_q += c;
201 	} while (--bits);
202 	rs->rec_q = rec_q;
203 }
204 
decode(struct rubin_state * rs,long A,long B)205 static int decode(struct rubin_state *rs, long A, long B)
206 {
207 	unsigned long p = rs->p, q = rs->q;
208 	long i0, threshold;
209 	int symbol;
210 
211 	if (q >= UPPER_BIT_RUBIN || ((p + q) <= UPPER_BIT_RUBIN))
212 		__do_decode(rs, p, q);
213 
214 	i0 = A * rs->p / (A + B);
215 	if (i0 <= 0)
216 		i0 = 1;
217 
218 	if (i0 >= rs->p)
219 		i0 = rs->p - 1;
220 
221 	threshold = rs->q + i0;
222 	symbol = rs->rec_q >= threshold;
223 	if (rs->rec_q >= threshold) {
224 		rs->q += i0;
225 		i0 = rs->p - i0;
226 	}
227 
228 	rs->p = i0;
229 
230 	return symbol;
231 }
232 
233 
234 
out_byte(struct rubin_state * rs,unsigned char byte)235 static int out_byte(struct rubin_state *rs, unsigned char byte)
236 {
237 	int i, ret;
238 	struct rubin_state rs_copy;
239 	rs_copy = *rs;
240 
241 	for (i=0; i<8; i++) {
242 		ret = encode(rs, rs->bit_divider-rs->bits[i],
243 			     rs->bits[i], byte & 1);
244 		if (ret) {
245 			/* Failed. Restore old state */
246 			*rs = rs_copy;
247 			return ret;
248 		}
249 		byte >>= 1 ;
250 	}
251 	return 0;
252 }
253 
in_byte(struct rubin_state * rs)254 static int in_byte(struct rubin_state *rs)
255 {
256 	int i, result = 0, bit_divider = rs->bit_divider;
257 
258 	for (i = 0; i < 8; i++)
259 		result |= decode(rs, bit_divider - rs->bits[i],
260 				 rs->bits[i]) << i;
261 
262 	return result;
263 }
264 
265 
266 
rubin_do_compress(int bit_divider,int * bits,unsigned char * data_in,unsigned char * cpage_out,uint32_t * sourcelen,uint32_t * dstlen)267 static int rubin_do_compress(int bit_divider, int *bits, unsigned char *data_in,
268 			     unsigned char *cpage_out, uint32_t *sourcelen,
269 			     uint32_t *dstlen)
270 	{
271 	int outpos = 0;
272 	int pos=0;
273 	struct rubin_state rs;
274 
275 	init_pushpull(&rs.pp, cpage_out, *dstlen * 8, 0, 32);
276 
277 	init_rubin(&rs, bit_divider, bits);
278 
279 	while (pos < (*sourcelen) && !out_byte(&rs, data_in[pos]))
280 		pos++;
281 
282 	end_rubin(&rs);
283 
284 	if (outpos > pos) {
285 		/* We failed */
286 		return -1;
287 	}
288 
289 	/* Tell the caller how much we managed to compress,
290 	 * and how much space it took */
291 
292 	outpos = (pushedbits(&rs.pp)+7)/8;
293 
294 	if (outpos >= pos)
295 		return -1; /* We didn't actually compress */
296 	*sourcelen = pos;
297 	*dstlen = outpos;
298 	return 0;
299 }
300 #if 0
301 /* _compress returns the compressed size, -1 if bigger */
302 int jffs2_rubinmips_compress(unsigned char *data_in, unsigned char *cpage_out,
303 		   uint32_t *sourcelen, uint32_t *dstlen)
304 {
305 	return rubin_do_compress(BIT_DIVIDER_MIPS, bits_mips, data_in,
306 				 cpage_out, sourcelen, dstlen);
307 }
308 #endif
jffs2_dynrubin_compress(unsigned char * data_in,unsigned char * cpage_out,uint32_t * sourcelen,uint32_t * dstlen)309 static int jffs2_dynrubin_compress(unsigned char *data_in,
310 				   unsigned char *cpage_out,
311 				   uint32_t *sourcelen, uint32_t *dstlen)
312 {
313 	int bits[8];
314 	unsigned char histo[256];
315 	int i;
316 	int ret;
317 	uint32_t mysrclen, mydstlen;
318 
319 	mysrclen = *sourcelen;
320 	mydstlen = *dstlen - 8;
321 
322 	if (*dstlen <= 12)
323 		return -1;
324 
325 	memset(histo, 0, 256);
326 	for (i=0; i<mysrclen; i++)
327 		histo[data_in[i]]++;
328 	memset(bits, 0, sizeof(int)*8);
329 	for (i=0; i<256; i++) {
330 		if (i&128)
331 			bits[7] += histo[i];
332 		if (i&64)
333 			bits[6] += histo[i];
334 		if (i&32)
335 			bits[5] += histo[i];
336 		if (i&16)
337 			bits[4] += histo[i];
338 		if (i&8)
339 			bits[3] += histo[i];
340 		if (i&4)
341 			bits[2] += histo[i];
342 		if (i&2)
343 			bits[1] += histo[i];
344 		if (i&1)
345 			bits[0] += histo[i];
346 	}
347 
348 	for (i=0; i<8; i++) {
349 		bits[i] = (bits[i] * 256) / mysrclen;
350 		if (!bits[i]) bits[i] = 1;
351 		if (bits[i] > 255) bits[i] = 255;
352 		cpage_out[i] = bits[i];
353 	}
354 
355 	ret = rubin_do_compress(256, bits, data_in, cpage_out+8, &mysrclen,
356 				&mydstlen);
357 	if (ret)
358 		return ret;
359 
360 	/* Add back the 8 bytes we took for the probabilities */
361 	mydstlen += 8;
362 
363 	if (mysrclen <= mydstlen) {
364 		/* We compressed */
365 		return -1;
366 	}
367 
368 	*sourcelen = mysrclen;
369 	*dstlen = mydstlen;
370 	return 0;
371 }
372 
rubin_do_decompress(int bit_divider,int * bits,unsigned char * cdata_in,unsigned char * page_out,uint32_t srclen,uint32_t destlen)373 static void rubin_do_decompress(int bit_divider, int *bits,
374 				unsigned char *cdata_in,
375 				unsigned char *page_out, uint32_t srclen,
376 				uint32_t destlen)
377 {
378 	int outpos = 0;
379 	struct rubin_state rs;
380 
381 	init_pushpull(&rs.pp, cdata_in, srclen, 0, 0);
382 	init_decode(&rs, bit_divider, bits);
383 
384 	while (outpos < destlen)
385 		page_out[outpos++] = in_byte(&rs);
386 }
387 
388 
jffs2_rubinmips_decompress(unsigned char * data_in,unsigned char * cpage_out,uint32_t sourcelen,uint32_t dstlen)389 static int jffs2_rubinmips_decompress(unsigned char *data_in,
390 				      unsigned char *cpage_out,
391 				      uint32_t sourcelen, uint32_t dstlen)
392 {
393 	rubin_do_decompress(BIT_DIVIDER_MIPS, bits_mips, data_in,
394 			    cpage_out, sourcelen, dstlen);
395 	return 0;
396 }
397 
jffs2_dynrubin_decompress(unsigned char * data_in,unsigned char * cpage_out,uint32_t sourcelen,uint32_t dstlen)398 static int jffs2_dynrubin_decompress(unsigned char *data_in,
399 				     unsigned char *cpage_out,
400 				     uint32_t sourcelen, uint32_t dstlen)
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 
jffs2_rubinmips_init(void)426 int jffs2_rubinmips_init(void)
427 {
428 	return jffs2_register_compressor(&jffs2_rubinmips_comp);
429 }
430 
jffs2_rubinmips_exit(void)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 
jffs2_dynrubin_init(void)449 int jffs2_dynrubin_init(void)
450 {
451 	return jffs2_register_compressor(&jffs2_dynrubin_comp);
452 }
453 
jffs2_dynrubin_exit(void)454 void jffs2_dynrubin_exit(void)
455 {
456 	jffs2_unregister_compressor(&jffs2_dynrubin_comp);
457 }
458