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
28static int bits_mips[8] = { 277, 249, 290, 267, 229, 341, 212, 241};
29
30struct pushpull {
31	unsigned char *buf;
32	unsigned int buflen;
33	unsigned int ofs;
34	unsigned int reserve;
35};
36
37struct 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
47static 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
57static 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
72static inline int pushedbits(struct pushpull *pp)
73{
74	return pp->ofs;
75}
76
77static 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
88static 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
102static 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
138static 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
151static 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
163static 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
200static 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
230static 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
249static 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
262static 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	if (outpos > pos) {
280		/* We failed */
281		return -1;
282	}
283
284	/* Tell the caller how much we managed to compress,
285	 * and how much space it took */
286
287	outpos = (pushedbits(&rs.pp)+7)/8;
288
289	if (outpos >= pos)
290		return -1; /* We didn't actually compress */
291	*sourcelen = pos;
292	*dstlen = outpos;
293	return 0;
294}
295#if 0
296/* _compress returns the compressed size, -1 if bigger */
297int jffs2_rubinmips_compress(unsigned char *data_in, unsigned char *cpage_out,
298		   uint32_t *sourcelen, uint32_t *dstlen)
299{
300	return rubin_do_compress(BIT_DIVIDER_MIPS, bits_mips, data_in,
301				 cpage_out, sourcelen, dstlen);
302}
303#endif
304static int jffs2_dynrubin_compress(unsigned char *data_in,
305				   unsigned char *cpage_out,
306				   uint32_t *sourcelen, uint32_t *dstlen)
307{
308	int bits[8];
309	unsigned char histo[256];
310	int i;
311	int ret;
312	uint32_t mysrclen, mydstlen;
313
314	mysrclen = *sourcelen;
315	mydstlen = *dstlen - 8;
316
317	if (*dstlen <= 12)
318		return -1;
319
320	memset(histo, 0, 256);
321	for (i=0; i<mysrclen; i++)
322		histo[data_in[i]]++;
323	memset(bits, 0, sizeof(int)*8);
324	for (i=0; i<256; i++) {
325		if (i&128)
326			bits[7] += histo[i];
327		if (i&64)
328			bits[6] += histo[i];
329		if (i&32)
330			bits[5] += histo[i];
331		if (i&16)
332			bits[4] += histo[i];
333		if (i&8)
334			bits[3] += histo[i];
335		if (i&4)
336			bits[2] += histo[i];
337		if (i&2)
338			bits[1] += histo[i];
339		if (i&1)
340			bits[0] += histo[i];
341	}
342
343	for (i=0; i<8; i++) {
344		bits[i] = (bits[i] * 256) / mysrclen;
345		if (!bits[i]) bits[i] = 1;
346		if (bits[i] > 255) bits[i] = 255;
347		cpage_out[i] = bits[i];
348	}
349
350	ret = rubin_do_compress(256, bits, data_in, cpage_out+8, &mysrclen,
351				&mydstlen);
352	if (ret)
353		return ret;
354
355	/* Add back the 8 bytes we took for the probabilities */
356	mydstlen += 8;
357
358	if (mysrclen <= mydstlen) {
359		/* We compressed */
360		return -1;
361	}
362
363	*sourcelen = mysrclen;
364	*dstlen = mydstlen;
365	return 0;
366}
367
368static void rubin_do_decompress(int bit_divider, int *bits,
369				unsigned char *cdata_in,
370				unsigned char *page_out, uint32_t srclen,
371				uint32_t destlen)
372{
373	int outpos = 0;
374	struct rubin_state rs;
375
376	init_pushpull(&rs.pp, cdata_in, srclen, 0, 0);
377	init_decode(&rs, bit_divider, bits);
378
379	while (outpos < destlen)
380		page_out[outpos++] = in_byte(&rs);
381}
382
383
384static int jffs2_rubinmips_decompress(unsigned char *data_in,
385				      unsigned char *cpage_out,
386				      uint32_t sourcelen, uint32_t dstlen)
387{
388	rubin_do_decompress(BIT_DIVIDER_MIPS, bits_mips, data_in,
389			    cpage_out, sourcelen, dstlen);
390	return 0;
391}
392
393static int jffs2_dynrubin_decompress(unsigned char *data_in,
394				     unsigned char *cpage_out,
395				     uint32_t sourcelen, uint32_t dstlen)
396{
397	int bits[8];
398	int c;
399
400	for (c=0; c<8; c++)
401		bits[c] = data_in[c];
402
403	rubin_do_decompress(256, bits, data_in+8, cpage_out, sourcelen-8,
404			    dstlen);
405	return 0;
406}
407
408static struct jffs2_compressor jffs2_rubinmips_comp = {
409	.priority = JFFS2_RUBINMIPS_PRIORITY,
410	.name = "rubinmips",
411	.compr = JFFS2_COMPR_DYNRUBIN,
412	.compress = NULL, /*&jffs2_rubinmips_compress,*/
413	.decompress = &jffs2_rubinmips_decompress,
414#ifdef JFFS2_RUBINMIPS_DISABLED
415	.disabled = 1,
416#else
417	.disabled = 0,
418#endif
419};
420
421int jffs2_rubinmips_init(void)
422{
423	return jffs2_register_compressor(&jffs2_rubinmips_comp);
424}
425
426void jffs2_rubinmips_exit(void)
427{
428	jffs2_unregister_compressor(&jffs2_rubinmips_comp);
429}
430
431static struct jffs2_compressor jffs2_dynrubin_comp = {
432	.priority = JFFS2_DYNRUBIN_PRIORITY,
433	.name = "dynrubin",
434	.compr = JFFS2_COMPR_RUBINMIPS,
435	.compress = jffs2_dynrubin_compress,
436	.decompress = &jffs2_dynrubin_decompress,
437#ifdef JFFS2_DYNRUBIN_DISABLED
438	.disabled = 1,
439#else
440	.disabled = 0,
441#endif
442};
443
444int jffs2_dynrubin_init(void)
445{
446	return jffs2_register_compressor(&jffs2_dynrubin_comp);
447}
448
449void jffs2_dynrubin_exit(void)
450{
451	jffs2_unregister_compressor(&jffs2_dynrubin_comp);
452}
453