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
87static inline int pulledbits(struct pushpull *pp)
88{
89	return pp->ofs;
90}
91
92
93static 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
107static 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
143static 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
156static 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
168static 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
205static 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
235static 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
254static 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
267static 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 */
302int 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
309static 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
373static 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
389static 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
398static 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
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