2 * JFFS2 -- Journalling Flash File System, Version 2.
4 * Copyright © 2001-2007 Red Hat, Inc.
6 * Created by Arjan van de Ven <arjanv@redhat.com>
8 * For licensing information, see the file 'LICENCE' in this directory.
12 #include <linux/string.h>
13 #include <linux/types.h>
14 #include <linux/jffs2.h>
15 #include <linux/errno.h>
19 #define RUBIN_REG_SIZE 16
20 #define UPPER_BIT_RUBIN (((long) 1)<<(RUBIN_REG_SIZE-1))
21 #define LOWER_BITS_RUBIN ((((long) 1)<<(RUBIN_REG_SIZE-1))-1)
24 #define BIT_DIVIDER_MIPS 1043
25 static int bits_mips[8] = { 277, 249, 290, 267, 229, 341, 212, 241};
44 static inline void init_pushpull(struct pushpull *pp, char *buf,
45 unsigned buflen, unsigned ofs,
51 pp->reserve = reserve;
54 static inline int pushbit(struct pushpull *pp, int bit, int use_reserved)
56 if (pp->ofs >= pp->buflen - (use_reserved?0:pp->reserve))
60 pp->buf[pp->ofs >> 3] |= (1<<(7-(pp->ofs & 7)));
62 pp->buf[pp->ofs >> 3] &= ~(1<<(7-(pp->ofs & 7)));
69 static inline int pushedbits(struct pushpull *pp)
74 static inline int pullbit(struct pushpull *pp)
78 bit = (pp->buf[pp->ofs >> 3] >> (7-(pp->ofs & 7))) & 1;
84 static inline int pulledbits(struct pushpull *pp)
90 static void init_rubin(struct rubin_state *rs, int div, int *bits)
95 rs->p = (long) (2 * UPPER_BIT_RUBIN);
96 rs->bit_number = (long) 0;
97 rs->bit_divider = div;
100 rs->bits[c] = bits[c];
104 static int encode(struct rubin_state *rs, long A, long B, int symbol)
110 while ((rs->q >= UPPER_BIT_RUBIN) ||
111 ((rs->p + rs->q) <= UPPER_BIT_RUBIN)) {
114 ret = pushbit(&rs->pp, (rs->q & UPPER_BIT_RUBIN) ? 1 : 0, 0);
117 rs->q &= LOWER_BITS_RUBIN;
121 i0 = A * rs->p / (A + B);
140 static void end_rubin(struct rubin_state *rs)
145 for (i = 0; i < RUBIN_REG_SIZE; i++) {
146 pushbit(&rs->pp, (UPPER_BIT_RUBIN & rs->q) ? 1 : 0, 1);
147 rs->q &= LOWER_BITS_RUBIN;
153 static void init_decode(struct rubin_state *rs, int div, int *bits)
155 init_rubin(rs, div, bits);
160 for (rs->bit_number = 0; rs->bit_number++ < RUBIN_REG_SIZE;
161 rs->rec_q = rs->rec_q * 2 + (long) (pullbit(&rs->pp)))
165 static void __do_decode(struct rubin_state *rs, unsigned long p,
168 register unsigned long lower_bits_rubin = LOWER_BITS_RUBIN;
173 * First, work out how many bits we need from the input stream.
174 * Note that we have already done the initial check on this
175 * loop prior to calling this function.
179 q &= lower_bits_rubin;
182 } while ((q >= UPPER_BIT_RUBIN) || ((p + q) <= UPPER_BIT_RUBIN));
187 rs->bit_number += bits;
190 * Now get the bits. We really want this to be "get n bits".
194 c = pullbit(&rs->pp);
195 rec_q &= lower_bits_rubin;
202 static int decode(struct rubin_state *rs, long A, long B)
204 unsigned long p = rs->p, q = rs->q;
208 if (q >= UPPER_BIT_RUBIN || ((p + q) <= UPPER_BIT_RUBIN))
209 __do_decode(rs, p, q);
211 i0 = A * rs->p / (A + B);
218 threshold = rs->q + i0;
219 symbol = rs->rec_q >= threshold;
220 if (rs->rec_q >= threshold) {
232 static int out_byte(struct rubin_state *rs, unsigned char byte)
235 struct rubin_state rs_copy;
238 for (i=0; i<8; i++) {
239 ret = encode(rs, rs->bit_divider-rs->bits[i],
240 rs->bits[i], byte & 1);
242 /* Failed. Restore old state */
251 static int in_byte(struct rubin_state *rs)
253 int i, result = 0, bit_divider = rs->bit_divider;
255 for (i = 0; i < 8; i++)
256 result |= decode(rs, bit_divider - rs->bits[i],
264 static int rubin_do_compress(int bit_divider, int *bits, unsigned char *data_in,
265 unsigned char *cpage_out, uint32_t *sourcelen,
270 struct rubin_state rs;
272 init_pushpull(&rs.pp, cpage_out, *dstlen * 8, 0, 32);
274 init_rubin(&rs, bit_divider, bits);
276 while (pos < (*sourcelen) && !out_byte(&rs, data_in[pos]))
286 /* Tell the caller how much we managed to compress,
287 * and how much space it took */
289 outpos = (pushedbits(&rs.pp)+7)/8;
292 return -1; /* We didn't actually compress */
298 /* _compress returns the compressed size, -1 if bigger */
299 int jffs2_rubinmips_compress(unsigned char *data_in, unsigned char *cpage_out,
300 uint32_t *sourcelen, uint32_t *dstlen, void *model)
302 return rubin_do_compress(BIT_DIVIDER_MIPS, bits_mips, data_in,
303 cpage_out, sourcelen, dstlen);
306 static int jffs2_dynrubin_compress(unsigned char *data_in,
307 unsigned char *cpage_out,
308 uint32_t *sourcelen, uint32_t *dstlen,
312 unsigned char histo[256];
315 uint32_t mysrclen, mydstlen;
317 mysrclen = *sourcelen;
318 mydstlen = *dstlen - 8;
323 memset(histo, 0, 256);
324 for (i=0; i<mysrclen; i++)
326 memset(bits, 0, sizeof(int)*8);
327 for (i=0; i<256; i++) {
346 for (i=0; i<8; i++) {
347 bits[i] = (bits[i] * 256) / mysrclen;
348 if (!bits[i]) bits[i] = 1;
349 if (bits[i] > 255) bits[i] = 255;
350 cpage_out[i] = bits[i];
353 ret = rubin_do_compress(256, bits, data_in, cpage_out+8, &mysrclen,
358 /* Add back the 8 bytes we took for the probabilities */
361 if (mysrclen <= mydstlen) {
366 *sourcelen = mysrclen;
371 static void rubin_do_decompress(int bit_divider, int *bits,
372 unsigned char *cdata_in,
373 unsigned char *page_out, uint32_t srclen,
377 struct rubin_state rs;
379 init_pushpull(&rs.pp, cdata_in, srclen, 0, 0);
380 init_decode(&rs, bit_divider, bits);
382 while (outpos < destlen)
383 page_out[outpos++] = in_byte(&rs);
387 static int jffs2_rubinmips_decompress(unsigned char *data_in,
388 unsigned char *cpage_out,
389 uint32_t sourcelen, uint32_t dstlen,
392 rubin_do_decompress(BIT_DIVIDER_MIPS, bits_mips, data_in,
393 cpage_out, sourcelen, dstlen);
397 static int jffs2_dynrubin_decompress(unsigned char *data_in,
398 unsigned char *cpage_out,
399 uint32_t sourcelen, uint32_t dstlen,
406 bits[c] = data_in[c];
408 rubin_do_decompress(256, bits, data_in+8, cpage_out, sourcelen-8,
413 static struct jffs2_compressor jffs2_rubinmips_comp = {
414 .priority = JFFS2_RUBINMIPS_PRIORITY,
416 .compr = JFFS2_COMPR_DYNRUBIN,
417 .compress = NULL, /*&jffs2_rubinmips_compress,*/
418 .decompress = &jffs2_rubinmips_decompress,
419 #ifdef JFFS2_RUBINMIPS_DISABLED
426 int jffs2_rubinmips_init(void)
428 return jffs2_register_compressor(&jffs2_rubinmips_comp);
431 void jffs2_rubinmips_exit(void)
433 jffs2_unregister_compressor(&jffs2_rubinmips_comp);
436 static struct jffs2_compressor jffs2_dynrubin_comp = {
437 .priority = JFFS2_DYNRUBIN_PRIORITY,
439 .compr = JFFS2_COMPR_RUBINMIPS,
440 .compress = jffs2_dynrubin_compress,
441 .decompress = &jffs2_dynrubin_decompress,
442 #ifdef JFFS2_DYNRUBIN_DISABLED
449 int jffs2_dynrubin_init(void)
451 return jffs2_register_compressor(&jffs2_dynrubin_comp);
454 void jffs2_dynrubin_exit(void)
456 jffs2_unregister_compressor(&jffs2_dynrubin_comp);