root/fs/jffs2/compr_rubin.c

DEFINITIONS

1. init_pushpull
2. pushbit
3. pushedbits
4. pullbit
5. init_rubin
6. encode
7. end_rubin
8. init_decode
9. __do_decode
10. decode
11. out_byte
12. in_byte
13. rubin_do_compress
14. jffs2_rubinmips_compress
15. jffs2_dynrubin_compress
16. rubin_do_decompress
17. jffs2_rubinmips_decompress
18. jffs2_dynrubin_decompress
19. jffs2_rubinmips_init
20. jffs2_rubinmips_exit
21. jffs2_dynrubin_init
22. jffs2_dynrubin_exit

   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 
  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 
  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 
  72 static inline int pushedbits(struct pushpull *pp)
  73 {
  74         return pp->ofs;
  75 }
  76 
  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 
  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 
 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 
 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 
 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 
 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 
 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 
 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 
 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 
 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         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 */
 297 int 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
 304 static 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 
 368 static 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 
 384 static 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 
 393 static 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 
 408 static 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 
 421 int jffs2_rubinmips_init(void)
 422 {
 423         return jffs2_register_compressor(&jffs2_rubinmips_comp);
 424 }
 425 
 426 void jffs2_rubinmips_exit(void)
 427 {
 428         jffs2_unregister_compressor(&jffs2_rubinmips_comp);
 429 }
 430 
 431 static 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 
 444 int jffs2_dynrubin_init(void)
 445 {
 446         return jffs2_register_compressor(&jffs2_dynrubin_comp);
 447 }
 448 
 449 void jffs2_dynrubin_exit(void)
 450 {
 451         jffs2_unregister_compressor(&jffs2_dynrubin_comp);
 452 }