fs/jffs2/compr_rubin.c

   1 /*
   2  * JFFS2 -- Journalling Flash File System, Version 2.
   3  *
   4  * Copyright © 2001-2007 Red Hat, Inc.
   5  *
   6  * Created by Arjan van de Ven <arjanv@redhat.com>
   7  *
   8  * For licensing information, see the file 'LICENCE' in this directory.
   9  *
  10  */
  11
  12 #include <linux/string.h>
  13 #include <linux/types.h>
  14 #include <linux/jffs2.h>
  15 #include <linux/errno.h>
  16 #include "compr.h"
  17
  18
  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)
  22
  23
  24 #define BIT_DIVIDER_MIPS 1043
  25 static int bits_mips[8] = { 277, 249, 290, 267, 229, 341, 212, 241};
  26
  27 struct pushpull {
  28         unsigned char *buf;
  29         unsigned int buflen;
  30         unsigned int ofs;
  31         unsigned int reserve;
  32 };
  33
  34 struct rubin_state {
  35         unsigned long p;
  36         unsigned long q;
  37         unsigned long rec_q;
  38         long bit_number;
  39         struct pushpull pp;
  40         int bit_divider;
  41         int bits[8];
  42 };
  43
  44 static inline void init_pushpull(struct pushpull *pp, char *buf,
  45                                  unsigned buflen, unsigned ofs,
  46                                  unsigned reserve)
  47 {
  48         pp->buf = buf;
  49         pp->buflen = buflen;
  50         pp->ofs = ofs;
  51         pp->reserve = reserve;
  52 }
  53
  54 static inline int pushbit(struct pushpull *pp, int bit, int use_reserved)
  55 {
  56         if (pp->ofs >= pp->buflen - (use_reserved?0:pp->reserve))
  57                 return -ENOSPC;
  58
  59         if (bit)
  60                 pp->buf[pp->ofs >> 3] |= (1<<(7-(pp->ofs & 7)));
  61         else
  62                 pp->buf[pp->ofs >> 3] &= ~(1<<(7-(pp->ofs & 7)));
  63
  64         pp->ofs++;
  65
  66         return 0;
  67 }
  68
  69 static inline int pushedbits(struct pushpull *pp)
  70 {
  71         return pp->ofs;
  72 }
  73
  74 static inline int pullbit(struct pushpull *pp)
  75 {
  76         int bit;
  77
  78         bit = (pp->buf[pp->ofs >> 3] >> (7-(pp->ofs & 7))) & 1;
  79
  80         pp->ofs++;
  81         return bit;
  82 }
  83
  84 static inline int pulledbits(struct pushpull *pp)
  85 {
  86         return pp->ofs;
  87 }
  88
  89
  90 static void init_rubin(struct rubin_state *rs, int div, int *bits)
  91 {
  92         int c;
  93
  94         rs->q = 0;
  95         rs->p = (long) (2 * UPPER_BIT_RUBIN);
  96         rs->bit_number = (long) 0;
  97         rs->bit_divider = div;
  98
  99         for (c=0; c<8; c++)
 100                 rs->bits[c] = bits[c];
 101 }
 102
 103
 104 static int encode(struct rubin_state *rs, long A, long B, int symbol)
 105 {
 106
 107         long i0, i1;
 108         int ret;
 109
 110         while ((rs->q >= UPPER_BIT_RUBIN) ||
 111                ((rs->p + rs->q) <= UPPER_BIT_RUBIN)) {
 112                 rs->bit_number++;
 113
 114                 ret = pushbit(&rs->pp, (rs->q & UPPER_BIT_RUBIN) ? 1 : 0, 0);
 115                 if (ret)
 116                         return ret;
 117                 rs->q &= LOWER_BITS_RUBIN;
 118                 rs->q <<= 1;
 119                 rs->p <<= 1;
 120         }
 121         i0 = A * rs->p / (A + B);
 122         if (i0 <= 0)
 123                 i0 = 1;
 124
 125         if (i0 >= rs->p)
 126                 i0 = rs->p - 1;
 127
 128         i1 = rs->p - i0;
 129
 130         if (symbol == 0)
 131                 rs->p = i0;
 132         else {
 133                 rs->p = i1;
 134                 rs->q += i0;
 135         }
 136         return 0;
 137 }
 138
 139
 140 static void end_rubin(struct rubin_state *rs)
 141 {
 142
 143         int i;
 144
 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;
 148                 rs->q <<= 1;
 149         }
 150 }
 151
 152
 153 static void init_decode(struct rubin_state *rs, int div, int *bits)
 154 {
 155         init_rubin(rs, div, bits);
 156
 157         /* behalve lower */
 158         rs->rec_q = 0;
 159
 160         for (rs->bit_number = 0; rs->bit_number++ < RUBIN_REG_SIZE;
 161              rs->rec_q = rs->rec_q * 2 + (long) (pullbit(&rs->pp)))
 162                 ;
 163 }
 164
 165 static void __do_decode(struct rubin_state *rs, unsigned long p,
 166                         unsigned long q)
 167 {
 168         register unsigned long lower_bits_rubin = LOWER_BITS_RUBIN;
 169         unsigned long rec_q;
 170         int c, bits = 0;
 171
 172         /*
 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.
 176          */
 177         do {
 178                 bits++;
 179                 q &= lower_bits_rubin;
 180                 q <<= 1;
 181                 p <<= 1;
 182         } while ((q >= UPPER_BIT_RUBIN) || ((p + q) <= UPPER_BIT_RUBIN));
 183
 184         rs->p = p;
 185         rs->q = q;
 186
 187         rs->bit_number += bits;
 188
 189         /*
 190          * Now get the bits.  We really want this to be "get n bits".
 191          */
 192         rec_q = rs->rec_q;
 193         do {
 194                 c = pullbit(&rs->pp);
 195                 rec_q &= lower_bits_rubin;
 196                 rec_q <<= 1;
 197                 rec_q += c;
 198         } while (--bits);
 199         rs->rec_q = rec_q;
 200 }
 201
 202 static int decode(struct rubin_state *rs, long A, long B)
 203 {
 204         unsigned long p = rs->p, q = rs->q;
 205         long i0, threshold;
 206         int symbol;
 207
 208         if (q >= UPPER_BIT_RUBIN || ((p + q) <= UPPER_BIT_RUBIN))
 209                 __do_decode(rs, p, q);
 210
 211         i0 = A * rs->p / (A + B);
 212         if (i0 <= 0)
 213                 i0 = 1;
 214
 215         if (i0 >= rs->p)
 216                 i0 = rs->p - 1;
 217
 218         threshold = rs->q + i0;
 219         symbol = rs->rec_q >= threshold;
 220         if (rs->rec_q >= threshold) {
 221                 rs->q += i0;
 222                 i0 = rs->p - i0;
 223         }
 224
 225         rs->p = i0;
 226
 227         return symbol;
 228 }
 229
 230
 231
 232 static int out_byte(struct rubin_state *rs, unsigned char byte)
 233 {
 234         int i, ret;
 235         struct rubin_state rs_copy;
 236         rs_copy = *rs;
 237
 238         for (i=0; i<8; i++) {
 239                 ret = encode(rs, rs->bit_divider-rs->bits[i],
 240                              rs->bits[i], byte & 1);
 241                 if (ret) {
 242                         /* Failed. Restore old state */
 243                         *rs = rs_copy;
 244                         return ret;
 245                 }
 246                 byte >>= 1 ;
 247         }
 248         return 0;
 249 }
 250
 251 static int in_byte(struct rubin_state *rs)
 252 {
 253         int i, result = 0, bit_divider = rs->bit_divider;
 254
 255         for (i = 0; i < 8; i++)
 256                 result |= decode(rs, bit_divider - rs->bits[i],
 257                                  rs->bits[i]) << i;
 258
 259         return result;
 260 }
 261
 262
 263
 264 static int rubin_do_compress(int bit_divider, int *bits, unsigned char *data_in,
 265                              unsigned char *cpage_out, uint32_t *sourcelen,
 266                              uint32_t *dstlen)
 267         {
 268         int outpos = 0;
 269         int pos=0;
 270         struct rubin_state rs;
 271
 272         init_pushpull(&rs.pp, cpage_out, *dstlen * 8, 0, 32);
 273
 274         init_rubin(&rs, bit_divider, bits);
 275
 276         while (pos < (*sourcelen) && !out_byte(&rs, data_in[pos]))
 277                 pos++;
 278
 279         end_rubin(&rs);
 280
 281         if (outpos > pos) {
 282                 /* We failed */
 283                 return -1;
 284         }
 285
 286         /* Tell the caller how much we managed to compress,
 287          * and how much space it took */
 288
 289         outpos = (pushedbits(&rs.pp)+7)/8;
 290
 291         if (outpos >= pos)
 292                 return -1; /* We didn't actually compress */
 293         *sourcelen = pos;
 294         *dstlen = outpos;
 295         return 0;
 296 }
 297 #if 0
 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)
 301 {
 302         return rubin_do_compress(BIT_DIVIDER_MIPS, bits_mips, data_in,
 303                                  cpage_out, sourcelen, dstlen);
 304 }
 305 #endif
 306 static int jffs2_dynrubin_compress(unsigned char *data_in,
 307                                    unsigned char *cpage_out,
 308                                    uint32_t *sourcelen, uint32_t *dstlen,
 309                                    void *model)
 310 {
 311         int bits[8];
 312         unsigned char histo[256];
 313         int i;
 314         int ret;
 315         uint32_t mysrclen, mydstlen;
 316
 317         mysrclen = *sourcelen;
 318         mydstlen = *dstlen - 8;
 319
 320         if (*dstlen <= 12)
 321                 return -1;
 322
 323         memset(histo, 0, 256);
 324         for (i=0; i<mysrclen; i++)
 325                 histo[data_in[i]]++;
 326         memset(bits, 0, sizeof(int)*8);
 327         for (i=0; i<256; i++) {
 328                 if (i&128)
 329                         bits[7] += histo[i];
 330                 if (i&64)
 331                         bits[6] += histo[i];
 332                 if (i&32)
 333                         bits[5] += histo[i];
 334                 if (i&16)
 335                         bits[4] += histo[i];
 336                 if (i&8)
 337                         bits[3] += histo[i];
 338                 if (i&4)
 339                         bits[2] += histo[i];
 340                 if (i&2)
 341                         bits[1] += histo[i];
 342                 if (i&1)
 343                         bits[0] += histo[i];
 344         }
 345
 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];
 351         }
 352
 353         ret = rubin_do_compress(256, bits, data_in, cpage_out+8, &mysrclen,
 354                                 &mydstlen);
 355         if (ret)
 356                 return ret;
 357
 358         /* Add back the 8 bytes we took for the probabilities */
 359         mydstlen += 8;
 360
 361         if (mysrclen <= mydstlen) {
 362                 /* We compressed */
 363                 return -1;
 364         }
 365
 366         *sourcelen = mysrclen;
 367         *dstlen = mydstlen;
 368         return 0;
 369 }
 370
 371 static void rubin_do_decompress(int bit_divider, int *bits,
 372                                 unsigned char *cdata_in,
 373                                 unsigned char *page_out, uint32_t srclen,
 374                                 uint32_t destlen)
 375 {
 376         int outpos = 0;
 377         struct rubin_state rs;
 378
 379         init_pushpull(&rs.pp, cdata_in, srclen, 0, 0);
 380         init_decode(&rs, bit_divider, bits);
 381
 382         while (outpos < destlen)
 383                 page_out[outpos++] = in_byte(&rs);
 384 }
 385
 386
 387 static int jffs2_rubinmips_decompress(unsigned char *data_in,
 388                                       unsigned char *cpage_out,
 389                                       uint32_t sourcelen, uint32_t dstlen,
 390                                       void *model)
 391 {
 392         rubin_do_decompress(BIT_DIVIDER_MIPS, bits_mips, data_in,
 393                             cpage_out, sourcelen, dstlen);
 394         return 0;
 395 }
 396
 397 static int jffs2_dynrubin_decompress(unsigned char *data_in,
 398                                      unsigned char *cpage_out,
 399                                      uint32_t sourcelen, uint32_t dstlen,
 400                                      void *model)
 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
 426 int jffs2_rubinmips_init(void)
 427 {
 428         return jffs2_register_compressor(&jffs2_rubinmips_comp);
 429 }
 430
 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
 449 int jffs2_dynrubin_init(void)
 450 {
 451         return jffs2_register_compressor(&jffs2_dynrubin_comp);
 452 }
 453
 454 void jffs2_dynrubin_exit(void)
 455 {
 456         jffs2_unregister_compressor(&jffs2_dynrubin_comp);
 457 }