fs/jffs2/compr_rubin.c

   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 #include <linux/string.h>
  14 #include <linux/types.h>
  15 #include <linux/jffs2.h>
  16 #include <linux/errno.h>
  17 #include "compr.h"
  18
  19
  20 #define RUBIN_REG_SIZE   16
  21 #define UPPER_BIT_RUBIN    (((long) 1)<<(RUBIN_REG_SIZE-1))
  22 #define LOWER_BITS_RUBIN   ((((long) 1)<<(RUBIN_REG_SIZE-1))-1)
  23
  24
  25 #define BIT_DIVIDER_MIPS 1043
  26 static int bits_mips[8] = { 277, 249, 290, 267, 229, 341, 212, 241};
  27
  28 struct pushpull {
  29         unsigned char *buf;
  30         unsigned int buflen;
  31         unsigned int ofs;
  32         unsigned int reserve;
  33 };
  34
  35 struct rubin_state {
  36         unsigned long p;
  37         unsigned long q;
  38         unsigned long rec_q;
  39         long bit_number;
  40         struct pushpull pp;
  41         int bit_divider;
  42         int bits[8];
  43 };
  44
  45 static inline void init_pushpull(struct pushpull *pp, char *buf,
  46                                  unsigned buflen, unsigned ofs,
  47                                  unsigned reserve)
  48 {
  49         pp->buf = buf;
  50         pp->buflen = buflen;
  51         pp->ofs = ofs;
  52         pp->reserve = reserve;
  53 }
  54
  55 static inline int pushbit(struct pushpull *pp, int bit, int use_reserved)
  56 {
  57         if (pp->ofs >= pp->buflen - (use_reserved?0:pp->reserve))
  58                 return -ENOSPC;
  59
  60         if (bit)
  61                 pp->buf[pp->ofs >> 3] |= (1<<(7-(pp->ofs & 7)));
  62         else
  63                 pp->buf[pp->ofs >> 3] &= ~(1<<(7-(pp->ofs & 7)));
  64
  65         pp->ofs++;
  66
  67         return 0;
  68 }
  69
  70 static inline int pushedbits(struct pushpull *pp)
  71 {
  72         return pp->ofs;
  73 }
  74
  75 static inline int pullbit(struct pushpull *pp)
  76 {
  77         int bit;
  78
  79         bit = (pp->buf[pp->ofs >> 3] >> (7-(pp->ofs & 7))) & 1;
  80
  81         pp->ofs++;
  82         return bit;
  83 }
  84
  85 static inline int pulledbits(struct pushpull *pp)
  86 {
  87         return pp->ofs;
  88 }
  89
  90
  91 static void init_rubin(struct rubin_state *rs, int div, int *bits)
  92 {
  93         int c;
  94
  95         rs->q = 0;
  96         rs->p = (long) (2 * UPPER_BIT_RUBIN);
  97         rs->bit_number = (long) 0;
  98         rs->bit_divider = div;
  99
 100         for (c=0; c<8; c++)
 101                 rs->bits[c] = bits[c];
 102 }
 103
 104
 105 static int encode(struct rubin_state *rs, long A, long B, int symbol)
 106 {
 107
 108         long i0, i1;
 109         int ret;
 110
 111         while ((rs->q >= UPPER_BIT_RUBIN) ||
 112                ((rs->p + rs->q) <= UPPER_BIT_RUBIN)) {
 113                 rs->bit_number++;
 114
 115                 ret = pushbit(&rs->pp, (rs->q & UPPER_BIT_RUBIN) ? 1 : 0, 0);
 116                 if (ret)
 117                         return ret;
 118                 rs->q &= LOWER_BITS_RUBIN;
 119                 rs->q <<= 1;
 120                 rs->p <<= 1;
 121         }
 122         i0 = A * rs->p / (A + B);
 123         if (i0 <= 0)
 124                 i0 = 1;
 125
 126         if (i0 >= rs->p)
 127                 i0 = rs->p - 1;
 128
 129         i1 = rs->p - i0;
 130
 131         if (symbol == 0)
 132                 rs->p = i0;
 133         else {
 134                 rs->p = i1;
 135                 rs->q += i0;
 136         }
 137         return 0;
 138 }
 139
 140
 141 static void end_rubin(struct rubin_state *rs)
 142 {
 143
 144         int i;
 145
 146         for (i = 0; i < RUBIN_REG_SIZE; i++) {
 147                 pushbit(&rs->pp, (UPPER_BIT_RUBIN & rs->q) ? 1 : 0, 1);
 148                 rs->q &= LOWER_BITS_RUBIN;
 149                 rs->q <<= 1;
 150         }
 151 }
 152
 153
 154 static void init_decode(struct rubin_state *rs, int div, int *bits)
 155 {
 156         init_rubin(rs, div, bits);
 157
 158         /* behalve lower */
 159         rs->rec_q = 0;
 160
 161         for (rs->bit_number = 0; rs->bit_number++ < RUBIN_REG_SIZE;
 162              rs->rec_q = rs->rec_q * 2 + (long) (pullbit(&rs->pp)))
 163                 ;
 164 }
 165
 166 static void __do_decode(struct rubin_state *rs, unsigned long p,
 167                         unsigned long q)
 168 {
 169         register unsigned long lower_bits_rubin = LOWER_BITS_RUBIN;
 170         unsigned long rec_q;
 171         int c, bits = 0;
 172
 173         /*
 174          * First, work out how many bits we need from the input stream.
 175          * Note that we have already done the initial check on this
 176          * loop prior to calling this function.
 177          */
 178         do {
 179                 bits++;
 180                 q &= lower_bits_rubin;
 181                 q <<= 1;
 182                 p <<= 1;
 183         } while ((q >= UPPER_BIT_RUBIN) || ((p + q) <= UPPER_BIT_RUBIN));
 184
 185         rs->p = p;
 186         rs->q = q;
 187
 188         rs->bit_number += bits;
 189
 190         /*
 191          * Now get the bits.  We really want this to be "get n bits".
 192          */
 193         rec_q = rs->rec_q;
 194         do {
 195                 c = pullbit(&rs->pp);
 196                 rec_q &= lower_bits_rubin;
 197                 rec_q <<= 1;
 198                 rec_q += c;
 199         } while (--bits);
 200         rs->rec_q = rec_q;
 201 }
 202
 203 static int decode(struct rubin_state *rs, long A, long B)
 204 {
 205         unsigned long p = rs->p, q = rs->q;
 206         long i0, threshold;
 207         int symbol;
 208
 209         if (q >= UPPER_BIT_RUBIN || ((p + q) <= UPPER_BIT_RUBIN))
 210                 __do_decode(rs, p, q);
 211
 212         i0 = A * rs->p / (A + B);
 213         if (i0 <= 0)
 214                 i0 = 1;
 215
 216         if (i0 >= rs->p)
 217                 i0 = rs->p - 1;
 218
 219         threshold = rs->q + i0;
 220         symbol = rs->rec_q >= threshold;
 221         if (rs->rec_q >= threshold) {
 222                 rs->q += i0;
 223                 i0 = rs->p - i0;
 224         }
 225
 226         rs->p = i0;
 227
 228         return symbol;
 229 }
 230
 231
 232
 233 static int out_byte(struct rubin_state *rs, unsigned char byte)
 234 {
 235         int i, ret;
 236         struct rubin_state rs_copy;
 237         rs_copy = *rs;
 238
 239         for (i=0; i<8; i++) {
 240                 ret = encode(rs, rs->bit_divider-rs->bits[i],
 241                              rs->bits[i], byte & 1);
 242                 if (ret) {
 243                         /* Failed. Restore old state */
 244                         *rs = rs_copy;
 245                         return ret;
 246                 }
 247                 byte >>= 1 ;
 248         }
 249         return 0;
 250 }
 251
 252 static int in_byte(struct rubin_state *rs)
 253 {
 254         int i, result = 0, bit_divider = rs->bit_divider;
 255
 256         for (i = 0; i < 8; i++)
 257                 result |= decode(rs, bit_divider - rs->bits[i],
 258                                  rs->bits[i]) << i;
 259
 260         return result;
 261 }
 262
 263
 264
 265 static int rubin_do_compress(int bit_divider, int *bits, unsigned char *data_in,
 266                              unsigned char *cpage_out, uint32_t *sourcelen,
 267                              uint32_t *dstlen)
 268         {
 269         int outpos = 0;
 270         int pos=0;
 271         struct rubin_state rs;
 272
 273         init_pushpull(&rs.pp, cpage_out, *dstlen * 8, 0, 32);
 274
 275         init_rubin(&rs, bit_divider, bits);
 276
 277         while (pos < (*sourcelen) && !out_byte(&rs, data_in[pos]))
 278                 pos++;
 279
 280         end_rubin(&rs);
 281
 282         if (outpos > pos) {
 283                 /* We failed */
 284                 return -1;
 285         }
 286
 287         /* Tell the caller how much we managed to compress,
 288          * and how much space it took */
 289
 290         outpos = (pushedbits(&rs.pp)+7)/8;
 291
 292         if (outpos >= pos)
 293                 return -1; /* We didn't actually compress */
 294         *sourcelen = pos;
 295         *dstlen = outpos;
 296         return 0;
 297 }
 298 #if 0
 299 /* _compress returns the compressed size, -1 if bigger */
 300 int jffs2_rubinmips_compress(unsigned char *data_in, unsigned char *cpage_out,
 301                    uint32_t *sourcelen, uint32_t *dstlen)
 302 {
 303         return rubin_do_compress(BIT_DIVIDER_MIPS, bits_mips, data_in,
 304                                  cpage_out, sourcelen, dstlen);
 305 }
 306 #endif
 307 static int jffs2_dynrubin_compress(unsigned char *data_in,
 308                                    unsigned char *cpage_out,
 309                                    uint32_t *sourcelen, uint32_t *dstlen)
 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 {
 391         rubin_do_decompress(BIT_DIVIDER_MIPS, bits_mips, data_in,
 392                             cpage_out, sourcelen, dstlen);
 393         return 0;
 394 }
 395
 396 static int jffs2_dynrubin_decompress(unsigned char *data_in,
 397                                      unsigned char *cpage_out,
 398                                      uint32_t sourcelen, uint32_t dstlen)
 399 {
 400         int bits[8];
 401         int c;
 402
 403         for (c=0; c<8; c++)
 404                 bits[c] = data_in[c];
 405
 406         rubin_do_decompress(256, bits, data_in+8, cpage_out, sourcelen-8,
 407                             dstlen);
 408         return 0;
 409 }
 410
 411 static struct jffs2_compressor jffs2_rubinmips_comp = {
 412         .priority = JFFS2_RUBINMIPS_PRIORITY,
 413         .name = "rubinmips",
 414         .compr = JFFS2_COMPR_DYNRUBIN,
 415         .compress = NULL, /*&jffs2_rubinmips_compress,*/
 416         .decompress = &jffs2_rubinmips_decompress,
 417 #ifdef JFFS2_RUBINMIPS_DISABLED
 418         .disabled = 1,
 419 #else
 420         .disabled = 0,
 421 #endif
 422 };
 423
 424 int jffs2_rubinmips_init(void)
 425 {
 426         return jffs2_register_compressor(&jffs2_rubinmips_comp);
 427 }
 428
 429 void jffs2_rubinmips_exit(void)
 430 {
 431         jffs2_unregister_compressor(&jffs2_rubinmips_comp);
 432 }
 433
 434 static struct jffs2_compressor jffs2_dynrubin_comp = {
 435         .priority = JFFS2_DYNRUBIN_PRIORITY,
 436         .name = "dynrubin",
 437         .compr = JFFS2_COMPR_RUBINMIPS,
 438         .compress = jffs2_dynrubin_compress,
 439         .decompress = &jffs2_dynrubin_decompress,
 440 #ifdef JFFS2_DYNRUBIN_DISABLED
 441         .disabled = 1,
 442 #else
 443         .disabled = 0,
 444 #endif
 445 };
 446
 447 int jffs2_dynrubin_init(void)
 448 {
 449         return jffs2_register_compressor(&jffs2_dynrubin_comp);
 450 }
 451
 452 void jffs2_dynrubin_exit(void)
 453 {
 454         jffs2_unregister_compressor(&jffs2_dynrubin_comp);
 455 }