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