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
  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         /* Tell the caller how much we managed to compress,
 280          * and how much space it took */
 281
 282         outpos = (pushedbits(&rs.pp)+7)/8;
 283
 284         if (outpos >= pos)
 285                 return -1; /* We didn't actually compress */
 286         *sourcelen = pos;
 287         *dstlen = outpos;
 288         return 0;
 289 }
 290 #if 0
 291 /* _compress returns the compressed size, -1 if bigger */
 292 int jffs2_rubinmips_compress(unsigned char *data_in, unsigned char *cpage_out,
 293                    uint32_t *sourcelen, uint32_t *dstlen)
 294 {
 295         return rubin_do_compress(BIT_DIVIDER_MIPS, bits_mips, data_in,
 296                                  cpage_out, sourcelen, dstlen);
 297 }
 298 #endif
 299 static int jffs2_dynrubin_compress(unsigned char *data_in,
 300                                    unsigned char *cpage_out,
 301                                    uint32_t *sourcelen, uint32_t *dstlen)
 302 {
 303         int bits[8];
 304         unsigned char histo[256];
 305         int i;
 306         int ret;
 307         uint32_t mysrclen, mydstlen;
 308
 309         mysrclen = *sourcelen;
 310         mydstlen = *dstlen - 8;
 311
 312         if (*dstlen <= 12)
 313                 return -1;
 314
 315         memset(histo, 0, 256);
 316         for (i=0; i<mysrclen; i++)
 317                 histo[data_in[i]]++;
 318         memset(bits, 0, sizeof(int)*8);
 319         for (i=0; i<256; i++) {
 320                 if (i&128)
 321                         bits[7] += histo[i];
 322                 if (i&64)
 323                         bits[6] += histo[i];
 324                 if (i&32)
 325                         bits[5] += histo[i];
 326                 if (i&16)
 327                         bits[4] += histo[i];
 328                 if (i&8)
 329                         bits[3] += histo[i];
 330                 if (i&4)
 331                         bits[2] += histo[i];
 332                 if (i&2)
 333                         bits[1] += histo[i];
 334                 if (i&1)
 335                         bits[0] += histo[i];
 336         }
 337
 338         for (i=0; i<8; i++) {
 339                 bits[i] = (bits[i] * 256) / mysrclen;
 340                 if (!bits[i]) bits[i] = 1;
 341                 if (bits[i] > 255) bits[i] = 255;
 342                 cpage_out[i] = bits[i];
 343         }
 344
 345         ret = rubin_do_compress(256, bits, data_in, cpage_out+8, &mysrclen,
 346                                 &mydstlen);
 347         if (ret)
 348                 return ret;
 349
 350         /* Add back the 8 bytes we took for the probabilities */
 351         mydstlen += 8;
 352
 353         if (mysrclen <= mydstlen) {
 354                 /* We compressed */
 355                 return -1;
 356         }
 357
 358         *sourcelen = mysrclen;
 359         *dstlen = mydstlen;
 360         return 0;
 361 }
 362
 363 static void rubin_do_decompress(int bit_divider, int *bits,
 364                                 unsigned char *cdata_in,
 365                                 unsigned char *page_out, uint32_t srclen,
 366                                 uint32_t destlen)
 367 {
 368         int outpos = 0;
 369         struct rubin_state rs;
 370
 371         init_pushpull(&rs.pp, cdata_in, srclen, 0, 0);
 372         init_decode(&rs, bit_divider, bits);
 373
 374         while (outpos < destlen)
 375                 page_out[outpos++] = in_byte(&rs);
 376 }
 377
 378
 379 static int jffs2_rubinmips_decompress(unsigned char *data_in,
 380                                       unsigned char *cpage_out,
 381                                       uint32_t sourcelen, uint32_t dstlen)
 382 {
 383         rubin_do_decompress(BIT_DIVIDER_MIPS, bits_mips, data_in,
 384                             cpage_out, sourcelen, dstlen);
 385         return 0;
 386 }
 387
 388 static int jffs2_dynrubin_decompress(unsigned char *data_in,
 389                                      unsigned char *cpage_out,
 390                                      uint32_t sourcelen, uint32_t dstlen)
 391 {
 392         int bits[8];
 393         int c;
 394
 395         for (c=0; c<8; c++)
 396                 bits[c] = data_in[c];
 397
 398         rubin_do_decompress(256, bits, data_in+8, cpage_out, sourcelen-8,
 399                             dstlen);
 400         return 0;
 401 }
 402
 403 static struct jffs2_compressor jffs2_rubinmips_comp = {
 404         .priority = JFFS2_RUBINMIPS_PRIORITY,
 405         .name = "rubinmips",
 406         .compr = JFFS2_COMPR_DYNRUBIN,
 407         .compress = NULL, /*&jffs2_rubinmips_compress,*/
 408         .decompress = &jffs2_rubinmips_decompress,
 409 #ifdef JFFS2_RUBINMIPS_DISABLED
 410         .disabled = 1,
 411 #else
 412         .disabled = 0,
 413 #endif
 414 };
 415
 416 int jffs2_rubinmips_init(void)
 417 {
 418         return jffs2_register_compressor(&jffs2_rubinmips_comp);
 419 }
 420
 421 void jffs2_rubinmips_exit(void)
 422 {
 423         jffs2_unregister_compressor(&jffs2_rubinmips_comp);
 424 }
 425
 426 static struct jffs2_compressor jffs2_dynrubin_comp = {
 427         .priority = JFFS2_DYNRUBIN_PRIORITY,
 428         .name = "dynrubin",
 429         .compr = JFFS2_COMPR_RUBINMIPS,
 430         .compress = jffs2_dynrubin_compress,
 431         .decompress = &jffs2_dynrubin_decompress,
 432 #ifdef JFFS2_DYNRUBIN_DISABLED
 433         .disabled = 1,
 434 #else
 435         .disabled = 0,
 436 #endif
 437 };
 438
 439 int jffs2_dynrubin_init(void)
 440 {
 441         return jffs2_register_compressor(&jffs2_dynrubin_comp);
 442 }
 443
 444 void jffs2_dynrubin_exit(void)
 445 {
 446         jffs2_unregister_compressor(&jffs2_dynrubin_comp);
 447 }