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}; /* mips32 */
  26
  27 #include <linux/errno.h>
  28
  29 struct pushpull {
  30         unsigned char *buf;
  31         unsigned int buflen;
  32         unsigned int ofs;
  33         unsigned int reserve;
  34 };
  35
  36 struct rubin_state {
  37         unsigned long p;
  38         unsigned long q;
  39         unsigned long rec_q;
  40         long bit_number;
  41         struct pushpull pp;
  42         int bit_divider;
  43         int bits[8];
  44 };
  45
  46 static inline void init_pushpull(struct pushpull *pp, char *buf, unsigned buflen, unsigned ofs, 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
  60         if (bit) {
  61                 pp->buf[pp->ofs >> 3] |= (1<<(7-(pp->ofs &7)));
  62         }
  63         else {
  64                 pp->buf[pp->ofs >> 3] &= ~(1<<(7-(pp->ofs &7)));
  65         }
  66         pp->ofs++;
  67
  68         return 0;
  69 }
  70
  71 static inline int pushedbits(struct pushpull *pp)
  72 {
  73         return pp->ofs;
  74 }
  75
  76 static inline int pullbit(struct pushpull *pp)
  77 {
  78         int bit;
  79
  80         bit = (pp->buf[pp->ofs >> 3] >> (7-(pp->ofs & 7))) & 1;
  81
  82         pp->ofs++;
  83         return bit;
  84 }
  85
  86 static inline int pulledbits(struct pushpull *pp)
  87 {
  88         return pp->ofs;
  89 }
  90
  91
  92 static void init_rubin(struct rubin_state *rs, int div, int *bits)
  93 {
  94         int c;
  95
  96         rs->q = 0;
  97         rs->p = (long) (2 * UPPER_BIT_RUBIN);
  98         rs->bit_number = (long) 0;
  99         rs->bit_divider = div;
 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) || ((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; rs->rec_q = rs->rec_q * 2 + (long) (pullbit(&rs->pp)))
 161                 ;
 162 }
 163
 164 static void __do_decode(struct rubin_state *rs, unsigned long p, 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
 217         threshold = rs->q + i0;
 218         symbol = rs->rec_q >= threshold;
 219         if (rs->rec_q >= threshold) {
 220                 rs->q += i0;
 221                 i0 = rs->p - i0;
 222         }
 223
 224         rs->p = i0;
 225
 226         return symbol;
 227 }
 228
 229
 230
 231 static int out_byte(struct rubin_state *rs, unsigned char byte)
 232 {
 233         int i, ret;
 234         struct rubin_state rs_copy;
 235         rs_copy = *rs;
 236
 237         for (i=0;i<8;i++) {
 238                 ret = encode(rs, rs->bit_divider-rs->bits[i],rs->bits[i],byte&1);
 239                 if (ret) {
 240                         /* Failed. Restore old state */
 241                         *rs = rs_copy;
 242                         return ret;
 243                 }
 244                 byte=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], rs->bits[i]) << i;
 255
 256         return result;
 257 }
 258
 259
 260
 261 static int rubin_do_compress(int bit_divider, int *bits, unsigned char *data_in,
 262                       unsigned char *cpage_out, uint32_t *sourcelen, uint32_t *dstlen)
 263         {
 264         int outpos = 0;
 265         int pos=0;
 266         struct rubin_state rs;
 267
 268         init_pushpull(&rs.pp, cpage_out, *dstlen * 8, 0, 32);
 269
 270         init_rubin(&rs, bit_divider, bits);
 271
 272         while (pos < (*sourcelen) && !out_byte(&rs, data_in[pos]))
 273                 pos++;
 274
 275         end_rubin(&rs);
 276
 277         if (outpos > pos) {
 278                 /* We failed */
 279                 return -1;
 280         }
 281
 282         /* Tell the caller how much we managed to compress,
 283          * and how much space it took */
 284
 285         outpos = (pushedbits(&rs.pp)+7)/8;
 286
 287         if (outpos >= pos)
 288                 return -1; /* We didn't actually compress */
 289         *sourcelen = pos;
 290         *dstlen = outpos;
 291         return 0;
 292 }
 293 #if 0
 294 /* _compress returns the compressed size, -1 if bigger */
 295 int jffs2_rubinmips_compress(unsigned char *data_in, unsigned char *cpage_out,
 296                    uint32_t *sourcelen, uint32_t *dstlen, void *model)
 297 {
 298         return rubin_do_compress(BIT_DIVIDER_MIPS, bits_mips, data_in, cpage_out, sourcelen, dstlen);
 299 }
 300 #endif
 301 static int jffs2_dynrubin_compress(unsigned char *data_in,
 302                                    unsigned char *cpage_out,
 303                                    uint32_t *sourcelen, uint32_t *dstlen,
 304                                    void *model)
 305 {
 306         int bits[8];
 307         unsigned char histo[256];
 308         int i;
 309         int ret;
 310         uint32_t mysrclen, mydstlen;
 311
 312         mysrclen = *sourcelen;
 313         mydstlen = *dstlen - 8;
 314
 315         if (*dstlen <= 12)
 316                 return -1;
 317
 318         memset(histo, 0, 256);
 319         for (i=0; i<mysrclen; i++) {
 320                 histo[data_in[i]]++;
 321         }
 322         memset(bits, 0, sizeof(int)*8);
 323         for (i=0; i<256; i++) {
 324                 if (i&128)
 325                         bits[7] += histo[i];
 326                 if (i&64)
 327                         bits[6] += histo[i];
 328                 if (i&32)
 329                         bits[5] += histo[i];
 330                 if (i&16)
 331                         bits[4] += histo[i];
 332                 if (i&8)
 333                         bits[3] += histo[i];
 334                 if (i&4)
 335                         bits[2] += histo[i];
 336                 if (i&2)
 337                         bits[1] += histo[i];
 338                 if (i&1)
 339                         bits[0] += histo[i];
 340         }
 341
 342         for (i=0; i<8; i++) {
 343                 bits[i] = (bits[i] * 256) / mysrclen;
 344                 if (!bits[i]) bits[i] = 1;
 345                 if (bits[i] > 255) bits[i] = 255;
 346                 cpage_out[i] = bits[i];
 347         }
 348
 349         ret = rubin_do_compress(256, bits, data_in, cpage_out+8, &mysrclen, &mydstlen);
 350         if (ret)
 351                 return ret;
 352
 353         /* Add back the 8 bytes we took for the probabilities */
 354         mydstlen += 8;
 355
 356         if (mysrclen <= mydstlen) {
 357                 /* We compressed */
 358                 return -1;
 359         }
 360
 361         *sourcelen = mysrclen;
 362         *dstlen = mydstlen;
 363         return 0;
 364 }
 365
 366 static void rubin_do_decompress(int bit_divider, int *bits, unsigned char *cdata_in,
 367                          unsigned char *page_out, uint32_t srclen, uint32_t destlen)
 368 {
 369         int outpos = 0;
 370         struct rubin_state rs;
 371
 372         init_pushpull(&rs.pp, cdata_in, srclen, 0, 0);
 373         init_decode(&rs, bit_divider, bits);
 374
 375         while (outpos < destlen) {
 376                 page_out[outpos++] = in_byte(&rs);
 377         }
 378 }
 379
 380
 381 static int jffs2_rubinmips_decompress(unsigned char *data_in,
 382                                       unsigned char *cpage_out,
 383                                       uint32_t sourcelen, uint32_t dstlen,
 384                                       void *model)
 385 {
 386         rubin_do_decompress(BIT_DIVIDER_MIPS, bits_mips, data_in, cpage_out, sourcelen, dstlen);
 387         return 0;
 388 }
 389
 390 static int jffs2_dynrubin_decompress(unsigned char *data_in,
 391                                      unsigned char *cpage_out,
 392                                      uint32_t sourcelen, uint32_t dstlen,
 393                                      void *model)
 394 {
 395         int bits[8];
 396         int c;
 397
 398         for (c=0; c<8; c++)
 399                 bits[c] = data_in[c];
 400
 401         rubin_do_decompress(256, bits, data_in+8, cpage_out, sourcelen-8, dstlen);
 402         return 0;
 403 }
 404
 405 static struct jffs2_compressor jffs2_rubinmips_comp = {
 406     .priority = JFFS2_RUBINMIPS_PRIORITY,
 407     .name = "rubinmips",
 408     .compr = JFFS2_COMPR_DYNRUBIN,
 409     .compress = NULL, /*&jffs2_rubinmips_compress,*/
 410     .decompress = &jffs2_rubinmips_decompress,
 411 #ifdef JFFS2_RUBINMIPS_DISABLED
 412     .disabled = 1,
 413 #else
 414     .disabled = 0,
 415 #endif
 416 };
 417
 418 int jffs2_rubinmips_init(void)
 419 {
 420     return jffs2_register_compressor(&jffs2_rubinmips_comp);
 421 }
 422
 423 void jffs2_rubinmips_exit(void)
 424 {
 425     jffs2_unregister_compressor(&jffs2_rubinmips_comp);
 426 }
 427
 428 static struct jffs2_compressor jffs2_dynrubin_comp = {
 429     .priority = JFFS2_DYNRUBIN_PRIORITY,
 430     .name = "dynrubin",
 431     .compr = JFFS2_COMPR_RUBINMIPS,
 432     .compress = jffs2_dynrubin_compress,
 433     .decompress = &jffs2_dynrubin_decompress,
 434 #ifdef JFFS2_DYNRUBIN_DISABLED
 435     .disabled = 1,
 436 #else
 437     .disabled = 0,
 438 #endif
 439 };
 440
 441 int jffs2_dynrubin_init(void)
 442 {
 443     return jffs2_register_compressor(&jffs2_dynrubin_comp);
 444 }
 445
 446 void jffs2_dynrubin_exit(void)
 447 {
 448     jffs2_unregister_compressor(&jffs2_dynrubin_comp);
 449 }