fs/jffs2/compr_rubin.c

   1 /*
   2  * JFFS2 -- Journalling Flash File System, Version 2.
   3  *
   4  * Copyright (C) 2001, 2002 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  * $Id: compr_rubin.c,v 1.20 2004/06/23 16:34:40 havasi Exp $
  11  *
  12  */
  13
  14
  15 #include <linux/string.h>
  16 #include <linux/types.h>
  17 #include <linux/jffs2.h>
  18 #include "compr_rubin.h"
  19 #include "histo_mips.h"
  20 #include "compr.h"
  21
  22 static void init_rubin(struct rubin_state *rs, int div, int *bits)
  23 {
  24         int c;
  25
  26         rs->q = 0;
  27         rs->p = (long) (2 * UPPER_BIT_RUBIN);
  28         rs->bit_number = (long) 0;
  29         rs->bit_divider = div;
  30         for (c=0; c<8; c++)
  31                 rs->bits[c] = bits[c];
  32 }
  33
  34
  35 static int encode(struct rubin_state *rs, long A, long B, int symbol)
  36 {
  37
  38         long i0, i1;
  39         int ret;
  40
  41         while ((rs->q >= UPPER_BIT_RUBIN) || ((rs->p + rs->q) <= UPPER_BIT_RUBIN)) {
  42                 rs->bit_number++;
  43
  44                 ret = pushbit(&rs->pp, (rs->q & UPPER_BIT_RUBIN) ? 1 : 0, 0);
  45                 if (ret)
  46                         return ret;
  47                 rs->q &= LOWER_BITS_RUBIN;
  48                 rs->q <<= 1;
  49                 rs->p <<= 1;
  50         }
  51         i0 = A * rs->p / (A + B);
  52         if (i0 <= 0) {
  53                 i0 = 1;
  54         }
  55         if (i0 >= rs->p) {
  56                 i0 = rs->p - 1;
  57         }
  58         i1 = rs->p - i0;
  59
  60         if (symbol == 0)
  61                 rs->p = i0;
  62         else {
  63                 rs->p = i1;
  64                 rs->q += i0;
  65         }
  66         return 0;
  67 }
  68
  69
  70 static void end_rubin(struct rubin_state *rs)
  71 {
  72
  73         int i;
  74
  75         for (i = 0; i < RUBIN_REG_SIZE; i++) {
  76                 pushbit(&rs->pp, (UPPER_BIT_RUBIN & rs->q) ? 1 : 0, 1);
  77                 rs->q &= LOWER_BITS_RUBIN;
  78                 rs->q <<= 1;
  79         }
  80 }
  81
  82
  83 static void init_decode(struct rubin_state *rs, int div, int *bits)
  84 {
  85         init_rubin(rs, div, bits);
  86
  87         /* behalve lower */
  88         rs->rec_q = 0;
  89
  90         for (rs->bit_number = 0; rs->bit_number++ < RUBIN_REG_SIZE; rs->rec_q = rs->rec_q * 2 + (long) (pullbit(&rs->pp)))
  91                 ;
  92 }
  93
  94 static void __do_decode(struct rubin_state *rs, unsigned long p, unsigned long q)
  95 {
  96         register unsigned long lower_bits_rubin = LOWER_BITS_RUBIN;
  97         unsigned long rec_q;
  98         int c, bits = 0;
  99
 100         /*
 101          * First, work out how many bits we need from the input stream.
 102          * Note that we have already done the initial check on this
 103          * loop prior to calling this function.
 104          */
 105         do {
 106                 bits++;
 107                 q &= lower_bits_rubin;
 108                 q <<= 1;
 109                 p <<= 1;
 110         } while ((q >= UPPER_BIT_RUBIN) || ((p + q) <= UPPER_BIT_RUBIN));
 111
 112         rs->p = p;
 113         rs->q = q;
 114
 115         rs->bit_number += bits;
 116
 117         /*
 118          * Now get the bits.  We really want this to be "get n bits".
 119          */
 120         rec_q = rs->rec_q;
 121         do {
 122                 c = pullbit(&rs->pp);
 123                 rec_q &= lower_bits_rubin;
 124                 rec_q <<= 1;
 125                 rec_q += c;
 126         } while (--bits);
 127         rs->rec_q = rec_q;
 128 }
 129
 130 static int decode(struct rubin_state *rs, long A, long B)
 131 {
 132         unsigned long p = rs->p, q = rs->q;
 133         long i0, threshold;
 134         int symbol;
 135
 136         if (q >= UPPER_BIT_RUBIN || ((p + q) <= UPPER_BIT_RUBIN))
 137                 __do_decode(rs, p, q);
 138
 139         i0 = A * rs->p / (A + B);
 140         if (i0 <= 0) {
 141                 i0 = 1;
 142         }
 143         if (i0 >= rs->p) {
 144                 i0 = rs->p - 1;
 145         }
 146
 147         threshold = rs->q + i0;
 148         symbol = rs->rec_q >= threshold;
 149         if (rs->rec_q >= threshold) {
 150                 rs->q += i0;
 151                 i0 = rs->p - i0;
 152         }
 153
 154         rs->p = i0;
 155
 156         return symbol;
 157 }
 158
 159
 160
 161 static int out_byte(struct rubin_state *rs, unsigned char byte)
 162 {
 163         int i, ret;
 164         struct rubin_state rs_copy;
 165         rs_copy = *rs;
 166
 167         for (i=0;i<8;i++) {
 168                 ret = encode(rs, rs->bit_divider-rs->bits[i],rs->bits[i],byte&1);
 169                 if (ret) {
 170                         /* Failed. Restore old state */
 171                         *rs = rs_copy;
 172                         return ret;
 173                 }
 174                 byte=byte>>1;
 175         }
 176         return 0;
 177 }
 178
 179 static int in_byte(struct rubin_state *rs)
 180 {
 181         int i, result = 0, bit_divider = rs->bit_divider;
 182
 183         for (i = 0; i < 8; i++)
 184                 result |= decode(rs, bit_divider - rs->bits[i], rs->bits[i]) << i;
 185
 186         return result;
 187 }
 188
 189
 190
 191 static int rubin_do_compress(int bit_divider, int *bits, unsigned char *data_in,
 192                       unsigned char *cpage_out, uint32_t *sourcelen, uint32_t *dstlen)
 193         {
 194         int outpos = 0;
 195         int pos=0;
 196         struct rubin_state rs;
 197
 198         init_pushpull(&rs.pp, cpage_out, *dstlen * 8, 0, 32);
 199
 200         init_rubin(&rs, bit_divider, bits);
 201
 202         while (pos < (*sourcelen) && !out_byte(&rs, data_in[pos]))
 203                 pos++;
 204
 205         end_rubin(&rs);
 206
 207         if (outpos > pos) {
 208                 /* We failed */
 209                 return -1;
 210         }
 211
 212         /* Tell the caller how much we managed to compress,
 213          * and how much space it took */
 214
 215         outpos = (pushedbits(&rs.pp)+7)/8;
 216
 217         if (outpos >= pos)
 218                 return -1; /* We didn't actually compress */
 219         *sourcelen = pos;
 220         *dstlen = outpos;
 221         return 0;
 222 }
 223 #if 0
 224 /* _compress returns the compressed size, -1 if bigger */
 225 int jffs2_rubinmips_compress(unsigned char *data_in, unsigned char *cpage_out,
 226                    uint32_t *sourcelen, uint32_t *dstlen, void *model)
 227 {
 228         return rubin_do_compress(BIT_DIVIDER_MIPS, bits_mips, data_in, cpage_out, sourcelen, dstlen);
 229 }
 230 #endif
 231 int jffs2_dynrubin_compress(unsigned char *data_in, unsigned char *cpage_out,
 232                    uint32_t *sourcelen, uint32_t *dstlen, void *model)
 233 {
 234         int bits[8];
 235         unsigned char histo[256];
 236         int i;
 237         int ret;
 238         uint32_t mysrclen, mydstlen;
 239
 240         mysrclen = *sourcelen;
 241         mydstlen = *dstlen - 8;
 242
 243         if (*dstlen <= 12)
 244                 return -1;
 245
 246         memset(histo, 0, 256);
 247         for (i=0; i<mysrclen; i++) {
 248                 histo[data_in[i]]++;
 249         }
 250         memset(bits, 0, sizeof(int)*8);
 251         for (i=0; i<256; i++) {
 252                 if (i&128)
 253                         bits[7] += histo[i];
 254                 if (i&64)
 255                         bits[6] += histo[i];
 256                 if (i&32)
 257                         bits[5] += histo[i];
 258                 if (i&16)
 259                         bits[4] += histo[i];
 260                 if (i&8)
 261                         bits[3] += histo[i];
 262                 if (i&4)
 263                         bits[2] += histo[i];
 264                 if (i&2)
 265                         bits[1] += histo[i];
 266                 if (i&1)
 267                         bits[0] += histo[i];
 268         }
 269
 270         for (i=0; i<8; i++) {
 271                 bits[i] = (bits[i] * 256) / mysrclen;
 272                 if (!bits[i]) bits[i] = 1;
 273                 if (bits[i] > 255) bits[i] = 255;
 274                 cpage_out[i] = bits[i];
 275         }
 276
 277         ret = rubin_do_compress(256, bits, data_in, cpage_out+8, &mysrclen, &mydstlen);
 278         if (ret)
 279                 return ret;
 280
 281         /* Add back the 8 bytes we took for the probabilities */
 282         mydstlen += 8;
 283
 284         if (mysrclen <= mydstlen) {
 285                 /* We compressed */
 286                 return -1;
 287         }
 288
 289         *sourcelen = mysrclen;
 290         *dstlen = mydstlen;
 291         return 0;
 292 }
 293
 294 static void rubin_do_decompress(int bit_divider, int *bits, unsigned char *cdata_in,
 295                          unsigned char *page_out, uint32_t srclen, uint32_t destlen)
 296 {
 297         int outpos = 0;
 298         struct rubin_state rs;
 299
 300         init_pushpull(&rs.pp, cdata_in, srclen, 0, 0);
 301         init_decode(&rs, bit_divider, bits);
 302
 303         while (outpos < destlen) {
 304                 page_out[outpos++] = in_byte(&rs);
 305         }
 306 }
 307
 308
 309 int jffs2_rubinmips_decompress(unsigned char *data_in, unsigned char *cpage_out,
 310                    uint32_t sourcelen, uint32_t dstlen, void *model)
 311 {
 312         rubin_do_decompress(BIT_DIVIDER_MIPS, bits_mips, data_in, cpage_out, sourcelen, dstlen);
 313         return 0;
 314 }
 315
 316 int jffs2_dynrubin_decompress(unsigned char *data_in, unsigned char *cpage_out,
 317                    uint32_t sourcelen, uint32_t dstlen, void *model)
 318 {
 319         int bits[8];
 320         int c;
 321
 322         for (c=0; c<8; c++)
 323                 bits[c] = data_in[c];
 324
 325         rubin_do_decompress(256, bits, data_in+8, cpage_out, sourcelen-8, dstlen);
 326         return 0;
 327 }
 328
 329 static struct jffs2_compressor jffs2_rubinmips_comp = {
 330     .priority = JFFS2_RUBINMIPS_PRIORITY,
 331     .name = "rubinmips",
 332     .compr = JFFS2_COMPR_DYNRUBIN,
 333     .compress = NULL, /*&jffs2_rubinmips_compress,*/
 334     .decompress = &jffs2_rubinmips_decompress,
 335 #ifdef JFFS2_RUBINMIPS_DISABLED
 336     .disabled = 1,
 337 #else
 338     .disabled = 0,
 339 #endif
 340 };
 341
 342 int jffs2_rubinmips_init(void)
 343 {
 344     return jffs2_register_compressor(&jffs2_rubinmips_comp);
 345 }
 346
 347 void jffs2_rubinmips_exit(void)
 348 {
 349     jffs2_unregister_compressor(&jffs2_rubinmips_comp);
 350 }
 351
 352 static struct jffs2_compressor jffs2_dynrubin_comp = {
 353     .priority = JFFS2_DYNRUBIN_PRIORITY,
 354     .name = "dynrubin",
 355     .compr = JFFS2_COMPR_RUBINMIPS,
 356     .compress = jffs2_dynrubin_compress,
 357     .decompress = &jffs2_dynrubin_decompress,
 358 #ifdef JFFS2_DYNRUBIN_DISABLED
 359     .disabled = 1,
 360 #else
 361     .disabled = 0,
 362 #endif
 363 };
 364
 365 int jffs2_dynrubin_init(void)
 366 {
 367     return jffs2_register_compressor(&jffs2_dynrubin_comp);
 368 }
 369
 370 void jffs2_dynrubin_exit(void)
 371 {
 372     jffs2_unregister_compressor(&jffs2_dynrubin_comp);
 373 }