unlzw.c

   1 /* unlzw.c -- decompress files in LZW format.
   2  * The code in this file is directly derived from the public domain 'compress'
   3  * written by Spencer Thomas, Joe Orost, James Woods, Jim McKie, Steve Davies,
   4  * Ken Turkowski, Dave Mack and Peter Jannesen.
   5  *
   6  * This is a temporary version which will be rewritten in some future version
   7  * to accommodate in-memory decompression.
   8  */
   9
  10 #include <config.h>
  11 #include "tailor.h"
  12
  13 #ifdef HAVE_UNISTD_H
  14 #  include <unistd.h>
  15 #endif
  16 #ifdef HAVE_FCNTL_H
  17 #  include <fcntl.h>
  18 #endif
  19
  20 #include "gzip.h"
  21 #include "lzw.h"
  22
  23 typedef unsigned char   char_type;
  24 typedef          long   code_int;
  25 typedef unsigned long   count_int;
  26 typedef unsigned short  count_short;
  27 typedef unsigned long   cmp_code_int;
  28
  29 #define MAXCODE(n)      (1L << (n))
  30
  31 #ifndef REGISTERS
  32 #       define  REGISTERS       2
  33 #endif
  34 #define REG1
  35 #define REG2
  36 #define REG3
  37 #define REG4
  38 #define REG5
  39 #define REG6
  40 #define REG7
  41 #define REG8
  42 #define REG9
  43 #define REG10
  44 #define REG11
  45 #define REG12
  46 #define REG13
  47 #define REG14
  48 #define REG15
  49 #define REG16
  50 #if REGISTERS >= 1
  51 #       undef   REG1
  52 #       define  REG1    register
  53 #endif
  54 #if REGISTERS >= 2
  55 #       undef   REG2
  56 #       define  REG2    register
  57 #endif
  58 #if REGISTERS >= 3
  59 #       undef   REG3
  60 #       define  REG3    register
  61 #endif
  62 #if REGISTERS >= 4
  63 #       undef   REG4
  64 #       define  REG4    register
  65 #endif
  66 #if REGISTERS >= 5
  67 #       undef   REG5
  68 #       define  REG5    register
  69 #endif
  70 #if REGISTERS >= 6
  71 #       undef   REG6
  72 #       define  REG6    register
  73 #endif
  74 #if REGISTERS >= 7
  75 #       undef   REG7
  76 #       define  REG7    register
  77 #endif
  78 #if REGISTERS >= 8
  79 #       undef   REG8
  80 #       define  REG8    register
  81 #endif
  82 #if REGISTERS >= 9
  83 #       undef   REG9
  84 #       define  REG9    register
  85 #endif
  86 #if REGISTERS >= 10
  87 #       undef   REG10
  88 #       define  REG10   register
  89 #endif
  90 #if REGISTERS >= 11
  91 #       undef   REG11
  92 #       define  REG11   register
  93 #endif
  94 #if REGISTERS >= 12
  95 #       undef   REG12
  96 #       define  REG12   register
  97 #endif
  98 #if REGISTERS >= 13
  99 #       undef   REG13
 100 #       define  REG13   register
 101 #endif
 102 #if REGISTERS >= 14
 103 #       undef   REG14
 104 #       define  REG14   register
 105 #endif
 106 #if REGISTERS >= 15
 107 #       undef   REG15
 108 #       define  REG15   register
 109 #endif
 110 #if REGISTERS >= 16
 111 #       undef   REG16
 112 #       define  REG16   register
 113 #endif
 114
 115 #ifndef BYTEORDER
 116 #       define  BYTEORDER       0000
 117 #endif
 118
 119 #ifndef NOALLIGN
 120 #       define  NOALLIGN        0
 121 #endif
 122
 123
 124 union   bytes {
 125     long  word;
 126     struct {
 127 #if BYTEORDER == 4321
 128         char_type       b1;
 129         char_type       b2;
 130         char_type       b3;
 131         char_type       b4;
 132 #else
 133 #if BYTEORDER == 1234
 134         char_type       b4;
 135         char_type       b3;
 136         char_type       b2;
 137         char_type       b1;
 138 #else
 139 #       undef   BYTEORDER
 140         int  dummy;
 141 #endif
 142 #endif
 143     } bytes;
 144 };
 145
 146 #if BYTEORDER == 4321 && NOALLIGN == 1
 147 #  define input(b,o,c,n,m){ \
 148      (c) = (*(long *)(&(b)[(o)>>3])>>((o)&0x7))&(m); \
 149      (o) += (n); \
 150    }
 151 #else
 152 #  define input(b,o,c,n,m){ \
 153      REG1 char_type *p = &(b)[(o)>>3]; \
 154      (c) = ((((long)(p[0]))|((long)(p[1])<<8)| \
 155      ((long)(p[2])<<16))>>((o)&0x7))&(m); \
 156      (o) += (n); \
 157    }
 158 #endif
 159
 160 #ifndef MAXSEG_64K
 161    /* DECLARE(ush, tab_prefix, (1<<BITS)); -- prefix code */
 162 #  define tab_prefixof(i) tab_prefix[i]
 163 #  define clear_tab_prefixof()  memzero(tab_prefix, 256);
 164 #else
 165    /* DECLARE(ush, tab_prefix0, (1<<(BITS-1)); -- prefix for even codes */
 166    /* DECLARE(ush, tab_prefix1, (1<<(BITS-1)); -- prefix for odd  codes */
 167    ush *tab_prefix[2];
 168 #  define tab_prefixof(i) tab_prefix[(i)&1][(i)>>1]
 169 #  define clear_tab_prefixof()  \
 170       memzero(tab_prefix0, 128), \
 171       memzero(tab_prefix1, 128);
 172 #endif
 173 #define de_stack        ((char_type *)(&d_buf[DIST_BUFSIZE-1]))
 174 #define tab_suffixof(i) tab_suffix[i]
 175
 176 int block_mode = BLOCK_MODE; /* block compress mode -C compatible with 2.0 */
 177
 178 /* ============================================================================
 179  * Decompress in to out.  This routine adapts to the codes in the
 180  * file building the "string" table on-the-fly; requiring no table to
 181  * be stored in the compressed file.
 182  * IN assertions: the buffer inbuf contains already the beginning of
 183  *   the compressed data, from offsets iptr to insize-1 included.
 184  *   The magic header has already been checked and skipped.
 185  *   bytes_in and bytes_out have been initialized.
 186  */
 187 int unlzw(in, out)
 188     int in, out;    /* input and output file descriptors */
 189 {
 190     REG2   char_type  *stackp;
 191     REG3   code_int   code;
 192     REG4   int        finchar;
 193     REG5   code_int   oldcode;
 194     REG6   code_int   incode;
 195     REG7   long       inbits;
 196     REG8   long       posbits;
 197     REG9   int        outpos;
 198 /*  REG10  int        insize; (global) */
 199     REG11  unsigned   bitmask;
 200     REG12  code_int   free_ent;
 201     REG13  code_int   maxcode;
 202     REG14  code_int   maxmaxcode;
 203     REG15  int        n_bits;
 204     REG16  int        rsize;
 205
 206 #ifdef MAXSEG_64K
 207     tab_prefix[0] = tab_prefix0;
 208     tab_prefix[1] = tab_prefix1;
 209 #endif
 210     maxbits = get_byte();
 211     block_mode = maxbits & BLOCK_MODE;
 212     if ((maxbits & LZW_RESERVED) != 0) {
 213         WARN((stderr, "\n%s: %s: warning, unknown flags 0x%x\n",
 214               program_name, ifname, maxbits & LZW_RESERVED));
 215     }
 216     maxbits &= BIT_MASK;
 217     maxmaxcode = MAXCODE(maxbits);
 218
 219     if (maxbits > BITS) {
 220         fprintf(stderr,
 221                 "\n%s: %s: compressed with %d bits, can only handle %d bits\n",
 222                 program_name, ifname, maxbits, BITS);
 223         exit_code = ERROR;
 224         return ERROR;
 225     }
 226     rsize = insize;
 227     maxcode = MAXCODE(n_bits = INIT_BITS)-1;
 228     bitmask = (1<<n_bits)-1;
 229     oldcode = -1;
 230     finchar = 0;
 231     outpos = 0;
 232     posbits = inptr<<3;
 233
 234     free_ent = ((block_mode) ? FIRST : 256);
 235
 236     clear_tab_prefixof(); /* Initialize the first 256 entries in the table. */
 237
 238     for (code = 255 ; code >= 0 ; --code) {
 239         tab_suffixof(code) = (char_type)code;
 240     }
 241     do {
 242         REG1 int i;
 243         int  e;
 244         int  o;
 245
 246     resetbuf:
 247         e = insize-(o = (posbits>>3));
 248
 249         for (i = 0 ; i < e ; ++i) {
 250             inbuf[i] = inbuf[i+o];
 251         }
 252         insize = e;
 253         posbits = 0;
 254
 255         if (insize < INBUF_EXTRA) {
 256             rsize = read_buffer (in, (char *) inbuf + insize, INBUFSIZ);
 257             if (rsize == -1) {
 258                 read_error();
 259             }
 260             insize += rsize;
 261             bytes_in += (off_t)rsize;
 262         }
 263         inbits = ((rsize != 0) ? ((long)insize - insize%n_bits)<<3 :
 264                   ((long)insize<<3)-(n_bits-1));
 265
 266         while (inbits > posbits) {
 267             if (free_ent > maxcode) {
 268                 posbits = ((posbits-1) +
 269                            ((n_bits<<3)-(posbits-1+(n_bits<<3))%(n_bits<<3)));
 270                 ++n_bits;
 271                 if (n_bits == maxbits) {
 272                     maxcode = maxmaxcode;
 273                 } else {
 274                     maxcode = MAXCODE(n_bits)-1;
 275                 }
 276                 bitmask = (1<<n_bits)-1;
 277                 goto resetbuf;
 278             }
 279             input(inbuf,posbits,code,n_bits,bitmask);
 280             Tracev((stderr, "%d ", code));
 281
 282             if (oldcode == -1) {
 283                 if (256 <= code)
 284                   gzip_error ("corrupt input.");
 285                 outbuf[outpos++] = (char_type)(finchar = (int)(oldcode=code));
 286                 continue;
 287             }
 288             if (code == CLEAR && block_mode) {
 289                 clear_tab_prefixof();
 290                 free_ent = FIRST - 1;
 291                 posbits = ((posbits-1) +
 292                            ((n_bits<<3)-(posbits-1+(n_bits<<3))%(n_bits<<3)));
 293                 maxcode = MAXCODE(n_bits = INIT_BITS)-1;
 294                 bitmask = (1<<n_bits)-1;
 295                 goto resetbuf;
 296             }
 297             incode = code;
 298             stackp = de_stack;
 299
 300             if (code >= free_ent) { /* Special case for KwKwK string. */
 301                 if (code > free_ent) {
 302 #ifdef DEBUG
 303                     char_type *p;
 304
 305                     posbits -= n_bits;
 306                     p = &inbuf[posbits>>3];
 307                     fprintf(stderr,
 308                             "code:%ld free_ent:%ld n_bits:%d insize:%u\n",
 309                             code, free_ent, n_bits, insize);
 310                     fprintf(stderr,
 311                             "posbits:%ld inbuf:%02X %02X %02X %02X %02X\n",
 312                             posbits, p[-1],p[0],p[1],p[2],p[3]);
 313 #endif
 314                     if (!test && outpos > 0) {
 315                         write_buf(out, (char*)outbuf, outpos);
 316                         bytes_out += (off_t)outpos;
 317                     }
 318                     gzip_error (to_stdout
 319                                 ? "corrupt input."
 320                                 : "corrupt input. Use zcat to recover some data.");
 321                 }
 322                 *--stackp = (char_type)finchar;
 323                 code = oldcode;
 324             }
 325
 326             while ((cmp_code_int)code >= (cmp_code_int)256) {
 327                 /* Generate output characters in reverse order */
 328                 *--stackp = tab_suffixof(code);
 329                 code = tab_prefixof(code);
 330             }
 331             *--stackp = (char_type)(finchar = tab_suffixof(code));
 332
 333             /* And put them out in forward order */
 334             {
 335                 REG1 int        i;
 336
 337                 if (outpos+(i = (de_stack-stackp)) >= OUTBUFSIZ) {
 338                     do {
 339                         if (i > OUTBUFSIZ-outpos) i = OUTBUFSIZ-outpos;
 340
 341                         if (i > 0) {
 342                             memcpy(outbuf+outpos, stackp, i);
 343                             outpos += i;
 344                         }
 345                         if (outpos >= OUTBUFSIZ) {
 346                             if (!test) {
 347                                 write_buf(out, (char*)outbuf, outpos);
 348                                 bytes_out += (off_t)outpos;
 349                             }
 350                             outpos = 0;
 351                         }
 352                         stackp+= i;
 353                     } while ((i = (de_stack-stackp)) > 0);
 354                 } else {
 355                     memcpy(outbuf+outpos, stackp, i);
 356                     outpos += i;
 357                 }
 358             }
 359
 360             if ((code = free_ent) < maxmaxcode) { /* Generate the new entry. */
 361
 362                 tab_prefixof(code) = (unsigned short)oldcode;
 363                 tab_suffixof(code) = (char_type)finchar;
 364                 free_ent = code+1;
 365             }
 366             oldcode = incode;   /* Remember previous code.      */
 367         }
 368     } while (rsize != 0);
 369
 370     if (!test && outpos > 0) {
 371         write_buf(out, (char*)outbuf, outpos);
 372         bytes_out += (off_t)outpos;
 373     }
 374     return OK;
 375 }