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
  12 #include <unistd.h>
  13 #include <fcntl.h>
  14
  15 #include "tailor.h"
  16 #include "gzip.h"
  17 #include "lzw.h"
  18
  19 typedef unsigned char char_type;
  20 typedef          long code_int;
  21 typedef unsigned long count_int;
  22 typedef unsigned short count_short;
  23 typedef unsigned long cmp_code_int;
  24
  25 #define MAXCODE(n)      (1L << (n))
  26
  27 #ifndef BYTEORDER
  28 #       define  BYTEORDER       0000
  29 #endif
  30
  31 #ifndef NOALLIGN
  32 #       define  NOALLIGN        0
  33 #endif
  34
  35
  36 union   bytes {
  37     long  word;
  38     struct {
  39 #if BYTEORDER == 4321
  40         char_type       b1;
  41         char_type       b2;
  42         char_type       b3;
  43         char_type       b4;
  44 #else
  45 #if BYTEORDER == 1234
  46         char_type       b4;
  47         char_type       b3;
  48         char_type       b2;
  49         char_type       b1;
  50 #else
  51 #       undef   BYTEORDER
  52         int  dummy;
  53 #endif
  54 #endif
  55     } bytes;
  56 };
  57
  58 #if BYTEORDER == 4321 && NOALLIGN == 1
  59 #  define input(b,o,c,n,m){ \
  60      (c) = (*(long *)(&(b)[(o)>>3])>>((o)&0x7))&(m); \
  61      (o) += (n); \
  62    }
  63 #else
  64 #  define input(b,o,c,n,m){ \
  65      char_type *p = &(b)[(o)>>3]; \
  66      (c) = ((((long)(p[0]))|((long)(p[1])<<8)| \
  67      ((long)(p[2])<<16))>>((o)&0x7))&(m); \
  68      (o) += (n); \
  69    }
  70 #endif
  71
  72 #ifndef MAXSEG_64K
  73    /* DECLARE(ush, tab_prefix, (1<<BITS)); -- prefix code */
  74 #  define tab_prefixof(i) tab_prefix[i]
  75 #  define clear_tab_prefixof()  memzero(tab_prefix, 256);
  76 #else
  77    /* DECLARE(ush, tab_prefix0, (1<<(BITS-1)); -- prefix for even codes */
  78    /* DECLARE(ush, tab_prefix1, (1<<(BITS-1)); -- prefix for odd  codes */
  79    ush *tab_prefix[2];
  80 #  define tab_prefixof(i) tab_prefix[(i)&1][(i)>>1]
  81 #  define clear_tab_prefixof()  \
  82       memzero(tab_prefix0, 128), \
  83       memzero(tab_prefix1, 128);
  84 #endif
  85 #define de_stack        ((char_type *)(&d_buf[DIST_BUFSIZE-1]))
  86 #define tab_suffixof(i) tab_suffix[i]
  87
  88 /* block compress mode -C compatible with 2.0 */
  89 static int block_mode = BLOCK_MODE;
  90
  91 /* ============================================================================
  92  * Decompress in to out.  This routine adapts to the codes in the
  93  * file building the "string" table on-the-fly; requiring no table to
  94  * be stored in the compressed file.
  95  * IN assertions: the buffer inbuf contains already the beginning of
  96  *   the compressed data, from offsets iptr to insize-1 included.
  97  *   The magic header has already been checked and skipped.
  98  *   bytes_in and bytes_out have been initialized.
  99  */
 100 int unlzw(in, out)
 101     int in, out;    /* input and output file descriptors */
 102 {
 103     char_type  *stackp;
 104     code_int   code;
 105     int        finchar;
 106     code_int   oldcode;
 107     code_int   incode;
 108     long       inbits;
 109     long       posbits;
 110     int        outpos;
 111 /*  int        insize; (global) */
 112     unsigned   bitmask;
 113     code_int   free_ent;
 114     code_int   maxcode;
 115     code_int   maxmaxcode;
 116     int        n_bits;
 117     int        rsize;
 118
 119 #ifdef MAXSEG_64K
 120     tab_prefix[0] = tab_prefix0;
 121     tab_prefix[1] = tab_prefix1;
 122 #endif
 123     maxbits = get_byte();
 124     block_mode = maxbits & BLOCK_MODE;
 125     if ((maxbits & LZW_RESERVED) != 0) {
 126         WARN((stderr, "\n%s: %s: warning, unknown flags 0x%x\n",
 127               program_name, ifname, (unsigned int) maxbits & LZW_RESERVED));
 128     }
 129     maxbits &= BIT_MASK;
 130     maxmaxcode = MAXCODE(maxbits);
 131
 132     if (maxbits > BITS) {
 133         fprintf(stderr,
 134                 "\n%s: %s: compressed with %d bits, can only handle %d bits\n",
 135                 program_name, ifname, maxbits, BITS);
 136         exit_code = ERROR;
 137         return ERROR;
 138     }
 139     rsize = insize;
 140     maxcode = MAXCODE(n_bits = INIT_BITS)-1;
 141     bitmask = (1<<n_bits)-1;
 142     oldcode = -1;
 143     finchar = 0;
 144     outpos = 0;
 145     posbits = inptr<<3;
 146
 147     free_ent = ((block_mode) ? FIRST : 256);
 148
 149     clear_tab_prefixof(); /* Initialize the first 256 entries in the table. */
 150
 151     for (code = 255 ; code >= 0 ; --code) {
 152         tab_suffixof(code) = (char_type)code;
 153     }
 154     do {
 155         int i;
 156         int  e;
 157         int  o;
 158
 159     resetbuf:
 160         o = posbits >> 3;
 161         e = o <= insize ? insize - o : 0;
 162
 163         for (i = 0 ; i < e ; ++i) {
 164             inbuf[i] = inbuf[i+o];
 165         }
 166         insize = e;
 167         posbits = 0;
 168
 169         if (insize < INBUF_EXTRA) {
 170             rsize = read_buffer (in, (char *) inbuf + insize, INBUFSIZ);
 171             if (rsize == -1) {
 172                 read_error();
 173             }
 174             insize += rsize;
 175             bytes_in += (off_t)rsize;
 176         }
 177         inbits = ((rsize != 0) ? ((long)insize - insize%n_bits)<<3 :
 178                   ((long)insize<<3)-(n_bits-1));
 179
 180         while (inbits > posbits) {
 181             if (free_ent > maxcode) {
 182                 posbits = ((posbits-1) +
 183                            ((n_bits<<3)-(posbits-1+(n_bits<<3))%(n_bits<<3)));
 184                 ++n_bits;
 185                 if (n_bits == maxbits) {
 186                     maxcode = maxmaxcode;
 187                 } else {
 188                     maxcode = MAXCODE(n_bits)-1;
 189                 }
 190                 bitmask = (1<<n_bits)-1;
 191                 goto resetbuf;
 192             }
 193             input(inbuf,posbits,code,n_bits,bitmask);
 194             Tracev((stderr, "%ld ", code));
 195
 196             if (oldcode == -1) {
 197                 if (256 <= code)
 198                   gzip_error ("corrupt input.");
 199                 outbuf[outpos++] = (char_type)(finchar = (int)(oldcode=code));
 200                 continue;
 201             }
 202             if (code == CLEAR && block_mode) {
 203                 clear_tab_prefixof();
 204                 free_ent = FIRST - 1;
 205                 posbits = ((posbits-1) +
 206                            ((n_bits<<3)-(posbits-1+(n_bits<<3))%(n_bits<<3)));
 207                 maxcode = MAXCODE(n_bits = INIT_BITS)-1;
 208                 bitmask = (1<<n_bits)-1;
 209                 goto resetbuf;
 210             }
 211             incode = code;
 212             stackp = de_stack;
 213
 214             if (code >= free_ent) { /* Special case for KwKwK string. */
 215                 if (code > free_ent) {
 216 #ifdef DEBUG
 217                     char_type *p;
 218
 219                     posbits -= n_bits;
 220                     p = &inbuf[posbits>>3];
 221                     fprintf(stderr,
 222                             "code:%ld free_ent:%ld n_bits:%d insize:%u\n",
 223                             code, free_ent, n_bits, insize);
 224                     fprintf(stderr,
 225                             "posbits:%ld inbuf:%02X %02X %02X %02X %02X\n",
 226                             posbits, p[-1],p[0],p[1],p[2],p[3]);
 227 #endif
 228                     if (outpos > 0)
 229                       write_buf (out, outbuf, outpos);
 230                     gzip_error (to_stdout
 231                                 ? "corrupt input."
 232                                 : "corrupt input. Use zcat to recover some data.");
 233                 }
 234                 *--stackp = (char_type)finchar;
 235                 code = oldcode;
 236             }
 237
 238             while ((cmp_code_int)code >= (cmp_code_int)256) {
 239                 /* Generate output characters in reverse order */
 240                 *--stackp = tab_suffixof(code);
 241                 code = tab_prefixof(code);
 242             }
 243             *--stackp = (char_type)(finchar = tab_suffixof(code));
 244
 245             /* And put them out in forward order */
 246             {
 247                 int i;
 248
 249                 if (outpos+(i = (de_stack-stackp)) >= OUTBUFSIZ) {
 250                     do {
 251                         if (i > OUTBUFSIZ-outpos) i = OUTBUFSIZ-outpos;
 252
 253                         if (i > 0) {
 254                             memcpy(outbuf+outpos, stackp, i);
 255                             outpos += i;
 256                         }
 257                         if (outpos >= OUTBUFSIZ) {
 258                             write_buf (out, outbuf, outpos);
 259                             outpos = 0;
 260                         }
 261                         stackp+= i;
 262                     } while ((i = (de_stack-stackp)) > 0);
 263                 } else {
 264                     memcpy(outbuf+outpos, stackp, i);
 265                     outpos += i;
 266                 }
 267             }
 268
 269             if ((code = free_ent) < maxmaxcode) { /* Generate the new entry. */
 270
 271                 tab_prefixof(code) = (unsigned short)oldcode;
 272                 tab_suffixof(code) = (char_type)finchar;
 273                 free_ent = code+1;
 274             }
 275             oldcode = incode;   /* Remember previous code.      */
 276         }
 277     } while (rsize != 0);
 278
 279     if (outpos > 0)
 280       write_buf (out, outbuf, outpos);
 281     return OK;
 282 }