1 /* infblock.c -- interpret and process block types to last block

     2  * Copyright (C) 1995-2002 Mark Adler

     3  * For conditions of distribution and use, see copyright notice in zlib.h

     4  */

     5 

     6 #include "zutil.h"

     7 #include "infblock.h"

     8 #include "inftrees.h"

     9 #include "infcodes.h"

    10 #include "infutil.h"

    11 

    12 

    13 /* simplify the use of the inflate_huft type with some defines */

    14 #define exop word.what.Exop

    15 #define bits word.what.Bits

    16 

    17 /* Table for deflate from PKZIP's appnote.txt. */

    18 local const uInt border[] = { /* Order of the bit length code lengths */

    19         16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};

    20 

    21 /*

    22    Notes beyond the 1.93a appnote.txt:

    23 

    24    1. Distance pointers never point before the beginning of the output

    25       stream.

    26    2. Distance pointers can point back across blocks, up to 32k away.

    27    3. There is an implied maximum of 7 bits for the bit length table and

    28       15 bits for the actual data.

    29    4. If only one code exists, then it is encoded using one bit.  (Zero

    30       would be more efficient, but perhaps a little confusing.)  If two

    31       codes exist, they are coded using one bit each (0 and 1).

    32    5. There is no way of sending zero distance codes--a dummy must be

    33       sent if there are none.  (History: a pre 2.0 version of PKZIP would

    34       store blocks with no distance codes, but this was discovered to be

    35       too harsh a criterion.)  Valid only for 1.93a.  2.04c does allow

    36       zero distance codes, which is sent as one code of zero bits in

    37       length.

    38    6. There are up to 286 literal/length codes.  Code 256 represents the

    39       end-of-block.  Note however that the static length tree defines

    40       288 codes just to fill out the Huffman codes.  Codes 286 and 287

    41       cannot be used though, since there is no length base or extra bits

    42       defined for them.  Similarily, there are up to 30 distance codes.

    43       However, static trees define 32 codes (all 5 bits) to fill out the

    44       Huffman codes, but the last two had better not show up in the data.

    45    7. Unzip can check dynamic Huffman blocks for complete code sets.

    46       The exception is that a single code would not be complete (see #4).

    47    8. The five bits following the block type is really the number of

    48       literal codes sent minus 257.

    49    9. Length codes 8,16,16 are interpreted as 13 length codes of 8 bits

    50       (1+6+6).  Therefore, to output three times the length, you output

    51       three codes (1+1+1), whereas to output four times the same length,

    52       you only need two codes (1+3).  Hmm.

    53   10. In the tree reconstruction algorithm, Code = Code + Increment

    54       only if BitLength(i) is not zero.  (Pretty obvious.)

    55   11. Correction: 4 Bits: # of Bit Length codes - 4     (4 - 19)

    56   12. Note: length code 284 can represent 227-258, but length code 285

    57       really is 258.  The last length deserves its own, short code

    58       since it gets used a lot in very redundant files.  The length

    59       258 is special since 258 - 3 (the min match length) is 255.

    60   13. The literal/length and distance code bit lengths are read as a

    61       single stream of lengths.  It is possible (and advantageous) for

    62       a repeat code (16, 17, or 18) to go across the boundary between

    63       the two sets of lengths.

    64  */

    65 

    66 

    67 local void inflate_blocks_reset( /* s, z, c) */

    68 inflate_blocks_statef *s,

    69 z_streamp z,

    70 uLongf *c )

    71 {

    72   if (c != Z_NULL)

    73     *c = s->check;

    74   if (s->mode == BTREE || s->mode == DTREE)

    75     ZFREE(z, s->sub.trees.blens);

    76   if (s->mode == CODES)

    77     inflate_codes_free(s->sub.decode.codes, z);

    78   s->mode = TYPE;

    79   s->bitk = 0;

    80   s->bitb = 0;

    81   s->read = s->write = s->window;

    82   if (s->checkfn != Z_NULL)

    83     z->adler = s->check = (*s->checkfn)(0L, (const Bytef *)Z_NULL, 0);

    84   Tracev((stderr, "inflate:   blocks reset\n"));

    85 }

    86 

    87 

    88 local inflate_blocks_statef *inflate_blocks_new( /* z, c, w) */

    89 z_streamp z,

    90 check_func c,

    91 uInt w )

    92 {

    93   inflate_blocks_statef *s;

    94 

    95   if ((s = (inflate_blocks_statef *)ZALLOC

    96        (z,1,sizeof(struct inflate_blocks_state))) == Z_NULL)

    97     return s;

    98   if ((s->hufts =

    99        (inflate_huft *)ZALLOC(z, sizeof(inflate_huft), MANY)) == Z_NULL)

   100   {

   101     ZFREE(z, s);

   102     return Z_NULL;

   103   }

   104   if ((s->window = (Bytef *)ZALLOC(z, 1, w)) == Z_NULL)

   105   {

   106     ZFREE(z, s->hufts);

   107     ZFREE(z, s);

   108     return Z_NULL;

   109   }

   110   s->end = s->window + w;

   111   s->checkfn = c;

   112   s->mode = TYPE;

   113   Tracev((stderr, "inflate:   blocks allocated\n"));

   114   inflate_blocks_reset(s, z, Z_NULL);

   115   return s;

   116 }

   117 

   118 

   119 local int inflate_blocks( /* s, z, r) */

   120 inflate_blocks_statef *s,

   121 z_streamp z,

   122 int r )

   123 {

   124   uInt t;               /* temporary storage */

   125   uLong b;              /* bit buffer */

   126   uInt k;               /* bits in bit buffer */

   127   Bytef *p;             /* input data pointer */

   128   uInt n;               /* bytes available there */

   129   Bytef *q;             /* output window write pointer */

   130   uInt m;               /* bytes to end of window or read pointer */

   131 

   132   /* copy input/output information to locals (UPDATE macro restores) */

   133   LOAD

   134 

   135   /* process input based on current state */

   136   while (1) switch (s->mode)

   137   {

   138     case TYPE:

   139       NEEDBITS(3)

   140       t = (uInt)b & 7;

   141       s->last = t & 1;

   142       switch (t >> 1)

   143       {

   144         case 0:                         /* stored */

   145           Tracev((stderr, "inflate:     stored block%s\n",

   146                  s->last ? " (last)" : ""));

   147           DUMPBITS(3)

   148           t = k & 7;                    /* go to byte boundary */

   149           DUMPBITS(t)

   150           s->mode = LENS;               /* get length of stored block */

   151           break;

   152         case 1:                         /* fixed */

   153           Tracev((stderr, "inflate:     fixed codes block%s\n",

   154                  s->last ? " (last)" : ""));

   155           {

   156             uInt bl, bd;

   157             inflate_huft *tl, *td;

   158 

   159             inflate_trees_fixed(&bl, &bd, (const inflate_huft**)&tl,

   160                                           (const inflate_huft**)&td, z);

   161             s->sub.decode.codes = inflate_codes_new(bl, bd, tl, td, z);

   162             if (s->sub.decode.codes == Z_NULL)

   163             {

   164               r = Z_MEM_ERROR;

   165               LEAVE

   166             }

   167           }

   168           DUMPBITS(3)

   169           s->mode = CODES;

   170           break;

   171         case 2:                         /* dynamic */

   172           Tracev((stderr, "inflate:     dynamic codes block%s\n",

   173                  s->last ? " (last)" : ""));

   174           DUMPBITS(3)

   175           s->mode = TABLE;

   176           break;

   177         case 3:                         /* illegal */

   178           DUMPBITS(3)

   179           s->mode = BAD;

   180           z->msg = (char*)"invalid block type";

   181           r = Z_DATA_ERROR;

   182           LEAVE

   183       }

   184       break;

   185     case LENS:

   186       NEEDBITS(32)

   187       if ((((~b) >> 16) & 0xffff) != (b & 0xffff))

   188       {

   189         s->mode = BAD;

   190         z->msg = (char*)"invalid stored block lengths";

   191         r = Z_DATA_ERROR;

   192         LEAVE

   193       }

   194       s->sub.left = (uInt)b & 0xffff;

   195       b = k = 0;                      /* dump bits */

   196       Tracev((stderr, "inflate:       stored length %u\n", s->sub.left));

   197       s->mode = s->sub.left ? STORED : (s->last ? DRY : TYPE);

   198       break;

   199     case STORED:

   200       if (n == 0)

   201         LEAVE

   202       NEEDOUT

   203       t = s->sub.left;

   204       if (t > n) t = n;

   205       if (t > m) t = m;

   206       zmemcpy(q, p, t);

   207       p += t;  n -= t;

   208       q += t;  m -= t;

   209       if ((s->sub.left -= t) != 0)

   210         break;

   211       Tracev((stderr, "inflate:       stored end, %lu total out\n",

   212               z->total_out + (q >= s->read ? q - s->read :

   213               (s->end - s->read) + (q - s->window))));

   214       s->mode = s->last ? DRY : TYPE;

   215       break;

   216     case TABLE:

   217       NEEDBITS(14)

   218       s->sub.trees.table = t = (uInt)b & 0x3fff;

   219 #ifndef PKZIP_BUG_WORKAROUND

   220       if ((t & 0x1f) > 29 || ((t >> 5) & 0x1f) > 29)

   221       {

   222         s->mode = BAD;

   223         z->msg = (char*)"too many length or distance symbols";

   224         r = Z_DATA_ERROR;

   225         LEAVE

   226       }

   227 #endif

   228       t = 258 + (t & 0x1f) + ((t >> 5) & 0x1f);

   229       if ((s->sub.trees.blens = (uIntf*)ZALLOC(z, t, sizeof(uInt))) == Z_NULL)

   230       {

   231         r = Z_MEM_ERROR;

   232         LEAVE

   233       }

   234       DUMPBITS(14)

   235       s->sub.trees.index = 0;

   236       Tracev((stderr, "inflate:       table sizes ok\n"));

   237       s->mode = BTREE;

   238     case BTREE:

   239       while (s->sub.trees.index < 4 + (s->sub.trees.table >> 10))

   240       {

   241         NEEDBITS(3)

   242         s->sub.trees.blens[border[s->sub.trees.index++]] = (uInt)b & 7;

   243         DUMPBITS(3)

   244       }

   245       while (s->sub.trees.index < 19)

   246         s->sub.trees.blens[border[s->sub.trees.index++]] = 0;

   247       s->sub.trees.bb = 7;

   248       t = inflate_trees_bits(s->sub.trees.blens, &s->sub.trees.bb,

   249                              &s->sub.trees.tb, s->hufts, z);

   250       if (t != Z_OK)

   251       {

   252         r = t;

   253         if (r == Z_DATA_ERROR)

   254         {

   255           ZFREE(z, s->sub.trees.blens);

   256           s->mode = BAD;

   257         }

   258         LEAVE

   259       }

   260       s->sub.trees.index = 0;

   261       Tracev((stderr, "inflate:       bits tree ok\n"));

   262       s->mode = DTREE;

   263     case DTREE:

   264       while (t = s->sub.trees.table,

   265              s->sub.trees.index < 258 + (t & 0x1f) + ((t >> 5) & 0x1f))

   266       {

   267         inflate_huft *h;

   268         uInt i, j, c;

   269 

   270         t = s->sub.trees.bb;

   271         NEEDBITS(t)

   272         h = s->sub.trees.tb + ((uInt)b & inflate_mask[t]);

   273         t = h->bits;

   274         c = h->base;

   275         if (c < 16)

   276         {

   277           DUMPBITS(t)

   278           s->sub.trees.blens[s->sub.trees.index++] = c;

   279         }

   280         else /* c == 16..18 */

   281         {

   282           i = c == 18 ? 7 : c - 14;

   283           j = c == 18 ? 11 : 3;

   284           NEEDBITS(t + i)

   285           DUMPBITS(t)

   286           j += (uInt)b & inflate_mask[i];

   287           DUMPBITS(i)

   288           i = s->sub.trees.index;

   289           t = s->sub.trees.table;

   290           if (i + j > 258 + (t & 0x1f) + ((t >> 5) & 0x1f) ||

   291               (c == 16 && i < 1))

   292           {

   293             ZFREE(z, s->sub.trees.blens);

   294             s->mode = BAD;

   295             z->msg = (char*)"invalid bit length repeat";

   296             r = Z_DATA_ERROR;

   297             LEAVE

   298           }

   299           c = c == 16 ? s->sub.trees.blens[i - 1] : 0;

   300           do {

   301             s->sub.trees.blens[i++] = c;

   302           } while (--j);

   303           s->sub.trees.index = i;

   304         }

   305       }

   306       s->sub.trees.tb = Z_NULL;

   307       {

   308         uInt bl, bd;

   309         inflate_huft *tl, *td;

   310         inflate_codes_statef *c;

   311 

   312         bl = 9;         /* must be <= 9 for lookahead assumptions */

   313         bd = 6;         /* must be <= 9 for lookahead assumptions */

   314         t = s->sub.trees.table;

   315         t = inflate_trees_dynamic(257 + (t & 0x1f), 1 + ((t >> 5) & 0x1f),

   316                                   s->sub.trees.blens, &bl, &bd, &tl, &td,

   317                                   s->hufts, z);

   318         if (t != Z_OK)

   319         {

   320           if (t == (uInt)Z_DATA_ERROR)

   321           {

   322             ZFREE(z, s->sub.trees.blens);

   323             s->mode = BAD;

   324           }

   325           r = t;

   326           LEAVE

   327         }

   328         Tracev((stderr, "inflate:       trees ok\n"));

   329         if ((c = inflate_codes_new(bl, bd, tl, td, z)) == Z_NULL)

   330         {

   331           r = Z_MEM_ERROR;

   332           LEAVE

   333         }

   334         s->sub.decode.codes = c;

   335       }

   336       ZFREE(z, s->sub.trees.blens);

   337       s->mode = CODES;

   338     case CODES:

   339       UPDATE

   340       if ((r = inflate_codes(s, z, r)) != Z_STREAM_END)

   341         return inflate_flush(s, z, r);

   342       r = Z_OK;

   343       inflate_codes_free(s->sub.decode.codes, z);

   344       LOAD

   345       Tracev((stderr, "inflate:       codes end, %lu total out\n",

   346               z->total_out + (q >= s->read ? q - s->read :

   347               (s->end - s->read) + (q - s->window))));

   348       if (!s->last)

   349       {

   350         s->mode = TYPE;

   351         break;

   352       }

   353       s->mode = DRY;

   354     case DRY:

   355       FLUSH

   356       if (s->read != s->write)

   357         LEAVE

   358       s->mode = DONE;

   359     case DONE:

   360       r = Z_STREAM_END;

   361       LEAVE

   362     case BAD:

   363       r = Z_DATA_ERROR;

   364       LEAVE

   365     default:

   366       r = Z_STREAM_ERROR;

   367       LEAVE

   368   }

   369 #ifdef NEED_DUMMY_RETURN

   370   return 0;

   371 #endif

   372 }

   373 

   374 

   375 local int inflate_blocks_free( /* s, z) */

   376 inflate_blocks_statef *s,

   377 z_streamp z )

   378 {

   379   inflate_blocks_reset(s, z, Z_NULL);

   380   ZFREE(z, s->window);

   381   ZFREE(z, s->hufts);

   382   ZFREE(z, s);

   383   Tracev((stderr, "inflate:   blocks freed\n"));

   384   return Z_OK;

   385 }

   386 

   387