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 struct inflate_codes_state {int dummy;}; /* for buggy compilers */

    13 

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

    15 #define exop word.what.Exop

    16 #define bits word.what.Bits

    17 

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

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

    20         16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};

    21 

    22 /*

    23    Notes beyond the 1.93a appnote.txt:

    24 

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

    26       stream.

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

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

    29       15 bits for the actual data.

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

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

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

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

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

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

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

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

    38       length.

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

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

    41       288 codes just to fill out the Huffman codes.  Codes 286 and 287

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

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

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

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

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

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

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

    49       literal codes sent minus 257.

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

    51       (1+6+6).  Therefore, to output three times the length, you output

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

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

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

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

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

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

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

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

    60       258 is special since 258 - 3 (the min match length) is 255.

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

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

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

    64       the two sets of lengths.

    65  */

    66 

    67 

    68 void inflate_blocks_reset(

    69 inflate_blocks_statef *s,

    70 z_streamp z,

    71 uLongf *c)

    72 {

    73   if (c != Z_NULL)

    74     *c = s->check;

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

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

    77   if (s->mode == CODES)

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

    79   s->mode = TYPE;

    80   s->bitk = 0;

    81   s->bitb = 0;

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

    83   if (s->checkfn != Z_NULL)

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

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

    86 }

    87 

    88 

    89 inflate_blocks_statef *inflate_blocks_new(

    90 z_streamp z,

    91 check_func c,

    92 uInt w)

    93 {

    94   inflate_blocks_statef *s;

    95 

    96   if ((s = (inflate_blocks_statef *)ZALLOC

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

    98     return s;

    99   if ((s->hufts =

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

   101   {

   102     ZFREE(z, s);

   103     return Z_NULL;

   104   }

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

   106   {

   107     ZFREE(z, s->hufts);

   108     ZFREE(z, s);

   109     return Z_NULL;

   110   }

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

   112   s->checkfn = c;

   113   s->mode = TYPE;

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

   115   inflate_blocks_reset(s, z, Z_NULL);

   116   return s;

   117 }

   118 

   119 

   120 int inflate_blocks(

   121 inflate_blocks_statef *s,

   122 z_streamp z,

   123 int r)

   124 {

   125   uInt t;               /* temporary storage */

   126   uLong b;              /* bit buffer */

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

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

   129   uInt n;               /* bytes available there */

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

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

   132 

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

   134   LOAD

   135 

   136   /* process input based on current state */

   137   for (;;) switch (s->mode)

   138   {

   139     case TYPE:

   140       NEEDBITS(3)

   141       t = (uInt)b & 7;

   142       s->last = t & 1;

   143       switch (t >> 1)

   144       {

   145         case 0:                         /* stored */

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

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

   148           DUMPBITS(3)

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

   150           DUMPBITS(t)

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

   152           break;

   153         case 1:                         /* fixed */

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

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

   156           {

   157             uInt bl, bd;

   158             const inflate_huft *tl, *td;

   159 

   160             inflate_trees_fixed(&bl, &bd, &tl, &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         

   319         if (t != Z_OK)

   320         {

   321           if (t == (uInt)Z_DATA_ERROR)

   322 			{

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

   324             s->mode = BAD;

   325 			}

   326           r = t;

   327           LEAVE

   328         }

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

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

   331         {

   332           r = Z_MEM_ERROR;

   333           LEAVE

   334         }

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

   336       }

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

   338       s->mode = CODES;

   339     case CODES:

   340       UPDATE

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

   342         return inflate_flush(s, z, r);

   343       r = Z_OK;

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

   345       LOAD

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

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

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

   349       if (!s->last)

   350       {

   351         s->mode = TYPE;

   352         break;

   353       }

   354       s->mode = DRY;

   355     case DRY:

   356       FLUSH

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

   358         LEAVE

   359       s->mode = DONE;

   360     case DONE:

   361       r = Z_STREAM_END;

   362       LEAVE

   363     case BAD:

   364       r = Z_DATA_ERROR;

   365       LEAVE

   366     default:

   367       r = Z_STREAM_ERROR;

   368       LEAVE

   369   }

   370 }

   371 

   372 

   373 int inflate_blocks_free(

   374 inflate_blocks_statef *s,

   375 z_streamp z)

   376 {

   377   inflate_blocks_reset(s, z, Z_NULL);

   378   ZFREE(z, s->window);

   379   ZFREE(z, s->hufts);

   380   ZFREE(z, s);

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

   382   return Z_OK;

   383 }

   384 

   385 

   386 void inflate_set_dictionary(

   387 inflate_blocks_statef *s,

   388 const Bytef *d,

   389 uInt  n)

   390 {

   391   zmemcpy(s->window, d, n);

   392   s->read = s->write = s->window + n;

   393 }

   394 

   395 

   396 /* Returns true if inflate is currently at the end of a block generated

   397  * by Z_SYNC_FLUSH or Z_FULL_FLUSH. 

   398  * IN assertion: s != Z_NULL

   399  */

   400 int inflate_blocks_sync_point(

   401 inflate_blocks_statef *s)

   402 {

   403   return s->mode == LENS;

   404 }