external/zlib-1.2.11/trees.c
author Sam Lantinga <slouken@libsdl.org>
Sat, 21 Oct 2017 21:05:43 -0700
changeset 521 9ed2f7d4a251
permissions -rw-r--r--
Added pristine code for zlib-1.2.11
     1 /* trees.c -- output deflated data using Huffman coding
     2  * Copyright (C) 1995-2017 Jean-loup Gailly
     3  * detect_data_type() function provided freely by Cosmin Truta, 2006
     4  * For conditions of distribution and use, see copyright notice in zlib.h
     5  */
     6 
     7 /*
     8  *  ALGORITHM
     9  *
    10  *      The "deflation" process uses several Huffman trees. The more
    11  *      common source values are represented by shorter bit sequences.
    12  *
    13  *      Each code tree is stored in a compressed form which is itself
    14  * a Huffman encoding of the lengths of all the code strings (in
    15  * ascending order by source values).  The actual code strings are
    16  * reconstructed from the lengths in the inflate process, as described
    17  * in the deflate specification.
    18  *
    19  *  REFERENCES
    20  *
    21  *      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
    22  *      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
    23  *
    24  *      Storer, James A.
    25  *          Data Compression:  Methods and Theory, pp. 49-50.
    26  *          Computer Science Press, 1988.  ISBN 0-7167-8156-5.
    27  *
    28  *      Sedgewick, R.
    29  *          Algorithms, p290.
    30  *          Addison-Wesley, 1983. ISBN 0-201-06672-6.
    31  */
    32 
    33 /* @(#) $Id$ */
    34 
    35 /* #define GEN_TREES_H */
    36 
    37 #include "deflate.h"
    38 
    39 #ifdef ZLIB_DEBUG
    40 #  include <ctype.h>
    41 #endif
    42 
    43 /* ===========================================================================
    44  * Constants
    45  */
    46 
    47 #define MAX_BL_BITS 7
    48 /* Bit length codes must not exceed MAX_BL_BITS bits */
    49 
    50 #define END_BLOCK 256
    51 /* end of block literal code */
    52 
    53 #define REP_3_6      16
    54 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
    55 
    56 #define REPZ_3_10    17
    57 /* repeat a zero length 3-10 times  (3 bits of repeat count) */
    58 
    59 #define REPZ_11_138  18
    60 /* repeat a zero length 11-138 times  (7 bits of repeat count) */
    61 
    62 local const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
    63    = {0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0};
    64 
    65 local const int extra_dbits[D_CODES] /* extra bits for each distance code */
    66    = {0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13};
    67 
    68 local const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
    69    = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
    70 
    71 local const uch bl_order[BL_CODES]
    72    = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
    73 /* The lengths of the bit length codes are sent in order of decreasing
    74  * probability, to avoid transmitting the lengths for unused bit length codes.
    75  */
    76 
    77 /* ===========================================================================
    78  * Local data. These are initialized only once.
    79  */
    80 
    81 #define DIST_CODE_LEN  512 /* see definition of array dist_code below */
    82 
    83 #if defined(GEN_TREES_H) || !defined(STDC)
    84 /* non ANSI compilers may not accept trees.h */
    85 
    86 local ct_data static_ltree[L_CODES+2];
    87 /* The static literal tree. Since the bit lengths are imposed, there is no
    88  * need for the L_CODES extra codes used during heap construction. However
    89  * The codes 286 and 287 are needed to build a canonical tree (see _tr_init
    90  * below).
    91  */
    92 
    93 local ct_data static_dtree[D_CODES];
    94 /* The static distance tree. (Actually a trivial tree since all codes use
    95  * 5 bits.)
    96  */
    97 
    98 uch _dist_code[DIST_CODE_LEN];
    99 /* Distance codes. The first 256 values correspond to the distances
   100  * 3 .. 258, the last 256 values correspond to the top 8 bits of
   101  * the 15 bit distances.
   102  */
   103 
   104 uch _length_code[MAX_MATCH-MIN_MATCH+1];
   105 /* length code for each normalized match length (0 == MIN_MATCH) */
   106 
   107 local int base_length[LENGTH_CODES];
   108 /* First normalized length for each code (0 = MIN_MATCH) */
   109 
   110 local int base_dist[D_CODES];
   111 /* First normalized distance for each code (0 = distance of 1) */
   112 
   113 #else
   114 #  include "trees.h"
   115 #endif /* GEN_TREES_H */
   116 
   117 struct static_tree_desc_s {
   118     const ct_data *static_tree;  /* static tree or NULL */
   119     const intf *extra_bits;      /* extra bits for each code or NULL */
   120     int     extra_base;          /* base index for extra_bits */
   121     int     elems;               /* max number of elements in the tree */
   122     int     max_length;          /* max bit length for the codes */
   123 };
   124 
   125 local const static_tree_desc  static_l_desc =
   126 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
   127 
   128 local const static_tree_desc  static_d_desc =
   129 {static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};
   130 
   131 local const static_tree_desc  static_bl_desc =
   132 {(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};
   133 
   134 /* ===========================================================================
   135  * Local (static) routines in this file.
   136  */
   137 
   138 local void tr_static_init OF((void));
   139 local void init_block     OF((deflate_state *s));
   140 local void pqdownheap     OF((deflate_state *s, ct_data *tree, int k));
   141 local void gen_bitlen     OF((deflate_state *s, tree_desc *desc));
   142 local void gen_codes      OF((ct_data *tree, int max_code, ushf *bl_count));
   143 local void build_tree     OF((deflate_state *s, tree_desc *desc));
   144 local void scan_tree      OF((deflate_state *s, ct_data *tree, int max_code));
   145 local void send_tree      OF((deflate_state *s, ct_data *tree, int max_code));
   146 local int  build_bl_tree  OF((deflate_state *s));
   147 local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
   148                               int blcodes));
   149 local void compress_block OF((deflate_state *s, const ct_data *ltree,
   150                               const ct_data *dtree));
   151 local int  detect_data_type OF((deflate_state *s));
   152 local unsigned bi_reverse OF((unsigned value, int length));
   153 local void bi_windup      OF((deflate_state *s));
   154 local void bi_flush       OF((deflate_state *s));
   155 
   156 #ifdef GEN_TREES_H
   157 local void gen_trees_header OF((void));
   158 #endif
   159 
   160 #ifndef ZLIB_DEBUG
   161 #  define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
   162    /* Send a code of the given tree. c and tree must not have side effects */
   163 
   164 #else /* !ZLIB_DEBUG */
   165 #  define send_code(s, c, tree) \
   166      { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
   167        send_bits(s, tree[c].Code, tree[c].Len); }
   168 #endif
   169 
   170 /* ===========================================================================
   171  * Output a short LSB first on the stream.
   172  * IN assertion: there is enough room in pendingBuf.
   173  */
   174 #define put_short(s, w) { \
   175     put_byte(s, (uch)((w) & 0xff)); \
   176     put_byte(s, (uch)((ush)(w) >> 8)); \
   177 }
   178 
   179 /* ===========================================================================
   180  * Send a value on a given number of bits.
   181  * IN assertion: length <= 16 and value fits in length bits.
   182  */
   183 #ifdef ZLIB_DEBUG
   184 local void send_bits      OF((deflate_state *s, int value, int length));
   185 
   186 local void send_bits(s, value, length)
   187     deflate_state *s;
   188     int value;  /* value to send */
   189     int length; /* number of bits */
   190 {
   191     Tracevv((stderr," l %2d v %4x ", length, value));
   192     Assert(length > 0 && length <= 15, "invalid length");
   193     s->bits_sent += (ulg)length;
   194 
   195     /* If not enough room in bi_buf, use (valid) bits from bi_buf and
   196      * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
   197      * unused bits in value.
   198      */
   199     if (s->bi_valid > (int)Buf_size - length) {
   200         s->bi_buf |= (ush)value << s->bi_valid;
   201         put_short(s, s->bi_buf);
   202         s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
   203         s->bi_valid += length - Buf_size;
   204     } else {
   205         s->bi_buf |= (ush)value << s->bi_valid;
   206         s->bi_valid += length;
   207     }
   208 }
   209 #else /* !ZLIB_DEBUG */
   210 
   211 #define send_bits(s, value, length) \
   212 { int len = length;\
   213   if (s->bi_valid > (int)Buf_size - len) {\
   214     int val = (int)value;\
   215     s->bi_buf |= (ush)val << s->bi_valid;\
   216     put_short(s, s->bi_buf);\
   217     s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
   218     s->bi_valid += len - Buf_size;\
   219   } else {\
   220     s->bi_buf |= (ush)(value) << s->bi_valid;\
   221     s->bi_valid += len;\
   222   }\
   223 }
   224 #endif /* ZLIB_DEBUG */
   225 
   226 
   227 /* the arguments must not have side effects */
   228 
   229 /* ===========================================================================
   230  * Initialize the various 'constant' tables.
   231  */
   232 local void tr_static_init()
   233 {
   234 #if defined(GEN_TREES_H) || !defined(STDC)
   235     static int static_init_done = 0;
   236     int n;        /* iterates over tree elements */
   237     int bits;     /* bit counter */
   238     int length;   /* length value */
   239     int code;     /* code value */
   240     int dist;     /* distance index */
   241     ush bl_count[MAX_BITS+1];
   242     /* number of codes at each bit length for an optimal tree */
   243 
   244     if (static_init_done) return;
   245 
   246     /* For some embedded targets, global variables are not initialized: */
   247 #ifdef NO_INIT_GLOBAL_POINTERS
   248     static_l_desc.static_tree = static_ltree;
   249     static_l_desc.extra_bits = extra_lbits;
   250     static_d_desc.static_tree = static_dtree;
   251     static_d_desc.extra_bits = extra_dbits;
   252     static_bl_desc.extra_bits = extra_blbits;
   253 #endif
   254 
   255     /* Initialize the mapping length (0..255) -> length code (0..28) */
   256     length = 0;
   257     for (code = 0; code < LENGTH_CODES-1; code++) {
   258         base_length[code] = length;
   259         for (n = 0; n < (1<<extra_lbits[code]); n++) {
   260             _length_code[length++] = (uch)code;
   261         }
   262     }
   263     Assert (length == 256, "tr_static_init: length != 256");
   264     /* Note that the length 255 (match length 258) can be represented
   265      * in two different ways: code 284 + 5 bits or code 285, so we
   266      * overwrite length_code[255] to use the best encoding:
   267      */
   268     _length_code[length-1] = (uch)code;
   269 
   270     /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
   271     dist = 0;
   272     for (code = 0 ; code < 16; code++) {
   273         base_dist[code] = dist;
   274         for (n = 0; n < (1<<extra_dbits[code]); n++) {
   275             _dist_code[dist++] = (uch)code;
   276         }
   277     }
   278     Assert (dist == 256, "tr_static_init: dist != 256");
   279     dist >>= 7; /* from now on, all distances are divided by 128 */
   280     for ( ; code < D_CODES; code++) {
   281         base_dist[code] = dist << 7;
   282         for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
   283             _dist_code[256 + dist++] = (uch)code;
   284         }
   285     }
   286     Assert (dist == 256, "tr_static_init: 256+dist != 512");
   287 
   288     /* Construct the codes of the static literal tree */
   289     for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
   290     n = 0;
   291     while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
   292     while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
   293     while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
   294     while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
   295     /* Codes 286 and 287 do not exist, but we must include them in the
   296      * tree construction to get a canonical Huffman tree (longest code
   297      * all ones)
   298      */
   299     gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
   300 
   301     /* The static distance tree is trivial: */
   302     for (n = 0; n < D_CODES; n++) {
   303         static_dtree[n].Len = 5;
   304         static_dtree[n].Code = bi_reverse((unsigned)n, 5);
   305     }
   306     static_init_done = 1;
   307 
   308 #  ifdef GEN_TREES_H
   309     gen_trees_header();
   310 #  endif
   311 #endif /* defined(GEN_TREES_H) || !defined(STDC) */
   312 }
   313 
   314 /* ===========================================================================
   315  * Genererate the file trees.h describing the static trees.
   316  */
   317 #ifdef GEN_TREES_H
   318 #  ifndef ZLIB_DEBUG
   319 #    include <stdio.h>
   320 #  endif
   321 
   322 #  define SEPARATOR(i, last, width) \
   323       ((i) == (last)? "\n};\n\n" :    \
   324        ((i) % (width) == (width)-1 ? ",\n" : ", "))
   325 
   326 void gen_trees_header()
   327 {
   328     FILE *header = fopen("trees.h", "w");
   329     int i;
   330 
   331     Assert (header != NULL, "Can't open trees.h");
   332     fprintf(header,
   333             "/* header created automatically with -DGEN_TREES_H */\n\n");
   334 
   335     fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");
   336     for (i = 0; i < L_CODES+2; i++) {
   337         fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,
   338                 static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
   339     }
   340 
   341     fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");
   342     for (i = 0; i < D_CODES; i++) {
   343         fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,
   344                 static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
   345     }
   346 
   347     fprintf(header, "const uch ZLIB_INTERNAL _dist_code[DIST_CODE_LEN] = {\n");
   348     for (i = 0; i < DIST_CODE_LEN; i++) {
   349         fprintf(header, "%2u%s", _dist_code[i],
   350                 SEPARATOR(i, DIST_CODE_LEN-1, 20));
   351     }
   352 
   353     fprintf(header,
   354         "const uch ZLIB_INTERNAL _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");
   355     for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {
   356         fprintf(header, "%2u%s", _length_code[i],
   357                 SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
   358     }
   359 
   360     fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");
   361     for (i = 0; i < LENGTH_CODES; i++) {
   362         fprintf(header, "%1u%s", base_length[i],
   363                 SEPARATOR(i, LENGTH_CODES-1, 20));
   364     }
   365 
   366     fprintf(header, "local const int base_dist[D_CODES] = {\n");
   367     for (i = 0; i < D_CODES; i++) {
   368         fprintf(header, "%5u%s", base_dist[i],
   369                 SEPARATOR(i, D_CODES-1, 10));
   370     }
   371 
   372     fclose(header);
   373 }
   374 #endif /* GEN_TREES_H */
   375 
   376 /* ===========================================================================
   377  * Initialize the tree data structures for a new zlib stream.
   378  */
   379 void ZLIB_INTERNAL _tr_init(s)
   380     deflate_state *s;
   381 {
   382     tr_static_init();
   383 
   384     s->l_desc.dyn_tree = s->dyn_ltree;
   385     s->l_desc.stat_desc = &static_l_desc;
   386 
   387     s->d_desc.dyn_tree = s->dyn_dtree;
   388     s->d_desc.stat_desc = &static_d_desc;
   389 
   390     s->bl_desc.dyn_tree = s->bl_tree;
   391     s->bl_desc.stat_desc = &static_bl_desc;
   392 
   393     s->bi_buf = 0;
   394     s->bi_valid = 0;
   395 #ifdef ZLIB_DEBUG
   396     s->compressed_len = 0L;
   397     s->bits_sent = 0L;
   398 #endif
   399 
   400     /* Initialize the first block of the first file: */
   401     init_block(s);
   402 }
   403 
   404 /* ===========================================================================
   405  * Initialize a new block.
   406  */
   407 local void init_block(s)
   408     deflate_state *s;
   409 {
   410     int n; /* iterates over tree elements */
   411 
   412     /* Initialize the trees. */
   413     for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
   414     for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
   415     for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
   416 
   417     s->dyn_ltree[END_BLOCK].Freq = 1;
   418     s->opt_len = s->static_len = 0L;
   419     s->last_lit = s->matches = 0;
   420 }
   421 
   422 #define SMALLEST 1
   423 /* Index within the heap array of least frequent node in the Huffman tree */
   424 
   425 
   426 /* ===========================================================================
   427  * Remove the smallest element from the heap and recreate the heap with
   428  * one less element. Updates heap and heap_len.
   429  */
   430 #define pqremove(s, tree, top) \
   431 {\
   432     top = s->heap[SMALLEST]; \
   433     s->heap[SMALLEST] = s->heap[s->heap_len--]; \
   434     pqdownheap(s, tree, SMALLEST); \
   435 }
   436 
   437 /* ===========================================================================
   438  * Compares to subtrees, using the tree depth as tie breaker when
   439  * the subtrees have equal frequency. This minimizes the worst case length.
   440  */
   441 #define smaller(tree, n, m, depth) \
   442    (tree[n].Freq < tree[m].Freq || \
   443    (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
   444 
   445 /* ===========================================================================
   446  * Restore the heap property by moving down the tree starting at node k,
   447  * exchanging a node with the smallest of its two sons if necessary, stopping
   448  * when the heap property is re-established (each father smaller than its
   449  * two sons).
   450  */
   451 local void pqdownheap(s, tree, k)
   452     deflate_state *s;
   453     ct_data *tree;  /* the tree to restore */
   454     int k;               /* node to move down */
   455 {
   456     int v = s->heap[k];
   457     int j = k << 1;  /* left son of k */
   458     while (j <= s->heap_len) {
   459         /* Set j to the smallest of the two sons: */
   460         if (j < s->heap_len &&
   461             smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
   462             j++;
   463         }
   464         /* Exit if v is smaller than both sons */
   465         if (smaller(tree, v, s->heap[j], s->depth)) break;
   466 
   467         /* Exchange v with the smallest son */
   468         s->heap[k] = s->heap[j];  k = j;
   469 
   470         /* And continue down the tree, setting j to the left son of k */
   471         j <<= 1;
   472     }
   473     s->heap[k] = v;
   474 }
   475 
   476 /* ===========================================================================
   477  * Compute the optimal bit lengths for a tree and update the total bit length
   478  * for the current block.
   479  * IN assertion: the fields freq and dad are set, heap[heap_max] and
   480  *    above are the tree nodes sorted by increasing frequency.
   481  * OUT assertions: the field len is set to the optimal bit length, the
   482  *     array bl_count contains the frequencies for each bit length.
   483  *     The length opt_len is updated; static_len is also updated if stree is
   484  *     not null.
   485  */
   486 local void gen_bitlen(s, desc)
   487     deflate_state *s;
   488     tree_desc *desc;    /* the tree descriptor */
   489 {
   490     ct_data *tree        = desc->dyn_tree;
   491     int max_code         = desc->max_code;
   492     const ct_data *stree = desc->stat_desc->static_tree;
   493     const intf *extra    = desc->stat_desc->extra_bits;
   494     int base             = desc->stat_desc->extra_base;
   495     int max_length       = desc->stat_desc->max_length;
   496     int h;              /* heap index */
   497     int n, m;           /* iterate over the tree elements */
   498     int bits;           /* bit length */
   499     int xbits;          /* extra bits */
   500     ush f;              /* frequency */
   501     int overflow = 0;   /* number of elements with bit length too large */
   502 
   503     for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
   504 
   505     /* In a first pass, compute the optimal bit lengths (which may
   506      * overflow in the case of the bit length tree).
   507      */
   508     tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
   509 
   510     for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
   511         n = s->heap[h];
   512         bits = tree[tree[n].Dad].Len + 1;
   513         if (bits > max_length) bits = max_length, overflow++;
   514         tree[n].Len = (ush)bits;
   515         /* We overwrite tree[n].Dad which is no longer needed */
   516 
   517         if (n > max_code) continue; /* not a leaf node */
   518 
   519         s->bl_count[bits]++;
   520         xbits = 0;
   521         if (n >= base) xbits = extra[n-base];
   522         f = tree[n].Freq;
   523         s->opt_len += (ulg)f * (unsigned)(bits + xbits);
   524         if (stree) s->static_len += (ulg)f * (unsigned)(stree[n].Len + xbits);
   525     }
   526     if (overflow == 0) return;
   527 
   528     Tracev((stderr,"\nbit length overflow\n"));
   529     /* This happens for example on obj2 and pic of the Calgary corpus */
   530 
   531     /* Find the first bit length which could increase: */
   532     do {
   533         bits = max_length-1;
   534         while (s->bl_count[bits] == 0) bits--;
   535         s->bl_count[bits]--;      /* move one leaf down the tree */
   536         s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
   537         s->bl_count[max_length]--;
   538         /* The brother of the overflow item also moves one step up,
   539          * but this does not affect bl_count[max_length]
   540          */
   541         overflow -= 2;
   542     } while (overflow > 0);
   543 
   544     /* Now recompute all bit lengths, scanning in increasing frequency.
   545      * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
   546      * lengths instead of fixing only the wrong ones. This idea is taken
   547      * from 'ar' written by Haruhiko Okumura.)
   548      */
   549     for (bits = max_length; bits != 0; bits--) {
   550         n = s->bl_count[bits];
   551         while (n != 0) {
   552             m = s->heap[--h];
   553             if (m > max_code) continue;
   554             if ((unsigned) tree[m].Len != (unsigned) bits) {
   555                 Tracev((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
   556                 s->opt_len += ((ulg)bits - tree[m].Len) * tree[m].Freq;
   557                 tree[m].Len = (ush)bits;
   558             }
   559             n--;
   560         }
   561     }
   562 }
   563 
   564 /* ===========================================================================
   565  * Generate the codes for a given tree and bit counts (which need not be
   566  * optimal).
   567  * IN assertion: the array bl_count contains the bit length statistics for
   568  * the given tree and the field len is set for all tree elements.
   569  * OUT assertion: the field code is set for all tree elements of non
   570  *     zero code length.
   571  */
   572 local void gen_codes (tree, max_code, bl_count)
   573     ct_data *tree;             /* the tree to decorate */
   574     int max_code;              /* largest code with non zero frequency */
   575     ushf *bl_count;            /* number of codes at each bit length */
   576 {
   577     ush next_code[MAX_BITS+1]; /* next code value for each bit length */
   578     unsigned code = 0;         /* running code value */
   579     int bits;                  /* bit index */
   580     int n;                     /* code index */
   581 
   582     /* The distribution counts are first used to generate the code values
   583      * without bit reversal.
   584      */
   585     for (bits = 1; bits <= MAX_BITS; bits++) {
   586         code = (code + bl_count[bits-1]) << 1;
   587         next_code[bits] = (ush)code;
   588     }
   589     /* Check that the bit counts in bl_count are consistent. The last code
   590      * must be all ones.
   591      */
   592     Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
   593             "inconsistent bit counts");
   594     Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
   595 
   596     for (n = 0;  n <= max_code; n++) {
   597         int len = tree[n].Len;
   598         if (len == 0) continue;
   599         /* Now reverse the bits */
   600         tree[n].Code = (ush)bi_reverse(next_code[len]++, len);
   601 
   602         Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
   603              n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
   604     }
   605 }
   606 
   607 /* ===========================================================================
   608  * Construct one Huffman tree and assigns the code bit strings and lengths.
   609  * Update the total bit length for the current block.
   610  * IN assertion: the field freq is set for all tree elements.
   611  * OUT assertions: the fields len and code are set to the optimal bit length
   612  *     and corresponding code. The length opt_len is updated; static_len is
   613  *     also updated if stree is not null. The field max_code is set.
   614  */
   615 local void build_tree(s, desc)
   616     deflate_state *s;
   617     tree_desc *desc; /* the tree descriptor */
   618 {
   619     ct_data *tree         = desc->dyn_tree;
   620     const ct_data *stree  = desc->stat_desc->static_tree;
   621     int elems             = desc->stat_desc->elems;
   622     int n, m;          /* iterate over heap elements */
   623     int max_code = -1; /* largest code with non zero frequency */
   624     int node;          /* new node being created */
   625 
   626     /* Construct the initial heap, with least frequent element in
   627      * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
   628      * heap[0] is not used.
   629      */
   630     s->heap_len = 0, s->heap_max = HEAP_SIZE;
   631 
   632     for (n = 0; n < elems; n++) {
   633         if (tree[n].Freq != 0) {
   634             s->heap[++(s->heap_len)] = max_code = n;
   635             s->depth[n] = 0;
   636         } else {
   637             tree[n].Len = 0;
   638         }
   639     }
   640 
   641     /* The pkzip format requires that at least one distance code exists,
   642      * and that at least one bit should be sent even if there is only one
   643      * possible code. So to avoid special checks later on we force at least
   644      * two codes of non zero frequency.
   645      */
   646     while (s->heap_len < 2) {
   647         node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
   648         tree[node].Freq = 1;
   649         s->depth[node] = 0;
   650         s->opt_len--; if (stree) s->static_len -= stree[node].Len;
   651         /* node is 0 or 1 so it does not have extra bits */
   652     }
   653     desc->max_code = max_code;
   654 
   655     /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
   656      * establish sub-heaps of increasing lengths:
   657      */
   658     for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
   659 
   660     /* Construct the Huffman tree by repeatedly combining the least two
   661      * frequent nodes.
   662      */
   663     node = elems;              /* next internal node of the tree */
   664     do {
   665         pqremove(s, tree, n);  /* n = node of least frequency */
   666         m = s->heap[SMALLEST]; /* m = node of next least frequency */
   667 
   668         s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
   669         s->heap[--(s->heap_max)] = m;
   670 
   671         /* Create a new node father of n and m */
   672         tree[node].Freq = tree[n].Freq + tree[m].Freq;
   673         s->depth[node] = (uch)((s->depth[n] >= s->depth[m] ?
   674                                 s->depth[n] : s->depth[m]) + 1);
   675         tree[n].Dad = tree[m].Dad = (ush)node;
   676 #ifdef DUMP_BL_TREE
   677         if (tree == s->bl_tree) {
   678             fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
   679                     node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
   680         }
   681 #endif
   682         /* and insert the new node in the heap */
   683         s->heap[SMALLEST] = node++;
   684         pqdownheap(s, tree, SMALLEST);
   685 
   686     } while (s->heap_len >= 2);
   687 
   688     s->heap[--(s->heap_max)] = s->heap[SMALLEST];
   689 
   690     /* At this point, the fields freq and dad are set. We can now
   691      * generate the bit lengths.
   692      */
   693     gen_bitlen(s, (tree_desc *)desc);
   694 
   695     /* The field len is now set, we can generate the bit codes */
   696     gen_codes ((ct_data *)tree, max_code, s->bl_count);
   697 }
   698 
   699 /* ===========================================================================
   700  * Scan a literal or distance tree to determine the frequencies of the codes
   701  * in the bit length tree.
   702  */
   703 local void scan_tree (s, tree, max_code)
   704     deflate_state *s;
   705     ct_data *tree;   /* the tree to be scanned */
   706     int max_code;    /* and its largest code of non zero frequency */
   707 {
   708     int n;                     /* iterates over all tree elements */
   709     int prevlen = -1;          /* last emitted length */
   710     int curlen;                /* length of current code */
   711     int nextlen = tree[0].Len; /* length of next code */
   712     int count = 0;             /* repeat count of the current code */
   713     int max_count = 7;         /* max repeat count */
   714     int min_count = 4;         /* min repeat count */
   715 
   716     if (nextlen == 0) max_count = 138, min_count = 3;
   717     tree[max_code+1].Len = (ush)0xffff; /* guard */
   718 
   719     for (n = 0; n <= max_code; n++) {
   720         curlen = nextlen; nextlen = tree[n+1].Len;
   721         if (++count < max_count && curlen == nextlen) {
   722             continue;
   723         } else if (count < min_count) {
   724             s->bl_tree[curlen].Freq += count;
   725         } else if (curlen != 0) {
   726             if (curlen != prevlen) s->bl_tree[curlen].Freq++;
   727             s->bl_tree[REP_3_6].Freq++;
   728         } else if (count <= 10) {
   729             s->bl_tree[REPZ_3_10].Freq++;
   730         } else {
   731             s->bl_tree[REPZ_11_138].Freq++;
   732         }
   733         count = 0; prevlen = curlen;
   734         if (nextlen == 0) {
   735             max_count = 138, min_count = 3;
   736         } else if (curlen == nextlen) {
   737             max_count = 6, min_count = 3;
   738         } else {
   739             max_count = 7, min_count = 4;
   740         }
   741     }
   742 }
   743 
   744 /* ===========================================================================
   745  * Send a literal or distance tree in compressed form, using the codes in
   746  * bl_tree.
   747  */
   748 local void send_tree (s, tree, max_code)
   749     deflate_state *s;
   750     ct_data *tree; /* the tree to be scanned */
   751     int max_code;       /* and its largest code of non zero frequency */
   752 {
   753     int n;                     /* iterates over all tree elements */
   754     int prevlen = -1;          /* last emitted length */
   755     int curlen;                /* length of current code */
   756     int nextlen = tree[0].Len; /* length of next code */
   757     int count = 0;             /* repeat count of the current code */
   758     int max_count = 7;         /* max repeat count */
   759     int min_count = 4;         /* min repeat count */
   760 
   761     /* tree[max_code+1].Len = -1; */  /* guard already set */
   762     if (nextlen == 0) max_count = 138, min_count = 3;
   763 
   764     for (n = 0; n <= max_code; n++) {
   765         curlen = nextlen; nextlen = tree[n+1].Len;
   766         if (++count < max_count && curlen == nextlen) {
   767             continue;
   768         } else if (count < min_count) {
   769             do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
   770 
   771         } else if (curlen != 0) {
   772             if (curlen != prevlen) {
   773                 send_code(s, curlen, s->bl_tree); count--;
   774             }
   775             Assert(count >= 3 && count <= 6, " 3_6?");
   776             send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
   777 
   778         } else if (count <= 10) {
   779             send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
   780 
   781         } else {
   782             send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
   783         }
   784         count = 0; prevlen = curlen;
   785         if (nextlen == 0) {
   786             max_count = 138, min_count = 3;
   787         } else if (curlen == nextlen) {
   788             max_count = 6, min_count = 3;
   789         } else {
   790             max_count = 7, min_count = 4;
   791         }
   792     }
   793 }
   794 
   795 /* ===========================================================================
   796  * Construct the Huffman tree for the bit lengths and return the index in
   797  * bl_order of the last bit length code to send.
   798  */
   799 local int build_bl_tree(s)
   800     deflate_state *s;
   801 {
   802     int max_blindex;  /* index of last bit length code of non zero freq */
   803 
   804     /* Determine the bit length frequencies for literal and distance trees */
   805     scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
   806     scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
   807 
   808     /* Build the bit length tree: */
   809     build_tree(s, (tree_desc *)(&(s->bl_desc)));
   810     /* opt_len now includes the length of the tree representations, except
   811      * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
   812      */
   813 
   814     /* Determine the number of bit length codes to send. The pkzip format
   815      * requires that at least 4 bit length codes be sent. (appnote.txt says
   816      * 3 but the actual value used is 4.)
   817      */
   818     for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
   819         if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
   820     }
   821     /* Update opt_len to include the bit length tree and counts */
   822     s->opt_len += 3*((ulg)max_blindex+1) + 5+5+4;
   823     Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
   824             s->opt_len, s->static_len));
   825 
   826     return max_blindex;
   827 }
   828 
   829 /* ===========================================================================
   830  * Send the header for a block using dynamic Huffman trees: the counts, the
   831  * lengths of the bit length codes, the literal tree and the distance tree.
   832  * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
   833  */
   834 local void send_all_trees(s, lcodes, dcodes, blcodes)
   835     deflate_state *s;
   836     int lcodes, dcodes, blcodes; /* number of codes for each tree */
   837 {
   838     int rank;                    /* index in bl_order */
   839 
   840     Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
   841     Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
   842             "too many codes");
   843     Tracev((stderr, "\nbl counts: "));
   844     send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
   845     send_bits(s, dcodes-1,   5);
   846     send_bits(s, blcodes-4,  4); /* not -3 as stated in appnote.txt */
   847     for (rank = 0; rank < blcodes; rank++) {
   848         Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
   849         send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
   850     }
   851     Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
   852 
   853     send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
   854     Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
   855 
   856     send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
   857     Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
   858 }
   859 
   860 /* ===========================================================================
   861  * Send a stored block
   862  */
   863 void ZLIB_INTERNAL _tr_stored_block(s, buf, stored_len, last)
   864     deflate_state *s;
   865     charf *buf;       /* input block */
   866     ulg stored_len;   /* length of input block */
   867     int last;         /* one if this is the last block for a file */
   868 {
   869     send_bits(s, (STORED_BLOCK<<1)+last, 3);    /* send block type */
   870     bi_windup(s);        /* align on byte boundary */
   871     put_short(s, (ush)stored_len);
   872     put_short(s, (ush)~stored_len);
   873     zmemcpy(s->pending_buf + s->pending, (Bytef *)buf, stored_len);
   874     s->pending += stored_len;
   875 #ifdef ZLIB_DEBUG
   876     s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
   877     s->compressed_len += (stored_len + 4) << 3;
   878     s->bits_sent += 2*16;
   879     s->bits_sent += stored_len<<3;
   880 #endif
   881 }
   882 
   883 /* ===========================================================================
   884  * Flush the bits in the bit buffer to pending output (leaves at most 7 bits)
   885  */
   886 void ZLIB_INTERNAL _tr_flush_bits(s)
   887     deflate_state *s;
   888 {
   889     bi_flush(s);
   890 }
   891 
   892 /* ===========================================================================
   893  * Send one empty static block to give enough lookahead for inflate.
   894  * This takes 10 bits, of which 7 may remain in the bit buffer.
   895  */
   896 void ZLIB_INTERNAL _tr_align(s)
   897     deflate_state *s;
   898 {
   899     send_bits(s, STATIC_TREES<<1, 3);
   900     send_code(s, END_BLOCK, static_ltree);
   901 #ifdef ZLIB_DEBUG
   902     s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
   903 #endif
   904     bi_flush(s);
   905 }
   906 
   907 /* ===========================================================================
   908  * Determine the best encoding for the current block: dynamic trees, static
   909  * trees or store, and write out the encoded block.
   910  */
   911 void ZLIB_INTERNAL _tr_flush_block(s, buf, stored_len, last)
   912     deflate_state *s;
   913     charf *buf;       /* input block, or NULL if too old */
   914     ulg stored_len;   /* length of input block */
   915     int last;         /* one if this is the last block for a file */
   916 {
   917     ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
   918     int max_blindex = 0;  /* index of last bit length code of non zero freq */
   919 
   920     /* Build the Huffman trees unless a stored block is forced */
   921     if (s->level > 0) {
   922 
   923         /* Check if the file is binary or text */
   924         if (s->strm->data_type == Z_UNKNOWN)
   925             s->strm->data_type = detect_data_type(s);
   926 
   927         /* Construct the literal and distance trees */
   928         build_tree(s, (tree_desc *)(&(s->l_desc)));
   929         Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
   930                 s->static_len));
   931 
   932         build_tree(s, (tree_desc *)(&(s->d_desc)));
   933         Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
   934                 s->static_len));
   935         /* At this point, opt_len and static_len are the total bit lengths of
   936          * the compressed block data, excluding the tree representations.
   937          */
   938 
   939         /* Build the bit length tree for the above two trees, and get the index
   940          * in bl_order of the last bit length code to send.
   941          */
   942         max_blindex = build_bl_tree(s);
   943 
   944         /* Determine the best encoding. Compute the block lengths in bytes. */
   945         opt_lenb = (s->opt_len+3+7)>>3;
   946         static_lenb = (s->static_len+3+7)>>3;
   947 
   948         Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
   949                 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
   950                 s->last_lit));
   951 
   952         if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
   953 
   954     } else {
   955         Assert(buf != (char*)0, "lost buf");
   956         opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
   957     }
   958 
   959 #ifdef FORCE_STORED
   960     if (buf != (char*)0) { /* force stored block */
   961 #else
   962     if (stored_len+4 <= opt_lenb && buf != (char*)0) {
   963                        /* 4: two words for the lengths */
   964 #endif
   965         /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
   966          * Otherwise we can't have processed more than WSIZE input bytes since
   967          * the last block flush, because compression would have been
   968          * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
   969          * transform a block into a stored block.
   970          */
   971         _tr_stored_block(s, buf, stored_len, last);
   972 
   973 #ifdef FORCE_STATIC
   974     } else if (static_lenb >= 0) { /* force static trees */
   975 #else
   976     } else if (s->strategy == Z_FIXED || static_lenb == opt_lenb) {
   977 #endif
   978         send_bits(s, (STATIC_TREES<<1)+last, 3);
   979         compress_block(s, (const ct_data *)static_ltree,
   980                        (const ct_data *)static_dtree);
   981 #ifdef ZLIB_DEBUG
   982         s->compressed_len += 3 + s->static_len;
   983 #endif
   984     } else {
   985         send_bits(s, (DYN_TREES<<1)+last, 3);
   986         send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
   987                        max_blindex+1);
   988         compress_block(s, (const ct_data *)s->dyn_ltree,
   989                        (const ct_data *)s->dyn_dtree);
   990 #ifdef ZLIB_DEBUG
   991         s->compressed_len += 3 + s->opt_len;
   992 #endif
   993     }
   994     Assert (s->compressed_len == s->bits_sent, "bad compressed size");
   995     /* The above check is made mod 2^32, for files larger than 512 MB
   996      * and uLong implemented on 32 bits.
   997      */
   998     init_block(s);
   999 
  1000     if (last) {
  1001         bi_windup(s);
  1002 #ifdef ZLIB_DEBUG
  1003         s->compressed_len += 7;  /* align on byte boundary */
  1004 #endif
  1005     }
  1006     Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
  1007            s->compressed_len-7*last));
  1008 }
  1009 
  1010 /* ===========================================================================
  1011  * Save the match info and tally the frequency counts. Return true if
  1012  * the current block must be flushed.
  1013  */
  1014 int ZLIB_INTERNAL _tr_tally (s, dist, lc)
  1015     deflate_state *s;
  1016     unsigned dist;  /* distance of matched string */
  1017     unsigned lc;    /* match length-MIN_MATCH or unmatched char (if dist==0) */
  1018 {
  1019     s->d_buf[s->last_lit] = (ush)dist;
  1020     s->l_buf[s->last_lit++] = (uch)lc;
  1021     if (dist == 0) {
  1022         /* lc is the unmatched char */
  1023         s->dyn_ltree[lc].Freq++;
  1024     } else {
  1025         s->matches++;
  1026         /* Here, lc is the match length - MIN_MATCH */
  1027         dist--;             /* dist = match distance - 1 */
  1028         Assert((ush)dist < (ush)MAX_DIST(s) &&
  1029                (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
  1030                (ush)d_code(dist) < (ush)D_CODES,  "_tr_tally: bad match");
  1031 
  1032         s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
  1033         s->dyn_dtree[d_code(dist)].Freq++;
  1034     }
  1035 
  1036 #ifdef TRUNCATE_BLOCK
  1037     /* Try to guess if it is profitable to stop the current block here */
  1038     if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
  1039         /* Compute an upper bound for the compressed length */
  1040         ulg out_length = (ulg)s->last_lit*8L;
  1041         ulg in_length = (ulg)((long)s->strstart - s->block_start);
  1042         int dcode;
  1043         for (dcode = 0; dcode < D_CODES; dcode++) {
  1044             out_length += (ulg)s->dyn_dtree[dcode].Freq *
  1045                 (5L+extra_dbits[dcode]);
  1046         }
  1047         out_length >>= 3;
  1048         Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
  1049                s->last_lit, in_length, out_length,
  1050                100L - out_length*100L/in_length));
  1051         if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
  1052     }
  1053 #endif
  1054     return (s->last_lit == s->lit_bufsize-1);
  1055     /* We avoid equality with lit_bufsize because of wraparound at 64K
  1056      * on 16 bit machines and because stored blocks are restricted to
  1057      * 64K-1 bytes.
  1058      */
  1059 }
  1060 
  1061 /* ===========================================================================
  1062  * Send the block data compressed using the given Huffman trees
  1063  */
  1064 local void compress_block(s, ltree, dtree)
  1065     deflate_state *s;
  1066     const ct_data *ltree; /* literal tree */
  1067     const ct_data *dtree; /* distance tree */
  1068 {
  1069     unsigned dist;      /* distance of matched string */
  1070     int lc;             /* match length or unmatched char (if dist == 0) */
  1071     unsigned lx = 0;    /* running index in l_buf */
  1072     unsigned code;      /* the code to send */
  1073     int extra;          /* number of extra bits to send */
  1074 
  1075     if (s->last_lit != 0) do {
  1076         dist = s->d_buf[lx];
  1077         lc = s->l_buf[lx++];
  1078         if (dist == 0) {
  1079             send_code(s, lc, ltree); /* send a literal byte */
  1080             Tracecv(isgraph(lc), (stderr," '%c' ", lc));
  1081         } else {
  1082             /* Here, lc is the match length - MIN_MATCH */
  1083             code = _length_code[lc];
  1084             send_code(s, code+LITERALS+1, ltree); /* send the length code */
  1085             extra = extra_lbits[code];
  1086             if (extra != 0) {
  1087                 lc -= base_length[code];
  1088                 send_bits(s, lc, extra);       /* send the extra length bits */
  1089             }
  1090             dist--; /* dist is now the match distance - 1 */
  1091             code = d_code(dist);
  1092             Assert (code < D_CODES, "bad d_code");
  1093 
  1094             send_code(s, code, dtree);       /* send the distance code */
  1095             extra = extra_dbits[code];
  1096             if (extra != 0) {
  1097                 dist -= (unsigned)base_dist[code];
  1098                 send_bits(s, dist, extra);   /* send the extra distance bits */
  1099             }
  1100         } /* literal or match pair ? */
  1101 
  1102         /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
  1103         Assert((uInt)(s->pending) < s->lit_bufsize + 2*lx,
  1104                "pendingBuf overflow");
  1105 
  1106     } while (lx < s->last_lit);
  1107 
  1108     send_code(s, END_BLOCK, ltree);
  1109 }
  1110 
  1111 /* ===========================================================================
  1112  * Check if the data type is TEXT or BINARY, using the following algorithm:
  1113  * - TEXT if the two conditions below are satisfied:
  1114  *    a) There are no non-portable control characters belonging to the
  1115  *       "black list" (0..6, 14..25, 28..31).
  1116  *    b) There is at least one printable character belonging to the
  1117  *       "white list" (9 {TAB}, 10 {LF}, 13 {CR}, 32..255).
  1118  * - BINARY otherwise.
  1119  * - The following partially-portable control characters form a
  1120  *   "gray list" that is ignored in this detection algorithm:
  1121  *   (7 {BEL}, 8 {BS}, 11 {VT}, 12 {FF}, 26 {SUB}, 27 {ESC}).
  1122  * IN assertion: the fields Freq of dyn_ltree are set.
  1123  */
  1124 local int detect_data_type(s)
  1125     deflate_state *s;
  1126 {
  1127     /* black_mask is the bit mask of black-listed bytes
  1128      * set bits 0..6, 14..25, and 28..31
  1129      * 0xf3ffc07f = binary 11110011111111111100000001111111
  1130      */
  1131     unsigned long black_mask = 0xf3ffc07fUL;
  1132     int n;
  1133 
  1134     /* Check for non-textual ("black-listed") bytes. */
  1135     for (n = 0; n <= 31; n++, black_mask >>= 1)
  1136         if ((black_mask & 1) && (s->dyn_ltree[n].Freq != 0))
  1137             return Z_BINARY;
  1138 
  1139     /* Check for textual ("white-listed") bytes. */
  1140     if (s->dyn_ltree[9].Freq != 0 || s->dyn_ltree[10].Freq != 0
  1141             || s->dyn_ltree[13].Freq != 0)
  1142         return Z_TEXT;
  1143     for (n = 32; n < LITERALS; n++)
  1144         if (s->dyn_ltree[n].Freq != 0)
  1145             return Z_TEXT;
  1146 
  1147     /* There are no "black-listed" or "white-listed" bytes:
  1148      * this stream either is empty or has tolerated ("gray-listed") bytes only.
  1149      */
  1150     return Z_BINARY;
  1151 }
  1152 
  1153 /* ===========================================================================
  1154  * Reverse the first len bits of a code, using straightforward code (a faster
  1155  * method would use a table)
  1156  * IN assertion: 1 <= len <= 15
  1157  */
  1158 local unsigned bi_reverse(code, len)
  1159     unsigned code; /* the value to invert */
  1160     int len;       /* its bit length */
  1161 {
  1162     register unsigned res = 0;
  1163     do {
  1164         res |= code & 1;
  1165         code >>= 1, res <<= 1;
  1166     } while (--len > 0);
  1167     return res >> 1;
  1168 }
  1169 
  1170 /* ===========================================================================
  1171  * Flush the bit buffer, keeping at most 7 bits in it.
  1172  */
  1173 local void bi_flush(s)
  1174     deflate_state *s;
  1175 {
  1176     if (s->bi_valid == 16) {
  1177         put_short(s, s->bi_buf);
  1178         s->bi_buf = 0;
  1179         s->bi_valid = 0;
  1180     } else if (s->bi_valid >= 8) {
  1181         put_byte(s, (Byte)s->bi_buf);
  1182         s->bi_buf >>= 8;
  1183         s->bi_valid -= 8;
  1184     }
  1185 }
  1186 
  1187 /* ===========================================================================
  1188  * Flush the bit buffer and align the output on a byte boundary
  1189  */
  1190 local void bi_windup(s)
  1191     deflate_state *s;
  1192 {
  1193     if (s->bi_valid > 8) {
  1194         put_short(s, s->bi_buf);
  1195     } else if (s->bi_valid > 0) {
  1196         put_byte(s, (Byte)s->bi_buf);
  1197     }
  1198     s->bi_buf = 0;
  1199     s->bi_valid = 0;
  1200 #ifdef ZLIB_DEBUG
  1201     s->bits_sent = (s->bits_sent+7) & ~7;
  1202 #endif
  1203 }