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    1 /* trees.c -- output deflated data using Huffman coding
    2  * Copyright (C) 1995-2010 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 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 #define Buf_size (8 * 2*sizeof(char))
   78 /* Number of bits used within bi_buf. (bi_buf might be implemented on
   79  * more than 16 bits on some systems.)
   80  */
   81 
   82 /* ===========================================================================
   83  * Local data. These are initialized only once.
   84  */
   85 
   86 #define DIST_CODE_LEN  512 /* see definition of array dist_code below */
   87 
   88 #if defined(GEN_TREES_H) || !defined(STDC)
   89 /* non ANSI compilers may not accept trees.h */
   90 
   91 local ct_data static_ltree[L_CODES+2];
   92 /* The static literal tree. Since the bit lengths are imposed, there is no
   93  * need for the L_CODES extra codes used during heap construction. However
   94  * The codes 286 and 287 are needed to build a canonical tree (see _tr_init
   95  * below).
   96  */
   97 
   98 local ct_data static_dtree[D_CODES];
   99 /* The static distance tree. (Actually a trivial tree since all codes use
  100  * 5 bits.)
  101  */
  102 
  103 uch _dist_code[DIST_CODE_LEN];
  104 /* Distance codes. The first 256 values correspond to the distances
  105  * 3 .. 258, the last 256 values correspond to the top 8 bits of
  106  * the 15 bit distances.
  107  */
  108 
  109 uch _length_code[MAX_MATCH-MIN_MATCH+1];
  110 /* length code for each normalized match length (0 == MIN_MATCH) */
  111 
  112 local int base_length[LENGTH_CODES];
  113 /* First normalized length for each code (0 = MIN_MATCH) */
  114 
  115 local int base_dist[D_CODES];
  116 /* First normalized distance for each code (0 = distance of 1) */
  117 
  118 #else
  119 #  include "trees.h"
  120 #endif /* GEN_TREES_H */
  121 
  122 struct static_tree_desc_s {
  123     const ct_data *static_tree;  /* static tree or NULL */
  124     const intf *extra_bits;      /* extra bits for each code or NULL */
  125     int     extra_base;          /* base index for extra_bits */
  126     int     elems;               /* max number of elements in the tree */
  127     int     max_length;          /* max bit length for the codes */
  128 };
  129 
  130 local static_tree_desc  static_l_desc =
  131 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
  132 
  133 local static_tree_desc  static_d_desc =
  134 {static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};
  135 
  136 local static_tree_desc  static_bl_desc =
  137 {(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};
  138 
  139 /* ===========================================================================
  140  * Local (static) routines in this file.
  141  */
  142 
  143 local void tr_static_init OF((void));
  144 local void init_block     OF((deflate_state *s));
  145 local void pqdownheap     OF((deflate_state *s, ct_data *tree, int k));
  146 local void gen_bitlen     OF((deflate_state *s, tree_desc *desc));
  147 local void gen_codes      OF((ct_data *tree, int max_code, ushf *bl_count));
  148 local void build_tree     OF((deflate_state *s, tree_desc *desc));
  149 local void scan_tree      OF((deflate_state *s, ct_data *tree, int max_code));
  150 local void send_tree      OF((deflate_state *s, ct_data *tree, int max_code));
  151 local int  build_bl_tree  OF((deflate_state *s));
  152 local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
  153                               int blcodes));
  154 local void compress_block OF((deflate_state *s, ct_data *ltree,
  155                               ct_data *dtree));
  156 local int  detect_data_type OF((deflate_state *s));
  157 local unsigned bi_reverse OF((unsigned value, int length));
  158 local void bi_windup      OF((deflate_state *s));
  159 local void bi_flush       OF((deflate_state *s));
  160 local void copy_block     OF((deflate_state *s, charf *buf, unsigned len,
  161                               int header));
  162 
  163 #ifdef GEN_TREES_H
  164 local void gen_trees_header OF((void));
  165 #endif
  166 
  167 #ifndef DEBUG
  168 #  define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
  169    /* Send a code of the given tree. c and tree must not have side effects */
  170 
  171 #else /* DEBUG */
  172 #  define send_code(s, c, tree) \
  173      { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
  174        send_bits(s, tree[c].Code, tree[c].Len); }
  175 #endif
  176 
  177 /* ===========================================================================
  178  * Output a short LSB first on the stream.
  179  * IN assertion: there is enough room in pendingBuf.
  180  */
  181 #define put_short(s, w) { \
  182     put_byte(s, (uch)((w) & 0xff)); \
  183     put_byte(s, (uch)((ush)(w) >> 8)); \
  184 }
  185 
  186 /* ===========================================================================
  187  * Send a value on a given number of bits.
  188  * IN assertion: length <= 16 and value fits in length bits.
  189  */
  190 #ifdef DEBUG
  191 local void send_bits      OF((deflate_state *s, int value, int length));
  192 
  193 local void send_bits(s, value, length)
  194     deflate_state *s;
  195     int value;  /* value to send */
  196     int length; /* number of bits */
  197 {
  198     Tracevv((stderr," l %2d v %4x ", length, value));
  199     Assert(length > 0 && length <= 15, "invalid length");
  200     s->bits_sent += (ulg)length;
  201 
  202     /* If not enough room in bi_buf, use (valid) bits from bi_buf and
  203      * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
  204      * unused bits in value.
  205      */
  206     if (s->bi_valid > (int)Buf_size - length) {
  207         s->bi_buf |= (ush)value << s->bi_valid;
  208         put_short(s, s->bi_buf);
  209         s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
  210         s->bi_valid += length - Buf_size;
  211     } else {
  212         s->bi_buf |= (ush)value << s->bi_valid;
  213         s->bi_valid += length;
  214     }
  215 }
  216 #else /* !DEBUG */
  217 
  218 #define send_bits(s, value, length) \
  219 { int len = length;\
  220   if (s->bi_valid > (int)Buf_size - len) {\
  221     int val = value;\
  222     s->bi_buf |= (ush)val << s->bi_valid;\
  223     put_short(s, s->bi_buf);\
  224     s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
  225     s->bi_valid += len - Buf_size;\
  226   } else {\
  227     s->bi_buf |= (ush)(value) << s->bi_valid;\
  228     s->bi_valid += len;\
  229   }\
  230 }
  231 #endif /* DEBUG */
  232 
  233 
  234 /* the arguments must not have side effects */
  235 
  236 /* ===========================================================================
  237  * Initialize the various 'constant' tables.
  238  */
  239 local void tr_static_init()
  240 {
  241 #if defined(GEN_TREES_H) || !defined(STDC)
  242     static int static_init_done = 0;
  243     int n;        /* iterates over tree elements */
  244     int bits;     /* bit counter */
  245     int length;   /* length value */
  246     int code;     /* code value */
  247     int dist;     /* distance index */
  248     ush bl_count[MAX_BITS+1];
  249     /* number of codes at each bit length for an optimal tree */
  250 
  251     if (static_init_done) return;
  252 
  253     /* For some embedded targets, global variables are not initialized: */
  254 #ifdef NO_INIT_GLOBAL_POINTERS
  255     static_l_desc.static_tree = static_ltree;
  256     static_l_desc.extra_bits = extra_lbits;
  257     static_d_desc.static_tree = static_dtree;
  258     static_d_desc.extra_bits = extra_dbits;
  259     static_bl_desc.extra_bits = extra_blbits;
  260 #endif
  261 
  262     /* Initialize the mapping length (0..255) -> length code (0..28) */
  263     length = 0;
  264     for (code = 0; code < LENGTH_CODES-1; code++) {
  265         base_length[code] = length;
  266         for (n = 0; n < (1<<extra_lbits[code]); n++) {
  267             _length_code[length++] = (uch)code;
  268         }
  269     }
  270     Assert (length == 256, "tr_static_init: length != 256");
  271     /* Note that the length 255 (match length 258) can be represented
  272      * in two different ways: code 284 + 5 bits or code 285, so we
  273      * overwrite length_code[255] to use the best encoding:
  274      */
  275     _length_code[length-1] = (uch)code;
  276 
  277     /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
  278     dist = 0;
  279     for (code = 0 ; code < 16; code++) {
  280         base_dist[code] = dist;
  281         for (n = 0; n < (1<<extra_dbits[code]); n++) {
  282             _dist_code[dist++] = (uch)code;
  283         }
  284     }
  285     Assert (dist == 256, "tr_static_init: dist != 256");
  286     dist >>= 7; /* from now on, all distances are divided by 128 */
  287     for ( ; code < D_CODES; code++) {
  288         base_dist[code] = dist << 7;
  289         for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
  290             _dist_code[256 + dist++] = (uch)code;
  291         }
  292     }
  293     Assert (dist == 256, "tr_static_init: 256+dist != 512");
  294 
  295     /* Construct the codes of the static literal tree */
  296     for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
  297     n = 0;
  298     while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
  299     while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
  300     while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
  301     while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
  302     /* Codes 286 and 287 do not exist, but we must include them in the
  303      * tree construction to get a canonical Huffman tree (longest code
  304      * all ones)
  305      */
  306     gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
  307 
  308     /* The static distance tree is trivial: */
  309     for (n = 0; n < D_CODES; n++) {
  310         static_dtree[n].Len = 5;
  311         static_dtree[n].Code = bi_reverse((unsigned)n, 5);
  312     }
  313     static_init_done = 1;
  314 
  315 #  ifdef GEN_TREES_H
  316     gen_trees_header();
  317 #  endif
  318 #endif /* defined(GEN_TREES_H) || !defined(STDC) */
  319 }
  320 
  321 /* ===========================================================================
  322  * Genererate the file trees.h describing the static trees.
  323  */
  324 #ifdef GEN_TREES_H
  325 #  ifndef DEBUG
  326 #    include <stdio.h>
  327 #  endif
  328 
  329 #  define SEPARATOR(i, last, width) \
  330       ((i) == (last)? "\n};\n\n" :    \
  331        ((i) % (width) == (width)-1 ? ",\n" : ", "))
  332 
  333 void gen_trees_header()
  334 {
  335     FILE *header = fopen("trees.h", "w");
  336     int i;
  337 
  338     Assert (header != NULL, "Can't open trees.h");
  339     fprintf(header,
  340             "/* header created automatically with -DGEN_TREES_H */\n\n");
  341 
  342     fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");
  343     for (i = 0; i < L_CODES+2; i++) {
  344         fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,
  345                 static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
  346     }
  347 
  348     fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");
  349     for (i = 0; i < D_CODES; i++) {
  350         fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,
  351                 static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
  352     }
  353 
  354     fprintf(header, "const uch ZLIB_INTERNAL _dist_code[DIST_CODE_LEN] = {\n");
  355     for (i = 0; i < DIST_CODE_LEN; i++) {
  356         fprintf(header, "%2u%s", _dist_code[i],
  357                 SEPARATOR(i, DIST_CODE_LEN-1, 20));
  358     }
  359 
  360     fprintf(header,
  361         "const uch ZLIB_INTERNAL _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");
  362     for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {
  363         fprintf(header, "%2u%s", _length_code[i],
  364                 SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
  365     }
  366 
  367     fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");
  368     for (i = 0; i < LENGTH_CODES; i++) {
  369         fprintf(header, "%1u%s", base_length[i],
  370                 SEPARATOR(i, LENGTH_CODES-1, 20));
  371     }
  372 
  373     fprintf(header, "local const int base_dist[D_CODES] = {\n");
  374     for (i = 0; i < D_CODES; i++) {
  375         fprintf(header, "%5u%s", base_dist[i],
  376                 SEPARATOR(i, D_CODES-1, 10));
  377     }
  378 
  379     fclose(header);
  380 }
  381 #endif /* GEN_TREES_H */
  382 
  383 /* ===========================================================================
  384  * Initialize the tree data structures for a new zlib stream.
  385  */
  386 void ZLIB_INTERNAL _tr_init(s)
  387     deflate_state *s;
  388 {
  389     tr_static_init();
  390 
  391     s->l_desc.dyn_tree = s->dyn_ltree;
  392     s->l_desc.stat_desc = &static_l_desc;
  393 
  394     s->d_desc.dyn_tree = s->dyn_dtree;
  395     s->d_desc.stat_desc = &static_d_desc;
  396 
  397     s->bl_desc.dyn_tree = s->bl_tree;
  398     s->bl_desc.stat_desc = &static_bl_desc;
  399 
  400     s->bi_buf = 0;
  401     s->bi_valid = 0;
  402     s->last_eob_len = 8; /* enough lookahead for inflate */
  403 #ifdef DEBUG
  404     s->compressed_len = 0L;
  405     s->bits_sent = 0L;
  406 #endif
  407 
  408     /* Initialize the first block of the first file: */
  409     init_block(s);
  410 }
  411 
  412 /* ===========================================================================
  413  * Initialize a new block.
  414  */
  415 local void init_block(s)
  416     deflate_state *s;
  417 {
  418     int n; /* iterates over tree elements */
  419 
  420     /* Initialize the trees. */
  421     for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
  422     for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
  423     for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
  424 
  425     s->dyn_ltree[END_BLOCK].Freq = 1;
  426     s->opt_len = s->static_len = 0L;
  427     s->last_lit = s->matches = 0;
  428 }
  429 
  430 #define SMALLEST 1
  431 /* Index within the heap array of least frequent node in the Huffman tree */
  432 
  433 
  434 /* ===========================================================================
  435  * Remove the smallest element from the heap and recreate the heap with
  436  * one less element. Updates heap and heap_len.
  437  */
  438 #define pqremove(s, tree, top) \
  439 {\
  440     top = s->heap[SMALLEST]; \
  441     s->heap[SMALLEST] = s->heap[s->heap_len--]; \
  442     pqdownheap(s, tree, SMALLEST); \
  443 }
  444 
  445 /* ===========================================================================
  446  * Compares to subtrees, using the tree depth as tie breaker when
  447  * the subtrees have equal frequency. This minimizes the worst case length.
  448  */
  449 #define smaller(tree, n, m, depth) \
  450    (tree[n].Freq < tree[m].Freq || \
  451    (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
  452 
  453 /* ===========================================================================
  454  * Restore the heap property by moving down the tree starting at node k,
  455  * exchanging a node with the smallest of its two sons if necessary, stopping
  456  * when the heap property is re-established (each father smaller than its
  457  * two sons).
  458  */
  459 local void pqdownheap(s, tree, k)
  460     deflate_state *s;
  461     ct_data *tree;  /* the tree to restore */
  462     int k;               /* node to move down */
  463 {
  464     int v = s->heap[k];
  465     int j = k << 1;  /* left son of k */
  466     while (j <= s->heap_len) {
  467         /* Set j to the smallest of the two sons: */
  468         if (j < s->heap_len &&
  469             smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
  470             j++;
  471         }
  472         /* Exit if v is smaller than both sons */
  473         if (smaller(tree, v, s->heap[j], s->depth)) break;
  474 
  475         /* Exchange v with the smallest son */
  476         s->heap[k] = s->heap[j];  k = j;
  477 
  478         /* And continue down the tree, setting j to the left son of k */
  479         j <<= 1;
  480     }
  481     s->heap[k] = v;
  482 }
  483 
  484 /* ===========================================================================
  485  * Compute the optimal bit lengths for a tree and update the total bit length
  486  * for the current block.
  487  * IN assertion: the fields freq and dad are set, heap[heap_max] and
  488  *    above are the tree nodes sorted by increasing frequency.
  489  * OUT assertions: the field len is set to the optimal bit length, the
  490  *     array bl_count contains the frequencies for each bit length.
  491  *     The length opt_len is updated; static_len is also updated if stree is
  492  *     not null.
  493  */
  494 local void gen_bitlen(s, desc)
  495     deflate_state *s;
  496     tree_desc *desc;    /* the tree descriptor */
  497 {
  498     ct_data *tree        = desc->dyn_tree;
  499     int max_code         = desc->max_code;
  500     const ct_data *stree = desc->stat_desc->static_tree;
  501     const intf *extra    = desc->stat_desc->extra_bits;
  502     int base             = desc->stat_desc->extra_base;
  503     int max_length       = desc->stat_desc->max_length;
  504     int h;              /* heap index */
  505     int n, m;           /* iterate over the tree elements */
  506     int bits;           /* bit length */
  507     int xbits;          /* extra bits */
  508     ush f;              /* frequency */
  509     int overflow = 0;   /* number of elements with bit length too large */
  510 
  511     for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
  512 
  513     /* In a first pass, compute the optimal bit lengths (which may
  514      * overflow in the case of the bit length tree).
  515      */
  516     tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
  517 
  518     for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
  519         n = s->heap[h];
  520         bits = tree[tree[n].Dad].Len + 1;
  521         if (bits > max_length) bits = max_length, overflow++;
  522         tree[n].Len = (ush)bits;
  523         /* We overwrite tree[n].Dad which is no longer needed */
  524 
  525         if (n > max_code) continue; /* not a leaf node */
  526 
  527         s->bl_count[bits]++;
  528         xbits = 0;
  529         if (n >= base) xbits = extra[n-base];
  530         f = tree[n].Freq;
  531         s->opt_len += (ulg)f * (bits + xbits);
  532         if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
  533     }
  534     if (overflow == 0) return;
  535 
  536     Trace((stderr,"\nbit length overflow\n"));
  537     /* This happens for example on obj2 and pic of the Calgary corpus */
  538 
  539     /* Find the first bit length which could increase: */
  540     do {
  541         bits = max_length-1;
  542         while (s->bl_count[bits] == 0) bits--;
  543         s->bl_count[bits]--;      /* move one leaf down the tree */
  544         s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
  545         s->bl_count[max_length]--;
  546         /* The brother of the overflow item also moves one step up,
  547          * but this does not affect bl_count[max_length]
  548          */
  549         overflow -= 2;
  550     } while (overflow > 0);
  551 
  552     /* Now recompute all bit lengths, scanning in increasing frequency.
  553      * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
  554      * lengths instead of fixing only the wrong ones. This idea is taken
  555      * from 'ar' written by Haruhiko Okumura.)
  556      */
  557     for (bits = max_length; bits != 0; bits--) {
  558         n = s->bl_count[bits];
  559         while (n != 0) {
  560             m = s->heap[--h];
  561             if (m > max_code) continue;
  562             if ((unsigned) tree[m].Len != (unsigned) bits) {
  563                 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
  564                 s->opt_len += ((long)bits - (long)tree[m].Len)
  565                               *(long)tree[m].Freq;
  566                 tree[m].Len = (ush)bits;
  567             }
  568             n--;
  569         }
  570     }
  571 }
  572 
  573 /* ===========================================================================
  574  * Generate the codes for a given tree and bit counts (which need not be
  575  * optimal).
  576  * IN assertion: the array bl_count contains the bit length statistics for
  577  * the given tree and the field len is set for all tree elements.
  578  * OUT assertion: the field code is set for all tree elements of non
  579  *     zero code length.
  580  */
  581 local void gen_codes (tree, max_code, bl_count)
  582     ct_data *tree;             /* the tree to decorate */
  583     int max_code;              /* largest code with non zero frequency */
  584     ushf *bl_count;            /* number of codes at each bit length */
  585 {
  586     ush next_code[MAX_BITS+1]; /* next code value for each bit length */
  587     ush code = 0;              /* running code value */
  588     int bits;                  /* bit index */
  589     int n;                     /* code index */
  590 
  591     /* The distribution counts are first used to generate the code values
  592      * without bit reversal.
  593      */
  594     for (bits = 1; bits <= MAX_BITS; bits++) {
  595         next_code[bits] = code = (code + bl_count[bits-1]) << 1;
  596     }
  597     /* Check that the bit counts in bl_count are consistent. The last code
  598      * must be all ones.
  599      */
  600     Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
  601             "inconsistent bit counts");
  602     Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
  603 
  604     for (n = 0;  n <= max_code; n++) {
  605         int len = tree[n].Len;
  606         if (len == 0) continue;
  607         /* Now reverse the bits */
  608         tree[n].Code = bi_reverse(next_code[len]++, len);
  609 
  610         Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
  611              n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
  612     }
  613 }
  614 
  615 /* ===========================================================================
  616  * Construct one Huffman tree and assigns the code bit strings and lengths.
  617  * Update the total bit length for the current block.
  618  * IN assertion: the field freq is set for all tree elements.
  619  * OUT assertions: the fields len and code are set to the optimal bit length
  620  *     and corresponding code. The length opt_len is updated; static_len is
  621  *     also updated if stree is not null. The field max_code is set.
  622  */
  623 local void build_tree(s, desc)
  624     deflate_state *s;
  625     tree_desc *desc; /* the tree descriptor */
  626 {
  627     ct_data *tree         = desc->dyn_tree;
  628     const ct_data *stree  = desc->stat_desc->static_tree;
  629     int elems             = desc->stat_desc->elems;
  630     int n, m;          /* iterate over heap elements */
  631     int max_code = -1; /* largest code with non zero frequency */
  632     int node;          /* new node being created */
  633 
  634     /* Construct the initial heap, with least frequent element in
  635      * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
  636      * heap[0] is not used.
  637      */
  638     s->heap_len = 0, s->heap_max = HEAP_SIZE;
  639 
  640     for (n = 0; n < elems; n++) {
  641         if (tree[n].Freq != 0) {
  642             s->heap[++(s->heap_len)] = max_code = n;
  643             s->depth[n] = 0;
  644         } else {
  645             tree[n].Len = 0;
  646         }
  647     }
  648 
  649     /* The pkzip format requires that at least one distance code exists,
  650      * and that at least one bit should be sent even if there is only one
  651      * possible code. So to avoid special checks later on we force at least
  652      * two codes of non zero frequency.
  653      */
  654     while (s->heap_len < 2) {
  655         node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
  656         tree[node].Freq = 1;
  657         s->depth[node] = 0;
  658         s->opt_len--; if (stree) s->static_len -= stree[node].Len;
  659         /* node is 0 or 1 so it does not have extra bits */
  660     }
  661     desc->max_code = max_code;
  662 
  663     /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
  664      * establish sub-heaps of increasing lengths:
  665      */
  666     for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
  667 
  668     /* Construct the Huffman tree by repeatedly combining the least two
  669      * frequent nodes.
  670      */
  671     node = elems;              /* next internal node of the tree */
  672     do {
  673         pqremove(s, tree, n);  /* n = node of least frequency */
  674         m = s->heap[SMALLEST]; /* m = node of next least frequency */
  675 
  676         s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
  677         s->heap[--(s->heap_max)] = m;
  678 
  679         /* Create a new node father of n and m */
  680         tree[node].Freq = tree[n].Freq + tree[m].Freq;
  681         s->depth[node] = (uch)((s->depth[n] >= s->depth[m] ?
  682                                 s->depth[n] : s->depth[m]) + 1);
  683         tree[n].Dad = tree[m].Dad = (ush)node;
  684 #ifdef DUMP_BL_TREE
  685         if (tree == s->bl_tree) {
  686             fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
  687                     node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
  688         }
  689 #endif
  690         /* and insert the new node in the heap */
  691         s->heap[SMALLEST] = node++;
  692         pqdownheap(s, tree, SMALLEST);
  693 
  694     } while (s->heap_len >= 2);
  695 
  696     s->heap[--(s->heap_max)] = s->heap[SMALLEST];
  697 
  698     /* At this point, the fields freq and dad are set. We can now
  699      * generate the bit lengths.
  700      */
  701     gen_bitlen(s, (tree_desc *)desc);
  702 
  703     /* The field len is now set, we can generate the bit codes */
  704     gen_codes ((ct_data *)tree, max_code, s->bl_count);
  705 }
  706 
  707 /* ===========================================================================
  708  * Scan a literal or distance tree to determine the frequencies of the codes
  709  * in the bit length tree.
  710  */
  711 local void scan_tree (s, tree, max_code)
  712     deflate_state *s;
  713     ct_data *tree;   /* the tree to be scanned */
  714     int max_code;    /* and its largest code of non zero frequency */
  715 {
  716     int n;                     /* iterates over all tree elements */
  717     int prevlen = -1;          /* last emitted length */
  718     int curlen;                /* length of current code */
  719     int nextlen = tree[0].Len; /* length of next code */
  720     int count = 0;             /* repeat count of the current code */
  721     int max_count = 7;         /* max repeat count */
  722     int min_count = 4;         /* min repeat count */
  723 
  724     if (nextlen == 0) max_count = 138, min_count = 3;
  725     tree[max_code+1].Len = (ush)0xffff; /* guard */
  726 
  727     for (n = 0; n <= max_code; n++) {
  728         curlen = nextlen; nextlen = tree[n+1].Len;
  729         if (++count < max_count && curlen == nextlen) {
  730             continue;
  731         } else if (count < min_count) {
  732             s->bl_tree[curlen].Freq += count;
  733         } else if (curlen != 0) {
  734             if (curlen != prevlen) s->bl_tree[curlen].Freq++;
  735             s->bl_tree[REP_3_6].Freq++;
  736         } else if (count <= 10) {
  737             s->bl_tree[REPZ_3_10].Freq++;
  738         } else {
  739             s->bl_tree[REPZ_11_138].Freq++;
  740         }
  741         count = 0; prevlen = curlen;
  742         if (nextlen == 0) {
  743             max_count = 138, min_count = 3;
  744         } else if (curlen == nextlen) {
  745             max_count = 6, min_count = 3;
  746         } else {
  747             max_count = 7, min_count = 4;
  748         }
  749     }
  750 }
  751 
  752 /* ===========================================================================
  753  * Send a literal or distance tree in compressed form, using the codes in
  754  * bl_tree.
  755  */
  756 local void send_tree (s, tree, max_code)
  757     deflate_state *s;
  758     ct_data *tree; /* the tree to be scanned */
  759     int max_code;       /* and its largest code of non zero frequency */
  760 {
  761     int n;                     /* iterates over all tree elements */
  762     int prevlen = -1;          /* last emitted length */
  763     int curlen;                /* length of current code */
  764     int nextlen = tree[0].Len; /* length of next code */
  765     int count = 0;             /* repeat count of the current code */
  766     int max_count = 7;         /* max repeat count */
  767     int min_count = 4;         /* min repeat count */
  768 
  769     /* tree[max_code+1].Len = -1; */  /* guard already set */
  770     if (nextlen == 0) max_count = 138, min_count = 3;
  771 
  772     for (n = 0; n <= max_code; n++) {
  773         curlen = nextlen; nextlen = tree[n+1].Len;
  774         if (++count < max_count && curlen == nextlen) {
  775             continue;
  776         } else if (count < min_count) {
  777             do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
  778 
  779         } else if (curlen != 0) {
  780             if (curlen != prevlen) {
  781                 send_code(s, curlen, s->bl_tree); count--;
  782             }
  783             Assert(count >= 3 && count <= 6, " 3_6?");
  784             send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
  785 
  786         } else if (count <= 10) {
  787             send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
  788 
  789         } else {
  790             send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
  791         }
  792         count = 0; prevlen = curlen;
  793         if (nextlen == 0) {
  794             max_count = 138, min_count = 3;
  795         } else if (curlen == nextlen) {
  796             max_count = 6, min_count = 3;
  797         } else {
  798             max_count = 7, min_count = 4;
  799         }
  800     }
  801 }
  802 
  803 /* ===========================================================================
  804  * Construct the Huffman tree for the bit lengths and return the index in
  805  * bl_order of the last bit length code to send.
  806  */
  807 local int build_bl_tree(s)
  808     deflate_state *s;
  809 {
  810     int max_blindex;  /* index of last bit length code of non zero freq */
  811 
  812     /* Determine the bit length frequencies for literal and distance trees */
  813     scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
  814     scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
  815 
  816     /* Build the bit length tree: */
  817     build_tree(s, (tree_desc *)(&(s->bl_desc)));
  818     /* opt_len now includes the length of the tree representations, except
  819      * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
  820      */
  821 
  822     /* Determine the number of bit length codes to send. The pkzip format
  823      * requires that at least 4 bit length codes be sent. (appnote.txt says
  824      * 3 but the actual value used is 4.)
  825      */
  826     for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
  827         if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
  828     }
  829     /* Update opt_len to include the bit length tree and counts */
  830     s->opt_len += 3*(max_blindex+1) + 5+5+4;
  831     Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
  832             s->opt_len, s->static_len));
  833 
  834     return max_blindex;
  835 }
  836 
  837 /* ===========================================================================
  838  * Send the header for a block using dynamic Huffman trees: the counts, the
  839  * lengths of the bit length codes, the literal tree and the distance tree.
  840  * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
  841  */
  842 local void send_all_trees(s, lcodes, dcodes, blcodes)
  843     deflate_state *s;
  844     int lcodes, dcodes, blcodes; /* number of codes for each tree */
  845 {
  846     int rank;                    /* index in bl_order */
  847 
  848     Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
  849     Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
  850             "too many codes");
  851     Tracev((stderr, "\nbl counts: "));
  852     send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
  853     send_bits(s, dcodes-1,   5);
  854     send_bits(s, blcodes-4,  4); /* not -3 as stated in appnote.txt */
  855     for (rank = 0; rank < blcodes; rank++) {
  856         Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
  857         send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
  858     }
  859     Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
  860 
  861     send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
  862     Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
  863 
  864     send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
  865     Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
  866 }
  867 
  868 /* ===========================================================================
  869  * Send a stored block
  870  */
  871 void ZLIB_INTERNAL _tr_stored_block(s, buf, stored_len, last)
  872     deflate_state *s;
  873     charf *buf;       /* input block */
  874     ulg stored_len;   /* length of input block */
  875     int last;         /* one if this is the last block for a file */
  876 {
  877     send_bits(s, (STORED_BLOCK<<1)+last, 3);    /* send block type */
  878 #ifdef DEBUG
  879     s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
  880     s->compressed_len += (stored_len + 4) << 3;
  881 #endif
  882     copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
  883 }
  884 
  885 /* ===========================================================================
  886  * Send one empty static block to give enough lookahead for inflate.
  887  * This takes 10 bits, of which 7 may remain in the bit buffer.
  888  * The current inflate code requires 9 bits of lookahead. If the
  889  * last two codes for the previous block (real code plus EOB) were coded
  890  * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
  891  * the last real code. In this case we send two empty static blocks instead
  892  * of one. (There are no problems if the previous block is stored or fixed.)
  893  * To simplify the code, we assume the worst case of last real code encoded
  894  * on one bit only.
  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 DEBUG
  902     s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
  903 #endif
  904     bi_flush(s);
  905     /* Of the 10 bits for the empty block, we have already sent
  906      * (10 - bi_valid) bits. The lookahead for the last real code (before
  907      * the EOB of the previous block) was thus at least one plus the length
  908      * of the EOB plus what we have just sent of the empty static block.
  909      */
  910     if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
  911         send_bits(s, STATIC_TREES<<1, 3);
  912         send_code(s, END_BLOCK, static_ltree);
  913 #ifdef DEBUG
  914         s->compressed_len += 10L;
  915 #endif
  916         bi_flush(s);
  917     }
  918     s->last_eob_len = 7;
  919 }
  920 
  921 /* ===========================================================================
  922  * Determine the best encoding for the current block: dynamic trees, static
  923  * trees or store, and output the encoded block to the zip file.
  924  */
  925 void ZLIB_INTERNAL _tr_flush_block(s, buf, stored_len, last)
  926     deflate_state *s;
  927     charf *buf;       /* input block, or NULL if too old */
  928     ulg stored_len;   /* length of input block */
  929     int last;         /* one if this is the last block for a file */
  930 {
  931     ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
  932     int max_blindex = 0;  /* index of last bit length code of non zero freq */
  933 
  934     /* Build the Huffman trees unless a stored block is forced */
  935     if (s->level > 0) {
  936 
  937         /* Check if the file is binary or text */
  938         if (s->strm->data_type == Z_UNKNOWN)
  939             s->strm->data_type = detect_data_type(s);
  940 
  941         /* Construct the literal and distance trees */
  942         build_tree(s, (tree_desc *)(&(s->l_desc)));
  943         Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
  944                 s->static_len));
  945 
  946         build_tree(s, (tree_desc *)(&(s->d_desc)));
  947         Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
  948                 s->static_len));
  949         /* At this point, opt_len and static_len are the total bit lengths of
  950          * the compressed block data, excluding the tree representations.
  951          */
  952 
  953         /* Build the bit length tree for the above two trees, and get the index
  954          * in bl_order of the last bit length code to send.
  955          */
  956         max_blindex = build_bl_tree(s);
  957 
  958         /* Determine the best encoding. Compute the block lengths in bytes. */
  959         opt_lenb = (s->opt_len+3+7)>>3;
  960         static_lenb = (s->static_len+3+7)>>3;
  961 
  962         Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
  963                 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
  964                 s->last_lit));
  965 
  966         if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
  967 
  968     } else {
  969         Assert(buf != (char*)0, "lost buf");
  970         opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
  971     }
  972 
  973 #ifdef FORCE_STORED
  974     if (buf != (char*)0) { /* force stored block */
  975 #else
  976     if (stored_len+4 <= opt_lenb && buf != (char*)0) {
  977                        /* 4: two words for the lengths */
  978 #endif
  979         /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
  980          * Otherwise we can't have processed more than WSIZE input bytes since
  981          * the last block flush, because compression would have been
  982          * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
  983          * transform a block into a stored block.
  984          */
  985         _tr_stored_block(s, buf, stored_len, last);
  986 
  987 #ifdef FORCE_STATIC
  988     } else if (static_lenb >= 0) { /* force static trees */
  989 #else
  990     } else if (s->strategy == Z_FIXED || static_lenb == opt_lenb) {
  991 #endif
  992         send_bits(s, (STATIC_TREES<<1)+last, 3);
  993         compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
  994 #ifdef DEBUG
  995         s->compressed_len += 3 + s->static_len;
  996 #endif
  997     } else {
  998         send_bits(s, (DYN_TREES<<1)+last, 3);
  999         send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
 1000                        max_blindex+1);
 1001         compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
 1002 #ifdef DEBUG
 1003         s->compressed_len += 3 + s->opt_len;
 1004 #endif
 1005     }
 1006     Assert (s->compressed_len == s->bits_sent, "bad compressed size");
 1007     /* The above check is made mod 2^32, for files larger than 512 MB
 1008      * and uLong implemented on 32 bits.
 1009      */
 1010     init_block(s);
 1011 
 1012     if (last) {
 1013         bi_windup(s);
 1014 #ifdef DEBUG
 1015         s->compressed_len += 7;  /* align on byte boundary */
 1016 #endif
 1017     }
 1018     Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
 1019            s->compressed_len-7*last));
 1020 }
 1021 
 1022 /* ===========================================================================
 1023  * Save the match info and tally the frequency counts. Return true if
 1024  * the current block must be flushed.
 1025  */
 1026 int ZLIB_INTERNAL _tr_tally (s, dist, lc)
 1027     deflate_state *s;
 1028     unsigned dist;  /* distance of matched string */
 1029     unsigned lc;    /* match length-MIN_MATCH or unmatched char (if dist==0) */
 1030 {
 1031     s->d_buf[s->last_lit] = (ush)dist;
 1032     s->l_buf[s->last_lit++] = (uch)lc;
 1033     if (dist == 0) {
 1034         /* lc is the unmatched char */
 1035         s->dyn_ltree[lc].Freq++;
 1036     } else {
 1037         s->matches++;
 1038         /* Here, lc is the match length - MIN_MATCH */
 1039         dist--;             /* dist = match distance - 1 */
 1040         Assert((ush)dist < (ush)MAX_DIST(s) &&
 1041                (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
 1042                (ush)d_code(dist) < (ush)D_CODES,  "_tr_tally: bad match");
 1043 
 1044         s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
 1045         s->dyn_dtree[d_code(dist)].Freq++;
 1046     }
 1047 
 1048 #ifdef TRUNCATE_BLOCK
 1049     /* Try to guess if it is profitable to stop the current block here */
 1050     if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
 1051         /* Compute an upper bound for the compressed length */
 1052         ulg out_length = (ulg)s->last_lit*8L;
 1053         ulg in_length = (ulg)((long)s->strstart - s->block_start);
 1054         int dcode;
 1055         for (dcode = 0; dcode < D_CODES; dcode++) {
 1056             out_length += (ulg)s->dyn_dtree[dcode].Freq *
 1057                 (5L+extra_dbits[dcode]);
 1058         }
 1059         out_length >>= 3;
 1060         Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
 1061                s->last_lit, in_length, out_length,
 1062                100L - out_length*100L/in_length));
 1063         if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
 1064     }
 1065 #endif
 1066     return (s->last_lit == s->lit_bufsize-1);
 1067     /* We avoid equality with lit_bufsize because of wraparound at 64K
 1068      * on 16 bit machines and because stored blocks are restricted to
 1069      * 64K-1 bytes.
 1070      */
 1071 }
 1072 
 1073 /* ===========================================================================
 1074  * Send the block data compressed using the given Huffman trees
 1075  */
 1076 local void compress_block(s, ltree, dtree)
 1077     deflate_state *s;
 1078     ct_data *ltree; /* literal tree */
 1079     ct_data *dtree; /* distance tree */
 1080 {
 1081     unsigned dist;      /* distance of matched string */
 1082     int lc;             /* match length or unmatched char (if dist == 0) */
 1083     unsigned lx = 0;    /* running index in l_buf */
 1084     unsigned code;      /* the code to send */
 1085     int extra;          /* number of extra bits to send */
 1086 
 1087     if (s->last_lit != 0) do {
 1088         dist = s->d_buf[lx];
 1089         lc = s->l_buf[lx++];
 1090         if (dist == 0) {
 1091             send_code(s, lc, ltree); /* send a literal byte */
 1092             Tracecv(isgraph(lc), (stderr," '%c' ", lc));
 1093         } else {
 1094             /* Here, lc is the match length - MIN_MATCH */
 1095             code = _length_code[lc];
 1096             send_code(s, code+LITERALS+1, ltree); /* send the length code */
 1097             extra = extra_lbits[code];
 1098             if (extra != 0) {
 1099                 lc -= base_length[code];
 1100                 send_bits(s, lc, extra);       /* send the extra length bits */
 1101             }
 1102             dist--; /* dist is now the match distance - 1 */
 1103             code = d_code(dist);
 1104             Assert (code < D_CODES, "bad d_code");
 1105 
 1106             send_code(s, code, dtree);       /* send the distance code */
 1107             extra = extra_dbits[code];
 1108             if (extra != 0) {
 1109                 dist -= base_dist[code];
 1110                 send_bits(s, dist, extra);   /* send the extra distance bits */
 1111             }
 1112         } /* literal or match pair ? */
 1113 
 1114         /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
 1115         Assert((uInt)(s->pending) < s->lit_bufsize + 2*lx,
 1116                "pendingBuf overflow");
 1117 
 1118     } while (lx < s->last_lit);
 1119 
 1120     send_code(s, END_BLOCK, ltree);
 1121     s->last_eob_len = ltree[END_BLOCK].Len;
 1122 }
 1123 
 1124 /* ===========================================================================
 1125  * Check if the data type is TEXT or BINARY, using the following algorithm:
 1126  * - TEXT if the two conditions below are satisfied:
 1127  *    a) There are no non-portable control characters belonging to the
 1128  *       "black list" (0..6, 14..25, 28..31).
 1129  *    b) There is at least one printable character belonging to the
 1130  *       "white list" (9 {TAB}, 10 {LF}, 13 {CR}, 32..255).
 1131  * - BINARY otherwise.
 1132  * - The following partially-portable control characters form a
 1133  *   "gray list" that is ignored in this detection algorithm:
 1134  *   (7 {BEL}, 8 {BS}, 11 {VT}, 12 {FF}, 26 {SUB}, 27 {ESC}).
 1135  * IN assertion: the fields Freq of dyn_ltree are set.
 1136  */
 1137 local int detect_data_type(s)
 1138     deflate_state *s;
 1139 {
 1140     /* black_mask is the bit mask of black-listed bytes
 1141      * set bits 0..6, 14..25, and 28..31
 1142      * 0xf3ffc07f = binary 11110011111111111100000001111111
 1143      */
 1144     unsigned long black_mask = 0xf3ffc07fUL;
 1145     int n;
 1146 
 1147     /* Check for non-textual ("black-listed") bytes. */
 1148     for (n = 0; n <= 31; n++, black_mask >>= 1)
 1149         if ((black_mask & 1) && (s->dyn_ltree[n].Freq != 0))
 1150             return Z_BINARY;
 1151 
 1152     /* Check for textual ("white-listed") bytes. */
 1153     if (s->dyn_ltree[9].Freq != 0 || s->dyn_ltree[10].Freq != 0
 1154             || s->dyn_ltree[13].Freq != 0)
 1155         return Z_TEXT;
 1156     for (n = 32; n < LITERALS; n++)
 1157         if (s->dyn_ltree[n].Freq != 0)
 1158             return Z_TEXT;
 1159 
 1160     /* There are no "black-listed" or "white-listed" bytes:
 1161      * this stream either is empty or has tolerated ("gray-listed") bytes only.
 1162      */
 1163     return Z_BINARY;
 1164 }
 1165 
 1166 /* ===========================================================================
 1167  * Reverse the first len bits of a code, using straightforward code (a faster
 1168  * method would use a table)
 1169  * IN assertion: 1 <= len <= 15
 1170  */
 1171 local unsigned bi_reverse(code, len)
 1172     unsigned code; /* the value to invert */
 1173     int len;       /* its bit length */
 1174 {
 1175     register unsigned res = 0;
 1176     do {
 1177         res |= code & 1;
 1178         code >>= 1, res <<= 1;
 1179     } while (--len > 0);
 1180     return res >> 1;
 1181 }
 1182 
 1183 /* ===========================================================================
 1184  * Flush the bit buffer, keeping at most 7 bits in it.
 1185  */
 1186 local void bi_flush(s)
 1187     deflate_state *s;
 1188 {
 1189     if (s->bi_valid == 16) {
 1190         put_short(s, s->bi_buf);
 1191         s->bi_buf = 0;
 1192         s->bi_valid = 0;
 1193     } else if (s->bi_valid >= 8) {
 1194         put_byte(s, (Byte)s->bi_buf);
 1195         s->bi_buf >>= 8;
 1196         s->bi_valid -= 8;
 1197     }
 1198 }
 1199 
 1200 /* ===========================================================================
 1201  * Flush the bit buffer and align the output on a byte boundary
 1202  */
 1203 local void bi_windup(s)
 1204     deflate_state *s;
 1205 {
 1206     if (s->bi_valid > 8) {
 1207         put_short(s, s->bi_buf);
 1208     } else if (s->bi_valid > 0) {
 1209         put_byte(s, (Byte)s->bi_buf);
 1210     }
 1211     s->bi_buf = 0;
 1212     s->bi_valid = 0;
 1213 #ifdef DEBUG
 1214     s->bits_sent = (s->bits_sent+7) & ~7;
 1215 #endif
 1216 }
 1217 
 1218 /* ===========================================================================
 1219  * Copy a stored block, storing first the length and its
 1220  * one's complement if requested.
 1221  */
 1222 local void copy_block(s, buf, len, header)
 1223     deflate_state *s;
 1224     charf    *buf;    /* the input data */
 1225     unsigned len;     /* its length */
 1226     int      header;  /* true if block header must be written */
 1227 {
 1228     bi_windup(s);        /* align on byte boundary */
 1229     s->last_eob_len = 8; /* enough lookahead for inflate */
 1230 
 1231     if (header) {
 1232         put_short(s, (ush)len);
 1233         put_short(s, (ush)~len);
 1234 #ifdef DEBUG
 1235         s->bits_sent += 2*16;
 1236 #endif
 1237     }
 1238 #ifdef DEBUG
 1239     s->bits_sent += (ulg)len<<3;
 1240 #endif
 1241     while (len--) {
 1242         put_byte(s, *buf++);
 1243     }
 1244 }