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      1 /* trees.c -- output deflated data using Huffman coding
      2  * Copyright (C) 1995-2005 Jean-loup Gailly
      3  * For conditions of distribution and use, see copyright notice in zlib.h
      4  */
      5 
      6 /*
      7  *  ALGORITHM
      8  *
      9  *      The "deflation" process uses several Huffman trees. The more
     10  *      common source values are represented by shorter bit sequences.
     11  *
     12  *      Each code tree is stored in a compressed form which is itself
     13  * a Huffman encoding of the lengths of all the code strings (in
     14  * ascending order by source values).  The actual code strings are
     15  * reconstructed from the lengths in the inflate process, as described
     16  * in the deflate specification.
     17  *
     18  *  REFERENCES
     19  *
     20  *      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
     21  *      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
     22  *
     23  *      Storer, James A.
     24  *          Data Compression:  Methods and Theory, pp. 49-50.
     25  *          Computer Science Press, 1988.  ISBN 0-7167-8156-5.
     26  *
     27  *      Sedgewick, R.
     28  *          Algorithms, p290.
     29  *          Addison-Wesley, 1983. ISBN 0-201-06672-6.
     30  */
     31 
     32 /* @(#) $Id$ */
     33 
     34 /* #define GEN_TREES_H */
     35 
     36 #include "deflate.h"
     37 
     38 #ifdef DEBUG
     39 #  include <ctype.h>
     40 #endif
     41 
     42 /* ===========================================================================
     43  * Constants
     44  */
     45 
     46 #define MAX_BL_BITS 7
     47 /* Bit length codes must not exceed MAX_BL_BITS bits */
     48 
     49 #define END_BLOCK 256
     50 /* end of block literal code */
     51 
     52 #define REP_3_6      16
     53 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
     54 
     55 #define REPZ_3_10    17
     56 /* repeat a zero length 3-10 times  (3 bits of repeat count) */
     57 
     58 #define REPZ_11_138  18
     59 /* repeat a zero length 11-138 times  (7 bits of repeat count) */
     60 
     61 local const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
     62    = {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};
     63 
     64 local const int extra_dbits[D_CODES] /* extra bits for each distance code */
     65    = {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};
     66 
     67 local const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
     68    = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
     69 
     70 local const uch bl_order[BL_CODES]
     71    = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
     72 /* The lengths of the bit length codes are sent in order of decreasing
     73  * probability, to avoid transmitting the lengths for unused bit length codes.
     74  */
     75 
     76 #define Buf_size (8 * 2*sizeof(char))
     77 /* Number of bits used within bi_buf. (bi_buf might be implemented on
     78  * more than 16 bits on some systems.)
     79  */
     80 
     81 /* ===========================================================================
     82  * Local data. These are initialized only once.
     83  */
     84 
     85 #define DIST_CODE_LEN  512 /* see definition of array dist_code below */
     86 
     87 #if defined(GEN_TREES_H) || !defined(STDC)
     88 /* non ANSI compilers may not accept trees.h */
     89 
     90 local ct_data static_ltree[L_CODES+2];
     91 /* The static literal tree. Since the bit lengths are imposed, there is no
     92  * need for the L_CODES extra codes used during heap construction. However
     93  * The codes 286 and 287 are needed to build a canonical tree (see _tr_init
     94  * below).
     95  */
     96 
     97 local ct_data static_dtree[D_CODES];
     98 /* The static distance tree. (Actually a trivial tree since all codes use
     99  * 5 bits.)
    100  */
    101 
    102 uch _dist_code[DIST_CODE_LEN];
    103 /* Distance codes. The first 256 values correspond to the distances
    104  * 3 .. 258, the last 256 values correspond to the top 8 bits of
    105  * the 15 bit distances.
    106  */
    107 
    108 uch _length_code[MAX_MATCH-MIN_MATCH+1];
    109 /* length code for each normalized match length (0 == MIN_MATCH) */
    110 
    111 local int base_length[LENGTH_CODES];
    112 /* First normalized length for each code (0 = MIN_MATCH) */
    113 
    114 local int base_dist[D_CODES];
    115 /* First normalized distance for each code (0 = distance of 1) */
    116 
    117 #else
    118 #  include "trees.h"
    119 #endif /* GEN_TREES_H */
    120 
    121 struct static_tree_desc_s {
    122     const ct_data *static_tree;  /* static tree or NULL */
    123     const intf *extra_bits;      /* extra bits for each code or NULL */
    124     int     extra_base;          /* base index for extra_bits */
    125     int     elems;               /* max number of elements in the tree */
    126     int     max_length;          /* max bit length for the codes */
    127 };
    128 
    129 local static_tree_desc  static_l_desc =
    130 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
    131 
    132 local static_tree_desc  static_d_desc =
    133 {static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};
    134 
    135 local static_tree_desc  static_bl_desc =
    136 {(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};
    137 
    138 /* ===========================================================================
    139  * Local (static) routines in this file.
    140  */
    141 
    142 local void tr_static_init OF((void));
    143 local void init_block     OF((deflate_state *s));
    144 local void pqdownheap     OF((deflate_state *s, ct_data *tree, int k));
    145 local void gen_bitlen     OF((deflate_state *s, tree_desc *desc));
    146 local void gen_codes      OF((ct_data *tree, int max_code, ushf *bl_count));
    147 local void build_tree     OF((deflate_state *s, tree_desc *desc));
    148 local void scan_tree      OF((deflate_state *s, ct_data *tree, int max_code));
    149 local void send_tree      OF((deflate_state *s, ct_data *tree, int max_code));
    150 local int  build_bl_tree  OF((deflate_state *s));
    151 local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
    152                               int blcodes));
    153 local void compress_block OF((deflate_state *s, ct_data *ltree,
    154                               ct_data *dtree));
    155 local void set_data_type  OF((deflate_state *s));
    156 local unsigned bi_reverse OF((unsigned value, int length));
    157 local void bi_windup      OF((deflate_state *s));
    158 local void bi_flush       OF((deflate_state *s));
    159 local void copy_block     OF((deflate_state *s, charf *buf, unsigned len,
    160                               int header));
    161 
    162 #ifdef GEN_TREES_H
    163 local void gen_trees_header OF((void));
    164 #endif
    165 
    166 #ifndef DEBUG
    167 #  define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
    168    /* Send a code of the given tree. c and tree must not have side effects */
    169 
    170 #else /* DEBUG */
    171 #  define send_code(s, c, tree) \
    172      { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
    173        send_bits(s, tree[c].Code, tree[c].Len); }
    174 #endif
    175 
    176 /* ===========================================================================
    177  * Output a short LSB first on the stream.
    178  * IN assertion: there is enough room in pendingBuf.
    179  */
    180 #define put_short(s, w) { \
    181     put_byte(s, (uch)((w) & 0xff)); \
    182     put_byte(s, (uch)((ush)(w) >> 8)); \
    183 }
    184 
    185 /* ===========================================================================
    186  * Send a value on a given number of bits.
    187  * IN assertion: length <= 16 and value fits in length bits.
    188  */
    189 #ifdef DEBUG
    190 local void send_bits      OF((deflate_state *s, int value, int length));
    191 
    192 local void send_bits(s, value, length)
    193     deflate_state *s;
    194     int value;  /* value to send */
    195     int length; /* number of bits */
    196 {
    197     Tracevv((stderr," l %2d v %4x ", length, value));
    198     Assert(length > 0 && length <= 15, "invalid length");
    199     s->bits_sent += (ulg)length;
    200 
    201     /* If not enough room in bi_buf, use (valid) bits from bi_buf and
    202      * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
    203      * unused bits in value.
    204      */
    205     if (s->bi_valid > (int)Buf_size - length) {
    206         s->bi_buf |= (value << s->bi_valid);
    207         put_short(s, s->bi_buf);
    208         s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
    209         s->bi_valid += length - Buf_size;
    210     } else {
    211         s->bi_buf |= value << s->bi_valid;
    212         s->bi_valid += length;
    213     }
    214 }
    215 #else /* !DEBUG */
    216 
    217 #define send_bits(s, value, length) \
    218 { int len = length;\
    219   if (s->bi_valid > (int)Buf_size - len) {\
    220     int val = value;\
    221     s->bi_buf |= (val << s->bi_valid);\
    222     put_short(s, s->bi_buf);\
    223     s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
    224     s->bi_valid += len - Buf_size;\
    225   } else {\
    226     s->bi_buf |= (value) << s->bi_valid;\
    227     s->bi_valid += len;\
    228   }\
    229 }
    230 #endif /* DEBUG */
    231 
    232 
    233 /* the arguments must not have side effects */
    234 
    235 /* ===========================================================================
    236  * Initialize the various 'constant' tables.
    237  */
    238 local void tr_static_init()
    239 {
    240 #if defined(GEN_TREES_H) || !defined(STDC)
    241     static int static_init_done = 0;
    242     int n;        /* iterates over tree elements */
    243     int bits;     /* bit counter */
    244     int length;   /* length value */
    245     int code;     /* code value */
    246     int dist;     /* distance index */
    247     ush bl_count[MAX_BITS+1];
    248     /* number of codes at each bit length for an optimal tree */
    249 
    250     if (static_init_done) return;
    251 
    252     /* For some embedded targets, global variables are not initialized: */
    253     static_l_desc.static_tree = static_ltree;
    254     static_l_desc.extra_bits = extra_lbits;
    255     static_d_desc.static_tree = static_dtree;
    256     static_d_desc.extra_bits = extra_dbits;
    257     static_bl_desc.extra_bits = extra_blbits;
    258 
    259     /* Initialize the mapping length (0..255) -> length code (0..28) */
    260     length = 0;
    261     for (code = 0; code < LENGTH_CODES-1; code++) {
    262         base_length[code] = length;
    263         for (n = 0; n < (1<<extra_lbits[code]); n++) {
    264             _length_code[length++] = (uch)code;
    265         }
    266     }
    267     Assert (length == 256, "tr_static_init: length != 256");
    268     /* Note that the length 255 (match length 258) can be represented
    269      * in two different ways: code 284 + 5 bits or code 285, so we
    270      * overwrite length_code[255] to use the best encoding:
    271      */
    272     _length_code[length-1] = (uch)code;
    273 
    274     /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
    275     dist = 0;
    276     for (code = 0 ; code < 16; code++) {
    277         base_dist[code] = dist;
    278         for (n = 0; n < (1<<extra_dbits[code]); n++) {
    279             _dist_code[dist++] = (uch)code;
    280         }
    281     }
    282     Assert (dist == 256, "tr_static_init: dist != 256");
    283     dist >>= 7; /* from now on, all distances are divided by 128 */
    284     for ( ; code < D_CODES; code++) {
    285         base_dist[code] = dist << 7;
    286         for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
    287             _dist_code[256 + dist++] = (uch)code;
    288         }
    289     }
    290     Assert (dist == 256, "tr_static_init: 256+dist != 512");
    291 
    292     /* Construct the codes of the static literal tree */
    293     for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
    294     n = 0;
    295     while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
    296     while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
    297     while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
    298     while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
    299     /* Codes 286 and 287 do not exist, but we must include them in the
    300      * tree construction to get a canonical Huffman tree (longest code
    301      * all ones)
    302      */
    303     gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
    304 
    305     /* The static distance tree is trivial: */
    306     for (n = 0; n < D_CODES; n++) {
    307         static_dtree[n].Len = 5;
    308         static_dtree[n].Code = bi_reverse((unsigned)n, 5);
    309     }
    310     static_init_done = 1;
    311 
    312 #  ifdef GEN_TREES_H
    313     gen_trees_header();
    314 #  endif
    315 #endif /* defined(GEN_TREES_H) || !defined(STDC) */
    316 }
    317 
    318 /* ===========================================================================
    319  * Genererate the file trees.h describing the static trees.
    320  */
    321 #ifdef GEN_TREES_H
    322 #  ifndef DEBUG
    323 #    include <stdio.h>
    324 #  endif
    325 
    326 #  define SEPARATOR(i, last, width) \
    327       ((i) == (last)? "\n};\n\n" :    \
    328        ((i) % (width) == (width)-1 ? ",\n" : ", "))
    329 
    330 void gen_trees_header()
    331 {
    332     FILE *header = fopen("trees.h", "w");
    333     int i;
    334 
    335     Assert (header != NULL, "Can't open trees.h");
    336     fprintf(header,
    337             "/* header created automatically with -DGEN_TREES_H */\n\n");
    338 
    339     fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");
    340     for (i = 0; i < L_CODES+2; i++) {
    341         fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,
    342                 static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
    343     }
    344 
    345     fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");
    346     for (i = 0; i < D_CODES; i++) {
    347         fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,
    348                 static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
    349     }
    350 
    351     fprintf(header, "const uch _dist_code[DIST_CODE_LEN] = {\n");
    352     for (i = 0; i < DIST_CODE_LEN; i++) {
    353         fprintf(header, "%2u%s", _dist_code[i],
    354                 SEPARATOR(i, DIST_CODE_LEN-1, 20));
    355     }
    356 
    357     fprintf(header, "const uch _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");
    358     for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {
    359         fprintf(header, "%2u%s", _length_code[i],
    360                 SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
    361     }
    362 
    363     fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");
    364     for (i = 0; i < LENGTH_CODES; i++) {
    365         fprintf(header, "%1u%s", base_length[i],
    366                 SEPARATOR(i, LENGTH_CODES-1, 20));
    367     }
    368 
    369     fprintf(header, "local const int base_dist[D_CODES] = {\n");
    370     for (i = 0; i < D_CODES; i++) {
    371         fprintf(header, "%5u%s", base_dist[i],
    372                 SEPARATOR(i, D_CODES-1, 10));
    373     }
    374 
    375     fclose(header);
    376 }
    377 #endif /* GEN_TREES_H */
    378 
    379 /* ===========================================================================
    380  * Initialize the tree data structures for a new zlib stream.
    381  */
    382 void _tr_init(s)
    383     deflate_state *s;
    384 {
    385     tr_static_init();
    386 
    387     s->l_desc.dyn_tree = s->dyn_ltree;
    388     s->l_desc.stat_desc = &static_l_desc;
    389 
    390     s->d_desc.dyn_tree = s->dyn_dtree;
    391     s->d_desc.stat_desc = &static_d_desc;
    392 
    393     s->bl_desc.dyn_tree = s->bl_tree;
    394     s->bl_desc.stat_desc = &static_bl_desc;
    395 
    396     s->bi_buf = 0;
    397     s->bi_valid = 0;
    398     s->last_eob_len = 8; /* enough lookahead for inflate */
    399 #ifdef DEBUG
    400     s->compressed_len = 0L;
    401     s->bits_sent = 0L;
    402 #endif
    403 
    404     /* Initialize the first block of the first file: */
    405     init_block(s);
    406 }
    407 
    408 /* ===========================================================================
    409  * Initialize a new block.
    410  */
    411 local void init_block(s)
    412     deflate_state *s;
    413 {
    414     int n; /* iterates over tree elements */
    415 
    416     /* Initialize the trees. */
    417     for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
    418     for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
    419     for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
    420 
    421     s->dyn_ltree[END_BLOCK].Freq = 1;
    422     s->opt_len = s->static_len = 0L;
    423     s->last_lit = s->matches = 0;
    424 }
    425 
    426 #define SMALLEST 1
    427 /* Index within the heap array of least frequent node in the Huffman tree */
    428 
    429 
    430 /* ===========================================================================
    431  * Remove the smallest element from the heap and recreate the heap with
    432  * one less element. Updates heap and heap_len.
    433  */
    434 #define pqremove(s, tree, top) \
    435 {\
    436     top = s->heap[SMALLEST]; \
    437     s->heap[SMALLEST] = s->heap[s->heap_len--]; \
    438     pqdownheap(s, tree, SMALLEST); \
    439 }
    440 
    441 /* ===========================================================================
    442  * Compares to subtrees, using the tree depth as tie breaker when
    443  * the subtrees have equal frequency. This minimizes the worst case length.
    444  */
    445 #define smaller(tree, n, m, depth) \
    446    (tree[n].Freq < tree[m].Freq || \
    447    (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
    448 
    449 /* ===========================================================================
    450  * Restore the heap property by moving down the tree starting at node k,
    451  * exchanging a node with the smallest of its two sons if necessary, stopping
    452  * when the heap property is re-established (each father smaller than its
    453  * two sons).
    454  */
    455 local void pqdownheap(s, tree, k)
    456     deflate_state *s;
    457     ct_data *tree;  /* the tree to restore */
    458     int k;               /* node to move down */
    459 {
    460     int v = s->heap[k];
    461     int j = k << 1;  /* left son of k */
    462     while (j <= s->heap_len) {
    463         /* Set j to the smallest of the two sons: */
    464         if (j < s->heap_len &&
    465             smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
    466             j++;
    467         }
    468         /* Exit if v is smaller than both sons */
    469         if (smaller(tree, v, s->heap[j], s->depth)) break;
    470 
    471         /* Exchange v with the smallest son */
    472         s->heap[k] = s->heap[j];  k = j;
    473 
    474         /* And continue down the tree, setting j to the left son of k */
    475         j <<= 1;
    476     }
    477     s->heap[k] = v;
    478 }
    479 
    480 /* ===========================================================================
    481  * Compute the optimal bit lengths for a tree and update the total bit length
    482  * for the current block.
    483  * IN assertion: the fields freq and dad are set, heap[heap_max] and
    484  *    above are the tree nodes sorted by increasing frequency.
    485  * OUT assertions: the field len is set to the optimal bit length, the
    486  *     array bl_count contains the frequencies for each bit length.
    487  *     The length opt_len is updated; static_len is also updated if stree is
    488  *     not null.
    489  */
    490 local void gen_bitlen(s, desc)
    491     deflate_state *s;
    492     tree_desc *desc;    /* the tree descriptor */
    493 {
    494     ct_data *tree        = desc->dyn_tree;
    495     int max_code         = desc->max_code;
    496     const ct_data *stree = desc->stat_desc->static_tree;
    497     const intf *extra    = desc->stat_desc->extra_bits;
    498     int base             = desc->stat_desc->extra_base;
    499     int max_length       = desc->stat_desc->max_length;
    500     int h;              /* heap index */
    501     int n, m;           /* iterate over the tree elements */
    502     int bits;           /* bit length */
    503     int xbits;          /* extra bits */
    504     ush f;              /* frequency */
    505     int overflow = 0;   /* number of elements with bit length too large */
    506 
    507     for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
    508 
    509     /* In a first pass, compute the optimal bit lengths (which may
    510      * overflow in the case of the bit length tree).
    511      */
    512     tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
    513 
    514     for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
    515         n = s->heap[h];
    516         bits = tree[tree[n].Dad].Len + 1;
    517         if (bits > max_length) bits = max_length, overflow++;
    518         tree[n].Len = (ush)bits;
    519         /* We overwrite tree[n].Dad which is no longer needed */
    520 
    521         if (n > max_code) continue; /* not a leaf node */
    522 
    523         s->bl_count[bits]++;
    524         xbits = 0;
    525         if (n >= base) xbits = extra[n-base];
    526         f = tree[n].Freq;
    527         s->opt_len += (ulg)f * (bits + xbits);
    528         if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
    529     }
    530     if (overflow == 0) return;
    531 
    532     Trace((stderr,"\nbit length overflow\n"));
    533     /* This happens for example on obj2 and pic of the Calgary corpus */
    534 
    535     /* Find the first bit length which could increase: */
    536     do {
    537         bits = max_length-1;
    538         while (s->bl_count[bits] == 0) bits--;
    539         s->bl_count[bits]--;      /* move one leaf down the tree */
    540         s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
    541         s->bl_count[max_length]--;
    542         /* The brother of the overflow item also moves one step up,
    543          * but this does not affect bl_count[max_length]
    544          */
    545         overflow -= 2;
    546     } while (overflow > 0);
    547 
    548     /* Now recompute all bit lengths, scanning in increasing frequency.
    549      * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
    550      * lengths instead of fixing only the wrong ones. This idea is taken
    551      * from 'ar' written by Haruhiko Okumura.)
    552      */
    553     for (bits = max_length; bits != 0; bits--) {
    554         n = s->bl_count[bits];
    555         while (n != 0) {
    556             m = s->heap[--h];
    557             if (m > max_code) continue;
    558             if ((unsigned) tree[m].Len != (unsigned) bits) {
    559                 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
    560                 s->opt_len += ((long)bits - (long)tree[m].Len)
    561                               *(long)tree[m].Freq;
    562                 tree[m].Len = (ush)bits;
    563             }
    564             n--;
    565         }
    566     }
    567 }
    568 
    569 /* ===========================================================================
    570  * Generate the codes for a given tree and bit counts (which need not be
    571  * optimal).
    572  * IN assertion: the array bl_count contains the bit length statistics for
    573  * the given tree and the field len is set for all tree elements.
    574  * OUT assertion: the field code is set for all tree elements of non
    575  *     zero code length.
    576  */
    577 local void gen_codes (tree, max_code, bl_count)
    578     ct_data *tree;             /* the tree to decorate */
    579     int max_code;              /* largest code with non zero frequency */
    580     ushf *bl_count;            /* number of codes at each bit length */
    581 {
    582     ush next_code[MAX_BITS+1]; /* next code value for each bit length */
    583     ush code = 0;              /* running code value */
    584     int bits;                  /* bit index */
    585     int n;                     /* code index */
    586 
    587     /* The distribution counts are first used to generate the code values
    588      * without bit reversal.
    589      */
    590     for (bits = 1; bits <= MAX_BITS; bits++) {
    591         next_code[bits] = code = (code + bl_count[bits-1]) << 1;
    592     }
    593     /* Check that the bit counts in bl_count are consistent. The last code
    594      * must be all ones.
    595      */
    596     Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
    597             "inconsistent bit counts");
    598     Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
    599 
    600     for (n = 0;  n <= max_code; n++) {
    601         int len = tree[n].Len;
    602         if (len == 0) continue;
    603         /* Now reverse the bits */
    604         tree[n].Code = bi_reverse(next_code[len]++, len);
    605 
    606         Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
    607              n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
    608     }
    609 }
    610 
    611 /* ===========================================================================
    612  * Construct one Huffman tree and assigns the code bit strings and lengths.
    613  * Update the total bit length for the current block.
    614  * IN assertion: the field freq is set for all tree elements.
    615  * OUT assertions: the fields len and code are set to the optimal bit length
    616  *     and corresponding code. The length opt_len is updated; static_len is
    617  *     also updated if stree is not null. The field max_code is set.
    618  */
    619 local void build_tree(s, desc)
    620     deflate_state *s;
    621     tree_desc *desc; /* the tree descriptor */
    622 {
    623     ct_data *tree         = desc->dyn_tree;
    624     const ct_data *stree  = desc->stat_desc->static_tree;
    625     int elems             = desc->stat_desc->elems;
    626     int n, m;          /* iterate over heap elements */
    627     int max_code = -1; /* largest code with non zero frequency */
    628     int node;          /* new node being created */
    629 
    630     /* Construct the initial heap, with least frequent element in
    631      * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
    632      * heap[0] is not used.
    633      */
    634     s->heap_len = 0, s->heap_max = HEAP_SIZE;
    635 
    636     for (n = 0; n < elems; n++) {
    637         if (tree[n].Freq != 0) {
    638             s->heap[++(s->heap_len)] = max_code = n;
    639             s->depth[n] = 0;
    640         } else {
    641             tree[n].Len = 0;
    642         }
    643     }
    644 
    645     /* The pkzip format requires that at least one distance code exists,
    646      * and that at least one bit should be sent even if there is only one
    647      * possible code. So to avoid special checks later on we force at least
    648      * two codes of non zero frequency.
    649      */
    650     while (s->heap_len < 2) {
    651         node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
    652         tree[node].Freq = 1;
    653         s->depth[node] = 0;
    654         s->opt_len--; if (stree) s->static_len -= stree[node].Len;
    655         /* node is 0 or 1 so it does not have extra bits */
    656     }
    657     desc->max_code = max_code;
    658 
    659     /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
    660      * establish sub-heaps of increasing lengths:
    661      */
    662     for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
    663 
    664     /* Construct the Huffman tree by repeatedly combining the least two
    665      * frequent nodes.
    666      */
    667     node = elems;              /* next internal node of the tree */
    668     do {
    669         pqremove(s, tree, n);  /* n = node of least frequency */
    670         m = s->heap[SMALLEST]; /* m = node of next least frequency */
    671 
    672         s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
    673         s->heap[--(s->heap_max)] = m;
    674 
    675         /* Create a new node father of n and m */
    676         tree[node].Freq = tree[n].Freq + tree[m].Freq;
    677         s->depth[node] = (uch)((s->depth[n] >= s->depth[m] ?
    678                                 s->depth[n] : s->depth[m]) + 1);
    679         tree[n].Dad = tree[m].Dad = (ush)node;
    680 #ifdef DUMP_BL_TREE
    681         if (tree == s->bl_tree) {
    682             fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
    683                     node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
    684         }
    685 #endif
    686         /* and insert the new node in the heap */
    687         s->heap[SMALLEST] = node++;
    688         pqdownheap(s, tree, SMALLEST);
    689 
    690     } while (s->heap_len >= 2);
    691 
    692     s->heap[--(s->heap_max)] = s->heap[SMALLEST];
    693 
    694     /* At this point, the fields freq and dad are set. We can now
    695      * generate the bit lengths.
    696      */
    697     gen_bitlen(s, (tree_desc *)desc);
    698 
    699     /* The field len is now set, we can generate the bit codes */
    700     gen_codes ((ct_data *)tree, max_code, s->bl_count);
    701 }
    702 
    703 /* ===========================================================================
    704  * Scan a literal or distance tree to determine the frequencies of the codes
    705  * in the bit length tree.
    706  */
    707 local void scan_tree (s, tree, max_code)
    708     deflate_state *s;
    709     ct_data *tree;   /* the tree to be scanned */
    710     int max_code;    /* and its largest code of non zero frequency */
    711 {
    712     int n;                     /* iterates over all tree elements */
    713     int prevlen = -1;          /* last emitted length */
    714     int curlen;                /* length of current code */
    715     int nextlen = tree[0].Len; /* length of next code */
    716     int count = 0;             /* repeat count of the current code */
    717     int max_count = 7;         /* max repeat count */
    718     int min_count = 4;         /* min repeat count */
    719 
    720     if (nextlen == 0) max_count = 138, min_count = 3;
    721     tree[max_code+1].Len = (ush)0xffff; /* guard */
    722 
    723     for (n = 0; n <= max_code; n++) {
    724         curlen = nextlen; nextlen = tree[n+1].Len;
    725         if (++count < max_count && curlen == nextlen) {
    726             continue;
    727         } else if (count < min_count) {
    728             s->bl_tree[curlen].Freq += count;
    729         } else if (curlen != 0) {
    730             if (curlen != prevlen) s->bl_tree[curlen].Freq++;
    731             s->bl_tree[REP_3_6].Freq++;
    732         } else if (count <= 10) {
    733             s->bl_tree[REPZ_3_10].Freq++;
    734         } else {
    735             s->bl_tree[REPZ_11_138].Freq++;
    736         }
    737         count = 0; prevlen = curlen;
    738         if (nextlen == 0) {
    739             max_count = 138, min_count = 3;
    740         } else if (curlen == nextlen) {
    741             max_count = 6, min_count = 3;
    742         } else {
    743             max_count = 7, min_count = 4;
    744         }
    745     }
    746 }
    747 
    748 /* ===========================================================================
    749  * Send a literal or distance tree in compressed form, using the codes in
    750  * bl_tree.
    751  */
    752 local void send_tree (s, tree, max_code)
    753     deflate_state *s;
    754     ct_data *tree; /* the tree to be scanned */
    755     int max_code;       /* and its largest code of non zero frequency */
    756 {
    757     int n;                     /* iterates over all tree elements */
    758     int prevlen = -1;          /* last emitted length */
    759     int curlen;                /* length of current code */
    760     int nextlen = tree[0].Len; /* length of next code */
    761     int count = 0;             /* repeat count of the current code */
    762     int max_count = 7;         /* max repeat count */
    763     int min_count = 4;         /* min repeat count */
    764 
    765     /* tree[max_code+1].Len = -1; */  /* guard already set */
    766     if (nextlen == 0) max_count = 138, min_count = 3;
    767 
    768     for (n = 0; n <= max_code; n++) {
    769         curlen = nextlen; nextlen = tree[n+1].Len;
    770         if (++count < max_count && curlen == nextlen) {
    771             continue;
    772         } else if (count < min_count) {
    773             do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
    774 
    775         } else if (curlen != 0) {
    776             if (curlen != prevlen) {
    777                 send_code(s, curlen, s->bl_tree); count--;
    778             }
    779             Assert(count >= 3 && count <= 6, " 3_6?");
    780             send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
    781 
    782         } else if (count <= 10) {
    783             send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
    784 
    785         } else {
    786             send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
    787         }
    788         count = 0; prevlen = curlen;
    789         if (nextlen == 0) {
    790             max_count = 138, min_count = 3;
    791         } else if (curlen == nextlen) {
    792             max_count = 6, min_count = 3;
    793         } else {
    794             max_count = 7, min_count = 4;
    795         }
    796     }
    797 }
    798 
    799 /* ===========================================================================
    800  * Construct the Huffman tree for the bit lengths and return the index in
    801  * bl_order of the last bit length code to send.
    802  */
    803 local int build_bl_tree(s)
    804     deflate_state *s;
    805 {
    806     int max_blindex;  /* index of last bit length code of non zero freq */
    807 
    808     /* Determine the bit length frequencies for literal and distance trees */
    809     scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
    810     scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
    811 
    812     /* Build the bit length tree: */
    813     build_tree(s, (tree_desc *)(&(s->bl_desc)));
    814     /* opt_len now includes the length of the tree representations, except
    815      * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
    816      */
    817 
    818     /* Determine the number of bit length codes to send. The pkzip format
    819      * requires that at least 4 bit length codes be sent. (appnote.txt says
    820      * 3 but the actual value used is 4.)
    821      */
    822     for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
    823         if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
    824     }
    825     /* Update opt_len to include the bit length tree and counts */
    826     s->opt_len += 3*(max_blindex+1) + 5+5+4;
    827     Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
    828             s->opt_len, s->static_len));
    829 
    830     return max_blindex;
    831 }
    832 
    833 /* ===========================================================================
    834  * Send the header for a block using dynamic Huffman trees: the counts, the
    835  * lengths of the bit length codes, the literal tree and the distance tree.
    836  * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
    837  */
    838 local void send_all_trees(s, lcodes, dcodes, blcodes)
    839     deflate_state *s;
    840     int lcodes, dcodes, blcodes; /* number of codes for each tree */
    841 {
    842     int rank;                    /* index in bl_order */
    843 
    844     Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
    845     Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
    846             "too many codes");
    847     Tracev((stderr, "\nbl counts: "));
    848     send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
    849     send_bits(s, dcodes-1,   5);
    850     send_bits(s, blcodes-4,  4); /* not -3 as stated in appnote.txt */
    851     for (rank = 0; rank < blcodes; rank++) {
    852         Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
    853         send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
    854     }
    855     Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
    856 
    857     send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
    858     Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
    859 
    860     send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
    861     Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
    862 }
    863 
    864 /* ===========================================================================
    865  * Send a stored block
    866  */
    867 void _tr_stored_block(s, buf, stored_len, eof)
    868     deflate_state *s;
    869     charf *buf;       /* input block */
    870     ulg stored_len;   /* length of input block */
    871     int eof;          /* true if this is the last block for a file */
    872 {
    873     send_bits(s, (STORED_BLOCK<<1)+eof, 3);  /* send block type */
    874 #ifdef DEBUG
    875     s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
    876     s->compressed_len += (stored_len + 4) << 3;
    877 #endif
    878     copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
    879 }
    880 
    881 /* ===========================================================================
    882  * Send one empty static block to give enough lookahead for inflate.
    883  * This takes 10 bits, of which 7 may remain in the bit buffer.
    884  * The current inflate code requires 9 bits of lookahead. If the
    885  * last two codes for the previous block (real code plus EOB) were coded
    886  * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
    887  * the last real code. In this case we send two empty static blocks instead
    888  * of one. (There are no problems if the previous block is stored or fixed.)
    889  * To simplify the code, we assume the worst case of last real code encoded
    890  * on one bit only.
    891  */
    892 void _tr_align(s)
    893     deflate_state *s;
    894 {
    895     send_bits(s, STATIC_TREES<<1, 3);
    896     send_code(s, END_BLOCK, static_ltree);
    897 #ifdef DEBUG
    898     s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
    899 #endif
    900     bi_flush(s);
    901     /* Of the 10 bits for the empty block, we have already sent
    902      * (10 - bi_valid) bits. The lookahead for the last real code (before
    903      * the EOB of the previous block) was thus at least one plus the length
    904      * of the EOB plus what we have just sent of the empty static block.
    905      */
    906     if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
    907         send_bits(s, STATIC_TREES<<1, 3);
    908         send_code(s, END_BLOCK, static_ltree);
    909 #ifdef DEBUG
    910         s->compressed_len += 10L;
    911 #endif
    912         bi_flush(s);
    913     }
    914     s->last_eob_len = 7;
    915 }
    916 
    917 /* ===========================================================================
    918  * Determine the best encoding for the current block: dynamic trees, static
    919  * trees or store, and output the encoded block to the zip file.
    920  */
    921 void _tr_flush_block(s, buf, stored_len, eof)
    922     deflate_state *s;
    923     charf *buf;       /* input block, or NULL if too old */
    924     ulg stored_len;   /* length of input block */
    925     int eof;          /* true if this is the last block for a file */
    926 {
    927     ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
    928     int max_blindex = 0;  /* index of last bit length code of non zero freq */
    929 
    930     /* Build the Huffman trees unless a stored block is forced */
    931     if (s->level > 0) {
    932 
    933         /* Check if the file is binary or text */
    934         if (stored_len > 0 && s->strm->data_type == Z_UNKNOWN)
    935             set_data_type(s);
    936 
    937         /* Construct the literal and distance trees */
    938         build_tree(s, (tree_desc *)(&(s->l_desc)));
    939         Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
    940                 s->static_len));
    941 
    942         build_tree(s, (tree_desc *)(&(s->d_desc)));
    943         Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
    944                 s->static_len));
    945         /* At this point, opt_len and static_len are the total bit lengths of
    946          * the compressed block data, excluding the tree representations.
    947          */
    948 
    949         /* Build the bit length tree for the above two trees, and get the index
    950          * in bl_order of the last bit length code to send.
    951          */
    952         max_blindex = build_bl_tree(s);
    953 
    954         /* Determine the best encoding. Compute the block lengths in bytes. */
    955         opt_lenb = (s->opt_len+3+7)>>3;
    956         static_lenb = (s->static_len+3+7)>>3;
    957 
    958         Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
    959                 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
    960                 s->last_lit));
    961 
    962         if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
    963 
    964     } else {
    965         Assert(buf != (char*)0, "lost buf");
    966         opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
    967     }
    968 
    969 #ifdef FORCE_STORED
    970     if (buf != (char*)0) { /* force stored block */
    971 #else
    972     if (stored_len+4 <= opt_lenb && buf != (char*)0) {
    973                        /* 4: two words for the lengths */
    974 #endif
    975         /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
    976          * Otherwise we can't have processed more than WSIZE input bytes since
    977          * the last block flush, because compression would have been
    978          * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
    979          * transform a block into a stored block.
    980          */
    981         _tr_stored_block(s, buf, stored_len, eof);
    982 
    983 #ifdef FORCE_STATIC
    984     } else if (static_lenb >= 0) { /* force static trees */
    985 #else
    986     } else if (s->strategy == Z_FIXED || static_lenb == opt_lenb) {
    987 #endif
    988         send_bits(s, (STATIC_TREES<<1)+eof, 3);
    989         compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
    990 #ifdef DEBUG
    991         s->compressed_len += 3 + s->static_len;
    992 #endif
    993     } else {
    994         send_bits(s, (DYN_TREES<<1)+eof, 3);
    995         send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
    996                        max_blindex+1);
    997         compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
    998 #ifdef DEBUG
    999         s->compressed_len += 3 + s->opt_len;
   1000 #endif
   1001     }
   1002     Assert (s->compressed_len == s->bits_sent, "bad compressed size");
   1003     /* The above check is made mod 2^32, for files larger than 512 MB
   1004      * and uLong implemented on 32 bits.
   1005      */
   1006     init_block(s);
   1007 
   1008     if (eof) {
   1009         bi_windup(s);
   1010 #ifdef DEBUG
   1011         s->compressed_len += 7;  /* align on byte boundary */
   1012 #endif
   1013     }
   1014     Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
   1015            s->compressed_len-7*eof));
   1016 }
   1017 
   1018 /* ===========================================================================
   1019  * Save the match info and tally the frequency counts. Return true if
   1020  * the current block must be flushed.
   1021  */
   1022 int _tr_tally (s, dist, lc)
   1023     deflate_state *s;
   1024     unsigned dist;  /* distance of matched string */
   1025     unsigned lc;    /* match length-MIN_MATCH or unmatched char (if dist==0) */
   1026 {
   1027     s->d_buf[s->last_lit] = (ush)dist;
   1028     s->l_buf[s->last_lit++] = (uch)lc;
   1029     if (dist == 0) {
   1030         /* lc is the unmatched char */
   1031         s->dyn_ltree[lc].Freq++;
   1032     } else {
   1033         s->matches++;
   1034         /* Here, lc is the match length - MIN_MATCH */
   1035         dist--;             /* dist = match distance - 1 */
   1036         Assert((ush)dist < (ush)MAX_DIST(s) &&
   1037                (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
   1038                (ush)d_code(dist) < (ush)D_CODES,  "_tr_tally: bad match");
   1039 
   1040         s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
   1041         s->dyn_dtree[d_code(dist)].Freq++;
   1042     }
   1043 
   1044 #ifdef TRUNCATE_BLOCK
   1045     /* Try to guess if it is profitable to stop the current block here */
   1046     if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
   1047         /* Compute an upper bound for the compressed length */
   1048         ulg out_length = (ulg)s->last_lit*8L;
   1049         ulg in_length = (ulg)((long)s->strstart - s->block_start);
   1050         int dcode;
   1051         for (dcode = 0; dcode < D_CODES; dcode++) {
   1052             out_length += (ulg)s->dyn_dtree[dcode].Freq *
   1053                 (5L+extra_dbits[dcode]);
   1054         }
   1055         out_length >>= 3;
   1056         Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
   1057                s->last_lit, in_length, out_length,
   1058                100L - out_length*100L/in_length));
   1059         if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
   1060     }
   1061 #endif
   1062     return (s->last_lit == s->lit_bufsize-1);
   1063     /* We avoid equality with lit_bufsize because of wraparound at 64K
   1064      * on 16 bit machines and because stored blocks are restricted to
   1065      * 64K-1 bytes.
   1066      */
   1067 }
   1068 
   1069 /* ===========================================================================
   1070  * Send the block data compressed using the given Huffman trees
   1071  */
   1072 local void compress_block(s, ltree, dtree)
   1073     deflate_state *s;
   1074     ct_data *ltree; /* literal tree */
   1075     ct_data *dtree; /* distance tree */
   1076 {
   1077     unsigned dist;      /* distance of matched string */
   1078     int lc;             /* match length or unmatched char (if dist == 0) */
   1079     unsigned lx = 0;    /* running index in l_buf */
   1080     unsigned code;      /* the code to send */
   1081     int extra;          /* number of extra bits to send */
   1082 
   1083     if (s->last_lit != 0) do {
   1084         dist = s->d_buf[lx];
   1085         lc = s->l_buf[lx++];
   1086         if (dist == 0) {
   1087             send_code(s, lc, ltree); /* send a literal byte */
   1088             Tracecv(isgraph(lc), (stderr," '%c' ", lc));
   1089         } else {
   1090             /* Here, lc is the match length - MIN_MATCH */
   1091             code = _length_code[lc];
   1092             send_code(s, code+LITERALS+1, ltree); /* send the length code */
   1093             extra = extra_lbits[code];
   1094             if (extra != 0) {
   1095                 lc -= base_length[code];
   1096                 send_bits(s, lc, extra);       /* send the extra length bits */
   1097             }
   1098             dist--; /* dist is now the match distance - 1 */
   1099             code = d_code(dist);
   1100             Assert (code < D_CODES, "bad d_code");
   1101 
   1102             send_code(s, code, dtree);       /* send the distance code */
   1103             extra = extra_dbits[code];
   1104             if (extra != 0) {
   1105                 dist -= base_dist[code];
   1106                 send_bits(s, dist, extra);   /* send the extra distance bits */
   1107             }
   1108         } /* literal or match pair ? */
   1109 
   1110         /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
   1111         Assert((uInt)(s->pending) < s->lit_bufsize + 2*lx,
   1112                "pendingBuf overflow");
   1113 
   1114     } while (lx < s->last_lit);
   1115 
   1116     send_code(s, END_BLOCK, ltree);
   1117     s->last_eob_len = ltree[END_BLOCK].Len;
   1118 }
   1119 
   1120 /* ===========================================================================
   1121  * Set the data type to BINARY or TEXT, using a crude approximation:
   1122  * set it to Z_TEXT if all symbols are either printable characters (33 to 255)
   1123  * or white spaces (9 to 13, or 32); or set it to Z_BINARY otherwise.
   1124  * IN assertion: the fields Freq of dyn_ltree are set.
   1125  */
   1126 local void set_data_type(s)
   1127     deflate_state *s;
   1128 {
   1129     int n;
   1130 
   1131     for (n = 0; n < 9; n++)
   1132         if (s->dyn_ltree[n].Freq != 0)
   1133             break;
   1134     if (n == 9)
   1135         for (n = 14; n < 32; n++)
   1136             if (s->dyn_ltree[n].Freq != 0)
   1137                 break;
   1138     s->strm->data_type = (n == 32) ? Z_TEXT : Z_BINARY;
   1139 }
   1140 
   1141 /* ===========================================================================
   1142  * Reverse the first len bits of a code, using straightforward code (a faster
   1143  * method would use a table)
   1144  * IN assertion: 1 <= len <= 15
   1145  */
   1146 local unsigned bi_reverse(code, len)
   1147     unsigned code; /* the value to invert */
   1148     int len;       /* its bit length */
   1149 {
   1150     register unsigned res = 0;
   1151     do {
   1152         res |= code & 1;
   1153         code >>= 1, res <<= 1;
   1154     } while (--len > 0);
   1155     return res >> 1;
   1156 }
   1157 
   1158 /* ===========================================================================
   1159  * Flush the bit buffer, keeping at most 7 bits in it.
   1160  */
   1161 local void bi_flush(s)
   1162     deflate_state *s;
   1163 {
   1164     if (s->bi_valid == 16) {
   1165         put_short(s, s->bi_buf);
   1166         s->bi_buf = 0;
   1167         s->bi_valid = 0;
   1168     } else if (s->bi_valid >= 8) {
   1169         put_byte(s, (Byte)s->bi_buf);
   1170         s->bi_buf >>= 8;
   1171         s->bi_valid -= 8;
   1172     }
   1173 }
   1174 
   1175 /* ===========================================================================
   1176  * Flush the bit buffer and align the output on a byte boundary
   1177  */
   1178 local void bi_windup(s)
   1179     deflate_state *s;
   1180 {
   1181     if (s->bi_valid > 8) {
   1182         put_short(s, s->bi_buf);
   1183     } else if (s->bi_valid > 0) {
   1184         put_byte(s, (Byte)s->bi_buf);
   1185     }
   1186     s->bi_buf = 0;
   1187     s->bi_valid = 0;
   1188 #ifdef DEBUG
   1189     s->bits_sent = (s->bits_sent+7) & ~7;
   1190 #endif
   1191 }
   1192 
   1193 /* ===========================================================================
   1194  * Copy a stored block, storing first the length and its
   1195  * one's complement if requested.
   1196  */
   1197 local void copy_block(s, buf, len, header)
   1198     deflate_state *s;
   1199     charf    *buf;    /* the input data */
   1200     unsigned len;     /* its length */
   1201     int      header;  /* true if block header must be written */
   1202 {
   1203     bi_windup(s);        /* align on byte boundary */
   1204     s->last_eob_len = 8; /* enough lookahead for inflate */
   1205 
   1206     if (header) {
   1207         put_short(s, (ush)len);
   1208         put_short(s, (ush)~len);
   1209 #ifdef DEBUG
   1210         s->bits_sent += 2*16;
   1211 #endif
   1212     }
   1213 #ifdef DEBUG
   1214     s->bits_sent += (ulg)len<<3;
   1215 #endif
   1216     while (len--) {
   1217         put_byte(s, *buf++);
   1218     }
   1219 }
   1220