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      1 /* trees.c -- output deflated data using Huffman coding
      2  * Copyright (C) 1995-2012 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 /* ===========================================================================
     78  * Local data. These are initialized only once.
     79  */
     80 
     81 #define DIST_CODE_LEN  512 /* see definition of array dist_code below */
     82 
     83 #if defined(GEN_TREES_H) || !defined(STDC)
     84 /* non ANSI compilers may not accept trees.h */
     85 
     86 local ct_data static_ltree[L_CODES+2];
     87 /* The static literal tree. Since the bit lengths are imposed, there is no
     88  * need for the L_CODES extra codes used during heap construction. However
     89  * The codes 286 and 287 are needed to build a canonical tree (see _tr_init
     90  * below).
     91  */
     92 
     93 local ct_data static_dtree[D_CODES];
     94 /* The static distance tree. (Actually a trivial tree since all codes use
     95  * 5 bits.)
     96  */
     97 
     98 uch _dist_code[DIST_CODE_LEN];
     99 /* Distance codes. The first 256 values correspond to the distances
    100  * 3 .. 258, the last 256 values correspond to the top 8 bits of
    101  * the 15 bit distances.
    102  */
    103 
    104 uch _length_code[MAX_MATCH-MIN_MATCH+1];
    105 /* length code for each normalized match length (0 == MIN_MATCH) */
    106 
    107 local int base_length[LENGTH_CODES];
    108 /* First normalized length for each code (0 = MIN_MATCH) */
    109 
    110 local int base_dist[D_CODES];
    111 /* First normalized distance for each code (0 = distance of 1) */
    112 
    113 #else
    114 #  include "trees.h"
    115 #endif /* GEN_TREES_H */
    116 
    117 struct static_tree_desc_s {
    118     const ct_data *static_tree;  /* static tree or NULL */
    119     const intf *extra_bits;      /* extra bits for each code or NULL */
    120     int     extra_base;          /* base index for extra_bits */
    121     int     elems;               /* max number of elements in the tree */
    122     int     max_length;          /* max bit length for the codes */
    123 };
    124 
    125 local static_tree_desc  static_l_desc =
    126 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
    127 
    128 local static_tree_desc  static_d_desc =
    129 {static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};
    130 
    131 local static_tree_desc  static_bl_desc =
    132 {(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};
    133 
    134 /* ===========================================================================
    135  * Local (static) routines in this file.
    136  */
    137 
    138 local void tr_static_init OF((void));
    139 local void init_block     OF((deflate_state *s));
    140 local void pqdownheap     OF((deflate_state *s, ct_data *tree, int k));
    141 local void gen_bitlen     OF((deflate_state *s, tree_desc *desc));
    142 local void gen_codes      OF((ct_data *tree, int max_code, ushf *bl_count));
    143 local void build_tree     OF((deflate_state *s, tree_desc *desc));
    144 local void scan_tree      OF((deflate_state *s, ct_data *tree, int max_code));
    145 local void send_tree      OF((deflate_state *s, ct_data *tree, int max_code));
    146 local int  build_bl_tree  OF((deflate_state *s));
    147 local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
    148                               int blcodes));
    149 local void compress_block OF((deflate_state *s, const ct_data *ltree,
    150                               const ct_data *dtree));
    151 local int  detect_data_type OF((deflate_state *s));
    152 local unsigned bi_reverse OF((unsigned value, int length));
    153 local void bi_windup      OF((deflate_state *s));
    154 local void bi_flush       OF((deflate_state *s));
    155 local void copy_block     OF((deflate_state *s, charf *buf, unsigned len,
    156                               int header));
    157 
    158 #ifdef GEN_TREES_H
    159 local void gen_trees_header OF((void));
    160 #endif
    161 
    162 #ifndef DEBUG
    163 #  define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
    164    /* Send a code of the given tree. c and tree must not have side effects */
    165 
    166 #else /* DEBUG */
    167 #  define send_code(s, c, tree) \
    168      { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
    169        send_bits(s, tree[c].Code, tree[c].Len); }
    170 #endif
    171 
    172 /* ===========================================================================
    173  * Output a short LSB first on the stream.
    174  * IN assertion: there is enough room in pendingBuf.
    175  */
    176 #define put_short(s, w) { \
    177     put_byte(s, (uch)((w) & 0xff)); \
    178     put_byte(s, (uch)((ush)(w) >> 8)); \
    179 }
    180 
    181 /* ===========================================================================
    182  * Send a value on a given number of bits.
    183  * IN assertion: length <= 16 and value fits in length bits.
    184  */
    185 #ifdef DEBUG
    186 local void send_bits      OF((deflate_state *s, int value, int length));
    187 
    188 local void send_bits(s, value, length)
    189     deflate_state *s;
    190     int value;  /* value to send */
    191     int length; /* number of bits */
    192 {
    193     Tracevv((stderr," l %2d v %4x ", length, value));
    194     Assert(length > 0 && length <= 15, "invalid length");
    195     s->bits_sent += (ulg)length;
    196 
    197     /* If not enough room in bi_buf, use (valid) bits from bi_buf and
    198      * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
    199      * unused bits in value.
    200      */
    201     if (s->bi_valid > (int)Buf_size - length) {
    202         s->bi_buf |= (ush)value << s->bi_valid;
    203         put_short(s, s->bi_buf);
    204         s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
    205         s->bi_valid += length - Buf_size;
    206     } else {
    207         s->bi_buf |= (ush)value << s->bi_valid;
    208         s->bi_valid += length;
    209     }
    210 }
    211 #else /* !DEBUG */
    212 
    213 #define send_bits(s, value, length) \
    214 { int len = length;\
    215   if (s->bi_valid > (int)Buf_size - len) {\
    216     int val = value;\
    217     s->bi_buf |= (ush)val << s->bi_valid;\
    218     put_short(s, s->bi_buf);\
    219     s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
    220     s->bi_valid += len - Buf_size;\
    221   } else {\
    222     s->bi_buf |= (ush)(value) << s->bi_valid;\
    223     s->bi_valid += len;\
    224   }\
    225 }
    226 #endif /* DEBUG */
    227 
    228 
    229 /* the arguments must not have side effects */
    230 
    231 /* ===========================================================================
    232  * Initialize the various 'constant' tables.
    233  */
    234 local void tr_static_init()
    235 {
    236 #if defined(GEN_TREES_H) || !defined(STDC)
    237     static int static_init_done = 0;
    238     int n;        /* iterates over tree elements */
    239     int bits;     /* bit counter */
    240     int length;   /* length value */
    241     int code;     /* code value */
    242     int dist;     /* distance index */
    243     ush bl_count[MAX_BITS+1];
    244     /* number of codes at each bit length for an optimal tree */
    245 
    246     if (static_init_done) return;
    247 
    248     /* For some embedded targets, global variables are not initialized: */
    249 #ifdef NO_INIT_GLOBAL_POINTERS
    250     static_l_desc.static_tree = static_ltree;
    251     static_l_desc.extra_bits = extra_lbits;
    252     static_d_desc.static_tree = static_dtree;
    253     static_d_desc.extra_bits = extra_dbits;
    254     static_bl_desc.extra_bits = extra_blbits;
    255 #endif
    256 
    257     /* Initialize the mapping length (0..255) -> length code (0..28) */
    258     length = 0;
    259     for (code = 0; code < LENGTH_CODES-1; code++) {
    260         base_length[code] = length;
    261         for (n = 0; n < (1<<extra_lbits[code]); n++) {
    262             _length_code[length++] = (uch)code;
    263         }
    264     }
    265     Assert (length == 256, "tr_static_init: length != 256");
    266     /* Note that the length 255 (match length 258) can be represented
    267      * in two different ways: code 284 + 5 bits or code 285, so we
    268      * overwrite length_code[255] to use the best encoding:
    269      */
    270     _length_code[length-1] = (uch)code;
    271 
    272     /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
    273     dist = 0;
    274     for (code = 0 ; code < 16; code++) {
    275         base_dist[code] = dist;
    276         for (n = 0; n < (1<<extra_dbits[code]); n++) {
    277             _dist_code[dist++] = (uch)code;
    278         }
    279     }
    280     Assert (dist == 256, "tr_static_init: dist != 256");
    281     dist >>= 7; /* from now on, all distances are divided by 128 */
    282     for ( ; code < D_CODES; code++) {
    283         base_dist[code] = dist << 7;
    284         for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
    285             _dist_code[256 + dist++] = (uch)code;
    286         }
    287     }
    288     Assert (dist == 256, "tr_static_init: 256+dist != 512");
    289 
    290     /* Construct the codes of the static literal tree */
    291     for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
    292     n = 0;
    293     while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
    294     while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
    295     while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
    296     while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
    297     /* Codes 286 and 287 do not exist, but we must include them in the
    298      * tree construction to get a canonical Huffman tree (longest code
    299      * all ones)
    300      */
    301     gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
    302 
    303     /* The static distance tree is trivial: */
    304     for (n = 0; n < D_CODES; n++) {
    305         static_dtree[n].Len = 5;
    306         static_dtree[n].Code = bi_reverse((unsigned)n, 5);
    307     }
    308     static_init_done = 1;
    309 
    310 #  ifdef GEN_TREES_H
    311     gen_trees_header();
    312 #  endif
    313 #endif /* defined(GEN_TREES_H) || !defined(STDC) */
    314 }
    315 
    316 /* ===========================================================================
    317  * Genererate the file trees.h describing the static trees.
    318  */
    319 #ifdef GEN_TREES_H
    320 #  ifndef DEBUG
    321 #    include <stdio.h>
    322 #  endif
    323 
    324 #  define SEPARATOR(i, last, width) \
    325       ((i) == (last)? "\n};\n\n" :    \
    326        ((i) % (width) == (width)-1 ? ",\n" : ", "))
    327 
    328 void gen_trees_header()
    329 {
    330     FILE *header = fopen("trees.h", "w");
    331     int i;
    332 
    333     Assert (header != NULL, "Can't open trees.h");
    334     fprintf(header,
    335             "/* header created automatically with -DGEN_TREES_H */\n\n");
    336 
    337     fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");
    338     for (i = 0; i < L_CODES+2; i++) {
    339         fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,
    340                 static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
    341     }
    342 
    343     fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");
    344     for (i = 0; i < D_CODES; i++) {
    345         fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,
    346                 static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
    347     }
    348 
    349     fprintf(header, "const uch ZLIB_INTERNAL _dist_code[DIST_CODE_LEN] = {\n");
    350     for (i = 0; i < DIST_CODE_LEN; i++) {
    351         fprintf(header, "%2u%s", _dist_code[i],
    352                 SEPARATOR(i, DIST_CODE_LEN-1, 20));
    353     }
    354 
    355     fprintf(header,
    356         "const uch ZLIB_INTERNAL _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");
    357     for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {
    358         fprintf(header, "%2u%s", _length_code[i],
    359                 SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
    360     }
    361 
    362     fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");
    363     for (i = 0; i < LENGTH_CODES; i++) {
    364         fprintf(header, "%1u%s", base_length[i],
    365                 SEPARATOR(i, LENGTH_CODES-1, 20));
    366     }
    367 
    368     fprintf(header, "local const int base_dist[D_CODES] = {\n");
    369     for (i = 0; i < D_CODES; i++) {
    370         fprintf(header, "%5u%s", base_dist[i],
    371                 SEPARATOR(i, D_CODES-1, 10));
    372     }
    373 
    374     fclose(header);
    375 }
    376 #endif /* GEN_TREES_H */
    377 
    378 /* ===========================================================================
    379  * Initialize the tree data structures for a new zlib stream.
    380  */
    381 void ZLIB_INTERNAL _tr_init(s)
    382     deflate_state *s;
    383 {
    384     tr_static_init();
    385 
    386     s->l_desc.dyn_tree = s->dyn_ltree;
    387     s->l_desc.stat_desc = &static_l_desc;
    388 
    389     s->d_desc.dyn_tree = s->dyn_dtree;
    390     s->d_desc.stat_desc = &static_d_desc;
    391 
    392     s->bl_desc.dyn_tree = s->bl_tree;
    393     s->bl_desc.stat_desc = &static_bl_desc;
    394 
    395     s->bi_buf = 0;
    396     s->bi_valid = 0;
    397 #ifdef DEBUG
    398     s->compressed_len = 0L;
    399     s->bits_sent = 0L;
    400 #endif
    401 
    402     /* Initialize the first block of the first file: */
    403     init_block(s);
    404 }
    405 
    406 /* ===========================================================================
    407  * Initialize a new block.
    408  */
    409 local void init_block(s)
    410     deflate_state *s;
    411 {
    412     int n; /* iterates over tree elements */
    413 
    414     /* Initialize the trees. */
    415     for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
    416     for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
    417     for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
    418 
    419     s->dyn_ltree[END_BLOCK].Freq = 1;
    420     s->opt_len = s->static_len = 0L;
    421     s->last_lit = s->matches = 0;
    422 }
    423 
    424 #define SMALLEST 1
    425 /* Index within the heap array of least frequent node in the Huffman tree */
    426 
    427 
    428 /* ===========================================================================
    429  * Remove the smallest element from the heap and recreate the heap with
    430  * one less element. Updates heap and heap_len.
    431  */
    432 #define pqremove(s, tree, top) \
    433 {\
    434     top = s->heap[SMALLEST]; \
    435     s->heap[SMALLEST] = s->heap[s->heap_len--]; \
    436     pqdownheap(s, tree, SMALLEST); \
    437 }
    438 
    439 /* ===========================================================================
    440  * Compares to subtrees, using the tree depth as tie breaker when
    441  * the subtrees have equal frequency. This minimizes the worst case length.
    442  */
    443 #define smaller(tree, n, m, depth) \
    444    (tree[n].Freq < tree[m].Freq || \
    445    (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
    446 
    447 /* ===========================================================================
    448  * Restore the heap property by moving down the tree starting at node k,
    449  * exchanging a node with the smallest of its two sons if necessary, stopping
    450  * when the heap property is re-established (each father smaller than its
    451  * two sons).
    452  */
    453 local void pqdownheap(s, tree, k)
    454     deflate_state *s;
    455     ct_data *tree;  /* the tree to restore */
    456     int k;               /* node to move down */
    457 {
    458     int v = s->heap[k];
    459     int j = k << 1;  /* left son of k */
    460     while (j <= s->heap_len) {
    461         /* Set j to the smallest of the two sons: */
    462         if (j < s->heap_len &&
    463             smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
    464             j++;
    465         }
    466         /* Exit if v is smaller than both sons */
    467         if (smaller(tree, v, s->heap[j], s->depth)) break;
    468 
    469         /* Exchange v with the smallest son */
    470         s->heap[k] = s->heap[j];  k = j;
    471 
    472         /* And continue down the tree, setting j to the left son of k */
    473         j <<= 1;
    474     }
    475     s->heap[k] = v;
    476 }
    477 
    478 /* ===========================================================================
    479  * Compute the optimal bit lengths for a tree and update the total bit length
    480  * for the current block.
    481  * IN assertion: the fields freq and dad are set, heap[heap_max] and
    482  *    above are the tree nodes sorted by increasing frequency.
    483  * OUT assertions: the field len is set to the optimal bit length, the
    484  *     array bl_count contains the frequencies for each bit length.
    485  *     The length opt_len is updated; static_len is also updated if stree is
    486  *     not null.
    487  */
    488 local void gen_bitlen(s, desc)
    489     deflate_state *s;
    490     tree_desc *desc;    /* the tree descriptor */
    491 {
    492     ct_data *tree        = desc->dyn_tree;
    493     int max_code         = desc->max_code;
    494     const ct_data *stree = desc->stat_desc->static_tree;
    495     const intf *extra    = desc->stat_desc->extra_bits;
    496     int base             = desc->stat_desc->extra_base;
    497     int max_length       = desc->stat_desc->max_length;
    498     int h;              /* heap index */
    499     int n, m;           /* iterate over the tree elements */
    500     int bits;           /* bit length */
    501     int xbits;          /* extra bits */
    502     ush f;              /* frequency */
    503     int overflow = 0;   /* number of elements with bit length too large */
    504 
    505     for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
    506 
    507     /* In a first pass, compute the optimal bit lengths (which may
    508      * overflow in the case of the bit length tree).
    509      */
    510     tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
    511 
    512     for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
    513         n = s->heap[h];
    514         bits = tree[tree[n].Dad].Len + 1;
    515         if (bits > max_length) bits = max_length, overflow++;
    516         tree[n].Len = (ush)bits;
    517         /* We overwrite tree[n].Dad which is no longer needed */
    518 
    519         if (n > max_code) continue; /* not a leaf node */
    520 
    521         s->bl_count[bits]++;
    522         xbits = 0;
    523         if (n >= base) xbits = extra[n-base];
    524         f = tree[n].Freq;
    525         s->opt_len += (ulg)f * (bits + xbits);
    526         if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
    527     }
    528     if (overflow == 0) return;
    529 
    530     Trace((stderr,"\nbit length overflow\n"));
    531     /* This happens for example on obj2 and pic of the Calgary corpus */
    532 
    533     /* Find the first bit length which could increase: */
    534     do {
    535         bits = max_length-1;
    536         while (s->bl_count[bits] == 0) bits--;
    537         s->bl_count[bits]--;      /* move one leaf down the tree */
    538         s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
    539         s->bl_count[max_length]--;
    540         /* The brother of the overflow item also moves one step up,
    541          * but this does not affect bl_count[max_length]
    542          */
    543         overflow -= 2;
    544     } while (overflow > 0);
    545 
    546     /* Now recompute all bit lengths, scanning in increasing frequency.
    547      * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
    548      * lengths instead of fixing only the wrong ones. This idea is taken
    549      * from 'ar' written by Haruhiko Okumura.)
    550      */
    551     for (bits = max_length; bits != 0; bits--) {
    552         n = s->bl_count[bits];
    553         while (n != 0) {
    554             m = s->heap[--h];
    555             if (m > max_code) continue;
    556             if ((unsigned) tree[m].Len != (unsigned) bits) {
    557                 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
    558                 s->opt_len += ((long)bits - (long)tree[m].Len)
    559                               *(long)tree[m].Freq;
    560                 tree[m].Len = (ush)bits;
    561             }
    562             n--;
    563         }
    564     }
    565 }
    566 
    567 /* ===========================================================================
    568  * Generate the codes for a given tree and bit counts (which need not be
    569  * optimal).
    570  * IN assertion: the array bl_count contains the bit length statistics for
    571  * the given tree and the field len is set for all tree elements.
    572  * OUT assertion: the field code is set for all tree elements of non
    573  *     zero code length.
    574  */
    575 local void gen_codes (tree, max_code, bl_count)
    576     ct_data *tree;             /* the tree to decorate */
    577     int max_code;              /* largest code with non zero frequency */
    578     ushf *bl_count;            /* number of codes at each bit length */
    579 {
    580     ush next_code[MAX_BITS+1]; /* next code value for each bit length */
    581     ush code = 0;              /* running code value */
    582     int bits;                  /* bit index */
    583     int n;                     /* code index */
    584 
    585     /* The distribution counts are first used to generate the code values
    586      * without bit reversal.
    587      */
    588     for (bits = 1; bits <= MAX_BITS; bits++) {
    589         next_code[bits] = code = (code + bl_count[bits-1]) << 1;
    590     }
    591     /* Check that the bit counts in bl_count are consistent. The last code
    592      * must be all ones.
    593      */
    594     Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
    595             "inconsistent bit counts");
    596     Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
    597 
    598     for (n = 0;  n <= max_code; n++) {
    599         int len = tree[n].Len;
    600         if (len == 0) continue;
    601         /* Now reverse the bits */
    602         tree[n].Code = bi_reverse(next_code[len]++, len);
    603 
    604         Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
    605              n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
    606     }
    607 }
    608 
    609 /* ===========================================================================
    610  * Construct one Huffman tree and assigns the code bit strings and lengths.
    611  * Update the total bit length for the current block.
    612  * IN assertion: the field freq is set for all tree elements.
    613  * OUT assertions: the fields len and code are set to the optimal bit length
    614  *     and corresponding code. The length opt_len is updated; static_len is
    615  *     also updated if stree is not null. The field max_code is set.
    616  */
    617 local void build_tree(s, desc)
    618     deflate_state *s;
    619     tree_desc *desc; /* the tree descriptor */
    620 {
    621     ct_data *tree         = desc->dyn_tree;
    622     const ct_data *stree  = desc->stat_desc->static_tree;
    623     int elems             = desc->stat_desc->elems;
    624     int n, m;          /* iterate over heap elements */
    625     int max_code = -1; /* largest code with non zero frequency */
    626     int node;          /* new node being created */
    627 
    628     /* Construct the initial heap, with least frequent element in
    629      * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
    630      * heap[0] is not used.
    631      */
    632     s->heap_len = 0, s->heap_max = HEAP_SIZE;
    633 
    634     for (n = 0; n < elems; n++) {
    635         if (tree[n].Freq != 0) {
    636             s->heap[++(s->heap_len)] = max_code = n;
    637             s->depth[n] = 0;
    638         } else {
    639             tree[n].Len = 0;
    640         }
    641     }
    642 
    643     /* The pkzip format requires that at least one distance code exists,
    644      * and that at least one bit should be sent even if there is only one
    645      * possible code. So to avoid special checks later on we force at least
    646      * two codes of non zero frequency.
    647      */
    648     while (s->heap_len < 2) {
    649         node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
    650         tree[node].Freq = 1;
    651         s->depth[node] = 0;
    652         s->opt_len--; if (stree) s->static_len -= stree[node].Len;
    653         /* node is 0 or 1 so it does not have extra bits */
    654     }
    655     desc->max_code = max_code;
    656 
    657     /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
    658      * establish sub-heaps of increasing lengths:
    659      */
    660     for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
    661 
    662     /* Construct the Huffman tree by repeatedly combining the least two
    663      * frequent nodes.
    664      */
    665     node = elems;              /* next internal node of the tree */
    666     do {
    667         pqremove(s, tree, n);  /* n = node of least frequency */
    668         m = s->heap[SMALLEST]; /* m = node of next least frequency */
    669 
    670         s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
    671         s->heap[--(s->heap_max)] = m;
    672 
    673         /* Create a new node father of n and m */
    674         tree[node].Freq = tree[n].Freq + tree[m].Freq;
    675         s->depth[node] = (uch)((s->depth[n] >= s->depth[m] ?
    676                                 s->depth[n] : s->depth[m]) + 1);
    677         tree[n].Dad = tree[m].Dad = (ush)node;
    678 #ifdef DUMP_BL_TREE
    679         if (tree == s->bl_tree) {
    680             fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
    681                     node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
    682         }
    683 #endif
    684         /* and insert the new node in the heap */
    685         s->heap[SMALLEST] = node++;
    686         pqdownheap(s, tree, SMALLEST);
    687 
    688     } while (s->heap_len >= 2);
    689 
    690     s->heap[--(s->heap_max)] = s->heap[SMALLEST];
    691 
    692     /* At this point, the fields freq and dad are set. We can now
    693      * generate the bit lengths.
    694      */
    695     gen_bitlen(s, (tree_desc *)desc);
    696 
    697     /* The field len is now set, we can generate the bit codes */
    698     gen_codes ((ct_data *)tree, max_code, s->bl_count);
    699 }
    700 
    701 /* ===========================================================================
    702  * Scan a literal or distance tree to determine the frequencies of the codes
    703  * in the bit length tree.
    704  */
    705 local void scan_tree (s, tree, max_code)
    706     deflate_state *s;
    707     ct_data *tree;   /* the tree to be scanned */
    708     int max_code;    /* and its largest code of non zero frequency */
    709 {
    710     int n;                     /* iterates over all tree elements */
    711     int prevlen = -1;          /* last emitted length */
    712     int curlen;                /* length of current code */
    713     int nextlen = tree[0].Len; /* length of next code */
    714     int count = 0;             /* repeat count of the current code */
    715     int max_count = 7;         /* max repeat count */
    716     int min_count = 4;         /* min repeat count */
    717 
    718     if (nextlen == 0) max_count = 138, min_count = 3;
    719     tree[max_code+1].Len = (ush)0xffff; /* guard */
    720 
    721     for (n = 0; n <= max_code; n++) {
    722         curlen = nextlen; nextlen = tree[n+1].Len;
    723         if (++count < max_count && curlen == nextlen) {
    724             continue;
    725         } else if (count < min_count) {
    726             s->bl_tree[curlen].Freq += count;
    727         } else if (curlen != 0) {
    728             if (curlen != prevlen) s->bl_tree[curlen].Freq++;
    729             s->bl_tree[REP_3_6].Freq++;
    730         } else if (count <= 10) {
    731             s->bl_tree[REPZ_3_10].Freq++;
    732         } else {
    733             s->bl_tree[REPZ_11_138].Freq++;
    734         }
    735         count = 0; prevlen = curlen;
    736         if (nextlen == 0) {
    737             max_count = 138, min_count = 3;
    738         } else if (curlen == nextlen) {
    739             max_count = 6, min_count = 3;
    740         } else {
    741             max_count = 7, min_count = 4;
    742         }
    743     }
    744 }
    745 
    746 /* ===========================================================================
    747  * Send a literal or distance tree in compressed form, using the codes in
    748  * bl_tree.
    749  */
    750 local void send_tree (s, tree, max_code)
    751     deflate_state *s;
    752     ct_data *tree; /* the tree to be scanned */
    753     int max_code;       /* and its largest code of non zero frequency */
    754 {
    755     int n;                     /* iterates over all tree elements */
    756     int prevlen = -1;          /* last emitted length */
    757     int curlen;                /* length of current code */
    758     int nextlen = tree[0].Len; /* length of next code */
    759     int count = 0;             /* repeat count of the current code */
    760     int max_count = 7;         /* max repeat count */
    761     int min_count = 4;         /* min repeat count */
    762 
    763     /* tree[max_code+1].Len = -1; */  /* guard already set */
    764     if (nextlen == 0) max_count = 138, min_count = 3;
    765 
    766     for (n = 0; n <= max_code; n++) {
    767         curlen = nextlen; nextlen = tree[n+1].Len;
    768         if (++count < max_count && curlen == nextlen) {
    769             continue;
    770         } else if (count < min_count) {
    771             do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
    772 
    773         } else if (curlen != 0) {
    774             if (curlen != prevlen) {
    775                 send_code(s, curlen, s->bl_tree); count--;
    776             }
    777             Assert(count >= 3 && count <= 6, " 3_6?");
    778             send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
    779 
    780         } else if (count <= 10) {
    781             send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
    782 
    783         } else {
    784             send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
    785         }
    786         count = 0; prevlen = curlen;
    787         if (nextlen == 0) {
    788             max_count = 138, min_count = 3;
    789         } else if (curlen == nextlen) {
    790             max_count = 6, min_count = 3;
    791         } else {
    792             max_count = 7, min_count = 4;
    793         }
    794     }
    795 }
    796 
    797 /* ===========================================================================
    798  * Construct the Huffman tree for the bit lengths and return the index in
    799  * bl_order of the last bit length code to send.
    800  */
    801 local int build_bl_tree(s)
    802     deflate_state *s;
    803 {
    804     int max_blindex;  /* index of last bit length code of non zero freq */
    805 
    806     /* Determine the bit length frequencies for literal and distance trees */
    807     scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
    808     scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
    809 
    810     /* Build the bit length tree: */
    811     build_tree(s, (tree_desc *)(&(s->bl_desc)));
    812     /* opt_len now includes the length of the tree representations, except
    813      * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
    814      */
    815 
    816     /* Determine the number of bit length codes to send. The pkzip format
    817      * requires that at least 4 bit length codes be sent. (appnote.txt says
    818      * 3 but the actual value used is 4.)
    819      */
    820     for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
    821         if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
    822     }
    823     /* Update opt_len to include the bit length tree and counts */
    824     s->opt_len += 3*(max_blindex+1) + 5+5+4;
    825     Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
    826             s->opt_len, s->static_len));
    827 
    828     return max_blindex;
    829 }
    830 
    831 /* ===========================================================================
    832  * Send the header for a block using dynamic Huffman trees: the counts, the
    833  * lengths of the bit length codes, the literal tree and the distance tree.
    834  * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
    835  */
    836 local void send_all_trees(s, lcodes, dcodes, blcodes)
    837     deflate_state *s;
    838     int lcodes, dcodes, blcodes; /* number of codes for each tree */
    839 {
    840     int rank;                    /* index in bl_order */
    841 
    842     Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
    843     Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
    844             "too many codes");
    845     Tracev((stderr, "\nbl counts: "));
    846     send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
    847     send_bits(s, dcodes-1,   5);
    848     send_bits(s, blcodes-4,  4); /* not -3 as stated in appnote.txt */
    849     for (rank = 0; rank < blcodes; rank++) {
    850         Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
    851         send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
    852     }
    853     Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
    854 
    855     send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
    856     Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
    857 
    858     send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
    859     Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
    860 }
    861 
    862 /* ===========================================================================
    863  * Send a stored block
    864  */
    865 void ZLIB_INTERNAL _tr_stored_block(s, buf, stored_len, last)
    866     deflate_state *s;
    867     charf *buf;       /* input block */
    868     ulg stored_len;   /* length of input block */
    869     int last;         /* one if this is the last block for a file */
    870 {
    871     send_bits(s, (STORED_BLOCK<<1)+last, 3);    /* send block type */
    872 #ifdef DEBUG
    873     s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
    874     s->compressed_len += (stored_len + 4) << 3;
    875 #endif
    876     copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
    877 }
    878 
    879 /* ===========================================================================
    880  * Flush the bits in the bit buffer to pending output (leaves at most 7 bits)
    881  */
    882 void ZLIB_INTERNAL _tr_flush_bits(s)
    883     deflate_state *s;
    884 {
    885     bi_flush(s);
    886 }
    887 
    888 /* ===========================================================================
    889  * Send one empty static block to give enough lookahead for inflate.
    890  * This takes 10 bits, of which 7 may remain in the bit buffer.
    891  */
    892 void ZLIB_INTERNAL _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 }
    902 
    903 /* ===========================================================================
    904  * Determine the best encoding for the current block: dynamic trees, static
    905  * trees or store, and output the encoded block to the zip file.
    906  */
    907 void ZLIB_INTERNAL _tr_flush_block(s, buf, stored_len, last)
    908     deflate_state *s;
    909     charf *buf;       /* input block, or NULL if too old */
    910     ulg stored_len;   /* length of input block */
    911     int last;         /* one if this is the last block for a file */
    912 {
    913     ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
    914     int max_blindex = 0;  /* index of last bit length code of non zero freq */
    915 
    916     /* Build the Huffman trees unless a stored block is forced */
    917     if (s->level > 0) {
    918 
    919         /* Check if the file is binary or text */
    920         if (s->strm->data_type == Z_UNKNOWN)
    921             s->strm->data_type = detect_data_type(s);
    922 
    923         /* Construct the literal and distance trees */
    924         build_tree(s, (tree_desc *)(&(s->l_desc)));
    925         Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
    926                 s->static_len));
    927 
    928         build_tree(s, (tree_desc *)(&(s->d_desc)));
    929         Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
    930                 s->static_len));
    931         /* At this point, opt_len and static_len are the total bit lengths of
    932          * the compressed block data, excluding the tree representations.
    933          */
    934 
    935         /* Build the bit length tree for the above two trees, and get the index
    936          * in bl_order of the last bit length code to send.
    937          */
    938         max_blindex = build_bl_tree(s);
    939 
    940         /* Determine the best encoding. Compute the block lengths in bytes. */
    941         opt_lenb = (s->opt_len+3+7)>>3;
    942         static_lenb = (s->static_len+3+7)>>3;
    943 
    944         Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
    945                 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
    946                 s->last_lit));
    947 
    948         if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
    949 
    950     } else {
    951         Assert(buf != (char*)0, "lost buf");
    952         opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
    953     }
    954 
    955 #ifdef FORCE_STORED
    956     if (buf != (char*)0) { /* force stored block */
    957 #else
    958     if (stored_len+4 <= opt_lenb && buf != (char*)0) {
    959                        /* 4: two words for the lengths */
    960 #endif
    961         /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
    962          * Otherwise we can't have processed more than WSIZE input bytes since
    963          * the last block flush, because compression would have been
    964          * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
    965          * transform a block into a stored block.
    966          */
    967         _tr_stored_block(s, buf, stored_len, last);
    968 
    969 #ifdef FORCE_STATIC
    970     } else if (static_lenb >= 0) { /* force static trees */
    971 #else
    972     } else if (s->strategy == Z_FIXED || static_lenb == opt_lenb) {
    973 #endif
    974         send_bits(s, (STATIC_TREES<<1)+last, 3);
    975         compress_block(s, (const ct_data *)static_ltree,
    976                        (const ct_data *)static_dtree);
    977 #ifdef DEBUG
    978         s->compressed_len += 3 + s->static_len;
    979 #endif
    980     } else {
    981         send_bits(s, (DYN_TREES<<1)+last, 3);
    982         send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
    983                        max_blindex+1);
    984         compress_block(s, (const ct_data *)s->dyn_ltree,
    985                        (const ct_data *)s->dyn_dtree);
    986 #ifdef DEBUG
    987         s->compressed_len += 3 + s->opt_len;
    988 #endif
    989     }
    990     Assert (s->compressed_len == s->bits_sent, "bad compressed size");
    991     /* The above check is made mod 2^32, for files larger than 512 MB
    992      * and uLong implemented on 32 bits.
    993      */
    994     init_block(s);
    995 
    996     if (last) {
    997         bi_windup(s);
    998 #ifdef DEBUG
    999         s->compressed_len += 7;  /* align on byte boundary */
   1000 #endif
   1001     }
   1002     Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
   1003            s->compressed_len-7*last));
   1004 }
   1005 
   1006 /* ===========================================================================
   1007  * Save the match info and tally the frequency counts. Return true if
   1008  * the current block must be flushed.
   1009  */
   1010 int ZLIB_INTERNAL _tr_tally (s, dist, lc)
   1011     deflate_state *s;
   1012     unsigned dist;  /* distance of matched string */
   1013     unsigned lc;    /* match length-MIN_MATCH or unmatched char (if dist==0) */
   1014 {
   1015     s->d_buf[s->last_lit] = (ush)dist;
   1016     s->l_buf[s->last_lit++] = (uch)lc;
   1017     if (dist == 0) {
   1018         /* lc is the unmatched char */
   1019         s->dyn_ltree[lc].Freq++;
   1020     } else {
   1021         s->matches++;
   1022         /* Here, lc is the match length - MIN_MATCH */
   1023         dist--;             /* dist = match distance - 1 */
   1024         Assert((ush)dist < (ush)MAX_DIST(s) &&
   1025                (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
   1026                (ush)d_code(dist) < (ush)D_CODES,  "_tr_tally: bad match");
   1027 
   1028         s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
   1029         s->dyn_dtree[d_code(dist)].Freq++;
   1030     }
   1031 
   1032 #ifdef TRUNCATE_BLOCK
   1033     /* Try to guess if it is profitable to stop the current block here */
   1034     if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
   1035         /* Compute an upper bound for the compressed length */
   1036         ulg out_length = (ulg)s->last_lit*8L;
   1037         ulg in_length = (ulg)((long)s->strstart - s->block_start);
   1038         int dcode;
   1039         for (dcode = 0; dcode < D_CODES; dcode++) {
   1040             out_length += (ulg)s->dyn_dtree[dcode].Freq *
   1041                 (5L+extra_dbits[dcode]);
   1042         }
   1043         out_length >>= 3;
   1044         Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
   1045                s->last_lit, in_length, out_length,
   1046                100L - out_length*100L/in_length));
   1047         if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
   1048     }
   1049 #endif
   1050     return (s->last_lit == s->lit_bufsize-1);
   1051     /* We avoid equality with lit_bufsize because of wraparound at 64K
   1052      * on 16 bit machines and because stored blocks are restricted to
   1053      * 64K-1 bytes.
   1054      */
   1055 }
   1056 
   1057 /* ===========================================================================
   1058  * Send the block data compressed using the given Huffman trees
   1059  */
   1060 local void compress_block(s, ltree, dtree)
   1061     deflate_state *s;
   1062     const ct_data *ltree; /* literal tree */
   1063     const ct_data *dtree; /* distance tree */
   1064 {
   1065     unsigned dist;      /* distance of matched string */
   1066     int lc;             /* match length or unmatched char (if dist == 0) */
   1067     unsigned lx = 0;    /* running index in l_buf */
   1068     unsigned code;      /* the code to send */
   1069     int extra;          /* number of extra bits to send */
   1070 
   1071     if (s->last_lit != 0) do {
   1072         dist = s->d_buf[lx];
   1073         lc = s->l_buf[lx++];
   1074         if (dist == 0) {
   1075             send_code(s, lc, ltree); /* send a literal byte */
   1076             Tracecv(isgraph(lc), (stderr," '%c' ", lc));
   1077         } else {
   1078             /* Here, lc is the match length - MIN_MATCH */
   1079             code = _length_code[lc];
   1080             send_code(s, code+LITERALS+1, ltree); /* send the length code */
   1081             extra = extra_lbits[code];
   1082             if (extra != 0) {
   1083                 lc -= base_length[code];
   1084                 send_bits(s, lc, extra);       /* send the extra length bits */
   1085             }
   1086             dist--; /* dist is now the match distance - 1 */
   1087             code = d_code(dist);
   1088             Assert (code < D_CODES, "bad d_code");
   1089 
   1090             send_code(s, code, dtree);       /* send the distance code */
   1091             extra = extra_dbits[code];
   1092             if (extra != 0) {
   1093                 dist -= base_dist[code];
   1094                 send_bits(s, dist, extra);   /* send the extra distance bits */
   1095             }
   1096         } /* literal or match pair ? */
   1097 
   1098         /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
   1099         Assert((uInt)(s->pending) < s->lit_bufsize + 2*lx,
   1100                "pendingBuf overflow");
   1101 
   1102     } while (lx < s->last_lit);
   1103 
   1104     send_code(s, END_BLOCK, ltree);
   1105 }
   1106 
   1107 /* ===========================================================================
   1108  * Check if the data type is TEXT or BINARY, using the following algorithm:
   1109  * - TEXT if the two conditions below are satisfied:
   1110  *    a) There are no non-portable control characters belonging to the
   1111  *       "black list" (0..6, 14..25, 28..31).
   1112  *    b) There is at least one printable character belonging to the
   1113  *       "white list" (9 {TAB}, 10 {LF}, 13 {CR}, 32..255).
   1114  * - BINARY otherwise.
   1115  * - The following partially-portable control characters form a
   1116  *   "gray list" that is ignored in this detection algorithm:
   1117  *   (7 {BEL}, 8 {BS}, 11 {VT}, 12 {FF}, 26 {SUB}, 27 {ESC}).
   1118  * IN assertion: the fields Freq of dyn_ltree are set.
   1119  */
   1120 local int detect_data_type(s)
   1121     deflate_state *s;
   1122 {
   1123     /* black_mask is the bit mask of black-listed bytes
   1124      * set bits 0..6, 14..25, and 28..31
   1125      * 0xf3ffc07f = binary 11110011111111111100000001111111
   1126      */
   1127     unsigned long black_mask = 0xf3ffc07fUL;
   1128     int n;
   1129 
   1130     /* Check for non-textual ("black-listed") bytes. */
   1131     for (n = 0; n <= 31; n++, black_mask >>= 1)
   1132         if ((black_mask & 1) && (s->dyn_ltree[n].Freq != 0))
   1133             return Z_BINARY;
   1134 
   1135     /* Check for textual ("white-listed") bytes. */
   1136     if (s->dyn_ltree[9].Freq != 0 || s->dyn_ltree[10].Freq != 0
   1137             || s->dyn_ltree[13].Freq != 0)
   1138         return Z_TEXT;
   1139     for (n = 32; n < LITERALS; n++)
   1140         if (s->dyn_ltree[n].Freq != 0)
   1141             return Z_TEXT;
   1142 
   1143     /* There are no "black-listed" or "white-listed" bytes:
   1144      * this stream either is empty or has tolerated ("gray-listed") bytes only.
   1145      */
   1146     return Z_BINARY;
   1147 }
   1148 
   1149 /* ===========================================================================
   1150  * Reverse the first len bits of a code, using straightforward code (a faster
   1151  * method would use a table)
   1152  * IN assertion: 1 <= len <= 15
   1153  */
   1154 local unsigned bi_reverse(code, len)
   1155     unsigned code; /* the value to invert */
   1156     int len;       /* its bit length */
   1157 {
   1158     register unsigned res = 0;
   1159     do {
   1160         res |= code & 1;
   1161         code >>= 1, res <<= 1;
   1162     } while (--len > 0);
   1163     return res >> 1;
   1164 }
   1165 
   1166 /* ===========================================================================
   1167  * Flush the bit buffer, keeping at most 7 bits in it.
   1168  */
   1169 local void bi_flush(s)
   1170     deflate_state *s;
   1171 {
   1172     if (s->bi_valid == 16) {
   1173         put_short(s, s->bi_buf);
   1174         s->bi_buf = 0;
   1175         s->bi_valid = 0;
   1176     } else if (s->bi_valid >= 8) {
   1177         put_byte(s, (Byte)s->bi_buf);
   1178         s->bi_buf >>= 8;
   1179         s->bi_valid -= 8;
   1180     }
   1181 }
   1182 
   1183 /* ===========================================================================
   1184  * Flush the bit buffer and align the output on a byte boundary
   1185  */
   1186 local void bi_windup(s)
   1187     deflate_state *s;
   1188 {
   1189     if (s->bi_valid > 8) {
   1190         put_short(s, s->bi_buf);
   1191     } else if (s->bi_valid > 0) {
   1192         put_byte(s, (Byte)s->bi_buf);
   1193     }
   1194     s->bi_buf = 0;
   1195     s->bi_valid = 0;
   1196 #ifdef DEBUG
   1197     s->bits_sent = (s->bits_sent+7) & ~7;
   1198 #endif
   1199 }
   1200 
   1201 /* ===========================================================================
   1202  * Copy a stored block, storing first the length and its
   1203  * one's complement if requested.
   1204  */
   1205 local void copy_block(s, buf, len, header)
   1206     deflate_state *s;
   1207     charf    *buf;    /* the input data */
   1208     unsigned len;     /* its length */
   1209     int      header;  /* true if block header must be written */
   1210 {
   1211     bi_windup(s);        /* align on byte boundary */
   1212 
   1213     if (header) {
   1214         put_short(s, (ush)len);
   1215         put_short(s, (ush)~len);
   1216 #ifdef DEBUG
   1217         s->bits_sent += 2*16;
   1218 #endif
   1219     }
   1220 #ifdef DEBUG
   1221     s->bits_sent += (ulg)len<<3;
   1222 #endif
   1223     while (len--) {
   1224         put_byte(s, *buf++);
   1225     }
   1226 }
   1227