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
62local 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
65local 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
68local 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
71local 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
86local 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
93local ct_data static_dtree[D_CODES];
94/* The static distance tree. (Actually a trivial tree since all codes use
95 * 5 bits.)
96 */
97
98uch _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
104uch _length_code[MAX_MATCH-MIN_MATCH+1];
105/* length code for each normalized match length (0 == MIN_MATCH) */
106
107local int base_length[LENGTH_CODES];
108/* First normalized length for each code (0 = MIN_MATCH) */
109
110local 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
117struct 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
125local static_tree_desc  static_l_desc =
126{static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
127
128local static_tree_desc  static_d_desc =
129{static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};
130
131local 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
138local void tr_static_init OF((void));
139local void init_block     OF((deflate_state *s));
140local void pqdownheap     OF((deflate_state *s, ct_data *tree, int k));
141local void gen_bitlen     OF((deflate_state *s, tree_desc *desc));
142local void gen_codes      OF((ct_data *tree, int max_code, ushf *bl_count));
143local void build_tree     OF((deflate_state *s, tree_desc *desc));
144local void scan_tree      OF((deflate_state *s, ct_data *tree, int max_code));
145local void send_tree      OF((deflate_state *s, ct_data *tree, int max_code));
146local int  build_bl_tree  OF((deflate_state *s));
147local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
148                              int blcodes));
149local void compress_block OF((deflate_state *s, const ct_data *ltree,
150                              const ct_data *dtree));
151local int  detect_data_type OF((deflate_state *s));
152local unsigned bi_reverse OF((unsigned value, int length));
153local void bi_windup      OF((deflate_state *s));
154local void bi_flush       OF((deflate_state *s));
155local void copy_block     OF((deflate_state *s, charf *buf, unsigned len,
156                              int header));
157
158#ifdef GEN_TREES_H
159local 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
186local void send_bits      OF((deflate_state *s, int value, int length));
187
188local 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 */
234local 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
328void 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 */
381void 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 */
409local 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 */
453local 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 */
488local 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 */
575local 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 */
617local 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 */
705local 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 */
750local 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 */
801local 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 */
836local 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 */
865void 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 */
882void 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 */
892void 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 */
907void 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 */
1010int 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 */
1060local 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 */
1120local 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 */
1154local 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 */
1169local 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 */
1186local 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 */
1205local 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