xref: /openbmc/linux/lib/zlib_deflate/deftree.c (revision aa5b395b)
1 /* +++ trees.c */
2 /* trees.c -- output deflated data using Huffman coding
3  * Copyright (C) 1995-1996 Jean-loup Gailly
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 /* From: trees.c,v 1.11 1996/07/24 13:41:06 me Exp $ */
34 
35 /* #include "deflate.h" */
36 
37 #include <linux/zutil.h>
38 #include <linux/bitrev.h>
39 #include "defutil.h"
40 
41 #ifdef DEBUG_ZLIB
42 #  include <ctype.h>
43 #endif
44 
45 /* ===========================================================================
46  * Constants
47  */
48 
49 #define MAX_BL_BITS 7
50 /* Bit length codes must not exceed MAX_BL_BITS bits */
51 
52 #define END_BLOCK 256
53 /* end of block literal code */
54 
55 #define REP_3_6      16
56 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
57 
58 #define REPZ_3_10    17
59 /* repeat a zero length 3-10 times  (3 bits of repeat count) */
60 
61 #define REPZ_11_138  18
62 /* repeat a zero length 11-138 times  (7 bits of repeat count) */
63 
64 static const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */
65    = {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};
66 
67 static const int extra_dbits[D_CODES] /* extra bits for each distance code */
68    = {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};
69 
70 static const int extra_blbits[BL_CODES]/* extra bits for each bit length code */
71    = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
72 
73 static const uch bl_order[BL_CODES]
74    = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
75 /* The lengths of the bit length codes are sent in order of decreasing
76  * probability, to avoid transmitting the lengths for unused bit length codes.
77  */
78 
79 /* ===========================================================================
80  * Local data. These are initialized only once.
81  */
82 
83 static ct_data static_ltree[L_CODES+2];
84 /* The static literal tree. Since the bit lengths are imposed, there is no
85  * need for the L_CODES extra codes used during heap construction. However
86  * The codes 286 and 287 are needed to build a canonical tree (see zlib_tr_init
87  * below).
88  */
89 
90 static ct_data static_dtree[D_CODES];
91 /* The static distance tree. (Actually a trivial tree since all codes use
92  * 5 bits.)
93  */
94 
95 static uch dist_code[512];
96 /* distance codes. The first 256 values correspond to the distances
97  * 3 .. 258, the last 256 values correspond to the top 8 bits of
98  * the 15 bit distances.
99  */
100 
101 static uch length_code[MAX_MATCH-MIN_MATCH+1];
102 /* length code for each normalized match length (0 == MIN_MATCH) */
103 
104 static int base_length[LENGTH_CODES];
105 /* First normalized length for each code (0 = MIN_MATCH) */
106 
107 static int base_dist[D_CODES];
108 /* First normalized distance for each code (0 = distance of 1) */
109 
110 struct static_tree_desc_s {
111     const ct_data *static_tree;  /* static tree or NULL */
112     const int *extra_bits;       /* extra bits for each code or NULL */
113     int     extra_base;          /* base index for extra_bits */
114     int     elems;               /* max number of elements in the tree */
115     int     max_length;          /* max bit length for the codes */
116 };
117 
118 static static_tree_desc  static_l_desc =
119 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
120 
121 static static_tree_desc  static_d_desc =
122 {static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};
123 
124 static static_tree_desc  static_bl_desc =
125 {(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};
126 
127 /* ===========================================================================
128  * Local (static) routines in this file.
129  */
130 
131 static void tr_static_init (void);
132 static void init_block     (deflate_state *s);
133 static void pqdownheap     (deflate_state *s, ct_data *tree, int k);
134 static void gen_bitlen     (deflate_state *s, tree_desc *desc);
135 static void gen_codes      (ct_data *tree, int max_code, ush *bl_count);
136 static void build_tree     (deflate_state *s, tree_desc *desc);
137 static void scan_tree      (deflate_state *s, ct_data *tree, int max_code);
138 static void send_tree      (deflate_state *s, ct_data *tree, int max_code);
139 static int  build_bl_tree  (deflate_state *s);
140 static void send_all_trees (deflate_state *s, int lcodes, int dcodes,
141                            int blcodes);
142 static void compress_block (deflate_state *s, ct_data *ltree,
143                            ct_data *dtree);
144 static void set_data_type  (deflate_state *s);
145 static void bi_flush       (deflate_state *s);
146 static void copy_block     (deflate_state *s, char *buf, unsigned len,
147                            int header);
148 
149 #ifndef DEBUG_ZLIB
150 #  define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
151    /* Send a code of the given tree. c and tree must not have side effects */
152 
153 #else /* DEBUG_ZLIB */
154 #  define send_code(s, c, tree) \
155      { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
156        send_bits(s, tree[c].Code, tree[c].Len); }
157 #endif
158 
159 #define d_code(dist) \
160    ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
161 /* Mapping from a distance to a distance code. dist is the distance - 1 and
162  * must not have side effects. dist_code[256] and dist_code[257] are never
163  * used.
164  */
165 
166 /* ===========================================================================
167  * Initialize the various 'constant' tables. In a multi-threaded environment,
168  * this function may be called by two threads concurrently, but this is
169  * harmless since both invocations do exactly the same thing.
170  */
tr_static_init(void)171 static void tr_static_init(void)
172 {
173     static int static_init_done;
174     int n;        /* iterates over tree elements */
175     int bits;     /* bit counter */
176     int length;   /* length value */
177     int code;     /* code value */
178     int dist;     /* distance index */
179     ush bl_count[MAX_BITS+1];
180     /* number of codes at each bit length for an optimal tree */
181 
182     if (static_init_done) return;
183 
184     /* Initialize the mapping length (0..255) -> length code (0..28) */
185     length = 0;
186     for (code = 0; code < LENGTH_CODES-1; code++) {
187         base_length[code] = length;
188         for (n = 0; n < (1<<extra_lbits[code]); n++) {
189             length_code[length++] = (uch)code;
190         }
191     }
192     Assert (length == 256, "tr_static_init: length != 256");
193     /* Note that the length 255 (match length 258) can be represented
194      * in two different ways: code 284 + 5 bits or code 285, so we
195      * overwrite length_code[255] to use the best encoding:
196      */
197     length_code[length-1] = (uch)code;
198 
199     /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
200     dist = 0;
201     for (code = 0 ; code < 16; code++) {
202         base_dist[code] = dist;
203         for (n = 0; n < (1<<extra_dbits[code]); n++) {
204             dist_code[dist++] = (uch)code;
205         }
206     }
207     Assert (dist == 256, "tr_static_init: dist != 256");
208     dist >>= 7; /* from now on, all distances are divided by 128 */
209     for ( ; code < D_CODES; code++) {
210         base_dist[code] = dist << 7;
211         for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
212             dist_code[256 + dist++] = (uch)code;
213         }
214     }
215     Assert (dist == 256, "tr_static_init: 256+dist != 512");
216 
217     /* Construct the codes of the static literal tree */
218     for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
219     n = 0;
220     while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
221     while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
222     while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
223     while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
224     /* Codes 286 and 287 do not exist, but we must include them in the
225      * tree construction to get a canonical Huffman tree (longest code
226      * all ones)
227      */
228     gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
229 
230     /* The static distance tree is trivial: */
231     for (n = 0; n < D_CODES; n++) {
232         static_dtree[n].Len = 5;
233         static_dtree[n].Code = bitrev32((u32)n) >> (32 - 5);
234     }
235     static_init_done = 1;
236 }
237 
238 /* ===========================================================================
239  * Initialize the tree data structures for a new zlib stream.
240  */
zlib_tr_init(deflate_state * s)241 void zlib_tr_init(
242 	deflate_state *s
243 )
244 {
245     tr_static_init();
246 
247     s->compressed_len = 0L;
248 
249     s->l_desc.dyn_tree = s->dyn_ltree;
250     s->l_desc.stat_desc = &static_l_desc;
251 
252     s->d_desc.dyn_tree = s->dyn_dtree;
253     s->d_desc.stat_desc = &static_d_desc;
254 
255     s->bl_desc.dyn_tree = s->bl_tree;
256     s->bl_desc.stat_desc = &static_bl_desc;
257 
258     s->bi_buf = 0;
259     s->bi_valid = 0;
260     s->last_eob_len = 8; /* enough lookahead for inflate */
261 #ifdef DEBUG_ZLIB
262     s->bits_sent = 0L;
263 #endif
264 
265     /* Initialize the first block of the first file: */
266     init_block(s);
267 }
268 
269 /* ===========================================================================
270  * Initialize a new block.
271  */
init_block(deflate_state * s)272 static void init_block(
273 	deflate_state *s
274 )
275 {
276     int n; /* iterates over tree elements */
277 
278     /* Initialize the trees. */
279     for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
280     for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
281     for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
282 
283     s->dyn_ltree[END_BLOCK].Freq = 1;
284     s->opt_len = s->static_len = 0L;
285     s->last_lit = s->matches = 0;
286 }
287 
288 #define SMALLEST 1
289 /* Index within the heap array of least frequent node in the Huffman tree */
290 
291 
292 /* ===========================================================================
293  * Remove the smallest element from the heap and recreate the heap with
294  * one less element. Updates heap and heap_len.
295  */
296 #define pqremove(s, tree, top) \
297 {\
298     top = s->heap[SMALLEST]; \
299     s->heap[SMALLEST] = s->heap[s->heap_len--]; \
300     pqdownheap(s, tree, SMALLEST); \
301 }
302 
303 /* ===========================================================================
304  * Compares to subtrees, using the tree depth as tie breaker when
305  * the subtrees have equal frequency. This minimizes the worst case length.
306  */
307 #define smaller(tree, n, m, depth) \
308    (tree[n].Freq < tree[m].Freq || \
309    (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
310 
311 /* ===========================================================================
312  * Restore the heap property by moving down the tree starting at node k,
313  * exchanging a node with the smallest of its two sons if necessary, stopping
314  * when the heap property is re-established (each father smaller than its
315  * two sons).
316  */
pqdownheap(deflate_state * s,ct_data * tree,int k)317 static void pqdownheap(
318 	deflate_state *s,
319 	ct_data *tree,  /* the tree to restore */
320 	int k		/* node to move down */
321 )
322 {
323     int v = s->heap[k];
324     int j = k << 1;  /* left son of k */
325     while (j <= s->heap_len) {
326         /* Set j to the smallest of the two sons: */
327         if (j < s->heap_len &&
328             smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
329             j++;
330         }
331         /* Exit if v is smaller than both sons */
332         if (smaller(tree, v, s->heap[j], s->depth)) break;
333 
334         /* Exchange v with the smallest son */
335         s->heap[k] = s->heap[j];  k = j;
336 
337         /* And continue down the tree, setting j to the left son of k */
338         j <<= 1;
339     }
340     s->heap[k] = v;
341 }
342 
343 /* ===========================================================================
344  * Compute the optimal bit lengths for a tree and update the total bit length
345  * for the current block.
346  * IN assertion: the fields freq and dad are set, heap[heap_max] and
347  *    above are the tree nodes sorted by increasing frequency.
348  * OUT assertions: the field len is set to the optimal bit length, the
349  *     array bl_count contains the frequencies for each bit length.
350  *     The length opt_len is updated; static_len is also updated if stree is
351  *     not null.
352  */
gen_bitlen(deflate_state * s,tree_desc * desc)353 static void gen_bitlen(
354 	deflate_state *s,
355 	tree_desc *desc    /* the tree descriptor */
356 )
357 {
358     ct_data *tree        = desc->dyn_tree;
359     int max_code         = desc->max_code;
360     const ct_data *stree = desc->stat_desc->static_tree;
361     const int *extra     = desc->stat_desc->extra_bits;
362     int base             = desc->stat_desc->extra_base;
363     int max_length       = desc->stat_desc->max_length;
364     int h;              /* heap index */
365     int n, m;           /* iterate over the tree elements */
366     int bits;           /* bit length */
367     int xbits;          /* extra bits */
368     ush f;              /* frequency */
369     int overflow = 0;   /* number of elements with bit length too large */
370 
371     for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
372 
373     /* In a first pass, compute the optimal bit lengths (which may
374      * overflow in the case of the bit length tree).
375      */
376     tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
377 
378     for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
379         n = s->heap[h];
380         bits = tree[tree[n].Dad].Len + 1;
381         if (bits > max_length) bits = max_length, overflow++;
382         tree[n].Len = (ush)bits;
383         /* We overwrite tree[n].Dad which is no longer needed */
384 
385         if (n > max_code) continue; /* not a leaf node */
386 
387         s->bl_count[bits]++;
388         xbits = 0;
389         if (n >= base) xbits = extra[n-base];
390         f = tree[n].Freq;
391         s->opt_len += (ulg)f * (bits + xbits);
392         if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
393     }
394     if (overflow == 0) return;
395 
396     Trace((stderr,"\nbit length overflow\n"));
397     /* This happens for example on obj2 and pic of the Calgary corpus */
398 
399     /* Find the first bit length which could increase: */
400     do {
401         bits = max_length-1;
402         while (s->bl_count[bits] == 0) bits--;
403         s->bl_count[bits]--;      /* move one leaf down the tree */
404         s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
405         s->bl_count[max_length]--;
406         /* The brother of the overflow item also moves one step up,
407          * but this does not affect bl_count[max_length]
408          */
409         overflow -= 2;
410     } while (overflow > 0);
411 
412     /* Now recompute all bit lengths, scanning in increasing frequency.
413      * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
414      * lengths instead of fixing only the wrong ones. This idea is taken
415      * from 'ar' written by Haruhiko Okumura.)
416      */
417     for (bits = max_length; bits != 0; bits--) {
418         n = s->bl_count[bits];
419         while (n != 0) {
420             m = s->heap[--h];
421             if (m > max_code) continue;
422             if (tree[m].Len != (unsigned) bits) {
423                 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
424                 s->opt_len += ((long)bits - (long)tree[m].Len)
425                               *(long)tree[m].Freq;
426                 tree[m].Len = (ush)bits;
427             }
428             n--;
429         }
430     }
431 }
432 
433 /* ===========================================================================
434  * Generate the codes for a given tree and bit counts (which need not be
435  * optimal).
436  * IN assertion: the array bl_count contains the bit length statistics for
437  * the given tree and the field len is set for all tree elements.
438  * OUT assertion: the field code is set for all tree elements of non
439  *     zero code length.
440  */
gen_codes(ct_data * tree,int max_code,ush * bl_count)441 static void gen_codes(
442 	ct_data *tree,             /* the tree to decorate */
443 	int max_code,              /* largest code with non zero frequency */
444 	ush *bl_count             /* number of codes at each bit length */
445 )
446 {
447     ush next_code[MAX_BITS+1]; /* next code value for each bit length */
448     ush code = 0;              /* running code value */
449     int bits;                  /* bit index */
450     int n;                     /* code index */
451 
452     /* The distribution counts are first used to generate the code values
453      * without bit reversal.
454      */
455     for (bits = 1; bits <= MAX_BITS; bits++) {
456         next_code[bits] = code = (code + bl_count[bits-1]) << 1;
457     }
458     /* Check that the bit counts in bl_count are consistent. The last code
459      * must be all ones.
460      */
461     Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
462             "inconsistent bit counts");
463     Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
464 
465     for (n = 0;  n <= max_code; n++) {
466         int len = tree[n].Len;
467         if (len == 0) continue;
468         /* Now reverse the bits */
469         tree[n].Code = bitrev32((u32)(next_code[len]++)) >> (32 - len);
470 
471         Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
472              n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
473     }
474 }
475 
476 /* ===========================================================================
477  * Construct one Huffman tree and assigns the code bit strings and lengths.
478  * Update the total bit length for the current block.
479  * IN assertion: the field freq is set for all tree elements.
480  * OUT assertions: the fields len and code are set to the optimal bit length
481  *     and corresponding code. The length opt_len is updated; static_len is
482  *     also updated if stree is not null. The field max_code is set.
483  */
build_tree(deflate_state * s,tree_desc * desc)484 static void build_tree(
485 	deflate_state *s,
486 	tree_desc *desc	 /* the tree descriptor */
487 )
488 {
489     ct_data *tree         = desc->dyn_tree;
490     const ct_data *stree  = desc->stat_desc->static_tree;
491     int elems             = desc->stat_desc->elems;
492     int n, m;          /* iterate over heap elements */
493     int max_code = -1; /* largest code with non zero frequency */
494     int node;          /* new node being created */
495 
496     /* Construct the initial heap, with least frequent element in
497      * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
498      * heap[0] is not used.
499      */
500     s->heap_len = 0, s->heap_max = HEAP_SIZE;
501 
502     for (n = 0; n < elems; n++) {
503         if (tree[n].Freq != 0) {
504             s->heap[++(s->heap_len)] = max_code = n;
505             s->depth[n] = 0;
506         } else {
507             tree[n].Len = 0;
508         }
509     }
510 
511     /* The pkzip format requires that at least one distance code exists,
512      * and that at least one bit should be sent even if there is only one
513      * possible code. So to avoid special checks later on we force at least
514      * two codes of non zero frequency.
515      */
516     while (s->heap_len < 2) {
517         node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
518         tree[node].Freq = 1;
519         s->depth[node] = 0;
520         s->opt_len--; if (stree) s->static_len -= stree[node].Len;
521         /* node is 0 or 1 so it does not have extra bits */
522     }
523     desc->max_code = max_code;
524 
525     /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
526      * establish sub-heaps of increasing lengths:
527      */
528     for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);
529 
530     /* Construct the Huffman tree by repeatedly combining the least two
531      * frequent nodes.
532      */
533     node = elems;              /* next internal node of the tree */
534     do {
535         pqremove(s, tree, n);  /* n = node of least frequency */
536         m = s->heap[SMALLEST]; /* m = node of next least frequency */
537 
538         s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
539         s->heap[--(s->heap_max)] = m;
540 
541         /* Create a new node father of n and m */
542         tree[node].Freq = tree[n].Freq + tree[m].Freq;
543         s->depth[node] = (uch) (max(s->depth[n], s->depth[m]) + 1);
544         tree[n].Dad = tree[m].Dad = (ush)node;
545 #ifdef DUMP_BL_TREE
546         if (tree == s->bl_tree) {
547             fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
548                     node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
549         }
550 #endif
551         /* and insert the new node in the heap */
552         s->heap[SMALLEST] = node++;
553         pqdownheap(s, tree, SMALLEST);
554 
555     } while (s->heap_len >= 2);
556 
557     s->heap[--(s->heap_max)] = s->heap[SMALLEST];
558 
559     /* At this point, the fields freq and dad are set. We can now
560      * generate the bit lengths.
561      */
562     gen_bitlen(s, (tree_desc *)desc);
563 
564     /* The field len is now set, we can generate the bit codes */
565     gen_codes ((ct_data *)tree, max_code, s->bl_count);
566 }
567 
568 /* ===========================================================================
569  * Scan a literal or distance tree to determine the frequencies of the codes
570  * in the bit length tree.
571  */
scan_tree(deflate_state * s,ct_data * tree,int max_code)572 static void scan_tree(
573 	deflate_state *s,
574 	ct_data *tree,   /* the tree to be scanned */
575 	int max_code     /* and its largest code of non zero frequency */
576 )
577 {
578     int n;                     /* iterates over all tree elements */
579     int prevlen = -1;          /* last emitted length */
580     int curlen;                /* length of current code */
581     int nextlen = tree[0].Len; /* length of next code */
582     int count = 0;             /* repeat count of the current code */
583     int max_count = 7;         /* max repeat count */
584     int min_count = 4;         /* min repeat count */
585 
586     if (nextlen == 0) max_count = 138, min_count = 3;
587     tree[max_code+1].Len = (ush)0xffff; /* guard */
588 
589     for (n = 0; n <= max_code; n++) {
590         curlen = nextlen; nextlen = tree[n+1].Len;
591         if (++count < max_count && curlen == nextlen) {
592             continue;
593         } else if (count < min_count) {
594             s->bl_tree[curlen].Freq += count;
595         } else if (curlen != 0) {
596             if (curlen != prevlen) s->bl_tree[curlen].Freq++;
597             s->bl_tree[REP_3_6].Freq++;
598         } else if (count <= 10) {
599             s->bl_tree[REPZ_3_10].Freq++;
600         } else {
601             s->bl_tree[REPZ_11_138].Freq++;
602         }
603         count = 0; prevlen = curlen;
604         if (nextlen == 0) {
605             max_count = 138, min_count = 3;
606         } else if (curlen == nextlen) {
607             max_count = 6, min_count = 3;
608         } else {
609             max_count = 7, min_count = 4;
610         }
611     }
612 }
613 
614 /* ===========================================================================
615  * Send a literal or distance tree in compressed form, using the codes in
616  * bl_tree.
617  */
send_tree(deflate_state * s,ct_data * tree,int max_code)618 static void send_tree(
619 	deflate_state *s,
620 	ct_data *tree, /* the tree to be scanned */
621 	int max_code   /* and its largest code of non zero frequency */
622 )
623 {
624     int n;                     /* iterates over all tree elements */
625     int prevlen = -1;          /* last emitted length */
626     int curlen;                /* length of current code */
627     int nextlen = tree[0].Len; /* length of next code */
628     int count = 0;             /* repeat count of the current code */
629     int max_count = 7;         /* max repeat count */
630     int min_count = 4;         /* min repeat count */
631 
632     /* tree[max_code+1].Len = -1; */  /* guard already set */
633     if (nextlen == 0) max_count = 138, min_count = 3;
634 
635     for (n = 0; n <= max_code; n++) {
636         curlen = nextlen; nextlen = tree[n+1].Len;
637         if (++count < max_count && curlen == nextlen) {
638             continue;
639         } else if (count < min_count) {
640             do { send_code(s, curlen, s->bl_tree); } while (--count != 0);
641 
642         } else if (curlen != 0) {
643             if (curlen != prevlen) {
644                 send_code(s, curlen, s->bl_tree); count--;
645             }
646             Assert(count >= 3 && count <= 6, " 3_6?");
647             send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);
648 
649         } else if (count <= 10) {
650             send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);
651 
652         } else {
653             send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
654         }
655         count = 0; prevlen = curlen;
656         if (nextlen == 0) {
657             max_count = 138, min_count = 3;
658         } else if (curlen == nextlen) {
659             max_count = 6, min_count = 3;
660         } else {
661             max_count = 7, min_count = 4;
662         }
663     }
664 }
665 
666 /* ===========================================================================
667  * Construct the Huffman tree for the bit lengths and return the index in
668  * bl_order of the last bit length code to send.
669  */
build_bl_tree(deflate_state * s)670 static int build_bl_tree(
671 	deflate_state *s
672 )
673 {
674     int max_blindex;  /* index of last bit length code of non zero freq */
675 
676     /* Determine the bit length frequencies for literal and distance trees */
677     scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
678     scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
679 
680     /* Build the bit length tree: */
681     build_tree(s, (tree_desc *)(&(s->bl_desc)));
682     /* opt_len now includes the length of the tree representations, except
683      * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
684      */
685 
686     /* Determine the number of bit length codes to send. The pkzip format
687      * requires that at least 4 bit length codes be sent. (appnote.txt says
688      * 3 but the actual value used is 4.)
689      */
690     for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
691         if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
692     }
693     /* Update opt_len to include the bit length tree and counts */
694     s->opt_len += 3*(max_blindex+1) + 5+5+4;
695     Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
696             s->opt_len, s->static_len));
697 
698     return max_blindex;
699 }
700 
701 /* ===========================================================================
702  * Send the header for a block using dynamic Huffman trees: the counts, the
703  * lengths of the bit length codes, the literal tree and the distance tree.
704  * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
705  */
send_all_trees(deflate_state * s,int lcodes,int dcodes,int blcodes)706 static void send_all_trees(
707 	deflate_state *s,
708 	int lcodes,  /* number of codes for each tree */
709 	int dcodes,  /* number of codes for each tree */
710 	int blcodes  /* number of codes for each tree */
711 )
712 {
713     int rank;                    /* index in bl_order */
714 
715     Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
716     Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
717             "too many codes");
718     Tracev((stderr, "\nbl counts: "));
719     send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
720     send_bits(s, dcodes-1,   5);
721     send_bits(s, blcodes-4,  4); /* not -3 as stated in appnote.txt */
722     for (rank = 0; rank < blcodes; rank++) {
723         Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
724         send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
725     }
726     Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));
727 
728     send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
729     Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));
730 
731     send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
732     Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
733 }
734 
735 /* ===========================================================================
736  * Send a stored block
737  */
zlib_tr_stored_block(deflate_state * s,char * buf,ulg stored_len,int eof)738 void zlib_tr_stored_block(
739 	deflate_state *s,
740 	char *buf,        /* input block */
741 	ulg stored_len,   /* length of input block */
742 	int eof           /* true if this is the last block for a file */
743 )
744 {
745     send_bits(s, (STORED_BLOCK<<1)+eof, 3);  /* send block type */
746     s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
747     s->compressed_len += (stored_len + 4) << 3;
748 
749     copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
750 }
751 
752 /* Send just the `stored block' type code without any length bytes or data.
753  */
zlib_tr_stored_type_only(deflate_state * s)754 void zlib_tr_stored_type_only(
755 	deflate_state *s
756 )
757 {
758     send_bits(s, (STORED_BLOCK << 1), 3);
759     bi_windup(s);
760     s->compressed_len = (s->compressed_len + 3) & ~7L;
761 }
762 
763 
764 /* ===========================================================================
765  * Send one empty static block to give enough lookahead for inflate.
766  * This takes 10 bits, of which 7 may remain in the bit buffer.
767  * The current inflate code requires 9 bits of lookahead. If the
768  * last two codes for the previous block (real code plus EOB) were coded
769  * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
770  * the last real code. In this case we send two empty static blocks instead
771  * of one. (There are no problems if the previous block is stored or fixed.)
772  * To simplify the code, we assume the worst case of last real code encoded
773  * on one bit only.
774  */
zlib_tr_align(deflate_state * s)775 void zlib_tr_align(
776 	deflate_state *s
777 )
778 {
779     send_bits(s, STATIC_TREES<<1, 3);
780     send_code(s, END_BLOCK, static_ltree);
781     s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
782     bi_flush(s);
783     /* Of the 10 bits for the empty block, we have already sent
784      * (10 - bi_valid) bits. The lookahead for the last real code (before
785      * the EOB of the previous block) was thus at least one plus the length
786      * of the EOB plus what we have just sent of the empty static block.
787      */
788     if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
789         send_bits(s, STATIC_TREES<<1, 3);
790         send_code(s, END_BLOCK, static_ltree);
791         s->compressed_len += 10L;
792         bi_flush(s);
793     }
794     s->last_eob_len = 7;
795 }
796 
797 /* ===========================================================================
798  * Determine the best encoding for the current block: dynamic trees, static
799  * trees or store, and output the encoded block to the zip file. This function
800  * returns the total compressed length for the file so far.
801  */
zlib_tr_flush_block(deflate_state * s,char * buf,ulg stored_len,int eof)802 ulg zlib_tr_flush_block(
803 	deflate_state *s,
804 	char *buf,        /* input block, or NULL if too old */
805 	ulg stored_len,   /* length of input block */
806 	int eof           /* true if this is the last block for a file */
807 )
808 {
809     ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
810     int max_blindex = 0;  /* index of last bit length code of non zero freq */
811 
812     /* Build the Huffman trees unless a stored block is forced */
813     if (s->level > 0) {
814 
815 	 /* Check if the file is ascii or binary */
816 	if (s->data_type == Z_UNKNOWN) set_data_type(s);
817 
818 	/* Construct the literal and distance trees */
819 	build_tree(s, (tree_desc *)(&(s->l_desc)));
820 	Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
821 		s->static_len));
822 
823 	build_tree(s, (tree_desc *)(&(s->d_desc)));
824 	Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
825 		s->static_len));
826 	/* At this point, opt_len and static_len are the total bit lengths of
827 	 * the compressed block data, excluding the tree representations.
828 	 */
829 
830 	/* Build the bit length tree for the above two trees, and get the index
831 	 * in bl_order of the last bit length code to send.
832 	 */
833 	max_blindex = build_bl_tree(s);
834 
835 	/* Determine the best encoding. Compute first the block length in bytes*/
836 	opt_lenb = (s->opt_len+3+7)>>3;
837 	static_lenb = (s->static_len+3+7)>>3;
838 
839 	Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
840 		opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
841 		s->last_lit));
842 
843 	if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
844 
845     } else {
846         Assert(buf != (char*)0, "lost buf");
847 	opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
848     }
849 
850     /* If compression failed and this is the first and last block,
851      * and if the .zip file can be seeked (to rewrite the local header),
852      * the whole file is transformed into a stored file:
853      */
854 #ifdef STORED_FILE_OK
855 #  ifdef FORCE_STORED_FILE
856     if (eof && s->compressed_len == 0L) { /* force stored file */
857 #  else
858     if (stored_len <= opt_lenb && eof && s->compressed_len==0L && seekable()) {
859 #  endif
860         /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
861         if (buf == (char*)0) error ("block vanished");
862 
863         copy_block(s, buf, (unsigned)stored_len, 0); /* without header */
864         s->compressed_len = stored_len << 3;
865         s->method = STORED;
866     } else
867 #endif /* STORED_FILE_OK */
868 
869 #ifdef FORCE_STORED
870     if (buf != (char*)0) { /* force stored block */
871 #else
872     if (stored_len+4 <= opt_lenb && buf != (char*)0) {
873                        /* 4: two words for the lengths */
874 #endif
875         /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
876          * Otherwise we can't have processed more than WSIZE input bytes since
877          * the last block flush, because compression would have been
878          * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
879          * transform a block into a stored block.
880          */
881         zlib_tr_stored_block(s, buf, stored_len, eof);
882 
883 #ifdef FORCE_STATIC
884     } else if (static_lenb >= 0) { /* force static trees */
885 #else
886     } else if (static_lenb == opt_lenb) {
887 #endif
888         send_bits(s, (STATIC_TREES<<1)+eof, 3);
889         compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
890         s->compressed_len += 3 + s->static_len;
891     } else {
892         send_bits(s, (DYN_TREES<<1)+eof, 3);
893         send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
894                        max_blindex+1);
895         compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
896         s->compressed_len += 3 + s->opt_len;
897     }
898     Assert (s->compressed_len == s->bits_sent, "bad compressed size");
899     init_block(s);
900 
901     if (eof) {
902         bi_windup(s);
903         s->compressed_len += 7;  /* align on byte boundary */
904     }
905     Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
906            s->compressed_len-7*eof));
907 
908     return s->compressed_len >> 3;
909 }
910 
911 /* ===========================================================================
912  * Save the match info and tally the frequency counts. Return true if
913  * the current block must be flushed.
914  */
915 int zlib_tr_tally(
916 	deflate_state *s,
917 	unsigned dist,  /* distance of matched string */
918 	unsigned lc     /* match length-MIN_MATCH or unmatched char (if dist==0) */
919 )
920 {
921     s->d_buf[s->last_lit] = (ush)dist;
922     s->l_buf[s->last_lit++] = (uch)lc;
923     if (dist == 0) {
924         /* lc is the unmatched char */
925         s->dyn_ltree[lc].Freq++;
926     } else {
927         s->matches++;
928         /* Here, lc is the match length - MIN_MATCH */
929         dist--;             /* dist = match distance - 1 */
930         Assert((ush)dist < (ush)MAX_DIST(s) &&
931                (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
932                (ush)d_code(dist) < (ush)D_CODES,  "zlib_tr_tally: bad match");
933 
934         s->dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
935         s->dyn_dtree[d_code(dist)].Freq++;
936     }
937 
938     /* Try to guess if it is profitable to stop the current block here */
939     if ((s->last_lit & 0xfff) == 0 && s->level > 2) {
940         /* Compute an upper bound for the compressed length */
941         ulg out_length = (ulg)s->last_lit*8L;
942         ulg in_length = (ulg)((long)s->strstart - s->block_start);
943         int dcode;
944         for (dcode = 0; dcode < D_CODES; dcode++) {
945             out_length += (ulg)s->dyn_dtree[dcode].Freq *
946                 (5L+extra_dbits[dcode]);
947         }
948         out_length >>= 3;
949         Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
950                s->last_lit, in_length, out_length,
951                100L - out_length*100L/in_length));
952         if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
953     }
954     return (s->last_lit == s->lit_bufsize-1);
955     /* We avoid equality with lit_bufsize because of wraparound at 64K
956      * on 16 bit machines and because stored blocks are restricted to
957      * 64K-1 bytes.
958      */
959 }
960 
961 /* ===========================================================================
962  * Send the block data compressed using the given Huffman trees
963  */
964 static void compress_block(
965 	deflate_state *s,
966 	ct_data *ltree, /* literal tree */
967 	ct_data *dtree  /* distance tree */
968 )
969 {
970     unsigned dist;      /* distance of matched string */
971     int lc;             /* match length or unmatched char (if dist == 0) */
972     unsigned lx = 0;    /* running index in l_buf */
973     unsigned code;      /* the code to send */
974     int extra;          /* number of extra bits to send */
975 
976     if (s->last_lit != 0) do {
977         dist = s->d_buf[lx];
978         lc = s->l_buf[lx++];
979         if (dist == 0) {
980             send_code(s, lc, ltree); /* send a literal byte */
981             Tracecv(isgraph(lc), (stderr," '%c' ", lc));
982         } else {
983             /* Here, lc is the match length - MIN_MATCH */
984             code = length_code[lc];
985             send_code(s, code+LITERALS+1, ltree); /* send the length code */
986             extra = extra_lbits[code];
987             if (extra != 0) {
988                 lc -= base_length[code];
989                 send_bits(s, lc, extra);       /* send the extra length bits */
990             }
991             dist--; /* dist is now the match distance - 1 */
992             code = d_code(dist);
993             Assert (code < D_CODES, "bad d_code");
994 
995             send_code(s, code, dtree);       /* send the distance code */
996             extra = extra_dbits[code];
997             if (extra != 0) {
998                 dist -= base_dist[code];
999                 send_bits(s, dist, extra);   /* send the extra distance bits */
1000             }
1001         } /* literal or match pair ? */
1002 
1003         /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
1004         Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow");
1005 
1006     } while (lx < s->last_lit);
1007 
1008     send_code(s, END_BLOCK, ltree);
1009     s->last_eob_len = ltree[END_BLOCK].Len;
1010 }
1011 
1012 /* ===========================================================================
1013  * Set the data type to ASCII or BINARY, using a crude approximation:
1014  * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
1015  * IN assertion: the fields freq of dyn_ltree are set and the total of all
1016  * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
1017  */
1018 static void set_data_type(
1019 	deflate_state *s
1020 )
1021 {
1022     int n = 0;
1023     unsigned ascii_freq = 0;
1024     unsigned bin_freq = 0;
1025     while (n < 7)        bin_freq += s->dyn_ltree[n++].Freq;
1026     while (n < 128)    ascii_freq += s->dyn_ltree[n++].Freq;
1027     while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq;
1028     s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII);
1029 }
1030 
1031 /* ===========================================================================
1032  * Copy a stored block, storing first the length and its
1033  * one's complement if requested.
1034  */
1035 static void copy_block(
1036 	deflate_state *s,
1037 	char    *buf,     /* the input data */
1038 	unsigned len,     /* its length */
1039 	int      header   /* true if block header must be written */
1040 )
1041 {
1042     bi_windup(s);        /* align on byte boundary */
1043     s->last_eob_len = 8; /* enough lookahead for inflate */
1044 
1045     if (header) {
1046         put_short(s, (ush)len);
1047         put_short(s, (ush)~len);
1048 #ifdef DEBUG_ZLIB
1049         s->bits_sent += 2*16;
1050 #endif
1051     }
1052 #ifdef DEBUG_ZLIB
1053     s->bits_sent += (ulg)len<<3;
1054 #endif
1055     /* bundle up the put_byte(s, *buf++) calls */
1056     memcpy(&s->pending_buf[s->pending], buf, len);
1057     s->pending += len;
1058 }
1059 
1060