1 /* trees.c -- output deflated data using Huffman coding
2 * Copyright (C) 1995-2017 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 #include "zbuild.h"
34 #include "deflate.h"
35 #include "trees.h"
36 #include "trees_emit.h"
37 #include "trees_tbl.h"
38
39 /* The lengths of the bit length codes are sent in order of decreasing
40 * probability, to avoid transmitting the lengths for unused bit length codes.
41 */
42
43 /* ===========================================================================
44 * Local data. These are initialized only once.
45 */
46
47 struct static_tree_desc_s {
48 const ct_data *static_tree; /* static tree or NULL */
49 const int *extra_bits; /* extra bits for each code or NULL */
50 int extra_base; /* base index for extra_bits */
51 int elems; /* max number of elements in the tree */
52 unsigned int max_length; /* max bit length for the codes */
53 };
54
55 static const static_tree_desc static_l_desc =
56 {static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
57
58 static const static_tree_desc static_d_desc =
59 {static_dtree, extra_dbits, 0, D_CODES, MAX_BITS};
60
61 static const static_tree_desc static_bl_desc =
62 {(const ct_data *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS};
63
64 /* ===========================================================================
65 * Local (static) routines in this file.
66 */
67
68 static void init_block (deflate_state *s);
69 static void pqdownheap (deflate_state *s, ct_data *tree, int k);
70 static void gen_bitlen (deflate_state *s, tree_desc *desc);
71 static void build_tree (deflate_state *s, tree_desc *desc);
72 static void scan_tree (deflate_state *s, ct_data *tree, int max_code);
73 static void send_tree (deflate_state *s, ct_data *tree, int max_code);
74 static int build_bl_tree (deflate_state *s);
75 static void send_all_trees (deflate_state *s, int lcodes, int dcodes, int blcodes);
76 static void compress_block (deflate_state *s, const ct_data *ltree, const ct_data *dtree);
77 static int detect_data_type (deflate_state *s);
78 static void bi_flush (deflate_state *s);
79
80 /* ===========================================================================
81 * Initialize the tree data structures for a new zlib stream.
82 */
zng_tr_init(deflate_state * s)83 void Z_INTERNAL zng_tr_init(deflate_state *s) {
84 s->l_desc.dyn_tree = s->dyn_ltree;
85 s->l_desc.stat_desc = &static_l_desc;
86
87 s->d_desc.dyn_tree = s->dyn_dtree;
88 s->d_desc.stat_desc = &static_d_desc;
89
90 s->bl_desc.dyn_tree = s->bl_tree;
91 s->bl_desc.stat_desc = &static_bl_desc;
92
93 s->bi_buf = 0;
94 s->bi_valid = 0;
95 #ifdef ZLIB_DEBUG
96 s->compressed_len = 0L;
97 s->bits_sent = 0L;
98 #endif
99
100 /* Initialize the first block of the first file: */
101 init_block(s);
102 }
103
104 /* ===========================================================================
105 * Initialize a new block.
106 */
init_block(deflate_state * s)107 static void init_block(deflate_state *s) {
108 int n; /* iterates over tree elements */
109
110 /* Initialize the trees. */
111 for (n = 0; n < L_CODES; n++)
112 s->dyn_ltree[n].Freq = 0;
113 for (n = 0; n < D_CODES; n++)
114 s->dyn_dtree[n].Freq = 0;
115 for (n = 0; n < BL_CODES; n++)
116 s->bl_tree[n].Freq = 0;
117
118 s->dyn_ltree[END_BLOCK].Freq = 1;
119 s->opt_len = s->static_len = 0L;
120 s->sym_next = s->matches = 0;
121 }
122
123 #define SMALLEST 1
124 /* Index within the heap array of least frequent node in the Huffman tree */
125
126
127 /* ===========================================================================
128 * Remove the smallest element from the heap and recreate the heap with
129 * one less element. Updates heap and heap_len.
130 */
131 #define pqremove(s, tree, top) \
132 {\
133 top = s->heap[SMALLEST]; \
134 s->heap[SMALLEST] = s->heap[s->heap_len--]; \
135 pqdownheap(s, tree, SMALLEST); \
136 }
137
138 /* ===========================================================================
139 * Compares to subtrees, using the tree depth as tie breaker when
140 * the subtrees have equal frequency. This minimizes the worst case length.
141 */
142 #define smaller(tree, n, m, depth) \
143 (tree[n].Freq < tree[m].Freq || \
144 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
145
146 /* ===========================================================================
147 * Restore the heap property by moving down the tree starting at node k,
148 * exchanging a node with the smallest of its two sons if necessary, stopping
149 * when the heap property is re-established (each father smaller than its
150 * two sons).
151 */
pqdownheap(deflate_state * s,ct_data * tree,int k)152 static void pqdownheap(deflate_state *s, ct_data *tree, int k) {
153 /* tree: the tree to restore */
154 /* k: node to move down */
155 int v = s->heap[k];
156 int j = k << 1; /* left son of k */
157 while (j <= s->heap_len) {
158 /* Set j to the smallest of the two sons: */
159 if (j < s->heap_len && smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
160 j++;
161 }
162 /* Exit if v is smaller than both sons */
163 if (smaller(tree, v, s->heap[j], s->depth))
164 break;
165
166 /* Exchange v with the smallest son */
167 s->heap[k] = s->heap[j];
168 k = j;
169
170 /* And continue down the tree, setting j to the left son of k */
171 j <<= 1;
172 }
173 s->heap[k] = v;
174 }
175
176 /* ===========================================================================
177 * Compute the optimal bit lengths for a tree and update the total bit length
178 * for the current block.
179 * IN assertion: the fields freq and dad are set, heap[heap_max] and
180 * above are the tree nodes sorted by increasing frequency.
181 * OUT assertions: the field len is set to the optimal bit length, the
182 * array bl_count contains the frequencies for each bit length.
183 * The length opt_len is updated; static_len is also updated if stree is
184 * not null.
185 */
gen_bitlen(deflate_state * s,tree_desc * desc)186 static void gen_bitlen(deflate_state *s, tree_desc *desc) {
187 /* desc: the tree descriptor */
188 ct_data *tree = desc->dyn_tree;
189 int max_code = desc->max_code;
190 const ct_data *stree = desc->stat_desc->static_tree;
191 const int *extra = desc->stat_desc->extra_bits;
192 int base = desc->stat_desc->extra_base;
193 unsigned int max_length = desc->stat_desc->max_length;
194 int h; /* heap index */
195 int n, m; /* iterate over the tree elements */
196 unsigned int bits; /* bit length */
197 int xbits; /* extra bits */
198 uint16_t f; /* frequency */
199 int overflow = 0; /* number of elements with bit length too large */
200
201 for (bits = 0; bits <= MAX_BITS; bits++)
202 s->bl_count[bits] = 0;
203
204 /* In a first pass, compute the optimal bit lengths (which may
205 * overflow in the case of the bit length tree).
206 */
207 tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
208
209 for (h = s->heap_max + 1; h < HEAP_SIZE; h++) {
210 n = s->heap[h];
211 bits = tree[tree[n].Dad].Len + 1u;
212 if (bits > max_length){
213 bits = max_length;
214 overflow++;
215 }
216 tree[n].Len = (uint16_t)bits;
217 /* We overwrite tree[n].Dad which is no longer needed */
218
219 if (n > max_code) /* not a leaf node */
220 continue;
221
222 s->bl_count[bits]++;
223 xbits = 0;
224 if (n >= base)
225 xbits = extra[n-base];
226 f = tree[n].Freq;
227 s->opt_len += (unsigned long)f * (unsigned int)(bits + xbits);
228 if (stree)
229 s->static_len += (unsigned long)f * (unsigned int)(stree[n].Len + xbits);
230 }
231 if (overflow == 0)
232 return;
233
234 Tracev((stderr, "\nbit length overflow\n"));
235 /* This happens for example on obj2 and pic of the Calgary corpus */
236
237 /* Find the first bit length which could increase: */
238 do {
239 bits = max_length - 1;
240 while (s->bl_count[bits] == 0)
241 bits--;
242 s->bl_count[bits]--; /* move one leaf down the tree */
243 s->bl_count[bits+1] += 2u; /* move one overflow item as its brother */
244 s->bl_count[max_length]--;
245 /* The brother of the overflow item also moves one step up,
246 * but this does not affect bl_count[max_length]
247 */
248 overflow -= 2;
249 } while (overflow > 0);
250
251 /* Now recompute all bit lengths, scanning in increasing frequency.
252 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
253 * lengths instead of fixing only the wrong ones. This idea is taken
254 * from 'ar' written by Haruhiko Okumura.)
255 */
256 for (bits = max_length; bits != 0; bits--) {
257 n = s->bl_count[bits];
258 while (n != 0) {
259 m = s->heap[--h];
260 if (m > max_code)
261 continue;
262 if (tree[m].Len != bits) {
263 Tracev((stderr, "code %d bits %d->%u\n", m, tree[m].Len, bits));
264 s->opt_len += (unsigned long)(bits * tree[m].Freq);
265 s->opt_len -= (unsigned long)(tree[m].Len * tree[m].Freq);
266 tree[m].Len = (uint16_t)bits;
267 }
268 n--;
269 }
270 }
271 }
272
273 /* ===========================================================================
274 * Generate the codes for a given tree and bit counts (which need not be
275 * optimal).
276 * IN assertion: the array bl_count contains the bit length statistics for
277 * the given tree and the field len is set for all tree elements.
278 * OUT assertion: the field code is set for all tree elements of non
279 * zero code length.
280 */
gen_codes(ct_data * tree,int max_code,uint16_t * bl_count)281 Z_INTERNAL void gen_codes(ct_data *tree, int max_code, uint16_t *bl_count) {
282 /* tree: the tree to decorate */
283 /* max_code: largest code with non zero frequency */
284 /* bl_count: number of codes at each bit length */
285 uint16_t next_code[MAX_BITS+1]; /* next code value for each bit length */
286 unsigned int code = 0; /* running code value */
287 int bits; /* bit index */
288 int n; /* code index */
289
290 /* The distribution counts are first used to generate the code values
291 * without bit reversal.
292 */
293 for (bits = 1; bits <= MAX_BITS; bits++) {
294 code = (code + bl_count[bits-1]) << 1;
295 next_code[bits] = (uint16_t)code;
296 }
297 /* Check that the bit counts in bl_count are consistent. The last code
298 * must be all ones.
299 */
300 Assert(code + bl_count[MAX_BITS]-1 == (1 << MAX_BITS)-1, "inconsistent bit counts");
301 Tracev((stderr, "\ngen_codes: max_code %d ", max_code));
302
303 for (n = 0; n <= max_code; n++) {
304 int len = tree[n].Len;
305 if (len == 0)
306 continue;
307 /* Now reverse the bits */
308 tree[n].Code = (uint16_t)bi_reverse(next_code[len]++, len);
309
310 Tracecv(tree != static_ltree, (stderr, "\nn %3d %c l %2d c %4x (%x) ",
311 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
312 }
313 }
314
315 /* ===========================================================================
316 * Construct one Huffman tree and assigns the code bit strings and lengths.
317 * Update the total bit length for the current block.
318 * IN assertion: the field freq is set for all tree elements.
319 * OUT assertions: the fields len and code are set to the optimal bit length
320 * and corresponding code. The length opt_len is updated; static_len is
321 * also updated if stree is not null. The field max_code is set.
322 */
build_tree(deflate_state * s,tree_desc * desc)323 static void build_tree(deflate_state *s, tree_desc *desc) {
324 /* desc: the tree descriptor */
325 ct_data *tree = desc->dyn_tree;
326 const ct_data *stree = desc->stat_desc->static_tree;
327 int elems = desc->stat_desc->elems;
328 int n, m; /* iterate over heap elements */
329 int max_code = -1; /* largest code with non zero frequency */
330 int node; /* new node being created */
331
332 /* Construct the initial heap, with least frequent element in
333 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
334 * heap[0] is not used.
335 */
336 s->heap_len = 0;
337 s->heap_max = HEAP_SIZE;
338
339 for (n = 0; n < elems; n++) {
340 if (tree[n].Freq != 0) {
341 s->heap[++(s->heap_len)] = max_code = n;
342 s->depth[n] = 0;
343 } else {
344 tree[n].Len = 0;
345 }
346 }
347
348 /* The pkzip format requires that at least one distance code exists,
349 * and that at least one bit should be sent even if there is only one
350 * possible code. So to avoid special checks later on we force at least
351 * two codes of non zero frequency.
352 */
353 while (s->heap_len < 2) {
354 node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
355 tree[node].Freq = 1;
356 s->depth[node] = 0;
357 s->opt_len--;
358 if (stree)
359 s->static_len -= stree[node].Len;
360 /* node is 0 or 1 so it does not have extra bits */
361 }
362 desc->max_code = max_code;
363
364 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
365 * establish sub-heaps of increasing lengths:
366 */
367 for (n = s->heap_len/2; n >= 1; n--)
368 pqdownheap(s, tree, n);
369
370 /* Construct the Huffman tree by repeatedly combining the least two
371 * frequent nodes.
372 */
373 node = elems; /* next internal node of the tree */
374 do {
375 pqremove(s, tree, n); /* n = node of least frequency */
376 m = s->heap[SMALLEST]; /* m = node of next least frequency */
377
378 s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
379 s->heap[--(s->heap_max)] = m;
380
381 /* Create a new node father of n and m */
382 tree[node].Freq = tree[n].Freq + tree[m].Freq;
383 s->depth[node] = (unsigned char)((s->depth[n] >= s->depth[m] ?
384 s->depth[n] : s->depth[m]) + 1);
385 tree[n].Dad = tree[m].Dad = (uint16_t)node;
386 #ifdef DUMP_BL_TREE
387 if (tree == s->bl_tree) {
388 fprintf(stderr, "\nnode %d(%d), sons %d(%d) %d(%d)",
389 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
390 }
391 #endif
392 /* and insert the new node in the heap */
393 s->heap[SMALLEST] = node++;
394 pqdownheap(s, tree, SMALLEST);
395 } while (s->heap_len >= 2);
396
397 s->heap[--(s->heap_max)] = s->heap[SMALLEST];
398
399 /* At this point, the fields freq and dad are set. We can now
400 * generate the bit lengths.
401 */
402 gen_bitlen(s, (tree_desc *)desc);
403
404 /* The field len is now set, we can generate the bit codes */
405 gen_codes((ct_data *)tree, max_code, s->bl_count);
406 }
407
408 /* ===========================================================================
409 * Scan a literal or distance tree to determine the frequencies of the codes
410 * in the bit length tree.
411 */
scan_tree(deflate_state * s,ct_data * tree,int max_code)412 static void scan_tree(deflate_state *s, ct_data *tree, int max_code) {
413 /* tree: the tree to be scanned */
414 /* max_code: and its largest code of non zero frequency */
415 int n; /* iterates over all tree elements */
416 int prevlen = -1; /* last emitted length */
417 int curlen; /* length of current code */
418 int nextlen = tree[0].Len; /* length of next code */
419 uint16_t count = 0; /* repeat count of the current code */
420 uint16_t max_count = 7; /* max repeat count */
421 uint16_t min_count = 4; /* min repeat count */
422
423 if (nextlen == 0)
424 max_count = 138, min_count = 3;
425
426 tree[max_code+1].Len = (uint16_t)0xffff; /* guard */
427
428 for (n = 0; n <= max_code; n++) {
429 curlen = nextlen;
430 nextlen = tree[n+1].Len;
431 if (++count < max_count && curlen == nextlen) {
432 continue;
433 } else if (count < min_count) {
434 s->bl_tree[curlen].Freq += count;
435 } else if (curlen != 0) {
436 if (curlen != prevlen)
437 s->bl_tree[curlen].Freq++;
438 s->bl_tree[REP_3_6].Freq++;
439 } else if (count <= 10) {
440 s->bl_tree[REPZ_3_10].Freq++;
441 } else {
442 s->bl_tree[REPZ_11_138].Freq++;
443 }
444 count = 0;
445 prevlen = curlen;
446 if (nextlen == 0) {
447 max_count = 138, min_count = 3;
448 } else if (curlen == nextlen) {
449 max_count = 6, min_count = 3;
450 } else {
451 max_count = 7, min_count = 4;
452 }
453 }
454 }
455
456 /* ===========================================================================
457 * Send a literal or distance tree in compressed form, using the codes in
458 * bl_tree.
459 */
send_tree(deflate_state * s,ct_data * tree,int max_code)460 static void send_tree(deflate_state *s, ct_data *tree, int max_code) {
461 /* tree: the tree to be scanned */
462 /* max_code and its largest code of non zero frequency */
463 int n; /* iterates over all tree elements */
464 int prevlen = -1; /* last emitted length */
465 int curlen; /* length of current code */
466 int nextlen = tree[0].Len; /* length of next code */
467 int count = 0; /* repeat count of the current code */
468 int max_count = 7; /* max repeat count */
469 int min_count = 4; /* min repeat count */
470
471 /* tree[max_code+1].Len = -1; */ /* guard already set */
472 if (nextlen == 0)
473 max_count = 138, min_count = 3;
474
475 // Temp local variables
476 uint32_t bi_valid = s->bi_valid;
477 uint64_t bi_buf = s->bi_buf;
478
479 for (n = 0; n <= max_code; n++) {
480 curlen = nextlen;
481 nextlen = tree[n+1].Len;
482 if (++count < max_count && curlen == nextlen) {
483 continue;
484 } else if (count < min_count) {
485 do {
486 send_code(s, curlen, s->bl_tree, bi_buf, bi_valid);
487 } while (--count != 0);
488
489 } else if (curlen != 0) {
490 if (curlen != prevlen) {
491 send_code(s, curlen, s->bl_tree, bi_buf, bi_valid);
492 count--;
493 }
494 Assert(count >= 3 && count <= 6, " 3_6?");
495 send_code(s, REP_3_6, s->bl_tree, bi_buf, bi_valid);
496 send_bits(s, count-3, 2, bi_buf, bi_valid);
497
498 } else if (count <= 10) {
499 send_code(s, REPZ_3_10, s->bl_tree, bi_buf, bi_valid);
500 send_bits(s, count-3, 3, bi_buf, bi_valid);
501
502 } else {
503 send_code(s, REPZ_11_138, s->bl_tree, bi_buf, bi_valid);
504 send_bits(s, count-11, 7, bi_buf, bi_valid);
505 }
506 count = 0;
507 prevlen = curlen;
508 if (nextlen == 0) {
509 max_count = 138, min_count = 3;
510 } else if (curlen == nextlen) {
511 max_count = 6, min_count = 3;
512 } else {
513 max_count = 7, min_count = 4;
514 }
515 }
516
517 // Store back temp variables
518 s->bi_buf = bi_buf;
519 s->bi_valid = bi_valid;
520 }
521
522 /* ===========================================================================
523 * Construct the Huffman tree for the bit lengths and return the index in
524 * bl_order of the last bit length code to send.
525 */
build_bl_tree(deflate_state * s)526 static int build_bl_tree(deflate_state *s) {
527 int max_blindex; /* index of last bit length code of non zero freq */
528
529 /* Determine the bit length frequencies for literal and distance trees */
530 scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
531 scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);
532
533 /* Build the bit length tree: */
534 build_tree(s, (tree_desc *)(&(s->bl_desc)));
535 /* opt_len now includes the length of the tree representations, except
536 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
537 */
538
539 /* Determine the number of bit length codes to send. The pkzip format
540 * requires that at least 4 bit length codes be sent. (appnote.txt says
541 * 3 but the actual value used is 4.)
542 */
543 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
544 if (s->bl_tree[bl_order[max_blindex]].Len != 0)
545 break;
546 }
547 /* Update opt_len to include the bit length tree and counts */
548 s->opt_len += 3*((unsigned long)max_blindex+1) + 5+5+4;
549 Tracev((stderr, "\ndyn trees: dyn %lu, stat %lu", s->opt_len, s->static_len));
550
551 return max_blindex;
552 }
553
554 /* ===========================================================================
555 * Send the header for a block using dynamic Huffman trees: the counts, the
556 * lengths of the bit length codes, the literal tree and the distance tree.
557 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
558 */
send_all_trees(deflate_state * s,int lcodes,int dcodes,int blcodes)559 static void send_all_trees(deflate_state *s, int lcodes, int dcodes, int blcodes) {
560 int rank; /* index in bl_order */
561
562 Assert(lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
563 Assert(lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES, "too many codes");
564
565 // Temp local variables
566 uint32_t bi_valid = s->bi_valid;
567 uint64_t bi_buf = s->bi_buf;
568
569 Tracev((stderr, "\nbl counts: "));
570 send_bits(s, lcodes-257, 5, bi_buf, bi_valid); /* not +255 as stated in appnote.txt */
571 send_bits(s, dcodes-1, 5, bi_buf, bi_valid);
572 send_bits(s, blcodes-4, 4, bi_buf, bi_valid); /* not -3 as stated in appnote.txt */
573 for (rank = 0; rank < blcodes; rank++) {
574 Tracev((stderr, "\nbl code %2u ", bl_order[rank]));
575 send_bits(s, s->bl_tree[bl_order[rank]].Len, 3, bi_buf, bi_valid);
576 }
577 Tracev((stderr, "\nbl tree: sent %lu", s->bits_sent));
578
579 // Store back temp variables
580 s->bi_buf = bi_buf;
581 s->bi_valid = bi_valid;
582
583 send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
584 Tracev((stderr, "\nlit tree: sent %lu", s->bits_sent));
585
586 send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
587 Tracev((stderr, "\ndist tree: sent %lu", s->bits_sent));
588 }
589
590 /* ===========================================================================
591 * Send a stored block
592 */
zng_tr_stored_block(deflate_state * s,char * buf,uint32_t stored_len,int last)593 void Z_INTERNAL zng_tr_stored_block(deflate_state *s, char *buf, uint32_t stored_len, int last) {
594 /* buf: input block */
595 /* stored_len: length of input block */
596 /* last: one if this is the last block for a file */
597 zng_tr_emit_tree(s, STORED_BLOCK, last); /* send block type */
598 zng_tr_emit_align(s); /* align on byte boundary */
599 cmpr_bits_align(s);
600 put_short(s, (uint16_t)stored_len);
601 put_short(s, (uint16_t)~stored_len);
602 cmpr_bits_add(s, 32);
603 sent_bits_add(s, 32);
604 if (stored_len) {
605 memcpy(s->pending_buf + s->pending, (unsigned char *)buf, stored_len);
606 s->pending += stored_len;
607 cmpr_bits_add(s, stored_len << 3);
608 sent_bits_add(s, stored_len << 3);
609 }
610 }
611
612 /* ===========================================================================
613 * Flush the bits in the bit buffer to pending output (leaves at most 7 bits)
614 */
zng_tr_flush_bits(deflate_state * s)615 void Z_INTERNAL zng_tr_flush_bits(deflate_state *s) {
616 bi_flush(s);
617 }
618
619 /* ===========================================================================
620 * Send one empty static block to give enough lookahead for inflate.
621 * This takes 10 bits, of which 7 may remain in the bit buffer.
622 */
zng_tr_align(deflate_state * s)623 void Z_INTERNAL zng_tr_align(deflate_state *s) {
624 zng_tr_emit_tree(s, STATIC_TREES, 0);
625 zng_tr_emit_end_block(s, static_ltree, 0);
626 bi_flush(s);
627 }
628
629 /* ===========================================================================
630 * Determine the best encoding for the current block: dynamic trees, static
631 * trees or store, and write out the encoded block.
632 */
zng_tr_flush_block(deflate_state * s,char * buf,uint32_t stored_len,int last)633 void Z_INTERNAL zng_tr_flush_block(deflate_state *s, char *buf, uint32_t stored_len, int last) {
634 /* buf: input block, or NULL if too old */
635 /* stored_len: length of input block */
636 /* last: one if this is the last block for a file */
637 unsigned long opt_lenb, static_lenb; /* opt_len and static_len in bytes */
638 int max_blindex = 0; /* index of last bit length code of non zero freq */
639
640 /* Build the Huffman trees unless a stored block is forced */
641 if (s->level > 0) {
642 /* Check if the file is binary or text */
643 if (s->strm->data_type == Z_UNKNOWN)
644 s->strm->data_type = detect_data_type(s);
645
646 /* Construct the literal and distance trees */
647 build_tree(s, (tree_desc *)(&(s->l_desc)));
648 Tracev((stderr, "\nlit data: dyn %lu, stat %lu", s->opt_len, s->static_len));
649
650 build_tree(s, (tree_desc *)(&(s->d_desc)));
651 Tracev((stderr, "\ndist data: dyn %lu, stat %lu", s->opt_len, s->static_len));
652 /* At this point, opt_len and static_len are the total bit lengths of
653 * the compressed block data, excluding the tree representations.
654 */
655
656 /* Build the bit length tree for the above two trees, and get the index
657 * in bl_order of the last bit length code to send.
658 */
659 max_blindex = build_bl_tree(s);
660
661 /* Determine the best encoding. Compute the block lengths in bytes. */
662 opt_lenb = (s->opt_len+3+7) >> 3;
663 static_lenb = (s->static_len+3+7) >> 3;
664
665 Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
666 opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
667 s->sym_next / 3));
668
669 if (static_lenb <= opt_lenb)
670 opt_lenb = static_lenb;
671
672 } else {
673 Assert(buf != NULL, "lost buf");
674 opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
675 }
676
677 #ifdef FORCE_STORED
678 if (buf != NULL) { /* force stored block */
679 #else
680 if (stored_len+4 <= opt_lenb && buf != NULL) {
681 /* 4: two words for the lengths */
682 #endif
683 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
684 * Otherwise we can't have processed more than WSIZE input bytes since
685 * the last block flush, because compression would have been
686 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
687 * transform a block into a stored block.
688 */
689 zng_tr_stored_block(s, buf, stored_len, last);
690
691 #ifdef FORCE_STATIC
692 } else if (static_lenb >= 0) { /* force static trees */
693 #else
694 } else if (s->strategy == Z_FIXED || static_lenb == opt_lenb) {
695 #endif
696 zng_tr_emit_tree(s, STATIC_TREES, last);
697 compress_block(s, (const ct_data *)static_ltree, (const ct_data *)static_dtree);
698 cmpr_bits_add(s, s->static_len);
699 } else {
700 zng_tr_emit_tree(s, DYN_TREES, last);
701 send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1, max_blindex+1);
702 compress_block(s, (const ct_data *)s->dyn_ltree, (const ct_data *)s->dyn_dtree);
703 cmpr_bits_add(s, s->opt_len);
704 }
705 Assert(s->compressed_len == s->bits_sent, "bad compressed size");
706 /* The above check is made mod 2^32, for files larger than 512 MB
707 * and unsigned long implemented on 32 bits.
708 */
709 init_block(s);
710
711 if (last) {
712 zng_tr_emit_align(s);
713 }
714 Tracev((stderr, "\ncomprlen %lu(%lu) ", s->compressed_len>>3, s->compressed_len-7*last));
715 }
716
717 /* ===========================================================================
718 * Send the block data compressed using the given Huffman trees
719 */
720 static void compress_block(deflate_state *s, const ct_data *ltree, const ct_data *dtree) {
721 /* ltree: literal tree */
722 /* dtree: distance tree */
723 unsigned dist; /* distance of matched string */
724 int lc; /* match length or unmatched char (if dist == 0) */
725 unsigned sx = 0; /* running index in sym_buf */
726
727 if (s->sym_next != 0) {
728 do {
729 dist = s->sym_buf[sx++] & 0xff;
730 dist += (unsigned)(s->sym_buf[sx++] & 0xff) << 8;
731 lc = s->sym_buf[sx++];
732 if (dist == 0) {
733 zng_emit_lit(s, ltree, lc);
734 } else {
735 zng_emit_dist(s, ltree, dtree, lc, dist);
736 } /* literal or match pair ? */
737
738 /* Check that the overlay between pending_buf and sym_buf is ok: */
739 Assert(s->pending < s->lit_bufsize + sx, "pending_buf overflow");
740 } while (sx < s->sym_next);
741 }
742
743 zng_emit_end_block(s, ltree, 0);
744 }
745
746 /* ===========================================================================
747 * Check if the data type is TEXT or BINARY, using the following algorithm:
748 * - TEXT if the two conditions below are satisfied:
749 * a) There are no non-portable control characters belonging to the
750 * "black list" (0..6, 14..25, 28..31).
751 * b) There is at least one printable character belonging to the
752 * "white list" (9 {TAB}, 10 {LF}, 13 {CR}, 32..255).
753 * - BINARY otherwise.
754 * - The following partially-portable control characters form a
755 * "gray list" that is ignored in this detection algorithm:
756 * (7 {BEL}, 8 {BS}, 11 {VT}, 12 {FF}, 26 {SUB}, 27 {ESC}).
757 * IN assertion: the fields Freq of dyn_ltree are set.
758 */
759 static int detect_data_type(deflate_state *s) {
760 /* black_mask is the bit mask of black-listed bytes
761 * set bits 0..6, 14..25, and 28..31
762 * 0xf3ffc07f = binary 11110011111111111100000001111111
763 */
764 unsigned long black_mask = 0xf3ffc07fUL;
765 int n;
766
767 /* Check for non-textual ("black-listed") bytes. */
768 for (n = 0; n <= 31; n++, black_mask >>= 1)
769 if ((black_mask & 1) && (s->dyn_ltree[n].Freq != 0))
770 return Z_BINARY;
771
772 /* Check for textual ("white-listed") bytes. */
773 if (s->dyn_ltree[9].Freq != 0 || s->dyn_ltree[10].Freq != 0 || s->dyn_ltree[13].Freq != 0)
774 return Z_TEXT;
775 for (n = 32; n < LITERALS; n++)
776 if (s->dyn_ltree[n].Freq != 0)
777 return Z_TEXT;
778
779 /* There are no "black-listed" or "white-listed" bytes:
780 * this stream either is empty or has tolerated ("gray-listed") bytes only.
781 */
782 return Z_BINARY;
783 }
784
785 /* ===========================================================================
786 * Flush the bit buffer, keeping at most 7 bits in it.
787 */
788 static void bi_flush(deflate_state *s) {
789 if (s->bi_valid == 64) {
790 put_uint64(s, s->bi_buf);
791 s->bi_buf = 0;
792 s->bi_valid = 0;
793 } else {
794 if (s->bi_valid >= 32) {
795 put_uint32(s, (uint32_t)s->bi_buf);
796 s->bi_buf >>= 32;
797 s->bi_valid -= 32;
798 }
799 if (s->bi_valid >= 16) {
800 put_short(s, (uint16_t)s->bi_buf);
801 s->bi_buf >>= 16;
802 s->bi_valid -= 16;
803 }
804 if (s->bi_valid >= 8) {
805 put_byte(s, s->bi_buf);
806 s->bi_buf >>= 8;
807 s->bi_valid -= 8;
808 }
809 }
810 }
811
812 /* ===========================================================================
813 * Reverse the first len bits of a code, using straightforward code (a faster
814 * method would use a table)
815 * IN assertion: 1 <= len <= 15
816 */
817 Z_INTERNAL unsigned bi_reverse(unsigned code, int len) {
818 /* code: the value to invert */
819 /* len: its bit length */
820 Z_REGISTER unsigned res = 0;
821 do {
822 res |= code & 1;
823 code >>= 1, res <<= 1;
824 } while (--len > 0);
825 return res >> 1;
826 }
827