1
/* deflate.c -- compress data using the deflation algorithm
2
* Copyright (C) 1995-2005 Jean-loup Gailly.
3
* For conditions of distribution and use, see copyright notice in zlib.h
9
* The "deflation" process depends on being able to identify portions
10
* of the input text which are identical to earlier input (within a
11
* sliding window trailing behind the input currently being processed).
13
* The most straightforward technique turns out to be the fastest for
14
* most input files: try all possible matches and select the longest.
15
* The key feature of this algorithm is that insertions into the string
16
* dictionary are very simple and thus fast, and deletions are avoided
17
* completely. Insertions are performed at each input character, whereas
18
* string matches are performed only when the previous match ends. So it
19
* is preferable to spend more time in matches to allow very fast string
20
* insertions and avoid deletions. The matching algorithm for small
21
* strings is inspired from that of Rabin & Karp. A brute force approach
22
* is used to find longer strings when a small match has been found.
23
* A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
24
* (by Leonid Broukhis).
25
* A previous version of this file used a more sophisticated algorithm
26
* (by Fiala and Greene) which is guaranteed to run in linear amortized
27
* time, but has a larger average cost, uses more memory and is patented.
28
* However the F&G algorithm may be faster for some highly redundant
29
* files if the parameter max_chain_length (described below) is too large.
33
* The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
34
* I found it in 'freeze' written by Leonid Broukhis.
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* Thanks to many people for bug reports and testing.
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* Deutsch, L.P.,"DEFLATE Compressed Data Format Specification".
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* Available in http://www.ietf.org/rfc/rfc1951.txt
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* A description of the Rabin and Karp algorithm is given in the book
43
* "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
45
* Fiala,E.R., and Greene,D.H.
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* Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595
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/* @(#) $Id: deflate.c,v 1.5 2005/07/20 20:32:42 wtchang%redhat.com Exp $ */
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const char deflate_copyright[] =
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" deflate 1.2.3 Copyright 1995-2005 Jean-loup Gailly ";
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If you use the zlib library in a product, an acknowledgment is welcome
58
in the documentation of your product. If for some reason you cannot
59
include such an acknowledgment, I would appreciate that you keep this
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copyright string in the executable of your product.
63
/* ===========================================================================
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* Function prototypes.
67
need_more, /* block not completed, need more input or more output */
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block_done, /* block flush performed */
69
finish_started, /* finish started, need only more output at next deflate */
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finish_done /* finish done, accept no more input or output */
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typedef block_state (*compress_func) OF((deflate_state *s, int flush));
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/* Compression function. Returns the block state after the call. */
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local void fill_window OF((deflate_state *s));
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local block_state deflate_stored OF((deflate_state *s, int flush));
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local block_state deflate_fast OF((deflate_state *s, int flush));
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local block_state deflate_slow OF((deflate_state *s, int flush));
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local void lm_init OF((deflate_state *s));
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local void putShortMSB OF((deflate_state *s, uInt b));
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local void flush_pending OF((z_streamp strm));
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local int read_buf OF((z_streamp strm, Bytef *buf, unsigned size));
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void match_init OF((void)); /* asm code initialization */
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uInt longest_match OF((deflate_state *s, IPos cur_match));
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local uInt longest_match OF((deflate_state *s, IPos cur_match));
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local uInt longest_match_fast OF((deflate_state *s, IPos cur_match));
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local void check_match OF((deflate_state *s, IPos start, IPos match,
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/* ===========================================================================
106
/* Tail of hash chains */
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# define TOO_FAR 4096
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/* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
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#define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
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/* Minimum amount of lookahead, except at the end of the input file.
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* See deflate.c for comments about the MIN_MATCH+1.
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/* Values for max_lazy_match, good_match and max_chain_length, depending on
119
* the desired pack level (0..9). The values given below have been tuned to
120
* exclude worst case performance for pathological files. Better values may be
121
* found for specific files.
123
typedef struct config_s {
124
ush good_length; /* reduce lazy search above this match length */
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ush max_lazy; /* do not perform lazy search above this match length */
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ush nice_length; /* quit search above this match length */
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local const config configuration_table[2] = {
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/* good lazy nice chain */
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/* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */
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/* 1 */ {4, 4, 8, 4, deflate_fast}}; /* max speed, no lazy matches */
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local const config configuration_table[10] = {
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/* good lazy nice chain */
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/* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */
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/* 1 */ {4, 4, 8, 4, deflate_fast}, /* max speed, no lazy matches */
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/* 2 */ {4, 5, 16, 8, deflate_fast},
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/* 3 */ {4, 6, 32, 32, deflate_fast},
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/* 4 */ {4, 4, 16, 16, deflate_slow}, /* lazy matches */
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/* 5 */ {8, 16, 32, 32, deflate_slow},
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/* 6 */ {8, 16, 128, 128, deflate_slow},
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/* 7 */ {8, 32, 128, 256, deflate_slow},
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/* 8 */ {32, 128, 258, 1024, deflate_slow},
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/* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* max compression */
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/* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
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* For deflate_fast() (levels <= 3) good is ignored and lazy has a different
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/* result of memcmp for equal strings */
160
#ifndef NO_DUMMY_DECL
161
struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
164
/* ===========================================================================
165
* Update a hash value with the given input byte
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* IN assertion: all calls to to UPDATE_HASH are made with consecutive
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* input characters, so that a running hash key can be computed from the
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* previous key instead of complete recalculation each time.
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#define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
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/* ===========================================================================
174
* Insert string str in the dictionary and set match_head to the previous head
175
* of the hash chain (the most recent string with same hash key). Return
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* the previous length of the hash chain.
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* If this file is compiled with -DFASTEST, the compression level is forced
178
* to 1, and no hash chains are maintained.
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* IN assertion: all calls to to INSERT_STRING are made with consecutive
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* input characters and the first MIN_MATCH bytes of str are valid
181
* (except for the last MIN_MATCH-1 bytes of the input file).
184
#define INSERT_STRING(s, str, match_head) \
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(UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
186
match_head = s->head[s->ins_h], \
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s->head[s->ins_h] = (Pos)(str))
189
#define INSERT_STRING(s, str, match_head) \
190
(UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
191
match_head = s->prev[(str) & s->w_mask] = s->head[s->ins_h], \
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s->head[s->ins_h] = (Pos)(str))
195
/* ===========================================================================
196
* Initialize the hash table (avoiding 64K overflow for 16 bit systems).
197
* prev[] will be initialized on the fly.
199
#define CLEAR_HASH(s) \
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s->head[s->hash_size-1] = NIL; \
201
zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
203
/* ========================================================================= */
204
int ZEXPORT deflateInit_(strm, level, version, stream_size)
210
return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,
211
Z_DEFAULT_STRATEGY, version, stream_size);
212
/* To do: ignore strm->next_in if we use it as window */
215
/* ========================================================================= */
216
int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
217
version, stream_size)
229
static const char my_version[] = ZLIB_VERSION;
232
/* We overlay pending_buf and d_buf+l_buf. This works since the average
233
* output size for (length,distance) codes is <= 24 bits.
236
if (version == Z_NULL || version[0] != my_version[0] ||
237
stream_size != sizeof(z_stream)) {
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return Z_VERSION_ERROR;
240
if (strm == Z_NULL) return Z_STREAM_ERROR;
243
if (strm->zalloc == (alloc_func)0) {
244
strm->zalloc = zcalloc;
245
strm->opaque = (voidpf)0;
247
if (strm->zfree == (free_func)0) strm->zfree = zcfree;
250
if (level != 0) level = 1;
252
if (level == Z_DEFAULT_COMPRESSION) level = 6;
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if (windowBits < 0) { /* suppress zlib wrapper */
257
windowBits = -windowBits;
260
else if (windowBits > 15) {
261
wrap = 2; /* write gzip wrapper instead */
265
if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
266
windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
267
strategy < 0 || strategy > Z_FIXED) {
268
return Z_STREAM_ERROR;
270
if (windowBits == 8) windowBits = 9; /* until 256-byte window bug fixed */
271
s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
272
if (s == Z_NULL) return Z_MEM_ERROR;
273
strm->state = (struct internal_state FAR *)s;
278
s->w_bits = windowBits;
279
s->w_size = 1 << s->w_bits;
280
s->w_mask = s->w_size - 1;
282
s->hash_bits = memLevel + 7;
283
s->hash_size = 1 << s->hash_bits;
284
s->hash_mask = s->hash_size - 1;
285
s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
287
s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
288
s->prev = (Posf *) ZALLOC(strm, s->w_size, sizeof(Pos));
289
s->head = (Posf *) ZALLOC(strm, s->hash_size, sizeof(Pos));
291
s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
293
overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
294
s->pending_buf = (uchf *) overlay;
295
s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
297
if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
298
s->pending_buf == Z_NULL) {
299
s->status = FINISH_STATE;
300
strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);
304
s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
305
s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
308
s->strategy = strategy;
309
s->method = (Byte)method;
311
return deflateReset(strm);
314
/* ========================================================================= */
315
int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
317
const Bytef *dictionary;
321
uInt length = dictLength;
325
if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL ||
326
strm->state->wrap == 2 ||
327
(strm->state->wrap == 1 && strm->state->status != INIT_STATE))
328
return Z_STREAM_ERROR;
332
strm->adler = adler32(strm->adler, dictionary, dictLength);
334
if (length < MIN_MATCH) return Z_OK;
335
if (length > MAX_DIST(s)) {
336
length = MAX_DIST(s);
337
dictionary += dictLength - length; /* use the tail of the dictionary */
339
zmemcpy(s->window, dictionary, length);
340
s->strstart = length;
341
s->block_start = (long)length;
343
/* Insert all strings in the hash table (except for the last two bytes).
344
* s->lookahead stays null, so s->ins_h will be recomputed at the next
345
* call of fill_window.
347
s->ins_h = s->window[0];
348
UPDATE_HASH(s, s->ins_h, s->window[1]);
349
for (n = 0; n <= length - MIN_MATCH; n++) {
350
INSERT_STRING(s, n, hash_head);
352
if (hash_head) hash_head = 0; /* to make compiler happy */
356
/* ========================================================================= */
357
int ZEXPORT deflateReset (strm)
362
if (strm == Z_NULL || strm->state == Z_NULL ||
363
strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
364
return Z_STREAM_ERROR;
367
strm->total_in = strm->total_out = 0;
368
strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
369
strm->data_type = Z_UNKNOWN;
371
s = (deflate_state *)strm->state;
373
s->pending_out = s->pending_buf;
376
s->wrap = -s->wrap; /* was made negative by deflate(..., Z_FINISH); */
378
s->status = s->wrap ? INIT_STATE : BUSY_STATE;
381
s->wrap == 2 ? crc32(0L, Z_NULL, 0) :
383
adler32(0L, Z_NULL, 0);
384
s->last_flush = Z_NO_FLUSH;
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/* ========================================================================= */
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int ZEXPORT deflateSetHeader (strm, head)
397
if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
398
if (strm->state->wrap != 2) return Z_STREAM_ERROR;
399
strm->state->gzhead = head;
403
/* ========================================================================= */
404
int ZEXPORT deflatePrime (strm, bits, value)
409
if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
410
strm->state->bi_valid = bits;
411
strm->state->bi_buf = (ush)(value & ((1 << bits) - 1));
415
/* ========================================================================= */
416
int ZEXPORT deflateParams(strm, level, strategy)
425
if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
429
if (level != 0) level = 1;
431
if (level == Z_DEFAULT_COMPRESSION) level = 6;
433
if (level < 0 || level > 9 || strategy < 0 || strategy > Z_FIXED) {
434
return Z_STREAM_ERROR;
436
func = configuration_table[s->level].func;
438
if (func != configuration_table[level].func && strm->total_in != 0) {
439
/* Flush the last buffer: */
440
err = deflate(strm, Z_PARTIAL_FLUSH);
442
if (s->level != level) {
444
s->max_lazy_match = configuration_table[level].max_lazy;
445
s->good_match = configuration_table[level].good_length;
446
s->nice_match = configuration_table[level].nice_length;
447
s->max_chain_length = configuration_table[level].max_chain;
449
s->strategy = strategy;
453
/* ========================================================================= */
454
int ZEXPORT deflateTune(strm, good_length, max_lazy, nice_length, max_chain)
463
if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
465
s->good_match = good_length;
466
s->max_lazy_match = max_lazy;
467
s->nice_match = nice_length;
468
s->max_chain_length = max_chain;
472
/* =========================================================================
473
* For the default windowBits of 15 and memLevel of 8, this function returns
474
* a close to exact, as well as small, upper bound on the compressed size.
475
* They are coded as constants here for a reason--if the #define's are
476
* changed, then this function needs to be changed as well. The return
477
* value for 15 and 8 only works for those exact settings.
479
* For any setting other than those defaults for windowBits and memLevel,
480
* the value returned is a conservative worst case for the maximum expansion
481
* resulting from using fixed blocks instead of stored blocks, which deflate
482
* can emit on compressed data for some combinations of the parameters.
484
* This function could be more sophisticated to provide closer upper bounds
485
* for every combination of windowBits and memLevel, as well as wrap.
486
* But even the conservative upper bound of about 14% expansion does not
487
* seem onerous for output buffer allocation.
489
uLong ZEXPORT deflateBound(strm, sourceLen)
496
/* conservative upper bound */
497
destLen = sourceLen +
498
((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 11;
500
/* if can't get parameters, return conservative bound */
501
if (strm == Z_NULL || strm->state == Z_NULL)
504
/* if not default parameters, return conservative bound */
506
if (s->w_bits != 15 || s->hash_bits != 8 + 7)
509
/* default settings: return tight bound for that case */
510
return compressBound(sourceLen);
513
/* =========================================================================
514
* Put a short in the pending buffer. The 16-bit value is put in MSB order.
515
* IN assertion: the stream state is correct and there is enough room in
518
local void putShortMSB (s, b)
522
put_byte(s, (Byte)(b >> 8));
523
put_byte(s, (Byte)(b & 0xff));
526
/* =========================================================================
527
* Flush as much pending output as possible. All deflate() output goes
528
* through this function so some applications may wish to modify it
529
* to avoid allocating a large strm->next_out buffer and copying into it.
530
* (See also read_buf()).
532
local void flush_pending(strm)
535
unsigned len = strm->state->pending;
537
if (len > strm->avail_out) len = strm->avail_out;
538
if (len == 0) return;
540
zmemcpy(strm->next_out, strm->state->pending_out, len);
541
strm->next_out += len;
542
strm->state->pending_out += len;
543
strm->total_out += len;
544
strm->avail_out -= len;
545
strm->state->pending -= len;
546
if (strm->state->pending == 0) {
547
strm->state->pending_out = strm->state->pending_buf;
551
/* ========================================================================= */
552
int ZEXPORT deflate (strm, flush)
556
int old_flush; /* value of flush param for previous deflate call */
559
if (strm == Z_NULL || strm->state == Z_NULL ||
560
flush > Z_FINISH || flush < 0) {
561
return Z_STREAM_ERROR;
565
if (strm->next_out == Z_NULL ||
566
(strm->next_in == Z_NULL && strm->avail_in != 0) ||
567
(s->status == FINISH_STATE && flush != Z_FINISH)) {
568
ERR_RETURN(strm, Z_STREAM_ERROR);
570
if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
572
s->strm = strm; /* just in case */
573
old_flush = s->last_flush;
574
s->last_flush = flush;
576
/* Write the header */
577
if (s->status == INIT_STATE) {
580
strm->adler = crc32(0L, Z_NULL, 0);
584
if (s->gzhead == NULL) {
590
put_byte(s, s->level == 9 ? 2 :
591
(s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
593
put_byte(s, OS_CODE);
594
s->status = BUSY_STATE;
597
put_byte(s, (s->gzhead->text ? 1 : 0) +
598
(s->gzhead->hcrc ? 2 : 0) +
599
(s->gzhead->extra == Z_NULL ? 0 : 4) +
600
(s->gzhead->name == Z_NULL ? 0 : 8) +
601
(s->gzhead->comment == Z_NULL ? 0 : 16)
603
put_byte(s, (Byte)(s->gzhead->time & 0xff));
604
put_byte(s, (Byte)((s->gzhead->time >> 8) & 0xff));
605
put_byte(s, (Byte)((s->gzhead->time >> 16) & 0xff));
606
put_byte(s, (Byte)((s->gzhead->time >> 24) & 0xff));
607
put_byte(s, s->level == 9 ? 2 :
608
(s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
610
put_byte(s, s->gzhead->os & 0xff);
611
if (s->gzhead->extra != NULL) {
612
put_byte(s, s->gzhead->extra_len & 0xff);
613
put_byte(s, (s->gzhead->extra_len >> 8) & 0xff);
616
strm->adler = crc32(strm->adler, s->pending_buf,
619
s->status = EXTRA_STATE;
625
uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
628
if (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2)
630
else if (s->level < 6)
632
else if (s->level == 6)
636
header |= (level_flags << 6);
637
if (s->strstart != 0) header |= PRESET_DICT;
638
header += 31 - (header % 31);
640
s->status = BUSY_STATE;
641
putShortMSB(s, header);
643
/* Save the adler32 of the preset dictionary: */
644
if (s->strstart != 0) {
645
putShortMSB(s, (uInt)(strm->adler >> 16));
646
putShortMSB(s, (uInt)(strm->adler & 0xffff));
648
strm->adler = adler32(0L, Z_NULL, 0);
652
if (s->status == EXTRA_STATE) {
653
if (s->gzhead->extra != NULL) {
654
uInt beg = s->pending; /* start of bytes to update crc */
656
while (s->gzindex < (s->gzhead->extra_len & 0xffff)) {
657
if (s->pending == s->pending_buf_size) {
658
if (s->gzhead->hcrc && s->pending > beg)
659
strm->adler = crc32(strm->adler, s->pending_buf + beg,
663
if (s->pending == s->pending_buf_size)
666
put_byte(s, s->gzhead->extra[s->gzindex]);
669
if (s->gzhead->hcrc && s->pending > beg)
670
strm->adler = crc32(strm->adler, s->pending_buf + beg,
672
if (s->gzindex == s->gzhead->extra_len) {
674
s->status = NAME_STATE;
678
s->status = NAME_STATE;
680
if (s->status == NAME_STATE) {
681
if (s->gzhead->name != NULL) {
682
uInt beg = s->pending; /* start of bytes to update crc */
686
if (s->pending == s->pending_buf_size) {
687
if (s->gzhead->hcrc && s->pending > beg)
688
strm->adler = crc32(strm->adler, s->pending_buf + beg,
692
if (s->pending == s->pending_buf_size) {
697
val = s->gzhead->name[s->gzindex++];
700
if (s->gzhead->hcrc && s->pending > beg)
701
strm->adler = crc32(strm->adler, s->pending_buf + beg,
705
s->status = COMMENT_STATE;
709
s->status = COMMENT_STATE;
711
if (s->status == COMMENT_STATE) {
712
if (s->gzhead->comment != NULL) {
713
uInt beg = s->pending; /* start of bytes to update crc */
717
if (s->pending == s->pending_buf_size) {
718
if (s->gzhead->hcrc && s->pending > beg)
719
strm->adler = crc32(strm->adler, s->pending_buf + beg,
723
if (s->pending == s->pending_buf_size) {
728
val = s->gzhead->comment[s->gzindex++];
731
if (s->gzhead->hcrc && s->pending > beg)
732
strm->adler = crc32(strm->adler, s->pending_buf + beg,
735
s->status = HCRC_STATE;
738
s->status = HCRC_STATE;
740
if (s->status == HCRC_STATE) {
741
if (s->gzhead->hcrc) {
742
if (s->pending + 2 > s->pending_buf_size)
744
if (s->pending + 2 <= s->pending_buf_size) {
745
put_byte(s, (Byte)(strm->adler & 0xff));
746
put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
747
strm->adler = crc32(0L, Z_NULL, 0);
748
s->status = BUSY_STATE;
752
s->status = BUSY_STATE;
756
/* Flush as much pending output as possible */
757
if (s->pending != 0) {
759
if (strm->avail_out == 0) {
760
/* Since avail_out is 0, deflate will be called again with
761
* more output space, but possibly with both pending and
762
* avail_in equal to zero. There won't be anything to do,
763
* but this is not an error situation so make sure we
764
* return OK instead of BUF_ERROR at next call of deflate:
770
/* Make sure there is something to do and avoid duplicate consecutive
771
* flushes. For repeated and useless calls with Z_FINISH, we keep
772
* returning Z_STREAM_END instead of Z_BUF_ERROR.
774
} else if (strm->avail_in == 0 && flush <= old_flush &&
776
ERR_RETURN(strm, Z_BUF_ERROR);
779
/* User must not provide more input after the first FINISH: */
780
if (s->status == FINISH_STATE && strm->avail_in != 0) {
781
ERR_RETURN(strm, Z_BUF_ERROR);
784
/* Start a new block or continue the current one.
786
if (strm->avail_in != 0 || s->lookahead != 0 ||
787
(flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
790
bstate = (*(configuration_table[s->level].func))(s, flush);
792
if (bstate == finish_started || bstate == finish_done) {
793
s->status = FINISH_STATE;
795
if (bstate == need_more || bstate == finish_started) {
796
if (strm->avail_out == 0) {
797
s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
800
/* If flush != Z_NO_FLUSH && avail_out == 0, the next call
801
* of deflate should use the same flush parameter to make sure
802
* that the flush is complete. So we don't have to output an
803
* empty block here, this will be done at next call. This also
804
* ensures that for a very small output buffer, we emit at most
808
if (bstate == block_done) {
809
if (flush == Z_PARTIAL_FLUSH) {
811
} else { /* FULL_FLUSH or SYNC_FLUSH */
812
_tr_stored_block(s, (char*)0, 0L, 0);
813
/* For a full flush, this empty block will be recognized
814
* as a special marker by inflate_sync().
816
if (flush == Z_FULL_FLUSH) {
817
CLEAR_HASH(s); /* forget history */
821
if (strm->avail_out == 0) {
822
s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
827
Assert(strm->avail_out > 0, "bug2");
829
if (flush != Z_FINISH) return Z_OK;
830
if (s->wrap <= 0) return Z_STREAM_END;
832
/* Write the trailer */
835
put_byte(s, (Byte)(strm->adler & 0xff));
836
put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
837
put_byte(s, (Byte)((strm->adler >> 16) & 0xff));
838
put_byte(s, (Byte)((strm->adler >> 24) & 0xff));
839
put_byte(s, (Byte)(strm->total_in & 0xff));
840
put_byte(s, (Byte)((strm->total_in >> 8) & 0xff));
841
put_byte(s, (Byte)((strm->total_in >> 16) & 0xff));
842
put_byte(s, (Byte)((strm->total_in >> 24) & 0xff));
847
putShortMSB(s, (uInt)(strm->adler >> 16));
848
putShortMSB(s, (uInt)(strm->adler & 0xffff));
851
/* If avail_out is zero, the application will call deflate again
854
if (s->wrap > 0) s->wrap = -s->wrap; /* write the trailer only once! */
855
return s->pending != 0 ? Z_OK : Z_STREAM_END;
858
/* ========================================================================= */
859
int ZEXPORT deflateEnd (strm)
864
if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
866
status = strm->state->status;
867
if (status != INIT_STATE &&
868
status != EXTRA_STATE &&
869
status != NAME_STATE &&
870
status != COMMENT_STATE &&
871
status != HCRC_STATE &&
872
status != BUSY_STATE &&
873
status != FINISH_STATE) {
874
return Z_STREAM_ERROR;
877
/* Deallocate in reverse order of allocations: */
878
TRY_FREE(strm, strm->state->pending_buf);
879
TRY_FREE(strm, strm->state->head);
880
TRY_FREE(strm, strm->state->prev);
881
TRY_FREE(strm, strm->state->window);
883
ZFREE(strm, strm->state);
884
strm->state = Z_NULL;
886
return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
889
/* =========================================================================
890
* Copy the source state to the destination state.
891
* To simplify the source, this is not supported for 16-bit MSDOS (which
892
* doesn't have enough memory anyway to duplicate compression states).
894
int ZEXPORT deflateCopy (dest, source)
899
return Z_STREAM_ERROR;
906
if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
907
return Z_STREAM_ERROR;
912
zmemcpy(dest, source, sizeof(z_stream));
914
ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
915
if (ds == Z_NULL) return Z_MEM_ERROR;
916
dest->state = (struct internal_state FAR *) ds;
917
zmemcpy(ds, ss, sizeof(deflate_state));
920
ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
921
ds->prev = (Posf *) ZALLOC(dest, ds->w_size, sizeof(Pos));
922
ds->head = (Posf *) ZALLOC(dest, ds->hash_size, sizeof(Pos));
923
overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
924
ds->pending_buf = (uchf *) overlay;
926
if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
927
ds->pending_buf == Z_NULL) {
931
/* following zmemcpy do not work for 16-bit MSDOS */
932
zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
933
zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
934
zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));
935
zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
937
ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
938
ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
939
ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
941
ds->l_desc.dyn_tree = ds->dyn_ltree;
942
ds->d_desc.dyn_tree = ds->dyn_dtree;
943
ds->bl_desc.dyn_tree = ds->bl_tree;
946
#endif /* MAXSEG_64K */
949
/* ===========================================================================
950
* Read a new buffer from the current input stream, update the adler32
951
* and total number of bytes read. All deflate() input goes through
952
* this function so some applications may wish to modify it to avoid
953
* allocating a large strm->next_in buffer and copying from it.
954
* (See also flush_pending()).
956
local int read_buf(strm, buf, size)
961
unsigned len = strm->avail_in;
963
if (len > size) len = size;
964
if (len == 0) return 0;
966
strm->avail_in -= len;
968
if (strm->state->wrap == 1) {
969
strm->adler = adler32(strm->adler, strm->next_in, len);
972
else if (strm->state->wrap == 2) {
973
strm->adler = crc32(strm->adler, strm->next_in, len);
976
zmemcpy(buf, strm->next_in, len);
977
strm->next_in += len;
978
strm->total_in += len;
983
/* ===========================================================================
984
* Initialize the "longest match" routines for a new zlib stream
986
local void lm_init (s)
989
s->window_size = (ulg)2L*s->w_size;
993
/* Set the default configuration parameters:
995
s->max_lazy_match = configuration_table[s->level].max_lazy;
996
s->good_match = configuration_table[s->level].good_length;
997
s->nice_match = configuration_table[s->level].nice_length;
998
s->max_chain_length = configuration_table[s->level].max_chain;
1001
s->block_start = 0L;
1003
s->match_length = s->prev_length = MIN_MATCH-1;
1004
s->match_available = 0;
1008
match_init(); /* initialize the asm code */
1014
/* ===========================================================================
1015
* Set match_start to the longest match starting at the given string and
1016
* return its length. Matches shorter or equal to prev_length are discarded,
1017
* in which case the result is equal to prev_length and match_start is
1019
* IN assertions: cur_match is the head of the hash chain for the current
1020
* string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
1021
* OUT assertion: the match length is not greater than s->lookahead.
1024
/* For 80x86 and 680x0, an optimized version will be provided in match.asm or
1025
* match.S. The code will be functionally equivalent.
1027
local uInt longest_match(s, cur_match)
1029
IPos cur_match; /* current match */
1031
unsigned chain_length = s->max_chain_length;/* max hash chain length */
1032
register Bytef *scan = s->window + s->strstart; /* current string */
1033
register Bytef *match; /* matched string */
1034
register int len; /* length of current match */
1035
int best_len = s->prev_length; /* best match length so far */
1036
int nice_match = s->nice_match; /* stop if match long enough */
1037
IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
1038
s->strstart - (IPos)MAX_DIST(s) : NIL;
1039
/* Stop when cur_match becomes <= limit. To simplify the code,
1040
* we prevent matches with the string of window index 0.
1042
Posf *prev = s->prev;
1043
uInt wmask = s->w_mask;
1046
/* Compare two bytes at a time. Note: this is not always beneficial.
1047
* Try with and without -DUNALIGNED_OK to check.
1049
register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
1050
register ush scan_start = *(ushf*)scan;
1051
register ush scan_end = *(ushf*)(scan+best_len-1);
1053
register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1054
register Byte scan_end1 = scan[best_len-1];
1055
register Byte scan_end = scan[best_len];
1058
/* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1059
* It is easy to get rid of this optimization if necessary.
1061
Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1063
/* Do not waste too much time if we already have a good match: */
1064
if (s->prev_length >= s->good_match) {
1067
/* Do not look for matches beyond the end of the input. This is necessary
1068
* to make deflate deterministic.
1070
if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
1072
Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1075
Assert(cur_match < s->strstart, "no future");
1076
match = s->window + cur_match;
1078
/* Skip to next match if the match length cannot increase
1079
* or if the match length is less than 2. Note that the checks below
1080
* for insufficient lookahead only occur occasionally for performance
1081
* reasons. Therefore uninitialized memory will be accessed, and
1082
* conditional jumps will be made that depend on those values.
1083
* However the length of the match is limited to the lookahead, so
1084
* the output of deflate is not affected by the uninitialized values.
1086
#if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
1087
/* This code assumes sizeof(unsigned short) == 2. Do not use
1088
* UNALIGNED_OK if your compiler uses a different size.
1090
if (*(ushf*)(match+best_len-1) != scan_end ||
1091
*(ushf*)match != scan_start) continue;
1093
/* It is not necessary to compare scan[2] and match[2] since they are
1094
* always equal when the other bytes match, given that the hash keys
1095
* are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
1096
* strstart+3, +5, ... up to strstart+257. We check for insufficient
1097
* lookahead only every 4th comparison; the 128th check will be made
1098
* at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
1099
* necessary to put more guard bytes at the end of the window, or
1100
* to check more often for insufficient lookahead.
1102
Assert(scan[2] == match[2], "scan[2]?");
1105
} while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1106
*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1107
*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1108
*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1110
/* The funny "do {}" generates better code on most compilers */
1112
/* Here, scan <= window+strstart+257 */
1113
Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1114
if (*scan == *match) scan++;
1116
len = (MAX_MATCH - 1) - (int)(strend-scan);
1117
scan = strend - (MAX_MATCH-1);
1119
#else /* UNALIGNED_OK */
1121
if (match[best_len] != scan_end ||
1122
match[best_len-1] != scan_end1 ||
1124
*++match != scan[1]) continue;
1126
/* The check at best_len-1 can be removed because it will be made
1127
* again later. (This heuristic is not always a win.)
1128
* It is not necessary to compare scan[2] and match[2] since they
1129
* are always equal when the other bytes match, given that
1130
* the hash keys are equal and that HASH_BITS >= 8.
1133
Assert(*scan == *match, "match[2]?");
1135
/* We check for insufficient lookahead only every 8th comparison;
1136
* the 256th check will be made at strstart+258.
1139
} while (*++scan == *++match && *++scan == *++match &&
1140
*++scan == *++match && *++scan == *++match &&
1141
*++scan == *++match && *++scan == *++match &&
1142
*++scan == *++match && *++scan == *++match &&
1145
Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1147
len = MAX_MATCH - (int)(strend - scan);
1148
scan = strend - MAX_MATCH;
1150
#endif /* UNALIGNED_OK */
1152
if (len > best_len) {
1153
s->match_start = cur_match;
1155
if (len >= nice_match) break;
1157
scan_end = *(ushf*)(scan+best_len-1);
1159
scan_end1 = scan[best_len-1];
1160
scan_end = scan[best_len];
1163
} while ((cur_match = prev[cur_match & wmask]) > limit
1164
&& --chain_length != 0);
1166
if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
1167
return s->lookahead;
1170
#endif /* FASTEST */
1172
/* ---------------------------------------------------------------------------
1173
* Optimized version for level == 1 or strategy == Z_RLE only
1175
local uInt longest_match_fast(s, cur_match)
1177
IPos cur_match; /* current match */
1179
register Bytef *scan = s->window + s->strstart; /* current string */
1180
register Bytef *match; /* matched string */
1181
register int len; /* length of current match */
1182
register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1184
/* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1185
* It is easy to get rid of this optimization if necessary.
1187
Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1189
Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1191
Assert(cur_match < s->strstart, "no future");
1193
match = s->window + cur_match;
1195
/* Return failure if the match length is less than 2:
1197
if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
1199
/* The check at best_len-1 can be removed because it will be made
1200
* again later. (This heuristic is not always a win.)
1201
* It is not necessary to compare scan[2] and match[2] since they
1202
* are always equal when the other bytes match, given that
1203
* the hash keys are equal and that HASH_BITS >= 8.
1205
scan += 2, match += 2;
1206
Assert(*scan == *match, "match[2]?");
1208
/* We check for insufficient lookahead only every 8th comparison;
1209
* the 256th check will be made at strstart+258.
1212
} while (*++scan == *++match && *++scan == *++match &&
1213
*++scan == *++match && *++scan == *++match &&
1214
*++scan == *++match && *++scan == *++match &&
1215
*++scan == *++match && *++scan == *++match &&
1218
Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1220
len = MAX_MATCH - (int)(strend - scan);
1222
if (len < MIN_MATCH) return MIN_MATCH - 1;
1224
s->match_start = cur_match;
1225
return (uInt)len <= s->lookahead ? (uInt)len : s->lookahead;
1229
/* ===========================================================================
1230
* Check that the match at match_start is indeed a match.
1232
local void check_match(s, start, match, length)
1237
/* check that the match is indeed a match */
1238
if (zmemcmp(s->window + match,
1239
s->window + start, length) != EQUAL) {
1240
fprintf(stderr, " start %u, match %u, length %d\n",
1241
start, match, length);
1243
fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
1244
} while (--length != 0);
1245
z_error("invalid match");
1247
if (z_verbose > 1) {
1248
fprintf(stderr,"\\[%d,%d]", start-match, length);
1249
do { putc(s->window[start++], stderr); } while (--length != 0);
1253
# define check_match(s, start, match, length)
1256
/* ===========================================================================
1257
* Fill the window when the lookahead becomes insufficient.
1258
* Updates strstart and lookahead.
1260
* IN assertion: lookahead < MIN_LOOKAHEAD
1261
* OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
1262
* At least one byte has been read, or avail_in == 0; reads are
1263
* performed for at least two bytes (required for the zip translate_eol
1264
* option -- not supported here).
1266
local void fill_window(s)
1269
register unsigned n, m;
1271
unsigned more; /* Amount of free space at the end of the window. */
1272
uInt wsize = s->w_size;
1275
more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
1277
/* Deal with !@#$% 64K limit: */
1278
if (sizeof(int) <= 2) {
1279
if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
1282
} else if (more == (unsigned)(-1)) {
1283
/* Very unlikely, but possible on 16 bit machine if
1284
* strstart == 0 && lookahead == 1 (input done a byte at time)
1290
/* If the window is almost full and there is insufficient lookahead,
1291
* move the upper half to the lower one to make room in the upper half.
1293
if (s->strstart >= wsize+MAX_DIST(s)) {
1295
zmemcpy(s->window, s->window+wsize, (unsigned)wsize);
1296
s->match_start -= wsize;
1297
s->strstart -= wsize; /* we now have strstart >= MAX_DIST */
1298
s->block_start -= (long) wsize;
1300
/* Slide the hash table (could be avoided with 32 bit values
1301
at the expense of memory usage). We slide even when level == 0
1302
to keep the hash table consistent if we switch back to level > 0
1303
later. (Using level 0 permanently is not an optimal usage of
1304
zlib, so we don't care about this pathological case.)
1306
/* %%% avoid this when Z_RLE */
1311
*p = (Pos)(m >= wsize ? m-wsize : NIL);
1319
*p = (Pos)(m >= wsize ? m-wsize : NIL);
1320
/* If n is not on any hash chain, prev[n] is garbage but
1321
* its value will never be used.
1327
if (s->strm->avail_in == 0) return;
1329
/* If there was no sliding:
1330
* strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
1331
* more == window_size - lookahead - strstart
1332
* => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
1333
* => more >= window_size - 2*WSIZE + 2
1334
* In the BIG_MEM or MMAP case (not yet supported),
1335
* window_size == input_size + MIN_LOOKAHEAD &&
1336
* strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
1337
* Otherwise, window_size == 2*WSIZE so more >= 2.
1338
* If there was sliding, more >= WSIZE. So in all cases, more >= 2.
1340
Assert(more >= 2, "more < 2");
1342
n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
1345
/* Initialize the hash value now that we have some input: */
1346
if (s->lookahead >= MIN_MATCH) {
1347
s->ins_h = s->window[s->strstart];
1348
UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1350
Call UPDATE_HASH() MIN_MATCH-3 more times
1353
/* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
1354
* but this is not important since only literal bytes will be emitted.
1357
} while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
1360
/* ===========================================================================
1361
* Flush the current block, with given end-of-file flag.
1362
* IN assertion: strstart is set to the end of the current match.
1364
#define FLUSH_BLOCK_ONLY(s, eof) { \
1365
_tr_flush_block(s, (s->block_start >= 0L ? \
1366
(charf *)&s->window[(unsigned)s->block_start] : \
1368
(ulg)((long)s->strstart - s->block_start), \
1370
s->block_start = s->strstart; \
1371
flush_pending(s->strm); \
1372
Tracev((stderr,"[FLUSH]")); \
1375
/* Same but force premature exit if necessary. */
1376
#define FLUSH_BLOCK(s, eof) { \
1377
FLUSH_BLOCK_ONLY(s, eof); \
1378
if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \
1381
/* ===========================================================================
1382
* Copy without compression as much as possible from the input stream, return
1383
* the current block state.
1384
* This function does not insert new strings in the dictionary since
1385
* uncompressible data is probably not useful. This function is used
1386
* only for the level=0 compression option.
1387
* NOTE: this function should be optimized to avoid extra copying from
1388
* window to pending_buf.
1390
local block_state deflate_stored(s, flush)
1394
/* Stored blocks are limited to 0xffff bytes, pending_buf is limited
1395
* to pending_buf_size, and each stored block has a 5 byte header:
1397
ulg max_block_size = 0xffff;
1400
if (max_block_size > s->pending_buf_size - 5) {
1401
max_block_size = s->pending_buf_size - 5;
1404
/* Copy as much as possible from input to output: */
1406
/* Fill the window as much as possible: */
1407
if (s->lookahead <= 1) {
1409
Assert(s->strstart < s->w_size+MAX_DIST(s) ||
1410
s->block_start >= (long)s->w_size, "slide too late");
1413
if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
1415
if (s->lookahead == 0) break; /* flush the current block */
1417
Assert(s->block_start >= 0L, "block gone");
1419
s->strstart += s->lookahead;
1422
/* Emit a stored block if pending_buf will be full: */
1423
max_start = s->block_start + max_block_size;
1424
if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
1425
/* strstart == 0 is possible when wraparound on 16-bit machine */
1426
s->lookahead = (uInt)(s->strstart - max_start);
1427
s->strstart = (uInt)max_start;
1430
/* Flush if we may have to slide, otherwise block_start may become
1431
* negative and the data will be gone:
1433
if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
1437
FLUSH_BLOCK(s, flush == Z_FINISH);
1438
return flush == Z_FINISH ? finish_done : block_done;
1441
/* ===========================================================================
1442
* Compress as much as possible from the input stream, return the current
1444
* This function does not perform lazy evaluation of matches and inserts
1445
* new strings in the dictionary only for unmatched strings or for short
1446
* matches. It is used only for the fast compression options.
1448
local block_state deflate_fast(s, flush)
1452
IPos hash_head = NIL; /* head of the hash chain */
1453
int bflush; /* set if current block must be flushed */
1456
/* Make sure that we always have enough lookahead, except
1457
* at the end of the input file. We need MAX_MATCH bytes
1458
* for the next match, plus MIN_MATCH bytes to insert the
1459
* string following the next match.
1461
if (s->lookahead < MIN_LOOKAHEAD) {
1463
if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1466
if (s->lookahead == 0) break; /* flush the current block */
1469
/* Insert the string window[strstart .. strstart+2] in the
1470
* dictionary, and set hash_head to the head of the hash chain:
1472
if (s->lookahead >= MIN_MATCH) {
1473
INSERT_STRING(s, s->strstart, hash_head);
1476
/* Find the longest match, discarding those <= prev_length.
1477
* At this point we have always match_length < MIN_MATCH
1479
if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
1480
/* To simplify the code, we prevent matches with the string
1481
* of window index 0 (in particular we have to avoid a match
1482
* of the string with itself at the start of the input file).
1485
if ((s->strategy != Z_HUFFMAN_ONLY && s->strategy != Z_RLE) ||
1486
(s->strategy == Z_RLE && s->strstart - hash_head == 1)) {
1487
s->match_length = longest_match_fast (s, hash_head);
1490
if (s->strategy != Z_HUFFMAN_ONLY && s->strategy != Z_RLE) {
1491
s->match_length = longest_match (s, hash_head);
1492
} else if (s->strategy == Z_RLE && s->strstart - hash_head == 1) {
1493
s->match_length = longest_match_fast (s, hash_head);
1496
/* longest_match() or longest_match_fast() sets match_start */
1498
if (s->match_length >= MIN_MATCH) {
1499
check_match(s, s->strstart, s->match_start, s->match_length);
1501
_tr_tally_dist(s, s->strstart - s->match_start,
1502
s->match_length - MIN_MATCH, bflush);
1504
s->lookahead -= s->match_length;
1506
/* Insert new strings in the hash table only if the match length
1507
* is not too large. This saves time but degrades compression.
1510
if (s->match_length <= s->max_insert_length &&
1511
s->lookahead >= MIN_MATCH) {
1512
s->match_length--; /* string at strstart already in table */
1515
INSERT_STRING(s, s->strstart, hash_head);
1516
/* strstart never exceeds WSIZE-MAX_MATCH, so there are
1517
* always MIN_MATCH bytes ahead.
1519
} while (--s->match_length != 0);
1524
s->strstart += s->match_length;
1525
s->match_length = 0;
1526
s->ins_h = s->window[s->strstart];
1527
UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1529
Call UPDATE_HASH() MIN_MATCH-3 more times
1531
/* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
1532
* matter since it will be recomputed at next deflate call.
1536
/* No match, output a literal byte */
1537
Tracevv((stderr,"%c", s->window[s->strstart]));
1538
_tr_tally_lit (s, s->window[s->strstart], bflush);
1542
if (bflush) FLUSH_BLOCK(s, 0);
1544
FLUSH_BLOCK(s, flush == Z_FINISH);
1545
return flush == Z_FINISH ? finish_done : block_done;
1549
/* ===========================================================================
1550
* Same as above, but achieves better compression. We use a lazy
1551
* evaluation for matches: a match is finally adopted only if there is
1552
* no better match at the next window position.
1554
local block_state deflate_slow(s, flush)
1558
IPos hash_head = NIL; /* head of hash chain */
1559
int bflush; /* set if current block must be flushed */
1561
/* Process the input block. */
1563
/* Make sure that we always have enough lookahead, except
1564
* at the end of the input file. We need MAX_MATCH bytes
1565
* for the next match, plus MIN_MATCH bytes to insert the
1566
* string following the next match.
1568
if (s->lookahead < MIN_LOOKAHEAD) {
1570
if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1573
if (s->lookahead == 0) break; /* flush the current block */
1576
/* Insert the string window[strstart .. strstart+2] in the
1577
* dictionary, and set hash_head to the head of the hash chain:
1579
if (s->lookahead >= MIN_MATCH) {
1580
INSERT_STRING(s, s->strstart, hash_head);
1583
/* Find the longest match, discarding those <= prev_length.
1585
s->prev_length = s->match_length, s->prev_match = s->match_start;
1586
s->match_length = MIN_MATCH-1;
1588
if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
1589
s->strstart - hash_head <= MAX_DIST(s)) {
1590
/* To simplify the code, we prevent matches with the string
1591
* of window index 0 (in particular we have to avoid a match
1592
* of the string with itself at the start of the input file).
1594
if (s->strategy != Z_HUFFMAN_ONLY && s->strategy != Z_RLE) {
1595
s->match_length = longest_match (s, hash_head);
1596
} else if (s->strategy == Z_RLE && s->strstart - hash_head == 1) {
1597
s->match_length = longest_match_fast (s, hash_head);
1599
/* longest_match() or longest_match_fast() sets match_start */
1601
if (s->match_length <= 5 && (s->strategy == Z_FILTERED
1602
#if TOO_FAR <= 32767
1603
|| (s->match_length == MIN_MATCH &&
1604
s->strstart - s->match_start > TOO_FAR)
1608
/* If prev_match is also MIN_MATCH, match_start is garbage
1609
* but we will ignore the current match anyway.
1611
s->match_length = MIN_MATCH-1;
1614
/* If there was a match at the previous step and the current
1615
* match is not better, output the previous match:
1617
if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
1618
uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
1619
/* Do not insert strings in hash table beyond this. */
1621
check_match(s, s->strstart-1, s->prev_match, s->prev_length);
1623
_tr_tally_dist(s, s->strstart -1 - s->prev_match,
1624
s->prev_length - MIN_MATCH, bflush);
1626
/* Insert in hash table all strings up to the end of the match.
1627
* strstart-1 and strstart are already inserted. If there is not
1628
* enough lookahead, the last two strings are not inserted in
1631
s->lookahead -= s->prev_length-1;
1632
s->prev_length -= 2;
1634
if (++s->strstart <= max_insert) {
1635
INSERT_STRING(s, s->strstart, hash_head);
1637
} while (--s->prev_length != 0);
1638
s->match_available = 0;
1639
s->match_length = MIN_MATCH-1;
1642
if (bflush) FLUSH_BLOCK(s, 0);
1644
} else if (s->match_available) {
1645
/* If there was no match at the previous position, output a
1646
* single literal. If there was a match but the current match
1647
* is longer, truncate the previous match to a single literal.
1649
Tracevv((stderr,"%c", s->window[s->strstart-1]));
1650
_tr_tally_lit(s, s->window[s->strstart-1], bflush);
1652
FLUSH_BLOCK_ONLY(s, 0);
1656
if (s->strm->avail_out == 0) return need_more;
1658
/* There is no previous match to compare with, wait for
1659
* the next step to decide.
1661
s->match_available = 1;
1666
Assert (flush != Z_NO_FLUSH, "no flush?");
1667
if (s->match_available) {
1668
Tracevv((stderr,"%c", s->window[s->strstart-1]));
1669
_tr_tally_lit(s, s->window[s->strstart-1], bflush);
1670
s->match_available = 0;
1672
FLUSH_BLOCK(s, flush == Z_FINISH);
1673
return flush == Z_FINISH ? finish_done : block_done;
1675
#endif /* FASTEST */
1678
/* ===========================================================================
1679
* For Z_RLE, simply look for runs of bytes, generate matches only of distance
1680
* one. Do not maintain a hash table. (It will be regenerated if this run of
1681
* deflate switches away from Z_RLE.)
1683
local block_state deflate_rle(s, flush)
1687
int bflush; /* set if current block must be flushed */
1688
uInt run; /* length of run */
1689
uInt max; /* maximum length of run */
1690
uInt prev; /* byte at distance one to match */
1691
Bytef *scan; /* scan for end of run */
1694
/* Make sure that we always have enough lookahead, except
1695
* at the end of the input file. We need MAX_MATCH bytes
1696
* for the longest encodable run.
1698
if (s->lookahead < MAX_MATCH) {
1700
if (s->lookahead < MAX_MATCH && flush == Z_NO_FLUSH) {
1703
if (s->lookahead == 0) break; /* flush the current block */
1706
/* See how many times the previous byte repeats */
1708
if (s->strstart > 0) { /* if there is a previous byte, that is */
1709
max = s->lookahead < MAX_MATCH ? s->lookahead : MAX_MATCH;
1710
scan = s->window + s->strstart - 1;
1713
if (*scan++ != prev)
1715
} while (++run < max);
1718
/* Emit match if have run of MIN_MATCH or longer, else emit literal */
1719
if (run >= MIN_MATCH) {
1720
check_match(s, s->strstart, s->strstart - 1, run);
1721
_tr_tally_dist(s, 1, run - MIN_MATCH, bflush);
1722
s->lookahead -= run;
1725
/* No match, output a literal byte */
1726
Tracevv((stderr,"%c", s->window[s->strstart]));
1727
_tr_tally_lit (s, s->window[s->strstart], bflush);
1731
if (bflush) FLUSH_BLOCK(s, 0);
1733
FLUSH_BLOCK(s, flush == Z_FINISH);
1734
return flush == Z_FINISH ? finish_done : block_done;
added
removed
mozilla/security/nss/cmd/zlib/deflate.c
