1
/* deflate.c -- compress data using the deflation algorithm
2
* Copyright (C) 1995-2010 Jean-loup Gailly and Mark Adler
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
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* completely. Insertions are performed at each input character, whereas
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* string matches are performed only when the previous match ends. So it
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* is preferable to spend more time in matches to allow very fast string
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* insertions and avoid deletions. The matching algorithm for small
21
* strings is inspired from that of Rabin & Karp. A brute force approach
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* is used to find longer strings when a small match has been found.
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* A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
24
* (by Leonid Broukhis).
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* A previous version of this file used a more sophisticated algorithm
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* (by Fiala and Greene) which is guaranteed to run in linear amortized
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* time, but has a larger average cost, uses more memory and is patented.
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* 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.
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* The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
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* 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
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* "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
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* 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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const char deflate_copyright[] =
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" deflate 1.2.5 Copyright 1995-2010 Jean-loup Gailly and Mark Adler ";
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If you use the zlib library in a product, an acknowledgment is welcome
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in the documentation of your product. If for some reason you cannot
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include such an acknowledgment, I would appreciate that you keep this
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copyright string in the executable of your product.
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/* ===========================================================================
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* Function prototypes.
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need_more, /* block not completed, need more input or more output */
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block_done, /* block flush performed */
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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 block_state deflate_rle OF((deflate_state *s, int flush));
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local block_state deflate_huff 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 void check_match OF((deflate_state *s, IPos start, IPos match,
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/* ===========================================================================
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/* 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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/* Values for max_lazy_match, good_match and max_chain_length, depending on
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* the desired pack level (0..9). The values given below have been tuned to
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* exclude worst case performance for pathological files. Better values may be
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* found for specific files.
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typedef struct config_s {
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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 */
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#ifndef NO_DUMMY_DECL
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struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
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/* ===========================================================================
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* 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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/* ===========================================================================
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* Insert string str in the dictionary and set match_head to the previous head
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* 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
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* 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
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* (except for the last MIN_MATCH-1 bytes of the input file).
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#define INSERT_STRING(s, str, match_head) \
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(UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
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match_head = s->head[s->ins_h], \
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s->head[s->ins_h] = (Pos)(str))
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#define INSERT_STRING(s, str, match_head) \
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(UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
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match_head = s->prev[(str) & s->w_mask] = s->head[s->ins_h], \
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s->head[s->ins_h] = (Pos)(str))
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/* ===========================================================================
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* Initialize the hash table (avoiding 64K overflow for 16 bit systems).
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* prev[] will be initialized on the fly.
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#define CLEAR_HASH(s) \
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s->head[s->hash_size-1] = NIL; \
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zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
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/* ========================================================================= */
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int ZEXPORT deflateInit_(strm, level, version, stream_size)
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return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,
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Z_DEFAULT_STRATEGY, version, stream_size);
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/* To do: ignore strm->next_in if we use it as window */
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/* ========================================================================= */
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int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
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version, stream_size)
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static const char my_version[] = ZLIB_VERSION;
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/* We overlay pending_buf and d_buf+l_buf. This works since the average
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* output size for (length,distance) codes is <= 24 bits.
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if (version == Z_NULL || version[0] != my_version[0] ||
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stream_size != sizeof(z_stream)) {
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return Z_VERSION_ERROR;
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if (strm == Z_NULL) return Z_STREAM_ERROR;
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if (strm->zalloc == (alloc_func)0) {
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strm->zalloc = zcalloc;
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strm->opaque = (voidpf)0;
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if (strm->zfree == (free_func)0) strm->zfree = zcfree;
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if (level != 0) level = 1;
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if (level == Z_DEFAULT_COMPRESSION) level = 6;
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if (windowBits < 0) { /* suppress zlib wrapper */
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windowBits = -windowBits;
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else if (windowBits > 15) {
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wrap = 2; /* write gzip wrapper instead */
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if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
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windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
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strategy < 0 || strategy > Z_FIXED) {
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return Z_STREAM_ERROR;
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if (windowBits == 8) windowBits = 9; /* until 256-byte window bug fixed */
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s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
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if (s == Z_NULL) return Z_MEM_ERROR;
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strm->state = (struct internal_state FAR *)s;
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s->w_bits = windowBits;
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s->w_size = 1 << s->w_bits;
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s->w_mask = s->w_size - 1;
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s->hash_bits = memLevel + 7;
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s->hash_size = 1 << s->hash_bits;
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s->hash_mask = s->hash_size - 1;
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s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
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s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
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s->prev = (Posf *) ZALLOC(strm, s->w_size, sizeof(Pos));
283
s->head = (Posf *) ZALLOC(strm, s->hash_size, sizeof(Pos));
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s->high_water = 0; /* nothing written to s->window yet */
287
s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
289
overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
290
s->pending_buf = (uchf *) overlay;
291
s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
293
if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
294
s->pending_buf == Z_NULL) {
295
s->status = FINISH_STATE;
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strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);
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s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
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s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
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s->strategy = strategy;
305
s->method = (Byte)method;
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return deflateReset(strm);
310
/* ========================================================================= */
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int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
313
const Bytef *dictionary;
317
uInt length = dictLength;
321
if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL ||
322
strm->state->wrap == 2 ||
323
(strm->state->wrap == 1 && strm->state->status != INIT_STATE))
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return Z_STREAM_ERROR;
328
strm->adler = adler32(strm->adler, dictionary, dictLength);
330
if (length < MIN_MATCH) return Z_OK;
331
if (length > s->w_size) {
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dictionary += dictLength - length; /* use the tail of the dictionary */
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zmemcpy(s->window, dictionary, length);
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s->strstart = length;
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s->block_start = (long)length;
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/* Insert all strings in the hash table (except for the last two bytes).
340
* s->lookahead stays null, so s->ins_h will be recomputed at the next
341
* call of fill_window.
343
s->ins_h = s->window[0];
344
UPDATE_HASH(s, s->ins_h, s->window[1]);
345
for (n = 0; n <= length - MIN_MATCH; n++) {
346
INSERT_STRING(s, n, hash_head);
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if (hash_head) hash_head = 0; /* to make compiler happy */
352
/* ========================================================================= */
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int ZEXPORT deflateReset (strm)
358
if (strm == Z_NULL || strm->state == Z_NULL ||
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strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
360
return Z_STREAM_ERROR;
363
strm->total_in = strm->total_out = 0;
364
strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
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strm->data_type = Z_UNKNOWN;
367
s = (deflate_state *)strm->state;
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s->pending_out = s->pending_buf;
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s->wrap = -s->wrap; /* was made negative by deflate(..., Z_FINISH); */
374
s->status = s->wrap ? INIT_STATE : BUSY_STATE;
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s->wrap == 2 ? crc32(0L, Z_NULL, 0) :
379
adler32(0L, Z_NULL, 0);
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s->last_flush = Z_NO_FLUSH;
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/* ========================================================================= */
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int ZEXPORT deflateSetHeader (strm, head)
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if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
394
if (strm->state->wrap != 2) return Z_STREAM_ERROR;
395
strm->state->gzhead = head;
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/* ========================================================================= */
400
int ZEXPORT deflatePrime (strm, bits, value)
405
if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
406
strm->state->bi_valid = bits;
407
strm->state->bi_buf = (ush)(value & ((1 << bits) - 1));
411
/* ========================================================================= */
412
int ZEXPORT deflateParams(strm, level, strategy)
421
if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
425
if (level != 0) level = 1;
427
if (level == Z_DEFAULT_COMPRESSION) level = 6;
429
if (level < 0 || level > 9 || strategy < 0 || strategy > Z_FIXED) {
430
return Z_STREAM_ERROR;
432
func = configuration_table[s->level].func;
434
if ((strategy != s->strategy || func != configuration_table[level].func) &&
435
strm->total_in != 0) {
436
/* Flush the last buffer: */
437
err = deflate(strm, Z_BLOCK);
439
if (s->level != level) {
441
s->max_lazy_match = configuration_table[level].max_lazy;
442
s->good_match = configuration_table[level].good_length;
443
s->nice_match = configuration_table[level].nice_length;
444
s->max_chain_length = configuration_table[level].max_chain;
446
s->strategy = strategy;
450
/* ========================================================================= */
451
int ZEXPORT deflateTune(strm, good_length, max_lazy, nice_length, max_chain)
460
if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
462
s->good_match = good_length;
463
s->max_lazy_match = max_lazy;
464
s->nice_match = nice_length;
465
s->max_chain_length = max_chain;
469
/* =========================================================================
470
* For the default windowBits of 15 and memLevel of 8, this function returns
471
* a close to exact, as well as small, upper bound on the compressed size.
472
* They are coded as constants here for a reason--if the #define's are
473
* changed, then this function needs to be changed as well. The return
474
* value for 15 and 8 only works for those exact settings.
476
* For any setting other than those defaults for windowBits and memLevel,
477
* the value returned is a conservative worst case for the maximum expansion
478
* resulting from using fixed blocks instead of stored blocks, which deflate
479
* can emit on compressed data for some combinations of the parameters.
481
* This function could be more sophisticated to provide closer upper bounds for
482
* every combination of windowBits and memLevel. But even the conservative
483
* upper bound of about 14% expansion does not seem onerous for output buffer
486
uLong ZEXPORT deflateBound(strm, sourceLen)
491
uLong complen, wraplen;
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/* conservative upper bound for compressed data */
495
complen = sourceLen +
496
((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 5;
498
/* if can't get parameters, return conservative bound plus zlib wrapper */
499
if (strm == Z_NULL || strm->state == Z_NULL)
502
/* compute wrapper length */
505
case 0: /* raw deflate */
508
case 1: /* zlib wrapper */
509
wraplen = 6 + (s->strstart ? 4 : 0);
511
case 2: /* gzip wrapper */
513
if (s->gzhead != Z_NULL) { /* user-supplied gzip header */
514
if (s->gzhead->extra != Z_NULL)
515
wraplen += 2 + s->gzhead->extra_len;
516
str = s->gzhead->name;
521
str = s->gzhead->comment;
530
default: /* for compiler happiness */
534
/* if not default parameters, return conservative bound */
535
if (s->w_bits != 15 || s->hash_bits != 8 + 7)
536
return complen + wraplen;
538
/* default settings: return tight bound for that case */
539
return sourceLen + (sourceLen >> 12) + (sourceLen >> 14) +
540
(sourceLen >> 25) + 13 - 6 + wraplen;
543
/* =========================================================================
544
* Put a short in the pending buffer. The 16-bit value is put in MSB order.
545
* IN assertion: the stream state is correct and there is enough room in
548
local void putShortMSB (s, b)
552
put_byte(s, (Byte)(b >> 8));
553
put_byte(s, (Byte)(b & 0xff));
556
/* =========================================================================
557
* Flush as much pending output as possible. All deflate() output goes
558
* through this function so some applications may wish to modify it
559
* to avoid allocating a large strm->next_out buffer and copying into it.
560
* (See also read_buf()).
562
local void flush_pending(strm)
565
unsigned len = strm->state->pending;
567
if (len > strm->avail_out) len = strm->avail_out;
568
if (len == 0) return;
570
zmemcpy(strm->next_out, strm->state->pending_out, len);
571
strm->next_out += len;
572
strm->state->pending_out += len;
573
strm->total_out += len;
574
strm->avail_out -= len;
575
strm->state->pending -= len;
576
if (strm->state->pending == 0) {
577
strm->state->pending_out = strm->state->pending_buf;
581
/* ========================================================================= */
582
int ZEXPORT deflate (strm, flush)
586
int old_flush; /* value of flush param for previous deflate call */
589
if (strm == Z_NULL || strm->state == Z_NULL ||
590
flush > Z_BLOCK || flush < 0) {
591
return Z_STREAM_ERROR;
595
if (strm->next_out == Z_NULL ||
596
(strm->next_in == Z_NULL && strm->avail_in != 0) ||
597
(s->status == FINISH_STATE && flush != Z_FINISH)) {
598
ERR_RETURN(strm, Z_STREAM_ERROR);
600
if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
602
s->strm = strm; /* just in case */
603
old_flush = s->last_flush;
604
s->last_flush = flush;
606
/* Write the header */
607
if (s->status == INIT_STATE) {
610
strm->adler = crc32(0L, Z_NULL, 0);
614
if (s->gzhead == Z_NULL) {
620
put_byte(s, s->level == 9 ? 2 :
621
(s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
623
put_byte(s, OS_CODE);
624
s->status = BUSY_STATE;
627
put_byte(s, (s->gzhead->text ? 1 : 0) +
628
(s->gzhead->hcrc ? 2 : 0) +
629
(s->gzhead->extra == Z_NULL ? 0 : 4) +
630
(s->gzhead->name == Z_NULL ? 0 : 8) +
631
(s->gzhead->comment == Z_NULL ? 0 : 16)
633
put_byte(s, (Byte)(s->gzhead->time & 0xff));
634
put_byte(s, (Byte)((s->gzhead->time >> 8) & 0xff));
635
put_byte(s, (Byte)((s->gzhead->time >> 16) & 0xff));
636
put_byte(s, (Byte)((s->gzhead->time >> 24) & 0xff));
637
put_byte(s, s->level == 9 ? 2 :
638
(s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
640
put_byte(s, s->gzhead->os & 0xff);
641
if (s->gzhead->extra != Z_NULL) {
642
put_byte(s, s->gzhead->extra_len & 0xff);
643
put_byte(s, (s->gzhead->extra_len >> 8) & 0xff);
646
strm->adler = crc32(strm->adler, s->pending_buf,
649
s->status = EXTRA_STATE;
655
uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
658
if (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2)
660
else if (s->level < 6)
662
else if (s->level == 6)
666
header |= (level_flags << 6);
667
if (s->strstart != 0) header |= PRESET_DICT;
668
header += 31 - (header % 31);
670
s->status = BUSY_STATE;
671
putShortMSB(s, header);
673
/* Save the adler32 of the preset dictionary: */
674
if (s->strstart != 0) {
675
putShortMSB(s, (uInt)(strm->adler >> 16));
676
putShortMSB(s, (uInt)(strm->adler & 0xffff));
678
strm->adler = adler32(0L, Z_NULL, 0);
682
if (s->status == EXTRA_STATE) {
683
if (s->gzhead->extra != Z_NULL) {
684
uInt beg = s->pending; /* start of bytes to update crc */
686
while (s->gzindex < (s->gzhead->extra_len & 0xffff)) {
687
if (s->pending == s->pending_buf_size) {
688
if (s->gzhead->hcrc && s->pending > beg)
689
strm->adler = crc32(strm->adler, s->pending_buf + beg,
693
if (s->pending == s->pending_buf_size)
696
put_byte(s, s->gzhead->extra[s->gzindex]);
699
if (s->gzhead->hcrc && s->pending > beg)
700
strm->adler = crc32(strm->adler, s->pending_buf + beg,
702
if (s->gzindex == s->gzhead->extra_len) {
704
s->status = NAME_STATE;
708
s->status = NAME_STATE;
710
if (s->status == NAME_STATE) {
711
if (s->gzhead->name != Z_NULL) {
712
uInt beg = s->pending; /* start of bytes to update crc */
716
if (s->pending == s->pending_buf_size) {
717
if (s->gzhead->hcrc && s->pending > beg)
718
strm->adler = crc32(strm->adler, s->pending_buf + beg,
722
if (s->pending == s->pending_buf_size) {
727
val = s->gzhead->name[s->gzindex++];
730
if (s->gzhead->hcrc && s->pending > beg)
731
strm->adler = crc32(strm->adler, s->pending_buf + beg,
735
s->status = COMMENT_STATE;
739
s->status = COMMENT_STATE;
741
if (s->status == COMMENT_STATE) {
742
if (s->gzhead->comment != Z_NULL) {
743
uInt beg = s->pending; /* start of bytes to update crc */
747
if (s->pending == s->pending_buf_size) {
748
if (s->gzhead->hcrc && s->pending > beg)
749
strm->adler = crc32(strm->adler, s->pending_buf + beg,
753
if (s->pending == s->pending_buf_size) {
758
val = s->gzhead->comment[s->gzindex++];
761
if (s->gzhead->hcrc && s->pending > beg)
762
strm->adler = crc32(strm->adler, s->pending_buf + beg,
765
s->status = HCRC_STATE;
768
s->status = HCRC_STATE;
770
if (s->status == HCRC_STATE) {
771
if (s->gzhead->hcrc) {
772
if (s->pending + 2 > s->pending_buf_size)
774
if (s->pending + 2 <= s->pending_buf_size) {
775
put_byte(s, (Byte)(strm->adler & 0xff));
776
put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
777
strm->adler = crc32(0L, Z_NULL, 0);
778
s->status = BUSY_STATE;
782
s->status = BUSY_STATE;
786
/* Flush as much pending output as possible */
787
if (s->pending != 0) {
789
if (strm->avail_out == 0) {
790
/* Since avail_out is 0, deflate will be called again with
791
* more output space, but possibly with both pending and
792
* avail_in equal to zero. There won't be anything to do,
793
* but this is not an error situation so make sure we
794
* return OK instead of BUF_ERROR at next call of deflate:
800
/* Make sure there is something to do and avoid duplicate consecutive
801
* flushes. For repeated and useless calls with Z_FINISH, we keep
802
* returning Z_STREAM_END instead of Z_BUF_ERROR.
804
} else if (strm->avail_in == 0 && flush <= old_flush &&
806
ERR_RETURN(strm, Z_BUF_ERROR);
809
/* User must not provide more input after the first FINISH: */
810
if (s->status == FINISH_STATE && strm->avail_in != 0) {
811
ERR_RETURN(strm, Z_BUF_ERROR);
814
/* Start a new block or continue the current one.
816
if (strm->avail_in != 0 || s->lookahead != 0 ||
817
(flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
820
bstate = s->strategy == Z_HUFFMAN_ONLY ? deflate_huff(s, flush) :
821
(s->strategy == Z_RLE ? deflate_rle(s, flush) :
822
(*(configuration_table[s->level].func))(s, flush));
824
if (bstate == finish_started || bstate == finish_done) {
825
s->status = FINISH_STATE;
827
if (bstate == need_more || bstate == finish_started) {
828
if (strm->avail_out == 0) {
829
s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
832
/* If flush != Z_NO_FLUSH && avail_out == 0, the next call
833
* of deflate should use the same flush parameter to make sure
834
* that the flush is complete. So we don't have to output an
835
* empty block here, this will be done at next call. This also
836
* ensures that for a very small output buffer, we emit at most
840
if (bstate == block_done) {
841
if (flush == Z_PARTIAL_FLUSH) {
843
} else if (flush != Z_BLOCK) { /* FULL_FLUSH or SYNC_FLUSH */
844
_tr_stored_block(s, (char*)0, 0L, 0);
845
/* For a full flush, this empty block will be recognized
846
* as a special marker by inflate_sync().
848
if (flush == Z_FULL_FLUSH) {
849
CLEAR_HASH(s); /* forget history */
850
if (s->lookahead == 0) {
857
if (strm->avail_out == 0) {
858
s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
863
Assert(strm->avail_out > 0, "bug2");
865
if (flush != Z_FINISH) return Z_OK;
866
if (s->wrap <= 0) return Z_STREAM_END;
868
/* Write the trailer */
871
put_byte(s, (Byte)(strm->adler & 0xff));
872
put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
873
put_byte(s, (Byte)((strm->adler >> 16) & 0xff));
874
put_byte(s, (Byte)((strm->adler >> 24) & 0xff));
875
put_byte(s, (Byte)(strm->total_in & 0xff));
876
put_byte(s, (Byte)((strm->total_in >> 8) & 0xff));
877
put_byte(s, (Byte)((strm->total_in >> 16) & 0xff));
878
put_byte(s, (Byte)((strm->total_in >> 24) & 0xff));
883
putShortMSB(s, (uInt)(strm->adler >> 16));
884
putShortMSB(s, (uInt)(strm->adler & 0xffff));
887
/* If avail_out is zero, the application will call deflate again
890
if (s->wrap > 0) s->wrap = -s->wrap; /* write the trailer only once! */
891
return s->pending != 0 ? Z_OK : Z_STREAM_END;
894
/* ========================================================================= */
895
int ZEXPORT deflateEnd (strm)
900
if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
902
status = strm->state->status;
903
if (status != INIT_STATE &&
904
status != EXTRA_STATE &&
905
status != NAME_STATE &&
906
status != COMMENT_STATE &&
907
status != HCRC_STATE &&
908
status != BUSY_STATE &&
909
status != FINISH_STATE) {
910
return Z_STREAM_ERROR;
913
/* Deallocate in reverse order of allocations: */
914
TRY_FREE(strm, strm->state->pending_buf);
915
TRY_FREE(strm, strm->state->head);
916
TRY_FREE(strm, strm->state->prev);
917
TRY_FREE(strm, strm->state->window);
919
ZFREE(strm, strm->state);
920
strm->state = Z_NULL;
922
return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
925
/* =========================================================================
926
* Copy the source state to the destination state.
927
* To simplify the source, this is not supported for 16-bit MSDOS (which
928
* doesn't have enough memory anyway to duplicate compression states).
930
int ZEXPORT deflateCopy (dest, source)
935
return Z_STREAM_ERROR;
942
if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
943
return Z_STREAM_ERROR;
948
zmemcpy(dest, source, sizeof(z_stream));
950
ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
951
if (ds == Z_NULL) return Z_MEM_ERROR;
952
dest->state = (struct internal_state FAR *) ds;
953
zmemcpy(ds, ss, sizeof(deflate_state));
956
ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
957
ds->prev = (Posf *) ZALLOC(dest, ds->w_size, sizeof(Pos));
958
ds->head = (Posf *) ZALLOC(dest, ds->hash_size, sizeof(Pos));
959
overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
960
ds->pending_buf = (uchf *) overlay;
962
if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
963
ds->pending_buf == Z_NULL) {
967
/* following zmemcpy do not work for 16-bit MSDOS */
968
zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
969
zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
970
zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));
971
zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
973
ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
974
ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
975
ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
977
ds->l_desc.dyn_tree = ds->dyn_ltree;
978
ds->d_desc.dyn_tree = ds->dyn_dtree;
979
ds->bl_desc.dyn_tree = ds->bl_tree;
982
#endif /* MAXSEG_64K */
985
/* ===========================================================================
986
* Read a new buffer from the current input stream, update the adler32
987
* and total number of bytes read. All deflate() input goes through
988
* this function so some applications may wish to modify it to avoid
989
* allocating a large strm->next_in buffer and copying from it.
990
* (See also flush_pending()).
992
local int read_buf(strm, buf, size)
997
unsigned len = strm->avail_in;
999
if (len > size) len = size;
1000
if (len == 0) return 0;
1002
strm->avail_in -= len;
1004
if (strm->state->wrap == 1) {
1005
strm->adler = adler32(strm->adler, strm->next_in, len);
1008
else if (strm->state->wrap == 2) {
1009
strm->adler = crc32(strm->adler, strm->next_in, len);
1012
zmemcpy(buf, strm->next_in, len);
1013
strm->next_in += len;
1014
strm->total_in += len;
1019
/* ===========================================================================
1020
* Initialize the "longest match" routines for a new zlib stream
1022
local void lm_init (s)
1025
s->window_size = (ulg)2L*s->w_size;
1029
/* Set the default configuration parameters:
1031
s->max_lazy_match = configuration_table[s->level].max_lazy;
1032
s->good_match = configuration_table[s->level].good_length;
1033
s->nice_match = configuration_table[s->level].nice_length;
1034
s->max_chain_length = configuration_table[s->level].max_chain;
1037
s->block_start = 0L;
1039
s->match_length = s->prev_length = MIN_MATCH-1;
1040
s->match_available = 0;
1044
match_init(); /* initialize the asm code */
1050
/* ===========================================================================
1051
* Set match_start to the longest match starting at the given string and
1052
* return its length. Matches shorter or equal to prev_length are discarded,
1053
* in which case the result is equal to prev_length and match_start is
1055
* IN assertions: cur_match is the head of the hash chain for the current
1056
* string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
1057
* OUT assertion: the match length is not greater than s->lookahead.
1060
/* For 80x86 and 680x0, an optimized version will be provided in match.asm or
1061
* match.S. The code will be functionally equivalent.
1063
local uInt longest_match(s, cur_match)
1065
IPos cur_match; /* current match */
1067
unsigned chain_length = s->max_chain_length;/* max hash chain length */
1068
register Bytef *scan = s->window + s->strstart; /* current string */
1069
register Bytef *match; /* matched string */
1070
register int len; /* length of current match */
1071
int best_len = s->prev_length; /* best match length so far */
1072
int nice_match = s->nice_match; /* stop if match long enough */
1073
IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
1074
s->strstart - (IPos)MAX_DIST(s) : NIL;
1075
/* Stop when cur_match becomes <= limit. To simplify the code,
1076
* we prevent matches with the string of window index 0.
1078
Posf *prev = s->prev;
1079
uInt wmask = s->w_mask;
1082
/* Compare two bytes at a time. Note: this is not always beneficial.
1083
* Try with and without -DUNALIGNED_OK to check.
1085
register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
1086
register ush scan_start = *(ushf*)scan;
1087
register ush scan_end = *(ushf*)(scan+best_len-1);
1089
register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1090
register Byte scan_end1 = scan[best_len-1];
1091
register Byte scan_end = scan[best_len];
1094
/* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1095
* It is easy to get rid of this optimization if necessary.
1097
Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1099
/* Do not waste too much time if we already have a good match: */
1100
if (s->prev_length >= s->good_match) {
1103
/* Do not look for matches beyond the end of the input. This is necessary
1104
* to make deflate deterministic.
1106
if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
1108
Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1111
Assert(cur_match < s->strstart, "no future");
1112
match = s->window + cur_match;
1114
/* Skip to next match if the match length cannot increase
1115
* or if the match length is less than 2. Note that the checks below
1116
* for insufficient lookahead only occur occasionally for performance
1117
* reasons. Therefore uninitialized memory will be accessed, and
1118
* conditional jumps will be made that depend on those values.
1119
* However the length of the match is limited to the lookahead, so
1120
* the output of deflate is not affected by the uninitialized values.
1122
#if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
1123
/* This code assumes sizeof(unsigned short) == 2. Do not use
1124
* UNALIGNED_OK if your compiler uses a different size.
1126
if (*(ushf*)(match+best_len-1) != scan_end ||
1127
*(ushf*)match != scan_start) continue;
1129
/* It is not necessary to compare scan[2] and match[2] since they are
1130
* always equal when the other bytes match, given that the hash keys
1131
* are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
1132
* strstart+3, +5, ... up to strstart+257. We check for insufficient
1133
* lookahead only every 4th comparison; the 128th check will be made
1134
* at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
1135
* necessary to put more guard bytes at the end of the window, or
1136
* to check more often for insufficient lookahead.
1138
Assert(scan[2] == match[2], "scan[2]?");
1141
} while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1142
*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1143
*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1144
*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
1146
/* The funny "do {}" generates better code on most compilers */
1148
/* Here, scan <= window+strstart+257 */
1149
Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1150
if (*scan == *match) scan++;
1152
len = (MAX_MATCH - 1) - (int)(strend-scan);
1153
scan = strend - (MAX_MATCH-1);
1155
#else /* UNALIGNED_OK */
1157
if (match[best_len] != scan_end ||
1158
match[best_len-1] != scan_end1 ||
1160
*++match != scan[1]) continue;
1162
/* The check at best_len-1 can be removed because it will be made
1163
* again later. (This heuristic is not always a win.)
1164
* It is not necessary to compare scan[2] and match[2] since they
1165
* are always equal when the other bytes match, given that
1166
* the hash keys are equal and that HASH_BITS >= 8.
1169
Assert(*scan == *match, "match[2]?");
1171
/* We check for insufficient lookahead only every 8th comparison;
1172
* the 256th check will be made at strstart+258.
1175
} while (*++scan == *++match && *++scan == *++match &&
1176
*++scan == *++match && *++scan == *++match &&
1177
*++scan == *++match && *++scan == *++match &&
1178
*++scan == *++match && *++scan == *++match &&
1181
Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1183
len = MAX_MATCH - (int)(strend - scan);
1184
scan = strend - MAX_MATCH;
1186
#endif /* UNALIGNED_OK */
1188
if (len > best_len) {
1189
s->match_start = cur_match;
1191
if (len >= nice_match) break;
1193
scan_end = *(ushf*)(scan+best_len-1);
1195
scan_end1 = scan[best_len-1];
1196
scan_end = scan[best_len];
1199
} while ((cur_match = prev[cur_match & wmask]) > limit
1200
&& --chain_length != 0);
1202
if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
1203
return s->lookahead;
1209
/* ---------------------------------------------------------------------------
1210
* Optimized version for FASTEST only
1212
local uInt longest_match(s, cur_match)
1214
IPos cur_match; /* current match */
1216
register Bytef *scan = s->window + s->strstart; /* current string */
1217
register Bytef *match; /* matched string */
1218
register int len; /* length of current match */
1219
register Bytef *strend = s->window + s->strstart + MAX_MATCH;
1221
/* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
1222
* It is easy to get rid of this optimization if necessary.
1224
Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
1226
Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
1228
Assert(cur_match < s->strstart, "no future");
1230
match = s->window + cur_match;
1232
/* Return failure if the match length is less than 2:
1234
if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
1236
/* The check at best_len-1 can be removed because it will be made
1237
* again later. (This heuristic is not always a win.)
1238
* It is not necessary to compare scan[2] and match[2] since they
1239
* are always equal when the other bytes match, given that
1240
* the hash keys are equal and that HASH_BITS >= 8.
1242
scan += 2, match += 2;
1243
Assert(*scan == *match, "match[2]?");
1245
/* We check for insufficient lookahead only every 8th comparison;
1246
* the 256th check will be made at strstart+258.
1249
} while (*++scan == *++match && *++scan == *++match &&
1250
*++scan == *++match && *++scan == *++match &&
1251
*++scan == *++match && *++scan == *++match &&
1252
*++scan == *++match && *++scan == *++match &&
1255
Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
1257
len = MAX_MATCH - (int)(strend - scan);
1259
if (len < MIN_MATCH) return MIN_MATCH - 1;
1261
s->match_start = cur_match;
1262
return (uInt)len <= s->lookahead ? (uInt)len : s->lookahead;
1265
#endif /* FASTEST */
1268
/* ===========================================================================
1269
* Check that the match at match_start is indeed a match.
1271
local void check_match(s, start, match, length)
1276
/* check that the match is indeed a match */
1277
if (zmemcmp(s->window + match,
1278
s->window + start, length) != EQUAL) {
1279
fprintf(stderr, " start %u, match %u, length %d\n",
1280
start, match, length);
1282
fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
1283
} while (--length != 0);
1284
z_error("invalid match");
1286
if (z_verbose > 1) {
1287
fprintf(stderr,"\\[%d,%d]", start-match, length);
1288
do { putc(s->window[start++], stderr); } while (--length != 0);
1292
# define check_match(s, start, match, length)
1295
/* ===========================================================================
1296
* Fill the window when the lookahead becomes insufficient.
1297
* Updates strstart and lookahead.
1299
* IN assertion: lookahead < MIN_LOOKAHEAD
1300
* OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
1301
* At least one byte has been read, or avail_in == 0; reads are
1302
* performed for at least two bytes (required for the zip translate_eol
1303
* option -- not supported here).
1305
local void fill_window(s)
1308
register unsigned n, m;
1310
unsigned more; /* Amount of free space at the end of the window. */
1311
uInt wsize = s->w_size;
1314
more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
1316
/* Deal with !@#$% 64K limit: */
1317
if (sizeof(int) <= 2) {
1318
if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
1321
} else if (more == (unsigned)(-1)) {
1322
/* Very unlikely, but possible on 16 bit machine if
1323
* strstart == 0 && lookahead == 1 (input done a byte at time)
1329
/* If the window is almost full and there is insufficient lookahead,
1330
* move the upper half to the lower one to make room in the upper half.
1332
if (s->strstart >= wsize+MAX_DIST(s)) {
1334
zmemcpy(s->window, s->window+wsize, (unsigned)wsize);
1335
s->match_start -= wsize;
1336
s->strstart -= wsize; /* we now have strstart >= MAX_DIST */
1337
s->block_start -= (long) wsize;
1339
/* Slide the hash table (could be avoided with 32 bit values
1340
at the expense of memory usage). We slide even when level == 0
1341
to keep the hash table consistent if we switch back to level > 0
1342
later. (Using level 0 permanently is not an optimal usage of
1343
zlib, so we don't care about this pathological case.)
1349
*p = (Pos)(m >= wsize ? m-wsize : NIL);
1357
*p = (Pos)(m >= wsize ? m-wsize : NIL);
1358
/* If n is not on any hash chain, prev[n] is garbage but
1359
* its value will never be used.
1365
if (s->strm->avail_in == 0) return;
1367
/* If there was no sliding:
1368
* strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
1369
* more == window_size - lookahead - strstart
1370
* => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
1371
* => more >= window_size - 2*WSIZE + 2
1372
* In the BIG_MEM or MMAP case (not yet supported),
1373
* window_size == input_size + MIN_LOOKAHEAD &&
1374
* strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
1375
* Otherwise, window_size == 2*WSIZE so more >= 2.
1376
* If there was sliding, more >= WSIZE. So in all cases, more >= 2.
1378
Assert(more >= 2, "more < 2");
1380
n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
1383
/* Initialize the hash value now that we have some input: */
1384
if (s->lookahead >= MIN_MATCH) {
1385
s->ins_h = s->window[s->strstart];
1386
UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1388
Call UPDATE_HASH() MIN_MATCH-3 more times
1391
/* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
1392
* but this is not important since only literal bytes will be emitted.
1395
} while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
1397
/* If the WIN_INIT bytes after the end of the current data have never been
1398
* written, then zero those bytes in order to avoid memory check reports of
1399
* the use of uninitialized (or uninitialised as Julian writes) bytes by
1400
* the longest match routines. Update the high water mark for the next
1401
* time through here. WIN_INIT is set to MAX_MATCH since the longest match
1402
* routines allow scanning to strstart + MAX_MATCH, ignoring lookahead.
1404
if (s->high_water < s->window_size) {
1405
ulg curr = s->strstart + (ulg)(s->lookahead);
1408
if (s->high_water < curr) {
1409
/* Previous high water mark below current data -- zero WIN_INIT
1410
* bytes or up to end of window, whichever is less.
1412
init = s->window_size - curr;
1413
if (init > WIN_INIT)
1415
zmemzero(s->window + curr, (unsigned)init);
1416
s->high_water = curr + init;
1418
else if (s->high_water < (ulg)curr + WIN_INIT) {
1419
/* High water mark at or above current data, but below current data
1420
* plus WIN_INIT -- zero out to current data plus WIN_INIT, or up
1421
* to end of window, whichever is less.
1423
init = (ulg)curr + WIN_INIT - s->high_water;
1424
if (init > s->window_size - s->high_water)
1425
init = s->window_size - s->high_water;
1426
zmemzero(s->window + s->high_water, (unsigned)init);
1427
s->high_water += init;
1432
/* ===========================================================================
1433
* Flush the current block, with given end-of-file flag.
1434
* IN assertion: strstart is set to the end of the current match.
1436
#define FLUSH_BLOCK_ONLY(s, last) { \
1437
_tr_flush_block(s, (s->block_start >= 0L ? \
1438
(charf *)&s->window[(unsigned)s->block_start] : \
1440
(ulg)((long)s->strstart - s->block_start), \
1442
s->block_start = s->strstart; \
1443
flush_pending(s->strm); \
1444
Tracev((stderr,"[FLUSH]")); \
1447
/* Same but force premature exit if necessary. */
1448
#define FLUSH_BLOCK(s, last) { \
1449
FLUSH_BLOCK_ONLY(s, last); \
1450
if (s->strm->avail_out == 0) return (last) ? finish_started : need_more; \
1453
/* ===========================================================================
1454
* Copy without compression as much as possible from the input stream, return
1455
* the current block state.
1456
* This function does not insert new strings in the dictionary since
1457
* uncompressible data is probably not useful. This function is used
1458
* only for the level=0 compression option.
1459
* NOTE: this function should be optimized to avoid extra copying from
1460
* window to pending_buf.
1462
local block_state deflate_stored(s, flush)
1466
/* Stored blocks are limited to 0xffff bytes, pending_buf is limited
1467
* to pending_buf_size, and each stored block has a 5 byte header:
1469
ulg max_block_size = 0xffff;
1472
if (max_block_size > s->pending_buf_size - 5) {
1473
max_block_size = s->pending_buf_size - 5;
1476
/* Copy as much as possible from input to output: */
1478
/* Fill the window as much as possible: */
1479
if (s->lookahead <= 1) {
1481
Assert(s->strstart < s->w_size+MAX_DIST(s) ||
1482
s->block_start >= (long)s->w_size, "slide too late");
1485
if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
1487
if (s->lookahead == 0) break; /* flush the current block */
1489
Assert(s->block_start >= 0L, "block gone");
1491
s->strstart += s->lookahead;
1494
/* Emit a stored block if pending_buf will be full: */
1495
max_start = s->block_start + max_block_size;
1496
if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
1497
/* strstart == 0 is possible when wraparound on 16-bit machine */
1498
s->lookahead = (uInt)(s->strstart - max_start);
1499
s->strstart = (uInt)max_start;
1502
/* Flush if we may have to slide, otherwise block_start may become
1503
* negative and the data will be gone:
1505
if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
1509
FLUSH_BLOCK(s, flush == Z_FINISH);
1510
return flush == Z_FINISH ? finish_done : block_done;
1513
/* ===========================================================================
1514
* Compress as much as possible from the input stream, return the current
1516
* This function does not perform lazy evaluation of matches and inserts
1517
* new strings in the dictionary only for unmatched strings or for short
1518
* matches. It is used only for the fast compression options.
1520
local block_state deflate_fast(s, flush)
1524
IPos hash_head; /* head of the hash chain */
1525
int bflush; /* set if current block must be flushed */
1528
/* Make sure that we always have enough lookahead, except
1529
* at the end of the input file. We need MAX_MATCH bytes
1530
* for the next match, plus MIN_MATCH bytes to insert the
1531
* string following the next match.
1533
if (s->lookahead < MIN_LOOKAHEAD) {
1535
if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1538
if (s->lookahead == 0) break; /* flush the current block */
1541
/* Insert the string window[strstart .. strstart+2] in the
1542
* dictionary, and set hash_head to the head of the hash chain:
1545
if (s->lookahead >= MIN_MATCH) {
1546
INSERT_STRING(s, s->strstart, hash_head);
1549
/* Find the longest match, discarding those <= prev_length.
1550
* At this point we have always match_length < MIN_MATCH
1552
if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
1553
/* To simplify the code, we prevent matches with the string
1554
* of window index 0 (in particular we have to avoid a match
1555
* of the string with itself at the start of the input file).
1557
s->match_length = longest_match (s, hash_head);
1558
/* longest_match() sets match_start */
1560
if (s->match_length >= MIN_MATCH) {
1561
check_match(s, s->strstart, s->match_start, s->match_length);
1563
_tr_tally_dist(s, s->strstart - s->match_start,
1564
s->match_length - MIN_MATCH, bflush);
1566
s->lookahead -= s->match_length;
1568
/* Insert new strings in the hash table only if the match length
1569
* is not too large. This saves time but degrades compression.
1572
if (s->match_length <= s->max_insert_length &&
1573
s->lookahead >= MIN_MATCH) {
1574
s->match_length--; /* string at strstart already in table */
1577
INSERT_STRING(s, s->strstart, hash_head);
1578
/* strstart never exceeds WSIZE-MAX_MATCH, so there are
1579
* always MIN_MATCH bytes ahead.
1581
} while (--s->match_length != 0);
1586
s->strstart += s->match_length;
1587
s->match_length = 0;
1588
s->ins_h = s->window[s->strstart];
1589
UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
1591
Call UPDATE_HASH() MIN_MATCH-3 more times
1593
/* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
1594
* matter since it will be recomputed at next deflate call.
1598
/* No match, output a literal byte */
1599
Tracevv((stderr,"%c", s->window[s->strstart]));
1600
_tr_tally_lit (s, s->window[s->strstart], bflush);
1604
if (bflush) FLUSH_BLOCK(s, 0);
1606
FLUSH_BLOCK(s, flush == Z_FINISH);
1607
return flush == Z_FINISH ? finish_done : block_done;
1611
/* ===========================================================================
1612
* Same as above, but achieves better compression. We use a lazy
1613
* evaluation for matches: a match is finally adopted only if there is
1614
* no better match at the next window position.
1616
local block_state deflate_slow(s, flush)
1620
IPos hash_head; /* head of hash chain */
1621
int bflush; /* set if current block must be flushed */
1623
/* Process the input block. */
1625
/* Make sure that we always have enough lookahead, except
1626
* at the end of the input file. We need MAX_MATCH bytes
1627
* for the next match, plus MIN_MATCH bytes to insert the
1628
* string following the next match.
1630
if (s->lookahead < MIN_LOOKAHEAD) {
1632
if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
1635
if (s->lookahead == 0) break; /* flush the current block */
1638
/* Insert the string window[strstart .. strstart+2] in the
1639
* dictionary, and set hash_head to the head of the hash chain:
1642
if (s->lookahead >= MIN_MATCH) {
1643
INSERT_STRING(s, s->strstart, hash_head);
1646
/* Find the longest match, discarding those <= prev_length.
1648
s->prev_length = s->match_length, s->prev_match = s->match_start;
1649
s->match_length = MIN_MATCH-1;
1651
if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
1652
s->strstart - hash_head <= MAX_DIST(s)) {
1653
/* To simplify the code, we prevent matches with the string
1654
* of window index 0 (in particular we have to avoid a match
1655
* of the string with itself at the start of the input file).
1657
s->match_length = longest_match (s, hash_head);
1658
/* longest_match() sets match_start */
1660
if (s->match_length <= 5 && (s->strategy == Z_FILTERED
1661
#if TOO_FAR <= 32767
1662
|| (s->match_length == MIN_MATCH &&
1663
s->strstart - s->match_start > TOO_FAR)
1667
/* If prev_match is also MIN_MATCH, match_start is garbage
1668
* but we will ignore the current match anyway.
1670
s->match_length = MIN_MATCH-1;
1673
/* If there was a match at the previous step and the current
1674
* match is not better, output the previous match:
1676
if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
1677
uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
1678
/* Do not insert strings in hash table beyond this. */
1680
check_match(s, s->strstart-1, s->prev_match, s->prev_length);
1682
_tr_tally_dist(s, s->strstart -1 - s->prev_match,
1683
s->prev_length - MIN_MATCH, bflush);
1685
/* Insert in hash table all strings up to the end of the match.
1686
* strstart-1 and strstart are already inserted. If there is not
1687
* enough lookahead, the last two strings are not inserted in
1690
s->lookahead -= s->prev_length-1;
1691
s->prev_length -= 2;
1693
if (++s->strstart <= max_insert) {
1694
INSERT_STRING(s, s->strstart, hash_head);
1696
} while (--s->prev_length != 0);
1697
s->match_available = 0;
1698
s->match_length = MIN_MATCH-1;
1701
if (bflush) FLUSH_BLOCK(s, 0);
1703
} else if (s->match_available) {
1704
/* If there was no match at the previous position, output a
1705
* single literal. If there was a match but the current match
1706
* is longer, truncate the previous match to a single literal.
1708
Tracevv((stderr,"%c", s->window[s->strstart-1]));
1709
_tr_tally_lit(s, s->window[s->strstart-1], bflush);
1711
FLUSH_BLOCK_ONLY(s, 0);
1715
if (s->strm->avail_out == 0) return need_more;
1717
/* There is no previous match to compare with, wait for
1718
* the next step to decide.
1720
s->match_available = 1;
1725
Assert (flush != Z_NO_FLUSH, "no flush?");
1726
if (s->match_available) {
1727
Tracevv((stderr,"%c", s->window[s->strstart-1]));
1728
_tr_tally_lit(s, s->window[s->strstart-1], bflush);
1729
s->match_available = 0;
1731
FLUSH_BLOCK(s, flush == Z_FINISH);
1732
return flush == Z_FINISH ? finish_done : block_done;
1734
#endif /* FASTEST */
1736
/* ===========================================================================
1737
* For Z_RLE, simply look for runs of bytes, generate matches only of distance
1738
* one. Do not maintain a hash table. (It will be regenerated if this run of
1739
* deflate switches away from Z_RLE.)
1741
local block_state deflate_rle(s, flush)
1745
int bflush; /* set if current block must be flushed */
1746
uInt prev; /* byte at distance one to match */
1747
Bytef *scan, *strend; /* scan goes up to strend for length of run */
1750
/* Make sure that we always have enough lookahead, except
1751
* at the end of the input file. We need MAX_MATCH bytes
1752
* for the longest encodable run.
1754
if (s->lookahead < MAX_MATCH) {
1756
if (s->lookahead < MAX_MATCH && flush == Z_NO_FLUSH) {
1759
if (s->lookahead == 0) break; /* flush the current block */
1762
/* See how many times the previous byte repeats */
1763
s->match_length = 0;
1764
if (s->lookahead >= MIN_MATCH && s->strstart > 0) {
1765
scan = s->window + s->strstart - 1;
1767
if (prev == *++scan && prev == *++scan && prev == *++scan) {
1768
strend = s->window + s->strstart + MAX_MATCH;
1770
} while (prev == *++scan && prev == *++scan &&
1771
prev == *++scan && prev == *++scan &&
1772
prev == *++scan && prev == *++scan &&
1773
prev == *++scan && prev == *++scan &&
1775
s->match_length = MAX_MATCH - (int)(strend - scan);
1776
if (s->match_length > s->lookahead)
1777
s->match_length = s->lookahead;
1781
/* Emit match if have run of MIN_MATCH or longer, else emit literal */
1782
if (s->match_length >= MIN_MATCH) {
1783
check_match(s, s->strstart, s->strstart - 1, s->match_length);
1785
_tr_tally_dist(s, 1, s->match_length - MIN_MATCH, bflush);
1787
s->lookahead -= s->match_length;
1788
s->strstart += s->match_length;
1789
s->match_length = 0;
1791
/* No match, output a literal byte */
1792
Tracevv((stderr,"%c", s->window[s->strstart]));
1793
_tr_tally_lit (s, s->window[s->strstart], bflush);
1797
if (bflush) FLUSH_BLOCK(s, 0);
1799
FLUSH_BLOCK(s, flush == Z_FINISH);
1800
return flush == Z_FINISH ? finish_done : block_done;
1803
/* ===========================================================================
1804
* For Z_HUFFMAN_ONLY, do not look for matches. Do not maintain a hash table.
1805
* (It will be regenerated if this run of deflate switches away from Huffman.)
1807
local block_state deflate_huff(s, flush)
1811
int bflush; /* set if current block must be flushed */
1814
/* Make sure that we have a literal to write. */
1815
if (s->lookahead == 0) {
1817
if (s->lookahead == 0) {
1818
if (flush == Z_NO_FLUSH)
1820
break; /* flush the current block */
1824
/* Output a literal byte */
1825
s->match_length = 0;
1826
Tracevv((stderr,"%c", s->window[s->strstart]));
1827
_tr_tally_lit (s, s->window[s->strstart], bflush);
1830
if (bflush) FLUSH_BLOCK(s, 0);
1832
FLUSH_BLOCK(s, flush == Z_FINISH);
1833
return flush == Z_FINISH ? finish_done : block_done;
added
removed
nss/lib/zlib/deflate.c
