1da177e4c3
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
1269 lines
44 KiB
C
1269 lines
44 KiB
C
/* +++ deflate.c */
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/* deflate.c -- compress data using the deflation algorithm
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* Copyright (C) 1995-1996 Jean-loup Gailly.
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* For conditions of distribution and use, see copyright notice in zlib.h
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*/
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/*
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* ALGORITHM
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*
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* The "deflation" process depends on being able to identify portions
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* of the input text which are identical to earlier input (within a
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* sliding window trailing behind the input currently being processed).
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*
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* The most straightforward technique turns out to be the fastest for
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* most input files: try all possible matches and select the longest.
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* The key feature of this algorithm is that insertions into the string
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* 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
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* 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
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* (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
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* files if the parameter max_chain_length (described below) is too large.
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*
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* ACKNOWLEDGEMENTS
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*
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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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*
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* REFERENCES
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*
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* Deutsch, L.P.,"DEFLATE Compressed Data Format Specification".
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* Available in ftp://ds.internic.net/rfc/rfc1951.txt
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*
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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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*
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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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*
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*/
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#include <linux/module.h>
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#include <linux/zutil.h>
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#include "defutil.h"
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/* ===========================================================================
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* Function prototypes.
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*/
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typedef enum {
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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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} block_state;
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typedef block_state (*compress_func) (deflate_state *s, int flush);
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/* Compression function. Returns the block state after the call. */
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static void fill_window (deflate_state *s);
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static block_state deflate_stored (deflate_state *s, int flush);
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static block_state deflate_fast (deflate_state *s, int flush);
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static block_state deflate_slow (deflate_state *s, int flush);
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static void lm_init (deflate_state *s);
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static void putShortMSB (deflate_state *s, uInt b);
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static void flush_pending (z_streamp strm);
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static int read_buf (z_streamp strm, Byte *buf, unsigned size);
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static uInt longest_match (deflate_state *s, IPos cur_match);
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#ifdef DEBUG_ZLIB
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static void check_match (deflate_state *s, IPos start, IPos match,
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int length);
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#endif
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/* ===========================================================================
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* Local data
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*/
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#define NIL 0
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/* Tail of hash chains */
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#ifndef TOO_FAR
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# define TOO_FAR 4096
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#endif
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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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*/
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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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*/
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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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ush max_chain;
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compress_func func;
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} config;
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static 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}, /* maximum 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}}; /* maximum 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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* meaning.
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*/
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#define EQUAL 0
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/* result of memcmp for equal strings */
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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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*/
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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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* 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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*/
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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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s->prev[(str) & s->w_mask] = match_head = 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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*/
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#define CLEAR_HASH(s) \
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s->head[s->hash_size-1] = NIL; \
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memset((char *)s->head, 0, (unsigned)(s->hash_size-1)*sizeof(*s->head));
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/* ========================================================================= */
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int zlib_deflateInit_(
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z_streamp strm,
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int level,
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const char *version,
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int stream_size
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)
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{
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return zlib_deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS,
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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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/* ========================================================================= */
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int zlib_deflateInit2_(
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z_streamp strm,
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int level,
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int method,
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int windowBits,
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int memLevel,
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int strategy,
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const char *version,
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int stream_size
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)
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{
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deflate_state *s;
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int noheader = 0;
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static char* my_version = ZLIB_VERSION;
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deflate_workspace *mem;
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ush *overlay;
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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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*/
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if (version == 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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}
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if (strm == NULL) return Z_STREAM_ERROR;
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strm->msg = NULL;
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if (level == Z_DEFAULT_COMPRESSION) level = 6;
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mem = (deflate_workspace *) strm->workspace;
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if (windowBits < 0) { /* undocumented feature: suppress zlib header */
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noheader = 1;
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windowBits = -windowBits;
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}
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if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
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windowBits < 9 || windowBits > 15 || level < 0 || level > 9 ||
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strategy < 0 || strategy > Z_HUFFMAN_ONLY) {
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return Z_STREAM_ERROR;
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}
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s = (deflate_state *) &(mem->deflate_memory);
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strm->state = (struct internal_state *)s;
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s->strm = strm;
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s->noheader = noheader;
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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 = (Byte *) mem->window_memory;
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s->prev = (Pos *) mem->prev_memory;
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s->head = (Pos *) mem->head_memory;
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s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
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overlay = (ush *) mem->overlay_memory;
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s->pending_buf = (uch *) overlay;
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s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
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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->level = level;
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s->strategy = strategy;
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s->method = (Byte)method;
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return zlib_deflateReset(strm);
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}
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/* ========================================================================= */
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int zlib_deflateSetDictionary(
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z_streamp strm,
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const Byte *dictionary,
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uInt dictLength
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)
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{
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deflate_state *s;
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uInt length = dictLength;
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uInt n;
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IPos hash_head = 0;
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if (strm == NULL || strm->state == NULL || dictionary == NULL)
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return Z_STREAM_ERROR;
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s = (deflate_state *) strm->state;
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if (s->status != INIT_STATE) return Z_STREAM_ERROR;
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strm->adler = zlib_adler32(strm->adler, dictionary, dictLength);
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if (length < MIN_MATCH) return Z_OK;
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if (length > MAX_DIST(s)) {
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length = MAX_DIST(s);
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#ifndef USE_DICT_HEAD
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dictionary += dictLength - length; /* use the tail of the dictionary */
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#endif
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}
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memcpy((char *)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).
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* s->lookahead stays null, so s->ins_h will be recomputed at the next
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* call of fill_window.
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*/
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s->ins_h = s->window[0];
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UPDATE_HASH(s, s->ins_h, s->window[1]);
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for (n = 0; n <= length - MIN_MATCH; n++) {
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INSERT_STRING(s, n, hash_head);
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}
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if (hash_head) hash_head = 0; /* to make compiler happy */
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return Z_OK;
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}
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/* ========================================================================= */
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int zlib_deflateReset(
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z_streamp strm
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)
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{
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deflate_state *s;
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if (strm == NULL || strm->state == NULL)
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return Z_STREAM_ERROR;
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strm->total_in = strm->total_out = 0;
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strm->msg = NULL;
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strm->data_type = Z_UNKNOWN;
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s = (deflate_state *)strm->state;
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s->pending = 0;
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s->pending_out = s->pending_buf;
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if (s->noheader < 0) {
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s->noheader = 0; /* was set to -1 by deflate(..., Z_FINISH); */
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}
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s->status = s->noheader ? BUSY_STATE : INIT_STATE;
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strm->adler = 1;
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s->last_flush = Z_NO_FLUSH;
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zlib_tr_init(s);
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lm_init(s);
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return Z_OK;
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}
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/* ========================================================================= */
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int zlib_deflateParams(
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z_streamp strm,
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int level,
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int strategy
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)
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{
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deflate_state *s;
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compress_func func;
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int err = Z_OK;
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if (strm == NULL || strm->state == NULL) return Z_STREAM_ERROR;
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s = (deflate_state *) strm->state;
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if (level == Z_DEFAULT_COMPRESSION) {
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level = 6;
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}
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if (level < 0 || level > 9 || strategy < 0 || strategy > Z_HUFFMAN_ONLY) {
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return Z_STREAM_ERROR;
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}
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func = configuration_table[s->level].func;
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if (func != configuration_table[level].func && strm->total_in != 0) {
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/* Flush the last buffer: */
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err = zlib_deflate(strm, Z_PARTIAL_FLUSH);
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}
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if (s->level != level) {
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s->level = level;
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s->max_lazy_match = configuration_table[level].max_lazy;
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s->good_match = configuration_table[level].good_length;
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s->nice_match = configuration_table[level].nice_length;
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s->max_chain_length = configuration_table[level].max_chain;
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}
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s->strategy = strategy;
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return err;
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}
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/* =========================================================================
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* Put a short in the pending buffer. The 16-bit value is put in MSB order.
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* IN assertion: the stream state is correct and there is enough room in
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* pending_buf.
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*/
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static void putShortMSB(
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deflate_state *s,
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uInt b
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)
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{
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put_byte(s, (Byte)(b >> 8));
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put_byte(s, (Byte)(b & 0xff));
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}
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/* =========================================================================
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* Flush as much pending output as possible. All deflate() output goes
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* through this function so some applications may wish to modify it
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* to avoid allocating a large strm->next_out buffer and copying into it.
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* (See also read_buf()).
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*/
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static void flush_pending(
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z_streamp strm
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)
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{
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deflate_state *s = (deflate_state *) strm->state;
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unsigned len = s->pending;
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if (len > strm->avail_out) len = strm->avail_out;
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if (len == 0) return;
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if (strm->next_out != NULL) {
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memcpy(strm->next_out, s->pending_out, len);
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strm->next_out += len;
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}
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s->pending_out += len;
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strm->total_out += len;
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strm->avail_out -= len;
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s->pending -= len;
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if (s->pending == 0) {
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s->pending_out = s->pending_buf;
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}
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}
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/* ========================================================================= */
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int zlib_deflate(
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z_streamp strm,
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int flush
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)
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{
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int old_flush; /* value of flush param for previous deflate call */
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deflate_state *s;
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if (strm == NULL || strm->state == NULL ||
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flush > Z_FINISH || flush < 0) {
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return Z_STREAM_ERROR;
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}
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s = (deflate_state *) strm->state;
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if ((strm->next_in == NULL && strm->avail_in != 0) ||
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(s->status == FINISH_STATE && flush != Z_FINISH)) {
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return Z_STREAM_ERROR;
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}
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if (strm->avail_out == 0) return Z_BUF_ERROR;
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s->strm = strm; /* just in case */
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old_flush = s->last_flush;
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s->last_flush = flush;
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/* Write the zlib header */
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if (s->status == INIT_STATE) {
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uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
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uInt level_flags = (s->level-1) >> 1;
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if (level_flags > 3) level_flags = 3;
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header |= (level_flags << 6);
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if (s->strstart != 0) header |= PRESET_DICT;
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header += 31 - (header % 31);
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s->status = BUSY_STATE;
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putShortMSB(s, header);
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/* Save the adler32 of the preset dictionary: */
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if (s->strstart != 0) {
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putShortMSB(s, (uInt)(strm->adler >> 16));
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putShortMSB(s, (uInt)(strm->adler & 0xffff));
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}
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strm->adler = 1L;
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}
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/* Flush as much pending output as possible */
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if (s->pending != 0) {
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flush_pending(strm);
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if (strm->avail_out == 0) {
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/* Since avail_out is 0, deflate will be called again with
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* more output space, but possibly with both pending and
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* avail_in equal to zero. There won't be anything to do,
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* but this is not an error situation so make sure we
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* return OK instead of BUF_ERROR at next call of deflate:
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*/
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s->last_flush = -1;
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return Z_OK;
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}
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/* Make sure there is something to do and avoid duplicate consecutive
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* flushes. For repeated and useless calls with Z_FINISH, we keep
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* returning Z_STREAM_END instead of Z_BUFF_ERROR.
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*/
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} else if (strm->avail_in == 0 && flush <= old_flush &&
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flush != Z_FINISH) {
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return Z_BUF_ERROR;
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}
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/* User must not provide more input after the first FINISH: */
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if (s->status == FINISH_STATE && strm->avail_in != 0) {
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return Z_BUF_ERROR;
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}
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/* Start a new block or continue the current one.
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*/
|
|
if (strm->avail_in != 0 || s->lookahead != 0 ||
|
|
(flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
|
|
block_state bstate;
|
|
|
|
bstate = (*(configuration_table[s->level].func))(s, flush);
|
|
|
|
if (bstate == finish_started || bstate == finish_done) {
|
|
s->status = FINISH_STATE;
|
|
}
|
|
if (bstate == need_more || bstate == finish_started) {
|
|
if (strm->avail_out == 0) {
|
|
s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
|
|
}
|
|
return Z_OK;
|
|
/* If flush != Z_NO_FLUSH && avail_out == 0, the next call
|
|
* of deflate should use the same flush parameter to make sure
|
|
* that the flush is complete. So we don't have to output an
|
|
* empty block here, this will be done at next call. This also
|
|
* ensures that for a very small output buffer, we emit at most
|
|
* one empty block.
|
|
*/
|
|
}
|
|
if (bstate == block_done) {
|
|
if (flush == Z_PARTIAL_FLUSH) {
|
|
zlib_tr_align(s);
|
|
} else if (flush == Z_PACKET_FLUSH) {
|
|
/* Output just the 3-bit `stored' block type value,
|
|
but not a zero length. */
|
|
zlib_tr_stored_type_only(s);
|
|
} else { /* FULL_FLUSH or SYNC_FLUSH */
|
|
zlib_tr_stored_block(s, (char*)0, 0L, 0);
|
|
/* For a full flush, this empty block will be recognized
|
|
* as a special marker by inflate_sync().
|
|
*/
|
|
if (flush == Z_FULL_FLUSH) {
|
|
CLEAR_HASH(s); /* forget history */
|
|
}
|
|
}
|
|
flush_pending(strm);
|
|
if (strm->avail_out == 0) {
|
|
s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
|
|
return Z_OK;
|
|
}
|
|
}
|
|
}
|
|
Assert(strm->avail_out > 0, "bug2");
|
|
|
|
if (flush != Z_FINISH) return Z_OK;
|
|
if (s->noheader) return Z_STREAM_END;
|
|
|
|
/* Write the zlib trailer (adler32) */
|
|
putShortMSB(s, (uInt)(strm->adler >> 16));
|
|
putShortMSB(s, (uInt)(strm->adler & 0xffff));
|
|
flush_pending(strm);
|
|
/* If avail_out is zero, the application will call deflate again
|
|
* to flush the rest.
|
|
*/
|
|
s->noheader = -1; /* write the trailer only once! */
|
|
return s->pending != 0 ? Z_OK : Z_STREAM_END;
|
|
}
|
|
|
|
/* ========================================================================= */
|
|
int zlib_deflateEnd(
|
|
z_streamp strm
|
|
)
|
|
{
|
|
int status;
|
|
deflate_state *s;
|
|
|
|
if (strm == NULL || strm->state == NULL) return Z_STREAM_ERROR;
|
|
s = (deflate_state *) strm->state;
|
|
|
|
status = s->status;
|
|
if (status != INIT_STATE && status != BUSY_STATE &&
|
|
status != FINISH_STATE) {
|
|
return Z_STREAM_ERROR;
|
|
}
|
|
|
|
strm->state = NULL;
|
|
|
|
return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
|
|
}
|
|
|
|
/* =========================================================================
|
|
* Copy the source state to the destination state.
|
|
*/
|
|
int zlib_deflateCopy (
|
|
z_streamp dest,
|
|
z_streamp source
|
|
)
|
|
{
|
|
#ifdef MAXSEG_64K
|
|
return Z_STREAM_ERROR;
|
|
#else
|
|
deflate_state *ds;
|
|
deflate_state *ss;
|
|
ush *overlay;
|
|
deflate_workspace *mem;
|
|
|
|
|
|
if (source == NULL || dest == NULL || source->state == NULL) {
|
|
return Z_STREAM_ERROR;
|
|
}
|
|
|
|
ss = (deflate_state *) source->state;
|
|
|
|
*dest = *source;
|
|
|
|
mem = (deflate_workspace *) dest->workspace;
|
|
|
|
ds = &(mem->deflate_memory);
|
|
|
|
dest->state = (struct internal_state *) ds;
|
|
*ds = *ss;
|
|
ds->strm = dest;
|
|
|
|
ds->window = (Byte *) mem->window_memory;
|
|
ds->prev = (Pos *) mem->prev_memory;
|
|
ds->head = (Pos *) mem->head_memory;
|
|
overlay = (ush *) mem->overlay_memory;
|
|
ds->pending_buf = (uch *) overlay;
|
|
|
|
memcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
|
|
memcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
|
|
memcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));
|
|
memcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
|
|
|
|
ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
|
|
ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
|
|
ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
|
|
|
|
ds->l_desc.dyn_tree = ds->dyn_ltree;
|
|
ds->d_desc.dyn_tree = ds->dyn_dtree;
|
|
ds->bl_desc.dyn_tree = ds->bl_tree;
|
|
|
|
return Z_OK;
|
|
#endif
|
|
}
|
|
|
|
/* ===========================================================================
|
|
* Read a new buffer from the current input stream, update the adler32
|
|
* and total number of bytes read. All deflate() input goes through
|
|
* this function so some applications may wish to modify it to avoid
|
|
* allocating a large strm->next_in buffer and copying from it.
|
|
* (See also flush_pending()).
|
|
*/
|
|
static int read_buf(
|
|
z_streamp strm,
|
|
Byte *buf,
|
|
unsigned size
|
|
)
|
|
{
|
|
unsigned len = strm->avail_in;
|
|
|
|
if (len > size) len = size;
|
|
if (len == 0) return 0;
|
|
|
|
strm->avail_in -= len;
|
|
|
|
if (!((deflate_state *)(strm->state))->noheader) {
|
|
strm->adler = zlib_adler32(strm->adler, strm->next_in, len);
|
|
}
|
|
memcpy(buf, strm->next_in, len);
|
|
strm->next_in += len;
|
|
strm->total_in += len;
|
|
|
|
return (int)len;
|
|
}
|
|
|
|
/* ===========================================================================
|
|
* Initialize the "longest match" routines for a new zlib stream
|
|
*/
|
|
static void lm_init(
|
|
deflate_state *s
|
|
)
|
|
{
|
|
s->window_size = (ulg)2L*s->w_size;
|
|
|
|
CLEAR_HASH(s);
|
|
|
|
/* Set the default configuration parameters:
|
|
*/
|
|
s->max_lazy_match = configuration_table[s->level].max_lazy;
|
|
s->good_match = configuration_table[s->level].good_length;
|
|
s->nice_match = configuration_table[s->level].nice_length;
|
|
s->max_chain_length = configuration_table[s->level].max_chain;
|
|
|
|
s->strstart = 0;
|
|
s->block_start = 0L;
|
|
s->lookahead = 0;
|
|
s->match_length = s->prev_length = MIN_MATCH-1;
|
|
s->match_available = 0;
|
|
s->ins_h = 0;
|
|
}
|
|
|
|
/* ===========================================================================
|
|
* Set match_start to the longest match starting at the given string and
|
|
* return its length. Matches shorter or equal to prev_length are discarded,
|
|
* in which case the result is equal to prev_length and match_start is
|
|
* garbage.
|
|
* IN assertions: cur_match is the head of the hash chain for the current
|
|
* string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
|
|
* OUT assertion: the match length is not greater than s->lookahead.
|
|
*/
|
|
/* For 80x86 and 680x0, an optimized version will be provided in match.asm or
|
|
* match.S. The code will be functionally equivalent.
|
|
*/
|
|
static uInt longest_match(
|
|
deflate_state *s,
|
|
IPos cur_match /* current match */
|
|
)
|
|
{
|
|
unsigned chain_length = s->max_chain_length;/* max hash chain length */
|
|
register Byte *scan = s->window + s->strstart; /* current string */
|
|
register Byte *match; /* matched string */
|
|
register int len; /* length of current match */
|
|
int best_len = s->prev_length; /* best match length so far */
|
|
int nice_match = s->nice_match; /* stop if match long enough */
|
|
IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
|
|
s->strstart - (IPos)MAX_DIST(s) : NIL;
|
|
/* Stop when cur_match becomes <= limit. To simplify the code,
|
|
* we prevent matches with the string of window index 0.
|
|
*/
|
|
Pos *prev = s->prev;
|
|
uInt wmask = s->w_mask;
|
|
|
|
#ifdef UNALIGNED_OK
|
|
/* Compare two bytes at a time. Note: this is not always beneficial.
|
|
* Try with and without -DUNALIGNED_OK to check.
|
|
*/
|
|
register Byte *strend = s->window + s->strstart + MAX_MATCH - 1;
|
|
register ush scan_start = *(ush*)scan;
|
|
register ush scan_end = *(ush*)(scan+best_len-1);
|
|
#else
|
|
register Byte *strend = s->window + s->strstart + MAX_MATCH;
|
|
register Byte scan_end1 = scan[best_len-1];
|
|
register Byte scan_end = scan[best_len];
|
|
#endif
|
|
|
|
/* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
|
|
* It is easy to get rid of this optimization if necessary.
|
|
*/
|
|
Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
|
|
|
|
/* Do not waste too much time if we already have a good match: */
|
|
if (s->prev_length >= s->good_match) {
|
|
chain_length >>= 2;
|
|
}
|
|
/* Do not look for matches beyond the end of the input. This is necessary
|
|
* to make deflate deterministic.
|
|
*/
|
|
if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
|
|
|
|
Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
|
|
|
|
do {
|
|
Assert(cur_match < s->strstart, "no future");
|
|
match = s->window + cur_match;
|
|
|
|
/* Skip to next match if the match length cannot increase
|
|
* or if the match length is less than 2:
|
|
*/
|
|
#if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
|
|
/* This code assumes sizeof(unsigned short) == 2. Do not use
|
|
* UNALIGNED_OK if your compiler uses a different size.
|
|
*/
|
|
if (*(ush*)(match+best_len-1) != scan_end ||
|
|
*(ush*)match != scan_start) continue;
|
|
|
|
/* It is not necessary to compare scan[2] and match[2] since they are
|
|
* always equal when the other bytes match, given that the hash keys
|
|
* are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
|
|
* strstart+3, +5, ... up to strstart+257. We check for insufficient
|
|
* lookahead only every 4th comparison; the 128th check will be made
|
|
* at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
|
|
* necessary to put more guard bytes at the end of the window, or
|
|
* to check more often for insufficient lookahead.
|
|
*/
|
|
Assert(scan[2] == match[2], "scan[2]?");
|
|
scan++, match++;
|
|
do {
|
|
} while (*(ush*)(scan+=2) == *(ush*)(match+=2) &&
|
|
*(ush*)(scan+=2) == *(ush*)(match+=2) &&
|
|
*(ush*)(scan+=2) == *(ush*)(match+=2) &&
|
|
*(ush*)(scan+=2) == *(ush*)(match+=2) &&
|
|
scan < strend);
|
|
/* The funny "do {}" generates better code on most compilers */
|
|
|
|
/* Here, scan <= window+strstart+257 */
|
|
Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
|
|
if (*scan == *match) scan++;
|
|
|
|
len = (MAX_MATCH - 1) - (int)(strend-scan);
|
|
scan = strend - (MAX_MATCH-1);
|
|
|
|
#else /* UNALIGNED_OK */
|
|
|
|
if (match[best_len] != scan_end ||
|
|
match[best_len-1] != scan_end1 ||
|
|
*match != *scan ||
|
|
*++match != scan[1]) continue;
|
|
|
|
/* The check at best_len-1 can be removed because it will be made
|
|
* again later. (This heuristic is not always a win.)
|
|
* It is not necessary to compare scan[2] and match[2] since they
|
|
* are always equal when the other bytes match, given that
|
|
* the hash keys are equal and that HASH_BITS >= 8.
|
|
*/
|
|
scan += 2, match++;
|
|
Assert(*scan == *match, "match[2]?");
|
|
|
|
/* We check for insufficient lookahead only every 8th comparison;
|
|
* the 256th check will be made at strstart+258.
|
|
*/
|
|
do {
|
|
} while (*++scan == *++match && *++scan == *++match &&
|
|
*++scan == *++match && *++scan == *++match &&
|
|
*++scan == *++match && *++scan == *++match &&
|
|
*++scan == *++match && *++scan == *++match &&
|
|
scan < strend);
|
|
|
|
Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
|
|
|
|
len = MAX_MATCH - (int)(strend - scan);
|
|
scan = strend - MAX_MATCH;
|
|
|
|
#endif /* UNALIGNED_OK */
|
|
|
|
if (len > best_len) {
|
|
s->match_start = cur_match;
|
|
best_len = len;
|
|
if (len >= nice_match) break;
|
|
#ifdef UNALIGNED_OK
|
|
scan_end = *(ush*)(scan+best_len-1);
|
|
#else
|
|
scan_end1 = scan[best_len-1];
|
|
scan_end = scan[best_len];
|
|
#endif
|
|
}
|
|
} while ((cur_match = prev[cur_match & wmask]) > limit
|
|
&& --chain_length != 0);
|
|
|
|
if ((uInt)best_len <= s->lookahead) return best_len;
|
|
return s->lookahead;
|
|
}
|
|
|
|
#ifdef DEBUG_ZLIB
|
|
/* ===========================================================================
|
|
* Check that the match at match_start is indeed a match.
|
|
*/
|
|
static void check_match(
|
|
deflate_state *s,
|
|
IPos start,
|
|
IPos match,
|
|
int length
|
|
)
|
|
{
|
|
/* check that the match is indeed a match */
|
|
if (memcmp((char *)s->window + match,
|
|
(char *)s->window + start, length) != EQUAL) {
|
|
fprintf(stderr, " start %u, match %u, length %d\n",
|
|
start, match, length);
|
|
do {
|
|
fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
|
|
} while (--length != 0);
|
|
z_error("invalid match");
|
|
}
|
|
if (z_verbose > 1) {
|
|
fprintf(stderr,"\\[%d,%d]", start-match, length);
|
|
do { putc(s->window[start++], stderr); } while (--length != 0);
|
|
}
|
|
}
|
|
#else
|
|
# define check_match(s, start, match, length)
|
|
#endif
|
|
|
|
/* ===========================================================================
|
|
* Fill the window when the lookahead becomes insufficient.
|
|
* Updates strstart and lookahead.
|
|
*
|
|
* IN assertion: lookahead < MIN_LOOKAHEAD
|
|
* OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
|
|
* At least one byte has been read, or avail_in == 0; reads are
|
|
* performed for at least two bytes (required for the zip translate_eol
|
|
* option -- not supported here).
|
|
*/
|
|
static void fill_window(
|
|
deflate_state *s
|
|
)
|
|
{
|
|
register unsigned n, m;
|
|
register Pos *p;
|
|
unsigned more; /* Amount of free space at the end of the window. */
|
|
uInt wsize = s->w_size;
|
|
|
|
do {
|
|
more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
|
|
|
|
/* Deal with !@#$% 64K limit: */
|
|
if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
|
|
more = wsize;
|
|
|
|
} else if (more == (unsigned)(-1)) {
|
|
/* Very unlikely, but possible on 16 bit machine if strstart == 0
|
|
* and lookahead == 1 (input done one byte at time)
|
|
*/
|
|
more--;
|
|
|
|
/* If the window is almost full and there is insufficient lookahead,
|
|
* move the upper half to the lower one to make room in the upper half.
|
|
*/
|
|
} else if (s->strstart >= wsize+MAX_DIST(s)) {
|
|
|
|
memcpy((char *)s->window, (char *)s->window+wsize,
|
|
(unsigned)wsize);
|
|
s->match_start -= wsize;
|
|
s->strstart -= wsize; /* we now have strstart >= MAX_DIST */
|
|
s->block_start -= (long) wsize;
|
|
|
|
/* Slide the hash table (could be avoided with 32 bit values
|
|
at the expense of memory usage). We slide even when level == 0
|
|
to keep the hash table consistent if we switch back to level > 0
|
|
later. (Using level 0 permanently is not an optimal usage of
|
|
zlib, so we don't care about this pathological case.)
|
|
*/
|
|
n = s->hash_size;
|
|
p = &s->head[n];
|
|
do {
|
|
m = *--p;
|
|
*p = (Pos)(m >= wsize ? m-wsize : NIL);
|
|
} while (--n);
|
|
|
|
n = wsize;
|
|
p = &s->prev[n];
|
|
do {
|
|
m = *--p;
|
|
*p = (Pos)(m >= wsize ? m-wsize : NIL);
|
|
/* If n is not on any hash chain, prev[n] is garbage but
|
|
* its value will never be used.
|
|
*/
|
|
} while (--n);
|
|
more += wsize;
|
|
}
|
|
if (s->strm->avail_in == 0) return;
|
|
|
|
/* If there was no sliding:
|
|
* strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
|
|
* more == window_size - lookahead - strstart
|
|
* => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
|
|
* => more >= window_size - 2*WSIZE + 2
|
|
* In the BIG_MEM or MMAP case (not yet supported),
|
|
* window_size == input_size + MIN_LOOKAHEAD &&
|
|
* strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
|
|
* Otherwise, window_size == 2*WSIZE so more >= 2.
|
|
* If there was sliding, more >= WSIZE. So in all cases, more >= 2.
|
|
*/
|
|
Assert(more >= 2, "more < 2");
|
|
|
|
n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
|
|
s->lookahead += n;
|
|
|
|
/* Initialize the hash value now that we have some input: */
|
|
if (s->lookahead >= MIN_MATCH) {
|
|
s->ins_h = s->window[s->strstart];
|
|
UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
|
|
#if MIN_MATCH != 3
|
|
Call UPDATE_HASH() MIN_MATCH-3 more times
|
|
#endif
|
|
}
|
|
/* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
|
|
* but this is not important since only literal bytes will be emitted.
|
|
*/
|
|
|
|
} while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
|
|
}
|
|
|
|
/* ===========================================================================
|
|
* Flush the current block, with given end-of-file flag.
|
|
* IN assertion: strstart is set to the end of the current match.
|
|
*/
|
|
#define FLUSH_BLOCK_ONLY(s, eof) { \
|
|
zlib_tr_flush_block(s, (s->block_start >= 0L ? \
|
|
(char *)&s->window[(unsigned)s->block_start] : \
|
|
NULL), \
|
|
(ulg)((long)s->strstart - s->block_start), \
|
|
(eof)); \
|
|
s->block_start = s->strstart; \
|
|
flush_pending(s->strm); \
|
|
Tracev((stderr,"[FLUSH]")); \
|
|
}
|
|
|
|
/* Same but force premature exit if necessary. */
|
|
#define FLUSH_BLOCK(s, eof) { \
|
|
FLUSH_BLOCK_ONLY(s, eof); \
|
|
if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \
|
|
}
|
|
|
|
/* ===========================================================================
|
|
* Copy without compression as much as possible from the input stream, return
|
|
* the current block state.
|
|
* This function does not insert new strings in the dictionary since
|
|
* uncompressible data is probably not useful. This function is used
|
|
* only for the level=0 compression option.
|
|
* NOTE: this function should be optimized to avoid extra copying from
|
|
* window to pending_buf.
|
|
*/
|
|
static block_state deflate_stored(
|
|
deflate_state *s,
|
|
int flush
|
|
)
|
|
{
|
|
/* Stored blocks are limited to 0xffff bytes, pending_buf is limited
|
|
* to pending_buf_size, and each stored block has a 5 byte header:
|
|
*/
|
|
ulg max_block_size = 0xffff;
|
|
ulg max_start;
|
|
|
|
if (max_block_size > s->pending_buf_size - 5) {
|
|
max_block_size = s->pending_buf_size - 5;
|
|
}
|
|
|
|
/* Copy as much as possible from input to output: */
|
|
for (;;) {
|
|
/* Fill the window as much as possible: */
|
|
if (s->lookahead <= 1) {
|
|
|
|
Assert(s->strstart < s->w_size+MAX_DIST(s) ||
|
|
s->block_start >= (long)s->w_size, "slide too late");
|
|
|
|
fill_window(s);
|
|
if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
|
|
|
|
if (s->lookahead == 0) break; /* flush the current block */
|
|
}
|
|
Assert(s->block_start >= 0L, "block gone");
|
|
|
|
s->strstart += s->lookahead;
|
|
s->lookahead = 0;
|
|
|
|
/* Emit a stored block if pending_buf will be full: */
|
|
max_start = s->block_start + max_block_size;
|
|
if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
|
|
/* strstart == 0 is possible when wraparound on 16-bit machine */
|
|
s->lookahead = (uInt)(s->strstart - max_start);
|
|
s->strstart = (uInt)max_start;
|
|
FLUSH_BLOCK(s, 0);
|
|
}
|
|
/* Flush if we may have to slide, otherwise block_start may become
|
|
* negative and the data will be gone:
|
|
*/
|
|
if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
|
|
FLUSH_BLOCK(s, 0);
|
|
}
|
|
}
|
|
FLUSH_BLOCK(s, flush == Z_FINISH);
|
|
return flush == Z_FINISH ? finish_done : block_done;
|
|
}
|
|
|
|
/* ===========================================================================
|
|
* Compress as much as possible from the input stream, return the current
|
|
* block state.
|
|
* This function does not perform lazy evaluation of matches and inserts
|
|
* new strings in the dictionary only for unmatched strings or for short
|
|
* matches. It is used only for the fast compression options.
|
|
*/
|
|
static block_state deflate_fast(
|
|
deflate_state *s,
|
|
int flush
|
|
)
|
|
{
|
|
IPos hash_head = NIL; /* head of the hash chain */
|
|
int bflush; /* set if current block must be flushed */
|
|
|
|
for (;;) {
|
|
/* Make sure that we always have enough lookahead, except
|
|
* at the end of the input file. We need MAX_MATCH bytes
|
|
* for the next match, plus MIN_MATCH bytes to insert the
|
|
* string following the next match.
|
|
*/
|
|
if (s->lookahead < MIN_LOOKAHEAD) {
|
|
fill_window(s);
|
|
if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
|
|
return need_more;
|
|
}
|
|
if (s->lookahead == 0) break; /* flush the current block */
|
|
}
|
|
|
|
/* Insert the string window[strstart .. strstart+2] in the
|
|
* dictionary, and set hash_head to the head of the hash chain:
|
|
*/
|
|
if (s->lookahead >= MIN_MATCH) {
|
|
INSERT_STRING(s, s->strstart, hash_head);
|
|
}
|
|
|
|
/* Find the longest match, discarding those <= prev_length.
|
|
* At this point we have always match_length < MIN_MATCH
|
|
*/
|
|
if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
|
|
/* To simplify the code, we prevent matches with the string
|
|
* of window index 0 (in particular we have to avoid a match
|
|
* of the string with itself at the start of the input file).
|
|
*/
|
|
if (s->strategy != Z_HUFFMAN_ONLY) {
|
|
s->match_length = longest_match (s, hash_head);
|
|
}
|
|
/* longest_match() sets match_start */
|
|
}
|
|
if (s->match_length >= MIN_MATCH) {
|
|
check_match(s, s->strstart, s->match_start, s->match_length);
|
|
|
|
bflush = zlib_tr_tally(s, s->strstart - s->match_start,
|
|
s->match_length - MIN_MATCH);
|
|
|
|
s->lookahead -= s->match_length;
|
|
|
|
/* Insert new strings in the hash table only if the match length
|
|
* is not too large. This saves time but degrades compression.
|
|
*/
|
|
if (s->match_length <= s->max_insert_length &&
|
|
s->lookahead >= MIN_MATCH) {
|
|
s->match_length--; /* string at strstart already in hash table */
|
|
do {
|
|
s->strstart++;
|
|
INSERT_STRING(s, s->strstart, hash_head);
|
|
/* strstart never exceeds WSIZE-MAX_MATCH, so there are
|
|
* always MIN_MATCH bytes ahead.
|
|
*/
|
|
} while (--s->match_length != 0);
|
|
s->strstart++;
|
|
} else {
|
|
s->strstart += s->match_length;
|
|
s->match_length = 0;
|
|
s->ins_h = s->window[s->strstart];
|
|
UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
|
|
#if MIN_MATCH != 3
|
|
Call UPDATE_HASH() MIN_MATCH-3 more times
|
|
#endif
|
|
/* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
|
|
* matter since it will be recomputed at next deflate call.
|
|
*/
|
|
}
|
|
} else {
|
|
/* No match, output a literal byte */
|
|
Tracevv((stderr,"%c", s->window[s->strstart]));
|
|
bflush = zlib_tr_tally (s, 0, s->window[s->strstart]);
|
|
s->lookahead--;
|
|
s->strstart++;
|
|
}
|
|
if (bflush) FLUSH_BLOCK(s, 0);
|
|
}
|
|
FLUSH_BLOCK(s, flush == Z_FINISH);
|
|
return flush == Z_FINISH ? finish_done : block_done;
|
|
}
|
|
|
|
/* ===========================================================================
|
|
* Same as above, but achieves better compression. We use a lazy
|
|
* evaluation for matches: a match is finally adopted only if there is
|
|
* no better match at the next window position.
|
|
*/
|
|
static block_state deflate_slow(
|
|
deflate_state *s,
|
|
int flush
|
|
)
|
|
{
|
|
IPos hash_head = NIL; /* head of hash chain */
|
|
int bflush; /* set if current block must be flushed */
|
|
|
|
/* Process the input block. */
|
|
for (;;) {
|
|
/* Make sure that we always have enough lookahead, except
|
|
* at the end of the input file. We need MAX_MATCH bytes
|
|
* for the next match, plus MIN_MATCH bytes to insert the
|
|
* string following the next match.
|
|
*/
|
|
if (s->lookahead < MIN_LOOKAHEAD) {
|
|
fill_window(s);
|
|
if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
|
|
return need_more;
|
|
}
|
|
if (s->lookahead == 0) break; /* flush the current block */
|
|
}
|
|
|
|
/* Insert the string window[strstart .. strstart+2] in the
|
|
* dictionary, and set hash_head to the head of the hash chain:
|
|
*/
|
|
if (s->lookahead >= MIN_MATCH) {
|
|
INSERT_STRING(s, s->strstart, hash_head);
|
|
}
|
|
|
|
/* Find the longest match, discarding those <= prev_length.
|
|
*/
|
|
s->prev_length = s->match_length, s->prev_match = s->match_start;
|
|
s->match_length = MIN_MATCH-1;
|
|
|
|
if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
|
|
s->strstart - hash_head <= MAX_DIST(s)) {
|
|
/* To simplify the code, we prevent matches with the string
|
|
* of window index 0 (in particular we have to avoid a match
|
|
* of the string with itself at the start of the input file).
|
|
*/
|
|
if (s->strategy != Z_HUFFMAN_ONLY) {
|
|
s->match_length = longest_match (s, hash_head);
|
|
}
|
|
/* longest_match() sets match_start */
|
|
|
|
if (s->match_length <= 5 && (s->strategy == Z_FILTERED ||
|
|
(s->match_length == MIN_MATCH &&
|
|
s->strstart - s->match_start > TOO_FAR))) {
|
|
|
|
/* If prev_match is also MIN_MATCH, match_start is garbage
|
|
* but we will ignore the current match anyway.
|
|
*/
|
|
s->match_length = MIN_MATCH-1;
|
|
}
|
|
}
|
|
/* If there was a match at the previous step and the current
|
|
* match is not better, output the previous match:
|
|
*/
|
|
if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
|
|
uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
|
|
/* Do not insert strings in hash table beyond this. */
|
|
|
|
check_match(s, s->strstart-1, s->prev_match, s->prev_length);
|
|
|
|
bflush = zlib_tr_tally(s, s->strstart -1 - s->prev_match,
|
|
s->prev_length - MIN_MATCH);
|
|
|
|
/* Insert in hash table all strings up to the end of the match.
|
|
* strstart-1 and strstart are already inserted. If there is not
|
|
* enough lookahead, the last two strings are not inserted in
|
|
* the hash table.
|
|
*/
|
|
s->lookahead -= s->prev_length-1;
|
|
s->prev_length -= 2;
|
|
do {
|
|
if (++s->strstart <= max_insert) {
|
|
INSERT_STRING(s, s->strstart, hash_head);
|
|
}
|
|
} while (--s->prev_length != 0);
|
|
s->match_available = 0;
|
|
s->match_length = MIN_MATCH-1;
|
|
s->strstart++;
|
|
|
|
if (bflush) FLUSH_BLOCK(s, 0);
|
|
|
|
} else if (s->match_available) {
|
|
/* If there was no match at the previous position, output a
|
|
* single literal. If there was a match but the current match
|
|
* is longer, truncate the previous match to a single literal.
|
|
*/
|
|
Tracevv((stderr,"%c", s->window[s->strstart-1]));
|
|
if (zlib_tr_tally (s, 0, s->window[s->strstart-1])) {
|
|
FLUSH_BLOCK_ONLY(s, 0);
|
|
}
|
|
s->strstart++;
|
|
s->lookahead--;
|
|
if (s->strm->avail_out == 0) return need_more;
|
|
} else {
|
|
/* There is no previous match to compare with, wait for
|
|
* the next step to decide.
|
|
*/
|
|
s->match_available = 1;
|
|
s->strstart++;
|
|
s->lookahead--;
|
|
}
|
|
}
|
|
Assert (flush != Z_NO_FLUSH, "no flush?");
|
|
if (s->match_available) {
|
|
Tracevv((stderr,"%c", s->window[s->strstart-1]));
|
|
zlib_tr_tally (s, 0, s->window[s->strstart-1]);
|
|
s->match_available = 0;
|
|
}
|
|
FLUSH_BLOCK(s, flush == Z_FINISH);
|
|
return flush == Z_FINISH ? finish_done : block_done;
|
|
}
|
|
|
|
int zlib_deflate_workspacesize(void)
|
|
{
|
|
return sizeof(deflate_workspace);
|
|
}
|