1007 lines
37 KiB
C++
Executable File
1007 lines
37 KiB
C++
Executable File
//
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// DEFLATE.CPP
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//
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// Source file for ArchiveLib 2.0
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//
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// No Copyright claimed by Greenleaf Software!
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//
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// DESCRIPTION
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//
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// This is one of the ZLIB source files, with as few changes as possible.
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//
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// REVISION HISTORY
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//
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// February 14, 1996 2.0A : New release
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#include "arclib.h"
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#if !defined( AL_IBM )
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#pragma hdrstop
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#endif
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#if defined( AL_BORLAND )
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#pragma option -w-
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#endif
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/* deflate.c -- compress data using the deflation algorithm
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* Copyright (C) 1995 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.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
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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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/* $Id: deflate.cpp,v 1.1.1.1 1997-10-09 16:08:45 alex Exp $ */
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#include "deflate.h"
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char copyright[] = " deflate Copyright 1995 Jean-loup Gailly ";
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/*
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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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#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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} config;
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local config configuration_table[10] = {
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/* good lazy nice chain */
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/* 0 */ {0, 0, 0, 0}, /* store only */
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/* 1 */ {4, 4, 8, 4}, /* maximum speed, no lazy matches */
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/* 2 */ {4, 5, 16, 8},
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/* 3 */ {4, 6, 32, 32},
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/* 4 */ {4, 4, 16, 16}, /* lazy matches */
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/* 5 */ {8, 16, 32, 32},
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/* 6 */ {8, 16, 128, 128},
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/* 7 */ {8, 32, 128, 256},
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/* 8 */ {32, 128, 258, 1024},
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/* 9 */ {32, 258, 258, 4096}}; /* 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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struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
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/* ===========================================================================
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* Prototypes for local functions.
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*/
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local void fill_window __P((deflate_state ZL_FAR *s));
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local int deflate_fast __P((deflate_state ZL_FAR *s, int flush));
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local int deflate_slow __P((deflate_state ZL_FAR *s, int flush));
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local void lm_init __P((deflate_state ZL_FAR *s));
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local inline int longest_match __P((deflate_state ZL_FAR *s, IPos cur_match));
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local void putShortMSB __P((deflate_state ZL_FAR *s, uInt b));
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local void flush_pending __P((z_stream *strm));
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local int read_buf __P((z_stream *strm, char ZL_FAR *buf, unsigned size));
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#ifdef ASMV
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void match_init __P((void)); /* asm code initialization */
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#endif
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#ifdef DEBUG
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local void check_match __P((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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* 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] = (Pos) (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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zmemzero((char ZL_FAR *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
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/* ========================================================================= */
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int deflateInit (
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z_stream *strm,
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int level )
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{
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return deflateInit2 (strm, level, DEFLATED, MAX_WBITS, DEF_MEM_LEVEL, 0);
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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 deflateInit2 (
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z_stream *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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{
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deflate_state ZL_FAR *s;
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int noheader = 0;
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if (strm == Z_NULL) return Z_STREAM_ERROR;
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strm->msg = Z_NULL;
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if (strm->zalloc == Z_NULL) strm->zalloc = zcalloc;
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if (strm->zfree == Z_NULL) strm->zfree = zcfree;
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if (level == Z_DEFAULT_COMPRESSION) level = 6;
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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 != DEFLATED ||
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windowBits < 8 || windowBits > 15 || level < 1 || level > 9) {
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strm->state = 0; /* MRN */
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return Z_STREAM_ERROR;
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}
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s = (deflate_state ZL_FAR *) 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 ZL_FAR *)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 ZL_FAR *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
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s->prev = (Pos ZL_FAR *) ZALLOC(strm, s->w_size, sizeof(Pos));
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s->head = (Pos ZL_FAR *) ZALLOC(strm, s->hash_size, sizeof(Pos));
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s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
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s->pending_buf = (uch ZL_FAR*) ZALLOC(strm, s->lit_bufsize, 2*sizeof(ush));
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if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
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s->pending_buf == Z_NULL) {
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strm->msg = z_errmsg[1-Z_MEM_ERROR];
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deflateEnd (strm);
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return Z_MEM_ERROR;
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}
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s->d_buf = (ush ZL_FAR*) &(s->pending_buf[s->lit_bufsize]);
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s->l_buf = (uch ZL_FAR *) &(s->pending_buf[3*s->lit_bufsize]);
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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 <= 32 bits (worst case
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* is 15+15+13=33).
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*/
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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 deflateReset(strm);
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}
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/* ========================================================================= */
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int deflateReset (
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z_stream *strm )
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{
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deflate_state ZL_FAR *s;
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if (strm == Z_NULL || strm->state == Z_NULL ||
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strm->zalloc == Z_NULL || strm->zfree == Z_NULL) return Z_STREAM_ERROR;
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strm->total_in = strm->total_out = 0;
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strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
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strm->data_type = Z_UNKNOWN;
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s = (deflate_state ZL_FAR *)strm->state;
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s->pending = 0;
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s->pending_out = s->pending_buf;
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s->status = s->noheader ? BUSY_STATE : INIT_STATE;
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s->adler = 1;
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ct_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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* Put a short the pending_out 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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* the pending_out buffer.
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*/
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local void putShortMSB (
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deflate_state ZL_FAR *s,
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uInt b )
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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.
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*/
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local void flush_pending(
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z_stream *strm )
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{
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unsigned len = strm->state->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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zmemcpy(strm->next_out, strm->state->pending_out, len);
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strm->next_out += len;
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strm->state->pending_out += len;
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strm->total_out += len;
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strm->avail_out -= len;
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strm->state->pending -= len;
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if (strm->state->pending == 0) {
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strm->state->pending_out = strm->state->pending_buf;
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}
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}
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/* ========================================================================= */
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int deflate (
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z_stream *strm,
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int flush )
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{
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if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
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if (strm->next_out == Z_NULL || strm->next_in == Z_NULL) {
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ERR_RETURN(strm, Z_STREAM_ERROR);
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}
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if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
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strm->state->strm = strm; /* just in case */
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/* Write the zlib header */
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if (strm->state->status == INIT_STATE) {
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uInt header = (DEFLATED + ((strm->state->w_bits-8)<<4)) << 8;
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uInt level_flags = (strm->state->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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header += 31 - (header % 31);
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strm->state->status = BUSY_STATE;
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putShortMSB(strm->state, header);
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}
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/* Flush as much pending output as possible */
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if (strm->state->pending != 0) {
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flush_pending(strm);
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if (strm->avail_out == 0) return Z_OK;
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}
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/* User must not provide more input after the first FINISH: */
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if (strm->state->status == FINISH_STATE && strm->avail_in != 0) {
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ERR_RETURN(strm, Z_BUF_ERROR);
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}
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/* Start a new block or continue the current one.
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*/
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if (strm->avail_in != 0 || strm->state->lookahead != 0 ||
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(flush != Z_NO_FLUSH && strm->state->status != FINISH_STATE)) {
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int quit;
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if (flush == Z_FINISH) {
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strm->state->status = FINISH_STATE;
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}
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if (strm->state->level <= 3) {
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quit = deflate_fast(strm->state, flush);
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} else {
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quit = deflate_slow(strm->state, flush);
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}
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if (flush == Z_FULL_FLUSH || flush == Z_SYNC_FLUSH) {
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ct_stored_block(strm->state, (char ZL_FAR *)0, 0L, 0); /* special marker */
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flush_pending(strm);
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if (flush == Z_FULL_FLUSH) {
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CLEAR_HASH(strm->state); /* forget history */
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}
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} else if (flush == Z_PARTIAL_FLUSH) {
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ct_align(strm->state);
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flush_pending(strm);
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}
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if (quit || strm->avail_out == 0) return Z_OK;
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}
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Assert(strm->avail_out > 0, "bug2");
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if (flush != Z_FINISH) return Z_OK;
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if (strm->state->noheader) return Z_STREAM_END;
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/* Write the zlib trailer (adler32) */
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putShortMSB(strm->state, (uInt)(strm->state->adler >> 16));
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putShortMSB(strm->state, (uInt)(strm->state->adler & 0xffff));
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flush_pending(strm);
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/* If avail_out is zero, the application will call deflate again
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* to flush the rest.
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*/
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strm->state->noheader = 1; /* write the trailer only once! */
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return strm->state->pending != 0 ? Z_OK : Z_STREAM_END;
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}
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/* ========================================================================= */
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int deflateEnd (
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z_stream *strm )
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{
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if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
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TRY_FREE(strm, strm->state->window);
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TRY_FREE(strm, strm->state->prev);
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TRY_FREE(strm, strm->state->head);
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TRY_FREE(strm, strm->state->pending_buf);
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if ( strm->state )
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ZFREE(strm, strm->state);
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strm->state = Z_NULL;
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return Z_OK;
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}
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/* ========================================================================= */
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int deflateCopy (
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z_stream *dest,
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z_stream *source )
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{
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if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
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return Z_STREAM_ERROR;
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}
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*dest = *source;
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return Z_STREAM_ERROR; /* to be implemented */
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#if 0
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dest->state = (struct internal_state ZL_FAR *)
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(*dest->zalloc)(1, sizeof(deflate_state));
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if (dest->state == Z_NULL) return Z_MEM_ERROR;
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*(dest->state) = *(source->state);
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return Z_OK;
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#endif
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}
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/* ===========================================================================
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* Read a new buffer from the current input stream, update the adler32
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* and total number of bytes read.
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*/
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local int read_buf(
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z_stream *strm,
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char ZL_FAR *buf,
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unsigned size )
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{
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unsigned len = strm->avail_in;
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if (len > size) len = size;
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if (len == 0) return 0;
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strm->avail_in -= len;
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if (!strm->state->noheader) {
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strm->state->adler = adler32(strm->state->adler, strm->next_in, len);
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}
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zmemcpy(buf, strm->next_in, len);
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strm->next_in += len;
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strm->total_in += len;
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return (int)len;
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}
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/* ===========================================================================
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* Initialize the "longest match" routines for a new zlib stream
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*/
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local void lm_init (
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deflate_state ZL_FAR *s )
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{
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s->window_size = (ulg)2L*s->w_size;
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CLEAR_HASH(s);
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|
|
/* 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 = MIN_MATCH-1;
|
|
s->match_available = 0;
|
|
s->ins_h = 0;
|
|
#ifdef ASMV
|
|
match_init(); /* initialize the asm code */
|
|
#endif
|
|
}
|
|
|
|
/* ===========================================================================
|
|
* 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
|
|
*/
|
|
#ifndef ASMV
|
|
/* For 80x86 and 680x0, an optimized version will be provided in match.asm or
|
|
* match.S. The code will be functionally equivalent.
|
|
*/
|
|
local inline int longest_match(
|
|
deflate_state ZL_FAR *s,
|
|
IPos cur_match ) /* current match */
|
|
{
|
|
unsigned chain_length = s->max_chain_length;/* max hash chain length */
|
|
register Byte ZL_FAR *scan = s->window + s->strstart; /* current string */
|
|
register Byte ZL_FAR *match; /* matched string */
|
|
register int len; /* length of current match */
|
|
int best_len = s->prev_length; /* best match length so far */
|
|
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 ZL_FAR *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 ZL_FAR *strend = s->window + s->strstart + MAX_MATCH - 1;
|
|
register ush scan_start = *(ush ZL_FAR*)scan;
|
|
register ush scan_end = *(ush ZL_FAR *)(scan+best_len-1);
|
|
#else
|
|
register Byte ZL_FAR *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;
|
|
}
|
|
Assert(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 ZL_FAR *)(match+best_len-1) != scan_end ||
|
|
*(ush ZL_FAR *)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.
|
|
*/
|
|
scan++, match++;
|
|
do {
|
|
} while (*(ush ZL_FAR *)(scan+=2) == *(ush ZL_FAR *)(match+=2) &&
|
|
*(ush ZL_FAR *)(scan+=2) == *(ush ZL_FAR *)(match+=2) &&
|
|
*(ush ZL_FAR *)(scan+=2) == *(ush ZL_FAR *)(match+=2) &&
|
|
*(ush ZL_FAR *)(scan+=2) == *(ush ZL_FAR *)(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++;
|
|
|
|
/* 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 >= s->nice_match) break;
|
|
#ifdef UNALIGNED_OK
|
|
scan_end = *(ush ZL_FAR *)(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);
|
|
|
|
return best_len;
|
|
}
|
|
#endif /* ASMV */
|
|
|
|
#ifdef DEBUG
|
|
/* ===========================================================================
|
|
* Check that the match at match_start is indeed a match.
|
|
*/
|
|
local void check_match(
|
|
deflate_state ZL_FAR *s,
|
|
IPos start,
|
|
IPos match,
|
|
int length )
|
|
{
|
|
/* check that the match is indeed a match */
|
|
if (fmemcmp((char ZL_FAR *)s->window + match,
|
|
(char ZL_FAR *)s->window + start, length) != EQUAL) {
|
|
fprintf(stderr,
|
|
" start %d, match %d, length %d\n",
|
|
start, match, length);
|
|
z_error("invalid match");
|
|
}
|
|
if (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).
|
|
*/
|
|
local void fill_window(
|
|
deflate_state ZL_FAR *s )
|
|
{
|
|
register unsigned n, m;
|
|
register Pos ZL_FAR *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)) {
|
|
|
|
/* By the IN assertion, the window is not empty so we can't confuse
|
|
* more == 0 with more == 64K on a 16 bit machine.
|
|
*/
|
|
zmemcpy((char ZL_FAR *)s->window, (char ZL_FAR *)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):
|
|
*/
|
|
n = s->hash_size;
|
|
p = &s->head[n-1];
|
|
do {
|
|
m = *p;
|
|
*p-- = (Pos)(m >= wsize ? m-wsize : NIL);
|
|
} while (--n);
|
|
|
|
n = wsize;
|
|
p = &s->prev[n-1];
|
|
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, (char ZL_FAR *)s->window + s->strstart + s->lookahead,
|
|
more);
|
|
s->lookahead += n;
|
|
|
|
/* Initialize the hash value now that we have some input: */
|
|
if (s->strstart == 0 && s->lookahead >= MIN_MATCH-1) {
|
|
for (n=0; n<MIN_MATCH-1; n++) {
|
|
UPDATE_HASH(s, s->ins_h, s->window[n]);
|
|
}
|
|
}
|
|
/* 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) { \
|
|
ct_flush_block(s, (s->block_start >= 0L ? \
|
|
(char ZL_FAR *)&s->window[(unsigned)s->block_start] : \
|
|
(char ZL_FAR *)Z_NULL), (long)s->strstart - s->block_start, (eof)); \
|
|
s->block_start = s->strstart; \
|
|
flush_pending(s->strm); \
|
|
}
|
|
|
|
/* Same but force premature exit if necessary. */
|
|
#define FLUSH_BLOCK(s, eof) { \
|
|
FLUSH_BLOCK_ONLY(s, eof); \
|
|
if (s->strm->avail_out == 0) return 1; \
|
|
}
|
|
|
|
/* ===========================================================================
|
|
* Compress as much as possible from the input stream, return true if
|
|
* processing was terminated prematurely (no more input or output space).
|
|
* This function does not perform lazy evaluationof 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.
|
|
*/
|
|
|
|
#if defined( AL_MICROSOFT )
|
|
#pragma optimize( "e", off )
|
|
#endif
|
|
|
|
local int deflate_fast(
|
|
deflate_state ZL_FAR *s,
|
|
int flush )
|
|
{
|
|
IPos hash_head; /* head of the hash chain */
|
|
int bflush; /* set if current block must be flushed */
|
|
|
|
s->prev_length = MIN_MATCH-1;
|
|
|
|
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 1;
|
|
|
|
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:
|
|
*/
|
|
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 > s->lookahead) s->match_length = s->lookahead;
|
|
}
|
|
if (s->match_length >= MIN_MATCH) {
|
|
check_match(s, s->strstart, s->match_start, s->match_length);
|
|
|
|
bflush = ct_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->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. If lookahead < MIN_MATCH
|
|
* these bytes are garbage, but it does not matter since
|
|
* the next lookahead bytes will be emitted as literals.
|
|
*/
|
|
} 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
|
|
}
|
|
} else {
|
|
/* No match, output a literal byte */
|
|
Tracevv((stderr,"%c", s->window[s->strstart]));
|
|
bflush = ct_tally (s, 0, s->window[s->strstart]);
|
|
s->lookahead--;
|
|
s->strstart++;
|
|
}
|
|
if (bflush) FLUSH_BLOCK(s, 0);
|
|
}
|
|
FLUSH_BLOCK(s, flush == Z_FINISH);
|
|
return 0; /* normal exit */
|
|
}
|
|
#if defined( AL_MICROSOFT )
|
|
#pragma optimize( "e", on )
|
|
#endif
|
|
|
|
/* ===========================================================================
|
|
* 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.
|
|
*/
|
|
local int deflate_slow(
|
|
deflate_state ZL_FAR *s,
|
|
int flush )
|
|
{
|
|
IPos hash_head; /* 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 1;
|
|
|
|
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:
|
|
*/
|
|
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 > s->lookahead) s->match_length = s->lookahead;
|
|
|
|
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) {
|
|
|
|
check_match(s, s->strstart-1, s->prev_match, s->prev_length);
|
|
|
|
bflush = ct_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.
|
|
*/
|
|
s->lookahead -= s->prev_length-1;
|
|
s->prev_length -= 2;
|
|
do {
|
|
s->strstart++;
|
|
INSERT_STRING(s, s->strstart, hash_head);
|
|
/* strstart never exceeds WSIZE-MAX_MATCH, so there are
|
|
* always MIN_MATCH bytes ahead. If lookahead < MIN_MATCH
|
|
* these bytes are garbage, but it does not matter since the
|
|
* next lookahead bytes will always be emitted as literals.
|
|
*/
|
|
} 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 (ct_tally (s, 0, s->window[s->strstart-1])) {
|
|
FLUSH_BLOCK_ONLY(s, 0);
|
|
}
|
|
s->strstart++;
|
|
s->lookahead--;
|
|
if (s->strm->avail_out == 0) return 1;
|
|
} else {
|
|
/* There is no previous match to compare with, wait for
|
|
* the next step to decide.
|
|
*/
|
|
s->match_available = 1;
|
|
s->strstart++;
|
|
s->lookahead--;
|
|
}
|
|
}
|
|
if (s->match_available) {
|
|
ct_tally (s, 0, s->window[s->strstart-1]);
|
|
s->match_available = 0;
|
|
}
|
|
FLUSH_BLOCK(s, flush == Z_FINISH);
|
|
return 0;
|
|
}
|
|
|