273 lines
9.8 KiB
C
273 lines
9.8 KiB
C
/* deflate.h -- internal compression state
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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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/* WARNING: this file should *not* be used by applications. It is
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part of the implementation of the compression library and is
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subject to change. Applications should only use zlib.h.
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*/
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/* $Id: deflate.h,v 1.4 1995/05/01 15:08:45 jloup Exp $ */
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#include "zutil.h"
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/* ===========================================================================
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* Internal compression state.
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*/
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/* Data type */
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#define BINARY 0
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#define ASCII 1
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#define UNKNOWN 2
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#define LENGTH_CODES 29
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/* number of length codes, not counting the special END_BLOCK code */
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#define LITERALS 256
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/* number of literal bytes 0..255 */
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#define L_CODES (LITERALS+1+LENGTH_CODES)
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/* number of Literal or Length codes, including the END_BLOCK code */
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#define D_CODES 30
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/* number of distance codes */
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#define BL_CODES 19
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/* number of codes used to transfer the bit lengths */
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#define HEAP_SIZE (2*L_CODES+1)
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/* maximum heap size */
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#define MAX_BITS 15
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/* All codes must not exceed MAX_BITS bits */
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#define INIT_STATE 42
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#define BUSY_STATE 113
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#define FINISH_STATE 666
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/* Stream status */
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/* Data structure describing a single value and its code string. */
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typedef struct ct_data_s {
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union {
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ush freq; /* frequency count */
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ush code; /* bit string */
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} fc;
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union {
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ush dad; /* father node in Huffman tree */
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ush len; /* length of bit string */
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} dl;
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} ct_data;
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#define Freq fc.freq
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#define Code fc.code
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#define Dad dl.dad
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#define Len dl.len
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typedef struct static_tree_desc_s static_tree_desc;
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typedef struct tree_desc_s {
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ct_data *dyn_tree; /* the dynamic tree */
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int max_code; /* largest code with non zero frequency */
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static_tree_desc *stat_desc; /* the corresponding static tree */
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} tree_desc;
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typedef ush Pos;
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typedef unsigned IPos;
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/* A Pos is an index in the character window. We use short instead of int to
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* save space in the various tables. IPos is used only for parameter passing.
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*/
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typedef struct internal_state {
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z_stream *strm; /* pointer back to this zlib stream */
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int status; /* as the name implies */
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Byte *pending_buf; /* output still pending */
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Byte *pending_out; /* next pending byte to output to the stream */
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int pending; /* nb of bytes in the pending buffer */
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uLong adler; /* adler32 of uncompressed data */
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int noheader; /* suppress zlib header and adler32 */
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Byte data_type; /* UNKNOWN, BINARY or ASCII */
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Byte method; /* STORED (for zip only) or DEFLATED */
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/* used by deflate.c: */
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uInt w_size; /* LZ77 window size (32K by default) */
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uInt w_bits; /* log2(w_size) (8..16) */
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uInt w_mask; /* w_size - 1 */
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Byte *window;
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/* Sliding window. Input bytes are read into the second half of the window,
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* and move to the first half later to keep a dictionary of at least wSize
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* bytes. With this organization, matches are limited to a distance of
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* wSize-MAX_MATCH bytes, but this ensures that IO is always
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* performed with a length multiple of the block size. Also, it limits
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* the window size to 64K, which is quite useful on MSDOS.
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* To do: use the user input buffer as sliding window.
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*/
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ulg window_size;
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/* Actual size of window: 2*wSize, except when the user input buffer
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* is directly used as sliding window.
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*/
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Pos *prev;
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/* Link to older string with same hash index. To limit the size of this
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* array to 64K, this link is maintained only for the last 32K strings.
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* An index in this array is thus a window index modulo 32K.
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*/
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Pos *head; /* Heads of the hash chains or NIL. */
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uInt ins_h; /* hash index of string to be inserted */
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uInt hash_size; /* number of elements in hash table */
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uInt hash_bits; /* log2(hash_size) */
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uInt hash_mask; /* hash_size-1 */
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uInt hash_shift;
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/* Number of bits by which ins_h must be shifted at each input
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* step. It must be such that after MIN_MATCH steps, the oldest
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* byte no longer takes part in the hash key, that is:
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* hash_shift * MIN_MATCH >= hash_bits
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*/
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long block_start;
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/* Window position at the beginning of the current output block. Gets
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* negative when the window is moved backwards.
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*/
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uInt match_length; /* length of best match */
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IPos prev_match; /* previous match */
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int match_available; /* set if previous match exists */
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uInt strstart; /* start of string to insert */
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uInt match_start; /* start of matching string */
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uInt lookahead; /* number of valid bytes ahead in window */
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uInt prev_length;
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/* Length of the best match at previous step. Matches not greater than this
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* are discarded. This is used in the lazy match evaluation.
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*/
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uInt max_chain_length;
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/* To speed up deflation, hash chains are never searched beyond this
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* length. A higher limit improves compression ratio but degrades the
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* speed.
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*/
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uInt max_lazy_match;
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/* Attempt to find a better match only when the current match is strictly
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* smaller than this value. This mechanism is used only for compression
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* levels >= 4.
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*/
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# define max_insert_length max_lazy_match
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/* Insert new strings in the hash table only if the match length is not
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* greater than this length. This saves time but degrades compression.
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* max_insert_length is used only for compression levels <= 3.
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*/
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int level; /* compression level (1..9) */
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int strategy; /* favor or force Huffman coding*/
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uInt good_match;
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/* Use a faster search when the previous match is longer than this */
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int nice_match; /* Stop searching when current match exceeds this */
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/* used by trees.c: */
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ct_data dyn_ltree[HEAP_SIZE]; /* literal and length tree */
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ct_data dyn_dtree[2*D_CODES+1]; /* distance tree */
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ct_data bl_tree[2*BL_CODES+1]; /* Huffman tree for the bit lengths */
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tree_desc l_desc; /* descriptor for literal tree */
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tree_desc d_desc; /* descriptor for distance tree */
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tree_desc bl_desc; /* descriptor for bit length tree */
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ush bl_count[MAX_BITS+1];
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/* number of codes at each bit length for an optimal tree */
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int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
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int heap_len; /* number of elements in the heap */
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int heap_max; /* element of largest frequency */
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/* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
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* The same heap array is used to build all trees.
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*/
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uch depth[2*L_CODES+1];
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/* Depth of each subtree used as tie breaker for trees of equal frequency
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*/
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uch *l_buf; /* buffer for literals or lengths */
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uInt lit_bufsize;
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/* Size of match buffer for literals/lengths. There are 4 reasons for
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* limiting lit_bufsize to 64K:
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* - frequencies can be kept in 16 bit counters
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* - if compression is not successful for the first block, all input
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* data is still in the window so we can still emit a stored block even
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* when input comes from standard input. (This can also be done for
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* all blocks if lit_bufsize is not greater than 32K.)
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* - if compression is not successful for a file smaller than 64K, we can
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* even emit a stored file instead of a stored block (saving 5 bytes).
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* This is applicable only for zip (not gzip or zlib).
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* - creating new Huffman trees less frequently may not provide fast
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* adaptation to changes in the input data statistics. (Take for
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* example a binary file with poorly compressible code followed by
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* a highly compressible string table.) Smaller buffer sizes give
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* fast adaptation but have of course the overhead of transmitting
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* trees more frequently.
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* - I can't count above 4
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*/
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uInt last_lit; /* running index in l_buf */
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ush *d_buf;
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/* Buffer for distances. To simplify the code, d_buf and l_buf have
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* the same number of elements. To use different lengths, an extra flag
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* array would be necessary.
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*/
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ulg opt_len; /* bit length of current block with optimal trees */
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ulg static_len; /* bit length of current block with static trees */
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ulg compressed_len; /* total bit length of compressed file */
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uInt matches; /* number of string matches in current block */
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#ifdef DEBUG
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ulg bits_sent; /* bit length of the compressed data */
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#endif
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ush bi_buf;
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/* Output buffer. bits are inserted starting at the bottom (least
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* significant bits).
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*/
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int bi_valid;
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/* Number of valid bits in bi_buf. All bits above the last valid bit
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* are always zero.
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*/
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} deflate_state;
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/* Output a byte on the stream.
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* IN assertion: there is enough room in pending_buf.
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*/
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#define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
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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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#define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD)
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/* In order to simplify the code, particularly on 16 bit machines, match
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* distances are limited to MAX_DIST instead of WSIZE.
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*/
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/* in trees.c */
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void ct_init __P((deflate_state *s));
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int ct_tally __P((deflate_state *s, int dist, int lc));
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ulg ct_flush_block __P((deflate_state *s, char *buf, ulg stored_len, int eof));
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void ct_stored_block __P((deflate_state *s, char *buf, ulg stored_len,
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int eof));
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