deflate.h

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/* deflate.h -- internal compression state
 * Copyright (C) 1995-2012 Jean-loup Gailly
 * For conditions of distribution and use, see copyright notice in zlib.h
 */

/* WARNING: this file should *not* be used by applications. It is
 part of the implementation of the compression library and is
 subject to change. Applications should only use zlib.h.
 */

/* @(#) $Id$ */

#ifndef DEFLATE_H
#define DEFLATE_H

#include "zutil.h"

/* define NO_GZIP when compiling if you want to disable gzip header and
 trailer creation by deflate(). NO_GZIP would be used to avoid linking in
 the crc code when it is not needed. For shared libraries, gzip encoding
 should be left enabled. */
#ifndef NO_GZIP
# define GZIP
#endif

/* ===========================================================================
 * Internal compression state.
 */

#define LENGTH_CODES 29
/* number of length codes, not counting the special END_BLOCK code */

#define LITERALS 256
/* number of literal bytes 0..255 */

#define L_CODES (LITERALS+1+LENGTH_CODES)
/* number of Literal or Length codes, including the END_BLOCK code */

#define D_CODES 30
/* number of distance codes */

#define BL_CODES 19
/* number of codes used to transfer the bit lengths */

#define HEAP_SIZE (2*L_CODES+1)
/* maximum heap size */

#define MAX_BITS 15
/* All codes must not exceed MAX_BITS bits */

#define Buf_size 16
/* size of bit buffer in bi_buf */

#define INIT_STATE 42
#define EXTRA_STATE 69
#define NAME_STATE 73
#define COMMENT_STATE 91
#define HCRC_STATE 103
#define BUSY_STATE 113
#define FINISH_STATE 666
/* Stream status */


/* Data structure describing a single value and its code string. */
typedef struct ct_data_s {
 union {
 ush freq; /* frequency count */
 ush code; /* bit string */
 } fc;
 union {
 ush dad; /* father node in Huffman tree */
 ush len; /* length of bit string */
 } dl;
} FAR ct_data;

#define Freq fc.freq
#define Code fc.code
#define Dad dl.dad
#define Len dl.len

typedef struct static_tree_desc_s static_tree_desc;

typedef struct tree_desc_s {
 ct_data *dyn_tree; /* the dynamic tree */
 int max_code; /* largest code with non zero frequency */
 static_tree_desc *stat_desc; /* the corresponding static tree */
} FAR tree_desc;

typedef ush Pos;
typedef Pos FAR Posf;
typedef unsigned IPos;

/* A Pos is an index in the character window. We use short instead of int to
 * save space in the various tables. IPos is used only for parameter passing.
 */

typedef struct internal_state {
 z_streamp strm; /* pointer back to this zlib stream */
 int status; /* as the name implies */
 Bytef *pending_buf; /* output still pending */
 ulg pending_buf_size; /* size of pending_buf */
 Bytef *pending_out; /* next pending byte to output to the stream */
 uInt pending; /* nb of bytes in the pending buffer */
 int wrap; /* bit 0 true for zlib, bit 1 true for gzip */
 gz_headerp gzhead; /* gzip header information to write */
 uInt gzindex; /* where in extra, name, or comment */
 Byte method; /* can only be DEFLATED */
 int last_flush; /* value of flush param for previous deflate call */

 /* used by deflate.c: */

 uInt w_size; /* LZ77 window size (32K by default) */
 uInt w_bits; /* log2(w_size) (8..16) */
 uInt w_mask; /* w_size - 1 */

 Bytef *window;
 /* Sliding window. Input bytes are read into the second half of the window,
 * and move to the first half later to keep a dictionary of at least wSize
 * bytes. With this organization, matches are limited to a distance of
 * wSize-MAX_MATCH bytes, but this ensures that IO is always
 * performed with a length multiple of the block size. Also, it limits
 * the window size to 64K, which is quite useful on MSDOS.
 * To do: use the user input buffer as sliding window.
 */

 ulg window_size;
 /* Actual size of window: 2*wSize, except when the user input buffer
 * is directly used as sliding window.
 */

 Posf *prev;
 /* Link to older string with same hash index. To limit the size of this
 * array to 64K, this link is maintained only for the last 32K strings.
 * An index in this array is thus a window index modulo 32K.
 */

 Posf *head; /* Heads of the hash chains or NIL. */

 uInt ins_h; /* hash index of string to be inserted */
 uInt hash_size; /* number of elements in hash table */
 uInt hash_bits; /* log2(hash_size) */
 uInt hash_mask; /* hash_size-1 */

 uInt hash_shift;
 /* Number of bits by which ins_h must be shifted at each input
 * step. It must be such that after MIN_MATCH steps, the oldest
 * byte no longer takes part in the hash key, that is:
 * hash_shift * MIN_MATCH >= hash_bits
 */

 long block_start;
 /* Window position at the beginning of the current output block. Gets
 * negative when the window is moved backwards.
 */

 uInt match_length; /* length of best match */
 IPos prev_match; /* previous match */
 int match_available; /* set if previous match exists */
 uInt strstart; /* start of string to insert */
 uInt match_start; /* start of matching string */
 uInt lookahead; /* number of valid bytes ahead in window */

 uInt prev_length;
 /* Length of the best match at previous step. Matches not greater than this
 * are discarded. This is used in the lazy match evaluation.
 */

 uInt max_chain_length;
 /* To speed up deflation, hash chains are never searched beyond this
 * length. A higher limit improves compression ratio but degrades the
 * speed.
 */

 uInt max_lazy_match;
 /* Attempt to find a better match only when the current match is strictly
 * smaller than this value. This mechanism is used only for compression
 * levels >= 4.
 */
# define max_insert_length max_lazy_match
 /* Insert new strings in the hash table only if the match length is not
 * greater than this length. This saves time but degrades compression.
 * max_insert_length is used only for compression levels <= 3.
 */

 int level; /* compression level (1..9) */
 int strategy; /* favor or force Huffman coding*/

 uInt good_match;
 /* Use a faster search when the previous match is longer than this */

 int nice_match; /* Stop searching when current match exceeds this */

 /* used by trees.c: */
 /* Didn't use ct_data typedef below to suppress compiler warning */
 struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */
 struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
 struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */

 struct tree_desc_s l_desc; /* desc. for literal tree */
 struct tree_desc_s d_desc; /* desc. for distance tree */
 struct tree_desc_s bl_desc; /* desc. for bit length tree */

 ush bl_count[MAX_BITS+1];
 /* number of codes at each bit length for an optimal tree */

 int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
 int heap_len; /* number of elements in the heap */
 int heap_max; /* element of largest frequency */
 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
 * The same heap array is used to build all trees.
 */

 uch depth[2*L_CODES+1];
 /* Depth of each subtree used as tie breaker for trees of equal frequency
 */

 uchf *l_buf; /* buffer for literals or lengths */

 uInt lit_bufsize;
 /* Size of match buffer for literals/lengths. There are 4 reasons for
 * limiting lit_bufsize to 64K:
 * - frequencies can be kept in 16 bit counters
 * - if compression is not successful for the first block, all input
 * data is still in the window so we can still emit a stored block even
 * when input comes from standard input. (This can also be done for
 * all blocks if lit_bufsize is not greater than 32K.)
 * - if compression is not successful for a file smaller than 64K, we can
 * even emit a stored file instead of a stored block (saving 5 bytes).
 * This is applicable only for zip (not gzip or zlib).
 * - creating new Huffman trees less frequently may not provide fast
 * adaptation to changes in the input data statistics. (Take for
 * example a binary file with poorly compressible code followed by
 * a highly compressible string table.) Smaller buffer sizes give
 * fast adaptation but have of course the overhead of transmitting
 * trees more frequently.
 * - I can't count above 4
 */

 uInt last_lit; /* running index in l_buf */

 ushf *d_buf;
 /* Buffer for distances. To simplify the code, d_buf and l_buf have
 * the same number of elements. To use different lengths, an extra flag
 * array would be necessary.
 */

 ulg opt_len; /* bit length of current block with optimal trees */
 ulg static_len; /* bit length of current block with static trees */
 uInt matches; /* number of string matches in current block */
 uInt insert; /* bytes at end of window left to insert */

#ifdef DEBUG
 ulg compressed_len; /* total bit length of compressed file mod 2^32 */
 ulg bits_sent; /* bit length of compressed data sent mod 2^32 */
#endif

 ush bi_buf;
 /* Output buffer. bits are inserted starting at the bottom (least
 * significant bits).
 */
 int bi_valid;
 /* Number of valid bits in bi_buf. All bits above the last valid bit
 * are always zero.
 */

 ulg high_water;
 /* High water mark offset in window for initialized bytes -- bytes above
 * this are set to zero in order to avoid memory check warnings when
 * longest match routines access bytes past the input. This is then
 * updated to the new high water mark.
 */

} FAR deflate_state;

/* Output a byte on the stream.
 * IN assertion: there is enough room in pending_buf.
 */
#define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}


#define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
/* Minimum amount of lookahead, except at the end of the input file.
 * See deflate.c for comments about the MIN_MATCH+1.
 */

#define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD)
/* In order to simplify the code, particularly on 16 bit machines, match
 * distances are limited to MAX_DIST instead of WSIZE.
 */

#define WIN_INIT MAX_MATCH
/* Number of bytes after end of data in window to initialize in order to avoid
 memory checker errors from longest match routines */

 /* in trees.c */
void ZLIB_INTERNAL _tr_init OF((deflate_state *s));
int ZLIB_INTERNAL _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
void ZLIB_INTERNAL _tr_flush_block OF((deflate_state *s, charf *buf,
 ulg stored_len, int last));
void ZLIB_INTERNAL _tr_flush_bits OF((deflate_state *s));
void ZLIB_INTERNAL _tr_align OF((deflate_state *s));
void ZLIB_INTERNAL _tr_stored_block OF((deflate_state *s, charf *buf,
 ulg stored_len, int last));

#define d_code(dist) \
 ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
/* Mapping from a distance to a distance code. dist is the distance - 1 and
 * must not have side effects. _dist_code[256] and _dist_code[257] are never
 * used.
 */

#ifndef DEBUG
/* Inline versions of _tr_tally for speed: */

#if defined(GEN_TREES_H) || !defined(STDC)
 extern uch ZLIB_INTERNAL _length_code[];
 extern uch ZLIB_INTERNAL _dist_code[];
#else
 extern const uch ZLIB_INTERNAL _length_code[];
 extern const uch ZLIB_INTERNAL _dist_code[];
#endif

# define _tr_tally_lit(s, c, flush) \
 { uch cc = (c); \
 s->d_buf[s->last_lit] = 0; \
 s->l_buf[s->last_lit++] = cc; \
 s->dyn_ltree[cc].Freq++; \
 flush = (s->last_lit == s->lit_bufsize-1); \
 }
# define _tr_tally_dist(s, distance, length, flush) \
 { uch len = (length); \
 ush dist = (distance); \
 s->d_buf[s->last_lit] = dist; \
 s->l_buf[s->last_lit++] = len; \
 dist--; \
 s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
 s->dyn_dtree[d_code(dist)].Freq++; \
 flush = (s->last_lit == s->lit_bufsize-1); \
 }
#else
# define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
# define _tr_tally_dist(s, distance, length, flush) \
 flush = _tr_tally(s, distance, length)
#endif

#endif /* DEFLATE_H */