ref: c4ecd0fee0f0cef485a223d6e638a56bafd5bbda
dir: /sys/src/cmd/gs/zlib/deflate.h/
/* deflate.h -- internal compression state
* Copyright (C) 1995-2002 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: deflate.h,v 1.1.1.1 2005/04/24 21:39:40 giles Exp $ */
#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 INIT_STATE 42
#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 */
int pending; /* nb of bytes in the pending buffer */
int wrap; /* bit 0 true for zlib, bit 1 true for gzip */
Byte method; /* STORED (for zip only) or 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 supress 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 */
int last_eob_len; /* bit length of EOB code for last block */
#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.
*/
} 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.
*/
/* in trees.c */
void _tr_init OF((deflate_state *s));
int _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
void _tr_flush_block OF((deflate_state *s, charf *buf, ulg stored_len,
int eof));
void _tr_align OF((deflate_state *s));
void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len,
int eof));
#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 _length_code[];
extern uch _dist_code[];
#else
extern const uch _length_code[];
extern const uch _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 */