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Diffstat (limited to 'zlib/deflate.h')
| -rw-r--r-- | zlib/deflate.h | 331 |
1 files changed, 331 insertions, 0 deletions
diff --git a/zlib/deflate.h b/zlib/deflate.h new file mode 100644 index 0000000..05a5ab3 --- /dev/null +++ b/zlib/deflate.h @@ -0,0 +1,331 @@ +/* deflate.h -- internal compression state + * Copyright (C) 1995-2004 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 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; /* 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 */ |