| /* deflate.h -- internal compression state |
| * Copyright (C) 1995 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 1.3 1995/04/14 12:39:45 jloup Exp $ */ |
| |
| #include "zutil.h" |
| |
| /* =========================================================================== |
| * Internal compression state. |
| */ |
| |
| /* Data type */ |
| #define BINARY 0 |
| #define ASCII 1 |
| #define UNKNOWN 2 |
| |
| #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; |
| } 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 */ |
| } tree_desc; |
| |
| typedef ush Pos; |
| 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_stream *strm; /* pointer back to this zlib stream */ |
| int status; /* as the name implies */ |
| Byte *pending_buf; /* output still pending */ |
| Byte *pending_out; /* next pending byte to output to the stream */ |
| int pending; /* nb of bytes in the pending buffer */ |
| uLong adler; /* adler32 of uncompressed data */ |
| int noheader; /* suppress zlib header and adler32 */ |
| Byte data_type; /* UNKNOWN, BINARY or ASCII */ |
| Byte method; /* STORED (for zip only) or DEFLATED */ |
| |
| /* 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 */ |
| |
| Byte *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. |
| */ |
| |
| Pos *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. |
| */ |
| |
| Pos *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: */ |
| |
| ct_data dyn_ltree[HEAP_SIZE]; /* literal and length tree */ |
| ct_data dyn_dtree[2*D_CODES+1]; /* distance tree */ |
| ct_data bl_tree[2*BL_CODES+1]; /* Huffman tree for the bit lengths */ |
| |
| tree_desc l_desc; /* descriptor for literal tree */ |
| tree_desc d_desc; /* descriptor for distance tree */ |
| tree_desc bl_desc; /* descriptor 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 |
| */ |
| |
| uch *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 */ |
| |
| ush *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 */ |
| ulg compressed_len; /* total bit length of compressed file */ |
| uInt matches; /* number of string matches in current block */ |
| |
| #ifdef DEBUG |
| ulg bits_sent; /* bit length of the compressed data */ |
| #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. |
| */ |
| |
| } 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 ct_init __P((deflate_state *s)); |
| int ct_tally __P((deflate_state *s, int dist, int lc)); |
| ulg ct_flush_block __P((deflate_state *s, char *buf, ulg stored_len, int eof)); |
