deflate.h

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file     |
   | See: http://www.mrpt.org/Authors - All rights reserved.                |
   | Released under BSD License. See details in http://www.mrpt.org/License |
   +------------------------------------------------------------------------+ */

/* 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 35458 2005-09-10 21:15:17Z MW $ */

#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 */