/* deflate.h -- internal compression state

 * Copyright (C) 1995-2016 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    /* zlib header -> BUSY_STATE */

#ifdef GZIP

#  define GZIP_STATE  57    /* gzip header -> BUSY_STATE | EXTRA_STATE */

#endif

#define EXTRA_STATE   69    /* gzip extra block -> NAME_STATE */

#define NAME_STATE    73    /* gzip file name -> COMMENT_STATE */

#define COMMENT_STATE 91    /* gzip comment -> HCRC_STATE */

#define HCRC_STATE   103    /* gzip header CRC -> BUSY_STATE */

#define BUSY_STATE   113    /* deflate -> FINISH_STATE */

#define FINISH_STATE 666    /* stream complete */

/* 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 */

    const 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 */

    ulg   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 */

    ulg   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 ZLIB_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++] = (Bytef)(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 ZLIB_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 = (uch)(length); \

    ush dist = (ush)(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 */