/* deflate.c -- compress data using the deflation algorithm

 * Copyright (C) 1995-2005 Jean-loup Gailly.

 * For conditions of distribution and use, see copyright notice in zlib.h

 */

/*

 *  ALGORITHM

 *

 *      The "deflation" process depends on being able to identify portions

 *      of the input text which are identical to earlier input (within a

 *      sliding window trailing behind the input currently being processed).

 *

 *      The most straightforward technique turns out to be the fastest for

 *      most input files: try all possible matches and select the longest.

 *      The key feature of this algorithm is that insertions into the string

 *      dictionary are very simple and thus fast, and deletions are avoided

 *      completely. Insertions are performed at each input character, whereas

 *      string matches are performed only when the previous match ends. So it

 *      is preferable to spend more time in matches to allow very fast string

 *      insertions and avoid deletions. The matching algorithm for small

 *      strings is inspired from that of Rabin & Karp. A brute force approach

 *      is used to find longer strings when a small match has been found.

 *      A similar algorithm is used in comic (by Jan-Mark Wams) and freeze

 *      (by Leonid Broukhis).

 *         A previous version of this file used a more sophisticated algorithm

 *      (by Fiala and Greene) which is guaranteed to run in linear amortized

 *      time, but has a larger average cost, uses more memory and is patented.

 *      However the F&G algorithm may be faster for some highly redundant

 *      files if the parameter max_chain_length (described below) is too large.

 *

 *  ACKNOWLEDGEMENTS

 *

 *      The idea of lazy evaluation of matches is due to Jan-Mark Wams, and

 *      I found it in 'freeze' written by Leonid Broukhis.

 *      Thanks to many people for bug reports and testing.

 *

 *  REFERENCES

 *

 *      Deutsch, L.P.,"DEFLATE Compressed Data Format Specification".

 *      Available in http://www.ietf.org/rfc/rfc1951.txt

 *

 *      A description of the Rabin and Karp algorithm is given in the book

 *         "Algorithms" by R. Sedgewick, Addison-Wesley, p252.

 *

 *      Fiala,E.R., and Greene,D.H.

 *         Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595

 *

 */

/* @(#) $Id: deflate.c,v 3.6 2005/08/04 19:14:14 tor%cs.brown.edu Exp $ */

#include "deflate.h"

const char deflate_copyright[] =

   " deflate 1.2.3 Copyright 1995-2005 Jean-loup Gailly ";

/*

  If you use the zlib library in a product, an acknowledgment is welcome

  in the documentation of your product. If for some reason you cannot

  include such an acknowledgment, I would appreciate that you keep this

  copyright string in the executable of your product.

 */

/* ===========================================================================

 *  Function prototypes.

 */

typedef enum {

    need_more,      /* block not completed, need more input or more output */

    block_done,     /* block flush performed */

    finish_started, /* finish started, need only more output at next deflate */

    finish_done     /* finish done, accept no more input or output */

} block_state;

typedef block_state (*compress_func) OF((deflate_state *s, int flush));

/* Compression function. Returns the block state after the call. */

local void fill_window    OF((deflate_state *s));

local block_state deflate_stored OF((deflate_state *s, int flush));

local block_state deflate_fast   OF((deflate_state *s, int flush));

#ifndef FASTEST

local block_state deflate_slow   OF((deflate_state *s, int flush));

#endif

local void lm_init        OF((deflate_state *s));

local void putShortMSB    OF((deflate_state *s, uInt b));

local void flush_pending  OF((z_streamp strm));

local int read_buf        OF((z_streamp strm, Bytef *buf, unsigned size));

#ifndef FASTEST

#ifdef ASMV

      void match_init OF((void)); /* asm code initialization */

      uInt longest_match  OF((deflate_state *s, IPos cur_match));

#else

local uInt longest_match  OF((deflate_state *s, IPos cur_match));

#endif

#endif

local uInt longest_match_fast OF((deflate_state *s, IPos cur_match));

#ifdef DEBUG

local  void check_match OF((deflate_state *s, IPos start, IPos match,

                            int length));

#endif

/* ===========================================================================

 * Local data

 */

#define NIL 0

/* Tail of hash chains */

#ifndef TOO_FAR

#  define TOO_FAR 4096

#endif

/* Matches of length 3 are discarded if their distance exceeds TOO_FAR */

#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.

 */

/* Values for max_lazy_match, good_match and max_chain_length, depending on

 * the desired pack level (0..9). The values given below have been tuned to

 * exclude worst case performance for pathological files. Better values may be

 * found for specific files.

 */

typedef struct config_s {

   ush good_length; /* reduce lazy search above this match length */

   ush max_lazy;    /* do not perform lazy search above this match length */

   ush nice_length; /* quit search above this match length */

   ush max_chain;

   compress_func func;

} config;

#ifdef FASTEST

local const config configuration_table[2] = {

/*      good lazy nice chain */

/* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */

/* 1 */ {4,    4,  8,    4, deflate_fast}}; /* max speed, no lazy matches */

#else

local const config configuration_table[10] = {

/*      good lazy nice chain */

/* 0 */ {0,    0,  0,    0, deflate_stored},  /* store only */

/* 1 */ {4,    4,  8,    4, deflate_fast}, /* max speed, no lazy matches */

/* 2 */ {4,    5, 16,    8, deflate_fast},

/* 3 */ {4,    6, 32,   32, deflate_fast},

/* 4 */ {4,    4, 16,   16, deflate_slow},  /* lazy matches */

/* 5 */ {8,   16, 32,   32, deflate_slow},

/* 6 */ {8,   16, 128, 128, deflate_slow},

/* 7 */ {8,   32, 128, 256, deflate_slow},

/* 8 */ {32, 128, 258, 1024, deflate_slow},

/* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* max compression */

#endif

/* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4

 * For deflate_fast() (levels <= 3) good is ignored and lazy has a different

 * meaning.

 */

#define EQUAL 0

/* result of memcmp for equal strings */

#ifndef NO_DUMMY_DECL

struct static_tree_desc_s {int dummy;}; /* for buggy compilers */

#endif

/* ===========================================================================

 * Update a hash value with the given input byte

 * IN  assertion: all calls to to UPDATE_HASH are made with consecutive

 *    input characters, so that a running hash key can be computed from the

 *    previous key instead of complete recalculation each time.

 */

#define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)

/* ===========================================================================

 * Insert string str in the dictionary and set match_head to the previous head

 * of the hash chain (the most recent string with same hash key). Return

 * the previous length of the hash chain.

 * If this file is compiled with -DFASTEST, the compression level is forced

 * to 1, and no hash chains are maintained.

 * IN  assertion: all calls to to INSERT_STRING are made with consecutive

 *    input characters and the first MIN_MATCH bytes of str are valid

 *    (except for the last MIN_MATCH-1 bytes of the input file).

 */

#ifdef FASTEST

#define INSERT_STRING(s, str, match_head) \

   (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \

    match_head = s->head[s->ins_h], \

    s->head[s->ins_h] = (Pos)(str))

#else

#define INSERT_STRING(s, str, match_head) \

   (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \

    match_head = s->prev[(str) & s->w_mask] = s->head[s->ins_h], \

    s->head[s->ins_h] = (Pos)(str))

#endif

/* ===========================================================================

 * Initialize the hash table (avoiding 64K overflow for 16 bit systems).

 * prev[] will be initialized on the fly.

 */

#define CLEAR_HASH(s) \

    s->head[s->hash_size-1] = NIL; \

    zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));

/* ========================================================================= */

int ZEXPORT deflateInit_(strm, level, version, stream_size)

    z_streamp strm;

    int level;

    const char *version;

    int stream_size;

{

    return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,

                         Z_DEFAULT_STRATEGY, version, stream_size);

    /* To do: ignore strm->next_in if we use it as window */

}

/* ========================================================================= */

int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,

                  version, stream_size)

    z_streamp strm;

    int  level;

    int  method;

    int  windowBits;

    int  memLevel;

    int  strategy;

    const char *version;

    int stream_size;

{

    deflate_state *s;

    int wrap = 1;

    static const char my_version[] = ZLIB_VERSION;

    ushf *overlay;

    /* We overlay pending_buf and d_buf+l_buf. This works since the average

     * output size for (length,distance) codes is <= 24 bits.

     */

    if (version == Z_NULL || version[0] != my_version[0] ||

        stream_size != sizeof(z_stream)) {

        return Z_VERSION_ERROR;

    }

    if (strm == Z_NULL) return Z_STREAM_ERROR;

    strm->msg = Z_NULL;

    if (strm->zalloc == (alloc_func)0) {

        strm->zalloc = zcalloc;

        strm->opaque = (voidpf)0;

    }

    if (strm->zfree == (free_func)0) strm->zfree = zcfree;

#ifdef FASTEST

    if (level != 0) level = 1;

#else

    if (level == Z_DEFAULT_COMPRESSION) level = 6;

#endif

    if (windowBits < 0) { /* suppress zlib wrapper */

        wrap = 0;

        windowBits = -windowBits;

    }

#ifdef GZIP

    else if (windowBits > 15) {

        wrap = 2;       /* write gzip wrapper instead */

        windowBits -= 16;

    }

#endif

    if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||

        windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||

        strategy < 0 || strategy > Z_FIXED) {

        return Z_STREAM_ERROR;

    }

    if (windowBits == 8) windowBits = 9;  /* until 256-byte window bug fixed */

    s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));

    if (s == Z_NULL) return Z_MEM_ERROR;

    strm->state = (struct internal_state FAR *)s;

    s->strm = strm;

    s->wrap = wrap;

    s->gzhead = Z_NULL;

    s->w_bits = windowBits;

    s->w_size = 1 << s->w_bits;

    s->w_mask = s->w_size - 1;

    s->hash_bits = memLevel + 7;

    s->hash_size = 1 << s->hash_bits;

    s->hash_mask = s->hash_size - 1;

    s->hash_shift =  ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);

    s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));

    s->prev   = (Posf *)  ZALLOC(strm, s->w_size, sizeof(Pos));

    s->head   = (Posf *)  ZALLOC(strm, s->hash_size, sizeof(Pos));

    s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */

    overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);

    s->pending_buf = (uchf *) overlay;

    s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);

    if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||

        s->pending_buf == Z_NULL) {

        s->status = FINISH_STATE;

        strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);

        deflateEnd (strm);

        return Z_MEM_ERROR;

    }

    s->d_buf = overlay + s->lit_bufsize/sizeof(ush);

    s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;

    s->level = level;

    s->strategy = strategy;

    s->method = (Byte)method;

    return deflateReset(strm);

}

/* ========================================================================= */

int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)

    z_streamp strm;

    const Bytef *dictionary;

    uInt  dictLength;

{

    deflate_state *s;

    uInt length = dictLength;

    uInt n;

    IPos hash_head = 0;

    if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL ||

        strm->state->wrap == 2 ||

        (strm->state->wrap == 1 && strm->state->status != INIT_STATE))

        return Z_STREAM_ERROR;

    s = strm->state;

    if (s->wrap)

        strm->adler = adler32(strm->adler, dictionary, dictLength);

    if (length < MIN_MATCH) return Z_OK;

    if (length > MAX_DIST(s)) {

        length = MAX_DIST(s);

        dictionary += dictLength - length; /* use the tail of the dictionary */

    }

    zmemcpy(s->window, dictionary, length);

    s->strstart = length;

    s->block_start = (long)length;

    /* Insert all strings in the hash table (except for the last two bytes).

     * s->lookahead stays null, so s->ins_h will be recomputed at the next

     * call of fill_window.

     */

    s->ins_h = s->window[0];

    UPDATE_HASH(s, s->ins_h, s->window[1]);

    for (n = 0; n <= length - MIN_MATCH; n++) {

        INSERT_STRING(s, n, hash_head);

    }

    if (hash_head) hash_head = 0;  /* to make compiler happy */

    return Z_OK;

}

/* ========================================================================= */

int ZEXPORT deflateReset (strm)

    z_streamp strm;

{

    deflate_state *s;

    if (strm == Z_NULL || strm->state == Z_NULL ||

        strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {

        return Z_STREAM_ERROR;

    }

    strm->total_in = strm->total_out = 0;

    strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */

    strm->data_type = Z_UNKNOWN;

    s = (deflate_state *)strm->state;

    s->pending = 0;

    s->pending_out = s->pending_buf;

    if (s->wrap < 0) {

        s->wrap = -s->wrap; /* was made negative by deflate(..., Z_FINISH); */

    }

    s->status = s->wrap ? INIT_STATE : BUSY_STATE;

    strm->adler =

#ifdef GZIP

        s->wrap == 2 ? crc32(0L, Z_NULL, 0) :

#endif

        adler32(0L, Z_NULL, 0);

    s->last_flush = Z_NO_FLUSH;

    _tr_init(s);

    lm_init(s);

    return Z_OK;

}

/* ========================================================================= */

int ZEXPORT deflateSetHeader (strm, head)

    z_streamp strm;

    gz_headerp head;

{

    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;

    if (strm->state->wrap != 2) return Z_STREAM_ERROR;

    strm->state->gzhead = head;

    return Z_OK;

}

/* ========================================================================= */

int ZEXPORT deflatePrime (strm, bits, value)

    z_streamp strm;

    int bits;

    int value;

{

    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;

    strm->state->bi_valid = bits;

    strm->state->bi_buf = (ush)(value & ((1 << bits) - 1));

    return Z_OK;

}

/* ========================================================================= */

int ZEXPORT deflateParams(strm, level, strategy)

    z_streamp strm;

    int level;

    int strategy;

{

    deflate_state *s;

    compress_func func;

    int err = Z_OK;

    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;

    s = strm->state;

#ifdef FASTEST

    if (level != 0) level = 1;

#else

    if (level == Z_DEFAULT_COMPRESSION) level = 6;

#endif

    if (level < 0 || level > 9 || strategy < 0 || strategy > Z_FIXED) {

        return Z_STREAM_ERROR;

    }

    func = configuration_table[s->level].func;

    if (func != configuration_table[level].func && strm->total_in != 0) {

        /* Flush the last buffer: */

        err = deflate(strm, Z_PARTIAL_FLUSH);

    }

    if (s->level != level) {

        s->level = level;

        s->max_lazy_match   = configuration_table[level].max_lazy;

        s->good_match       = configuration_table[level].good_length;

        s->nice_match       = configuration_table[level].nice_length;

        s->max_chain_length = configuration_table[level].max_chain;

    }

    s->strategy = strategy;

    return err;

}

/* ========================================================================= */

int ZEXPORT deflateTune(strm, good_length, max_lazy, nice_length, max_chain)

    z_streamp strm;

    int good_length;

    int max_lazy;

    int nice_length;

    int max_chain;

{

    deflate_state *s;

    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;

    s = strm->state;

    s->good_match = good_length;

    s->max_lazy_match = max_lazy;

    s->nice_match = nice_length;

    s->max_chain_length = max_chain;

    return Z_OK;

}

/* =========================================================================

 * For the default windowBits of 15 and memLevel of 8, this function returns

 * a close to exact, as well as small, upper bound on the compressed size.

 * They are coded as constants here for a reason--if the #define's are

 * changed, then this function needs to be changed as well.  The return

 * value for 15 and 8 only works for those exact settings.

 *

 * For any setting other than those defaults for windowBits and memLevel,

 * the value returned is a conservative worst case for the maximum expansion

 * resulting from using fixed blocks instead of stored blocks, which deflate

 * can emit on compressed data for some combinations of the parameters.

 *

 * This function could be more sophisticated to provide closer upper bounds

 * for every combination of windowBits and memLevel, as well as wrap.

 * But even the conservative upper bound of about 14% expansion does not

 * seem onerous for output buffer allocation.

 */

uLong ZEXPORT deflateBound(strm, sourceLen)

    z_streamp strm;

    uLong sourceLen;

{

    deflate_state *s;

    uLong destLen;

    /* conservative upper bound */

    destLen = sourceLen +

              ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 11;

    /* if can't get parameters, return conservative bound */

    if (strm == Z_NULL || strm->state == Z_NULL)

        return destLen;

    /* if not default parameters, return conservative bound */

    s = strm->state;

    if (s->w_bits != 15 || s->hash_bits != 8 + 7)

        return destLen;

    /* default settings: return tight bound for that case */

    return compressBound(sourceLen);

}

/* =========================================================================

 * Put a short in the pending buffer. The 16-bit value is put in MSB order.

 * IN assertion: the stream state is correct and there is enough room in

 * pending_buf.

 */

local void putShortMSB (s, b)

    deflate_state *s;

    uInt b;

{

    put_byte(s, (Byte)(b >> 8));

    put_byte(s, (Byte)(b & 0xff));

}

/* =========================================================================

 * Flush as much pending output as possible. All deflate() output goes

 * through this function so some applications may wish to modify it