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

 * Copyright (C) 1995-2002 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 ftp://ds.internic.net/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 1.1 2003-03-24 11:13:44 pj Exp $ */

#include "deflate.h"

const char deflate_copyright[] =

   " deflate 1.1.4 Copyright 1995-2002 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));

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

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));

#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

#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;

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}, /* maximum 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}}; /* maximum compression */

/* 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 */

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

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

 * 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)]), \

    s->prev[(str) & s->w_mask] = match_head = 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 noheader = 0;

    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 == Z_NULL) {

        strm->zalloc = zcalloc;

        strm->opaque = (voidpf)0;

    }

    if (strm->zfree == Z_NULL) strm->zfree = zcfree;

    if (level == Z_DEFAULT_COMPRESSION) level = 6;

#ifdef FASTEST

    level = 1;

#endif

    if (windowBits < 0) { /* undocumented feature: suppress zlib header */

        noheader = 1;

        windowBits = -windowBits;

    }

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

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

        strategy < 0 || strategy > Z_HUFFMAN_ONLY) {

        return Z_STREAM_ERROR;

    }

    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->noheader = noheader;

    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) {

        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->status != INIT_STATE) return Z_STREAM_ERROR;

    s = strm->state;

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

    if (length < MIN_MATCH) return Z_OK;

    if (length > MAX_DIST(s)) {

        length = MAX_DIST(s);

#ifndef USE_DICT_HEAD

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

#endif

    }

    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 == Z_NULL || strm->zfree == Z_NULL) 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->noheader < 0) {

        s->noheader = 0; /* was set to -1 by deflate(..., Z_FINISH); */

    }

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

    strm->adler = 1;

    s->last_flush = Z_NO_FLUSH;

    _tr_init(s);

    lm_init(s);

    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;

    if (level == Z_DEFAULT_COMPRESSION) {

        level = 6;

    }

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

        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;

}

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

 * 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

 * to avoid allocating a large strm->next_out buffer and copying into it.

 * (See also read_buf()).

 */

local void flush_pending(strm)

    z_streamp strm;

{

    unsigned len = strm->state->pending;

    if (len > strm->avail_out) len = strm->avail_out;

    if (len == 0) return;

    zmemcpy(strm->next_out, strm->state->pending_out, len);

    strm->next_out  += len;

    strm->state->pending_out  += len;

    strm->total_out += len;

    strm->avail_out  -= len;

    strm->state->pending -= len;

    if (strm->state->pending == 0) {

        strm->state->pending_out = strm->state->pending_buf;

    }

}

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

int ZEXPORT deflate (strm, flush)

    z_streamp strm;

    int flush;

{

    int old_flush; /* value of flush param for previous deflate call */

    deflate_state *s;

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

        flush > Z_FINISH || flush < 0) {

        return Z_STREAM_ERROR;

    }

    s = strm->state;

    if (strm->next_out == Z_NULL ||

        (strm->next_in == Z_NULL && strm->avail_in != 0) ||

        (s->status == FINISH_STATE && flush != Z_FINISH)) {

        ERR_RETURN(strm, Z_STREAM_ERROR);

    }

    if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);

    s->strm = strm; /* just in case */

    old_flush = s->last_flush;

    s->last_flush = flush;

    /* Write the zlib header */

    if (s->status == INIT_STATE) {

        uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;

        uInt level_flags = (s->level-1) >> 1;

        if (level_flags > 3) level_flags = 3;

        header |= (level_flags << 6);

        if (s->strstart != 0) header |= PRESET_DICT;

        header += 31 - (header % 31);

        s->status = BUSY_STATE;

        putShortMSB(s, header);

        /* Save the adler32 of the preset dictionary: */

        if (s->strstart != 0) {

            putShortMSB(s, (uInt)(strm->adler >> 16));

            putShortMSB(s, (uInt)(strm->adler & 0xffff));

        }

        strm->adler = 1L;

    }

    /* Flush as much pending output as possible */

    if (s->pending != 0) {

        flush_pending(strm);

        if (strm->avail_out == 0) {

            /* Since avail_out is 0, deflate will be called again with

             * more output space, but possibly with both pending and

             * avail_in equal to zero. There won't be anything to do,

             * but this is not an error situation so make sure we

             * return OK instead of BUF_ERROR at next call of deflate:

             */

            s->last_flush = -1;

            return Z_OK;

        }

    /* Make sure there is something to do and avoid duplicate consecutive

     * flushes. For repeated and useless calls with Z_FINISH, we keep

     * returning Z_STREAM_END instead of Z_BUFF_ERROR.

     */

    } else if (strm->avail_in == 0 && flush <= old_flush &&

               flush != Z_FINISH) {

        ERR_RETURN(strm, Z_BUF_ERROR);

    }

    /* User must not provide more input after the first FINISH: */

    if (s->status == FINISH_STATE && strm->avail_in != 0) {

        ERR_RETURN(strm, Z_BUF_ERROR);

    }

    /* Start a new block or continue the current one.

     */

    if (strm->avail_in != 0 || s->lookahead != 0 ||

        (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {

        block_state bstate;

        bstate = (*(configuration_table[s->level].func))(s, flush);

        if (bstate == finish_started || bstate == finish_done) {

            s->status = FINISH_STATE;

        }

        if (bstate == need_more || bstate == finish_started) {

            if (strm->avail_out == 0) {

                s->last_flush = -1; /* avoid BUF_ERROR next call, see above */

            }

            return Z_OK;

            /* If flush != Z_NO_FLUSH && avail_out == 0, the next call

             * of deflate should use the same flush parameter to make sure

             * that the flush is complete. So we don't have to output an

             * empty block here, this will be done at next call. This also

             * ensures that for a very small output buffer, we emit at most

             * one empty block.

             */

        }

        if (bstate == block_done) {

            if (flush == Z_PARTIAL_FLUSH) {

                _tr_align(s);

            } else { /* FULL_FLUSH or SYNC_FLUSH */

                _tr_stored_block(s, (char*)0, 0L, 0);

                /* For a full flush, this empty block will be recognized

                 * as a special marker by inflate_sync().

                 */

                if (flush == Z_FULL_FLUSH) {

                    CLEAR_HASH(s);             /* forget history */

                }

            }

            flush_pending(strm);

            if (strm->avail_out == 0) {

              s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */

              return Z_OK;

            }

        }

    }

    Assert(strm->avail_out > 0, "bug2");

    if (flush != Z_FINISH) return Z_OK;

    if (s->noheader) return Z_STREAM_END;

    /* Write the zlib trailer (adler32) */

    putShortMSB(s, (uInt)(strm->adler >> 16));

    putShortMSB(s, (uInt)(strm->adler & 0xffff));

    flush_pending(strm);

    /* If avail_out is zero, the application will call deflate again

     * to flush the rest.

     */

    s->noheader = -1; /* write the trailer only once! */

    return s->pending != 0 ? Z_OK : Z_STREAM_END;

}

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

int ZEXPORT deflateEnd (strm)

    z_streamp strm;

{

    int status;

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

    status = strm->state->status;

    if (status != INIT_STATE && status != BUSY_STATE &&

        status != FINISH_STATE) {

      return Z_STREAM_ERROR;

    }

    /* Deallocate in reverse order of allocations: */

    TRY_FREE(strm, strm->state->pending_buf);

    TRY_FREE(strm, strm->state->head);

    TRY_FREE(strm, strm->state->prev);

    TRY_FREE(strm, strm->state->window);

    ZFREE(strm, strm->state);

    strm->state = Z_NULL;

    return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;

}

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

 * Copy the source state to the destination state.

 * To simplify the source, this is not supported for 16-bit MSDOS (which

 * doesn't have enough memory anyway to duplicate compression states).

 */

int ZEXPORT deflateCopy (dest, source)

    z_streamp dest;

    z_streamp source;

{

#ifdef MAXSEG_64K

    return Z_STREAM_ERROR;

#else

    deflate_state *ds;

    deflate_state *ss;

    ushf *overlay;

    if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {

        return Z_STREAM_ERROR;

    }

    ss = source->state;

    *dest = *source;

    ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));

    if (ds == Z_NULL) return Z_MEM_ERROR;

    dest->state = (struct internal_state FAR *) ds;

    *ds = *ss;

    ds->strm = dest;

    ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));

    ds->prev   = (Posf *)  ZALLOC(dest, ds->w_size, sizeof(Pos));

    ds->head   = (Posf *)  ZALLOC(dest, ds->hash_size, sizeof(Pos));

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

    ds->pending_buf = (uchf *) overlay;

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

        ds->pending_buf == Z_NULL) {

        deflateEnd (dest);

        return Z_MEM_ERROR;

    }

    /* following zmemcpy do not work for 16-bit MSDOS */

    zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));

    zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));

    zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));

    zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);

    ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);

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

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

    ds->l_desc.dyn_tree = ds->dyn_ltree;

    ds->d_desc.dyn_tree = ds->dyn_dtree;

    ds->bl_desc.dyn_tree = ds->bl_tree;

    return Z_OK;

#endif

}

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

 * Read a new buffer from the current input stream, update the adler32

 * and total number of bytes read.  All deflate() input goes through

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

 * allocating a large strm->next_in buffer and copying from it.

 * (See also flush_pending()).

 */

local int read_buf(strm, buf, size)

    z_streamp strm;

    Bytef *buf;

    unsigned size;

{

    unsigned len = strm->avail_in;

    if (len > size) len = size;

    if (len == 0) return 0;

    strm->avail_in  -= len;

    if (!strm->state->noheader) {

        strm->adler = adler32(strm->adler, strm->next_in, len);

    }

    zmemcpy(buf, strm->next_in, len);

    strm->next_in  += len;

    strm->total_in += len;

    return (int)len;

}

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

 * Initialize the "longest match" routines for a new zlib stream

 */

local void lm_init (s)

    deflate_state *s;

{

    s->window_size = (ulg)2L*s->w_size;

    CLEAR_HASH(s);

    /* Set the default configuration parameters:

     */

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

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

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

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

    s->strstart = 0;

    s->block_start = 0L;

    s->lookahead = 0;

    s->match_length = s->prev_length = MIN_MATCH-1;

    s->match_available = 0;

    s->ins_h = 0;

#ifdef ASMV

    match_init(); /* initialize the asm code */

#endif

}

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

 * Set match_start to the longest match starting at the given string and

 * return its length. Matches shorter or equal to prev_length are discarded,

 * in which case the result is equal to prev_length and match_start is

 * garbage.

 * IN assertions: cur_match is the head of the hash chain for the current

 *   string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1

 * OUT assertion: the match length is not greater than s->lookahead.

 */

#ifndef ASMV

/* For 80x86 and 680x0, an optimized version will be provided in match.asm or

 * match.S. The code will be functionally equivalent.

 */

#ifndef FASTEST

local uInt longest_match(s, cur_match)

    deflate_state *s;

    IPos cur_match;                             /* current match */

{

    unsigned chain_length = s->max_chain_length;/* max hash chain length */

    register Bytef *scan = s->window + s->strstart; /* current string */

    register Bytef *match;                       /* matched string */

    register int len;                           /* length of current match */

    int best_len = s->prev_length;              /* best match length so far */

    int nice_match = s->nice_match;             /* stop if match long enough */

    IPos limit = s->strstart > (IPos)MAX_DIST(s) ?

        s->strstart - (IPos)MAX_DIST(s) : NIL;

    /* Stop when cur_match becomes <= limit. To simplify the code,

     * we prevent matches with the string of window index 0.

     */

    Posf *prev = s->prev;

    uInt wmask = s->w_mask;

#ifdef UNALIGNED_OK

    /* Compare two bytes at a time. Note: this is not always beneficial.

     * Try with and without -DUNALIGNED_OK to check.

     */

    register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;

    register ush scan_start = *(ushf*)scan;

    register ush scan_end   = *(ushf*)(scan+best_len-1);

#else

    register Bytef *strend = s->window + s->strstart + MAX_MATCH;

    register Byte scan_end1  = scan[best_len-1];

    register Byte scan_end   = scan[best_len];

#endif

    /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.

     * It is easy to get rid of this optimization if necessary.

     */

    Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");

    /* Do not waste too much time if we already have a good match: */

    if (s->prev_length >= s->good_match) {

        chain_length >>= 2;

    }

    /* Do not look for matches beyond the end of the input. This is necessary

     * to make deflate deterministic.

     */

    if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;

    Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");

    do {

        Assert(cur_match < s->strstart, "no future");

        match = s->window + cur_match;

        /* Skip to next match if the match length cannot increase

         * or if the match length is less than 2:

         */

#if (defined(UNALIGNED_OK) && MAX_MATCH == 258)

        /* This code assumes sizeof(unsigned short) == 2. Do not use

         * UNALIGNED_OK if your compiler uses a different size.

         */

        if (*(ushf*)(match+best_len-1) != scan_end ||