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

  * Copyright (C) 1995-1998 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

  *

  */

 /* @(#) $Id$ */

 #include "deflate.h"

 const char deflate_copyright[] =

    " deflate 1.1.3 Copyright 1995-1998 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_(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_(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 < 8 || 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 (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 (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(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 (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(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 (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 (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 (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(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 (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(deflate_state *s, IPos cur_match)

 /* 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 ||

             *(ushf*)match != scan_start) continue;

         /* It is not necessary to compare scan[2] and match[2] since they are

          * always equal when the other bytes match, given that the hash keys

          * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at

          * strstart+3, +5, ... up to strstart+257. We check for insufficient

          * lookahead only every 4th comparison; the 128th check will be made

          * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is

          * necessary to put more guard bytes at the end of the window, or

          * to check more often for insufficient lookahead.

          */

         Assert(scan[2] == match[2], "scan[2]?");

         scan++, match++;

         do {

         } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&

                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&

                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&

                  *(ushf*)(scan+=2) == *(ushf*)(match+=2) &&

                  scan < strend);

         /* The funny "do {}" generates better code on most compilers */

         /* Here, scan <= window+strstart+257 */

         Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");

         if (*scan == *match) scan++;

         len = (MAX_MATCH - 1) - (int)(strend-scan);

         scan = strend - (MAX_MATCH-1);

 #else /* UNALIGNED_OK */

         if (match[best_len]   != scan_end  ||

             match[best_len-1] != scan_end1 ||

             *match            != *scan     ||

             *++match          != scan[1])      continue;

         /* The check at best_len-1 can be removed because it will be made

          * again later. (This heuristic is not always a win.)

          * It is not necessary to compare scan[2] and match[2] since they

          * are always equal when the other bytes match, given that

          * the hash keys are equal and that HASH_BITS >= 8.

          */

         scan += 2, match++;

         Assert(*scan == *match, "match[2]?");

         /* We check for insufficient lookahead only every 8th comparison;

          * the 256th check will be made at strstart+258.

          */

         do {

         } while (*++scan == *++match && *++scan == *++match &&

                  *++scan == *++match && *++scan == *++match &&

                  *++scan == *++match && *++scan == *++match &&

                  *++scan == *++match && *++scan == *++match &&

                  scan < strend);

         Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");

         len = MAX_MATCH - (int)(strend - scan);

         scan = strend - MAX_MATCH;

 #endif /* UNALIGNED_OK */

         if (len > best_len) {

             s->match_start = cur_match;

             best_len = len;

             if (len >= nice_match) break;

 #ifdef UNALIGNED_OK

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

 #else

             scan_end1  = scan[best_len-1];

             scan_end   = scan[best_len];

 #endif

         }

     } while ((cur_match = prev[cur_match & wmask]) > limit

              && --chain_length != 0);

     if ((uInt)best_len <= s->lookahead) return (uInt)best_len;

     return s->lookahead;

 }

 #else /* FASTEST */

 /* ---------------------------------------------------------------------------

  * Optimized version for level == 1 only

  */

 local uInt longest_match(deflate_state *s, IPos cur_match)

 /*  IPos cur_match      current match. */

 {

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

     register Bytef *match;                       /* matched string */

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

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

     /* 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");

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

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

     match = s->window + cur_match;

     /* Return failure if the match length is less than 2:

      */

     if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;

     /* The check at best_len-1 can be removed because it will be made

      * again later. (This heuristic is not always a win.)

      * It is not necessary to compare scan[2] and match[2] since they

      * are always equal when the other bytes match, given that

      * the hash keys are equal and that HASH_BITS >= 8.

      */

     scan += 2, match += 2;

     Assert(*scan == *match, "match[2]?");

     /* We check for insufficient lookahead only every 8th comparison;

      * the 256th check will be made at strstart+258.

      */

     do {

     } while (*++scan == *++match && *++scan == *++match &&

 	     *++scan == *++match && *++scan == *++match &&

 	     *++scan == *++match && *++scan == *++match &&

 	     *++scan == *++match && *++scan == *++match &&

 	     scan < strend);

     Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");

     len = MAX_MATCH - (int)(strend - scan);

     if (len < MIN_MATCH) return MIN_MATCH - 1;

     s->match_start = cur_match;

     return len <= s->lookahead ? len : s->lookahead;

 }

 #endif /* FASTEST */

 #endif /* ASMV */

 #ifdef DEBUG

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

  * Check that the match at match_start is indeed a match.

  */

 local void check_match(deflate_state *s, IPos start, IPos match, int length)

 {

     /* check that the match is indeed a match */

     if (zmemcmp(s->window + match,

                 s->window + start, length) != EQUAL) {

         fprintf(stderr, " start %u, match %u, length %d\n",

 		start, match, length);

         do {

 	    fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);

 	} while (--length != 0);

         z_error("invalid match");

     }

     if (z_verbose > 1) {

         fprintf(stderr,"\\[%d,%d]", start-match, length);

         do { putc(s->window[start++], stderr); } while (--length != 0);

     }

 }

 #else

 #  define check_match(s, start, match, length)

 #endif

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

  * Fill the window when the lookahead becomes insufficient.

  * Updates strstart and lookahead.

  *

  * IN assertion: lookahead < MIN_LOOKAHEAD

  * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD

  *    At least one byte has been read, or avail_in == 0; reads are

  *    performed for at least two bytes (required for the zip translate_eol

  *    option -- not supported here).

  */

 local void fill_window(deflate_state *s)

 {

     register unsigned n, m;

     register Posf *p;

     unsigned more;    /* Amount of free space at the end of the window. */

     uInt wsize = s->w_size;

     do {

         more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);

         /* Deal with !@#$% 64K limit: */

         if (more == 0 && s->strstart == 0 && s->lookahead == 0) {

             more = wsize;

         } else if (more == (unsigned)(-1)) {

             /* Very unlikely, but possible on 16 bit machine if strstart == 0

              * and lookahead == 1 (input done one byte at time)

              */

             more--;

         /* If the window is almost full and there is insufficient lookahead,

          * move the upper half to the lower one to make room in the upper half.

          */

         } else if (s->strstart >= wsize+MAX_DIST(s)) {

             zmemcpy(s->window, s->window+wsize, (unsigned)wsize);

             s->match_start -= wsize;

             s->strstart    -= wsize; /* we now have strstart >= MAX_DIST */

             s->block_start -= (long) wsize;

             /* Slide the hash table (could be avoided with 32 bit values

                at the expense of memory usage). We slide even when level == 0

                to keep the hash table consistent if we switch back to level > 0

                later. (Using level 0 permanently is not an optimal usage of

                zlib, so we don't care about this pathological case.)

              */

 	    n = s->hash_size;

 	    p = &s->head[n];

 	    do {

 		m = *--p;

 		*p = (Pos)(m >= wsize ? m-wsize : NIL);

 	    } while (--n);

 	    n = wsize;

 #ifndef FASTEST

 	    p = &s->prev[n];

 	    do {

 		m = *--p;

 		*p = (Pos)(m >= wsize ? m-wsize : NIL);

 		/* If n is not on any hash chain, prev[n] is garbage but

 		 * its value will never be used.

 		 */

 	    } while (--n);

 #endif

             more += wsize;

         }

         if (s->strm->avail_in == 0) return;

         /* If there was no sliding:

          *    strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&

          *    more == window_size - lookahead - strstart

          * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)

          * => more >= window_size - 2*WSIZE + 2

          * In the BIG_MEM or MMAP case (not yet supported),

          *   window_size == input_size + MIN_LOOKAHEAD  &&

          *   strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.

          * Otherwise, window_size == 2*WSIZE so more >= 2.

          * If there was sliding, more >= WSIZE. So in all cases, more >= 2.

          */

         Assert(more >= 2, "more < 2");

         n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);

         s->lookahead += n;

         /* Initialize the hash value now that we have some input: */

         if (s->lookahead >= MIN_MATCH) {

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

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

 #if MIN_MATCH != 3

             Call UPDATE_HASH() MIN_MATCH-3 more times

 #endif

         }

         /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,

          * but this is not important since only literal bytes will be emitted.

          */

     } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);

 }

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

  * Flush the current block, with given end-of-file flag.

  * IN assertion: strstart is set to the end of the current match.

  */

 #define FLUSH_BLOCK_ONLY(s, eof) { \

    _tr_flush_block(s, (s->block_start >= 0L ? \

                    (charf *)&s->window[(unsigned)s->block_start] : \

                    (charf *)Z_NULL), \

 		(ulg)((long)s->strstart - s->block_start), \

 		(eof)); \

    s->block_start = s->strstart; \

    flush_pending(s->strm); \

    Tracev((stderr,"[FLUSH]")); \

 }

 /* Same but force premature exit if necessary. */

 #define FLUSH_BLOCK(s, eof) { \

    FLUSH_BLOCK_ONLY(s, eof); \

    if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \

 }

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

  * Copy without compression as much as possible from the input stream, return

  * the current block state.

  * This function does not insert new strings in the dictionary since

  * uncompressible data is probably not useful. This function is used

  * only for the level=0 compression option.

  * NOTE: this function should be optimized to avoid extra copying from

  * window to pending_buf.

  */

 local block_state deflate_stored(deflate_state *s, int flush)

 {

     /* Stored blocks are limited to 0xffff bytes, pending_buf is limited

      * to pending_buf_size, and each stored block has a 5 byte header:

      */

     ulg max_block_size = 0xffff;

     ulg max_start;

     if (max_block_size > s->pending_buf_size - 5) {

         max_block_size = s->pending_buf_size - 5;

     }

     /* Copy as much as possible from input to output: */

     for (;;) {

         /* Fill the window as much as possible: */

         if (s->lookahead <= 1) {

             Assert(s->strstart < s->w_size+MAX_DIST(s) ||

 		   s->block_start >= (long)s->w_size, "slide too late");

             fill_window(s);

             if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;

             if (s->lookahead == 0) break; /* flush the current block */

         }

 	Assert(s->block_start >= 0L, "block gone");

 	s->strstart += s->lookahead;

 	s->lookahead = 0;

 	/* Emit a stored block if pending_buf will be full: */

  	max_start = s->block_start + max_block_size;

         if (s->strstart == 0 || (ulg)s->strstart >= max_start) {

 	    /* strstart == 0 is possible when wraparound on 16-bit machine */

 	    s->lookahead = (uInt)(s->strstart - max_start);

 	    s->strstart = (uInt)max_start;

             FLUSH_BLOCK(s, 0);

 	}

 	/* Flush if we may have to slide, otherwise block_start may become

          * negative and the data will be gone:

          */

         if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {

             FLUSH_BLOCK(s, 0);

 	}

     }

     FLUSH_BLOCK(s, flush == Z_FINISH);

     return flush == Z_FINISH ? finish_done : block_done;

 }

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

  * Compress as much as possible from the input stream, return the current

  * block state.

  * This function does not perform lazy evaluation of matches and inserts

  * new strings in the dictionary only for unmatched strings or for short

  * matches. It is used only for the fast compression options.

  */

 local block_state deflate_fast(deflate_state *s, int flush)

 {

     IPos hash_head = NIL; /* head of the hash chain */

     int bflush;           /* set if current block must be flushed */

     for (;;) {

         /* Make sure that we always have enough lookahead, except

          * at the end of the input file. We need MAX_MATCH bytes

          * for the next match, plus MIN_MATCH bytes to insert the

          * string following the next match.

          */

         if (s->lookahead < MIN_LOOKAHEAD) {

             fill_window(s);

             if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {

 	        return need_more;

 	    }

             if (s->lookahead == 0) break; /* flush the current block */

         }

         /* Insert the string window[strstart .. strstart+2] in the

          * dictionary, and set hash_head to the head of the hash chain:

          */

         if (s->lookahead >= MIN_MATCH) {

             INSERT_STRING(s, s->strstart, hash_head);

         }

         /* Find the longest match, discarding those <= prev_length.

          * At this point we have always match_length < MIN_MATCH

          */

         if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {

             /* To simplify the code, we prevent matches with the string

              * of window index 0 (in particular we have to avoid a match

              * of the string with itself at the start of the input file).

              */

             if (s->strategy != Z_HUFFMAN_ONLY) {

                 s->match_length = longest_match (s, hash_head);

             }

             /* longest_match() sets match_start */

         }

         if (s->match_length >= MIN_MATCH) {

             check_match(s, s->strstart, s->match_start, s->match_length);

             _tr_tally_dist(s, s->strstart - s->match_start,

                            s->match_length - MIN_MATCH, bflush);

             s->lookahead -= s->match_length;

             /* Insert new strings in the hash table only if the match length

              * is not too large. This saves time but degrades compression.

              */

 #ifndef FASTEST

             if (s->match_length <= s->max_insert_length &&

                 s->lookahead >= MIN_MATCH) {

                 s->match_length--; /* string at strstart already in hash table */

                 do {

                     s->strstart++;

                     INSERT_STRING(s, s->strstart, hash_head);

                     /* strstart never exceeds WSIZE-MAX_MATCH, so there are

                      * always MIN_MATCH bytes ahead.

                      */

                 } while (--s->match_length != 0);

                 s->strstart++; 

             } else

 #endif

 	    {

                 s->strstart += s->match_length;

                 s->match_length = 0;

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

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

 #if MIN_MATCH != 3

                 Call UPDATE_HASH() MIN_MATCH-3 more times

 #endif

                 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not

                  * matter since it will be recomputed at next deflate call.

                  */

             }

         } else {

             /* No match, output a literal byte */

             Tracevv((stderr,"%c", s->window[s->strstart]));

             _tr_tally_lit (s, s->window[s->strstart], bflush);

             s->lookahead--;

             s->strstart++; 

         }

         if (bflush) FLUSH_BLOCK(s, 0);

     }

     FLUSH_BLOCK(s, flush == Z_FINISH);

     return flush == Z_FINISH ? finish_done : block_done;

 }

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

  * Same as above, but achieves better compression. We use a lazy

  * evaluation for matches: a match is finally adopted only if there is

  * no better match at the next window position.

  */

 local block_state deflate_slow(deflate_state *s, int flush)

 {

     IPos hash_head = NIL;    /* head of hash chain */

     int bflush;              /* set if current block must be flushed */

     /* Process the input block. */

     for (;;) {

         /* Make sure that we always have enough lookahead, except

          * at the end of the input file. We need MAX_MATCH bytes

          * for the next match, plus MIN_MATCH bytes to insert the

          * string following the next match.

          */

         if (s->lookahead < MIN_LOOKAHEAD) {

             fill_window(s);

             if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {

 	        return need_more;

 	    }

             if (s->lookahead == 0) break; /* flush the current block */

         }

         /* Insert the string window[strstart .. strstart+2] in the

          * dictionary, and set hash_head to the head of the hash chain:

          */

         if (s->lookahead >= MIN_MATCH) {

             INSERT_STRING(s, s->strstart, hash_head);

         }

         /* Find the longest match, discarding those <= prev_length.

          */

         s->prev_length = s->match_length, s->prev_match = s->match_start;

         s->match_length = MIN_MATCH-1;

         if (hash_head != NIL && s->prev_length < s->max_lazy_match &&

             s->strstart - hash_head <= MAX_DIST(s)) {

             /* To simplify the code, we prevent matches with the string

              * of window index 0 (in particular we have to avoid a match

              * of the string with itself at the start of the input file).

              */

             if (s->strategy != Z_HUFFMAN_ONLY) {

                 s->match_length = longest_match (s, hash_head);

             }

             /* longest_match() sets match_start */

             if (s->match_length <= 5 && (s->strategy == Z_FILTERED ||

                  (s->match_length == MIN_MATCH &&

                   s->strstart - s->match_start > TOO_FAR))) {

                 /* If prev_match is also MIN_MATCH, match_start is garbage

                  * but we will ignore the current match anyway.

                  */

                 s->match_length = MIN_MATCH-1;

             }

         }

         /* If there was a match at the previous step and the current

          * match is not better, output the previous match:

          */

         if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {

             uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;

             /* Do not insert strings in hash table beyond this. */

             check_match(s, s->strstart-1, s->prev_match, s->prev_length);

             _tr_tally_dist(s, s->strstart -1 - s->prev_match,

 			   s->prev_length - MIN_MATCH, bflush);

             /* Insert in hash table all strings up to the end of the match.

              * strstart-1 and strstart are already inserted. If there is not

              * enough lookahead, the last two strings are not inserted in

              * the hash table.

              */

             s->lookahead -= s->prev_length-1;

             s->prev_length -= 2;

             do {

                 if (++s->strstart <= max_insert) {

                     INSERT_STRING(s, s->strstart, hash_head);

                 }

             } while (--s->prev_length != 0);

             s->match_available = 0;

             s->match_length = MIN_MATCH-1;

             s->strstart++;

             if (bflush) FLUSH_BLOCK(s, 0);

         } else if (s->match_available) {

             /* If there was no match at the previous position, output a

              * single literal. If there was a match but the current match

              * is longer, truncate the previous match to a single literal.

              */

             Tracevv((stderr,"%c", s->window[s->strstart-1]));

 	    _tr_tally_lit(s, s->window[s->strstart-1], bflush);

 	    if (bflush) {

                 FLUSH_BLOCK_ONLY(s, 0);

             }

             s->strstart++;

             s->lookahead--;

             if (s->strm->avail_out == 0) return need_more;

         } else {

             /* There is no previous match to compare with, wait for

              * the next step to decide.

              */

             s->match_available = 1;

             s->strstart++;

             s->lookahead--;

         }

     }

     Assert (flush != Z_NO_FLUSH, "no flush?");

     if (s->match_available) {

         Tracevv((stderr,"%c", s->window[s->strstart-1]));

         _tr_tally_lit(s, s->window[s->strstart-1], bflush);

         s->match_available = 0;

     }

     FLUSH_BLOCK(s, flush == Z_FINISH);

     return flush == Z_FINISH ? finish_done : block_done;

 }