FreeBSD/Linux Kernel Cross Reference
sys/libkern/zlib/deflate.c

     /*
      * Copyright (c) 2008 Apple Inc. All rights reserved.
      *
      * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
      * 
      * This file contains Original Code and/or Modifications of Original Code
      * as defined in and that are subject to the Apple Public Source License
      * Version 2.0 (the 'License'). You may not use this file except in
      * compliance with the License. The rights granted to you under the License
     * may not be used to create, or enable the creation or redistribution of,
     * unlawful or unlicensed copies of an Apple operating system, or to
     * circumvent, violate, or enable the circumvention or violation of, any
     * terms of an Apple operating system software license agreement.
     * 
     * Please obtain a copy of the License at
     * http://www.opensource.apple.com/apsl/ and read it before using this file.
     * 
     * The Original Code and all software distributed under the License are
     * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
     * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
     * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
     * Please see the License for the specific language governing rights and
     * limitations under the License.
     * 
     * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
     */
    /* 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
     *
     */
    
    /* @(#) $Id$ */
    
    #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;
   #ifndef NO_ZCFUNCS
       if (strm->zalloc == (alloc_func)0) {
           strm->zalloc = zcalloc;
           strm->opaque = (voidpf)0;
       }
       if (strm->zfree == (free_func)0) strm->zfree = zcfree;
   #endif /* NO_ZCFUNCS */
   
   #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 ? z_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
    * 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 header */
       if (s->status == INIT_STATE) {
   #ifdef GZIP
           if (s->wrap == 2) {
               strm->adler = z_crc32(0L, Z_NULL, 0);
               put_byte(s, 31);
               put_byte(s, 139);
               put_byte(s, 8);
               if (s->gzhead == NULL) {
                   put_byte(s, 0);
                   put_byte(s, 0);
                   put_byte(s, 0);
                   put_byte(s, 0);
                   put_byte(s, 0);
                   put_byte(s, s->level == 9 ? 2 :
                               (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
                                4 : 0));
                   put_byte(s, OS_CODE);
                   s->status = BUSY_STATE;
               }
               else {
                   put_byte(s, (s->gzhead->text ? 1 : 0) +
                               (s->gzhead->hcrc ? 2 : 0) +
                               (s->gzhead->extra == Z_NULL ? 0 : 4) +
                               (s->gzhead->name == Z_NULL ? 0 : 8) +
                               (s->gzhead->comment == Z_NULL ? 0 : 16)
                           );
                   put_byte(s, (Byte)(s->gzhead->time & 0xff));
                   put_byte(s, (Byte)((s->gzhead->time >> 8) & 0xff));
                   put_byte(s, (Byte)((s->gzhead->time >> 16) & 0xff));
                   put_byte(s, (Byte)((s->gzhead->time >> 24) & 0xff));
                   put_byte(s, s->level == 9 ? 2 :
                               (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2 ?
                                4 : 0));
                   put_byte(s, s->gzhead->os & 0xff);
                   if (s->gzhead->extra != NULL) {
                       put_byte(s, s->gzhead->extra_len & 0xff);
                       put_byte(s, (s->gzhead->extra_len >> 8) & 0xff);
                   }
                   if (s->gzhead->hcrc)
                       strm->adler = z_crc32(strm->adler, s->pending_buf,
                                           s->pending);
                   s->gzindex = 0;
                   s->status = EXTRA_STATE;
               }
           }
           else
   #endif
           {
               uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
               uInt level_flags;
   
               if (s->strategy >= Z_HUFFMAN_ONLY || s->level < 2)
                   level_flags = 0;
               else if (s->level < 6)
                   level_flags = 1;
               else if (s->level == 6)
                   level_flags = 2;
               else
                   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 = adler32(0L, Z_NULL, 0);
           }
       }
   #ifdef GZIP
       if (s->status == EXTRA_STATE) {
           if (s->gzhead->extra != NULL) {
               uInt beg = s->pending;  /* start of bytes to update crc */
   
               while (s->gzindex < (s->gzhead->extra_len & 0xffff)) {
                   if (s->pending == s->pending_buf_size) {
                       if (s->gzhead->hcrc && s->pending > beg)
                           strm->adler = z_crc32(strm->adler, s->pending_buf + beg,
                                               s->pending - beg);
                       flush_pending(strm);
                       beg = s->pending;
                       if (s->pending == s->pending_buf_size)
                           break;
                   }
                   put_byte(s, s->gzhead->extra[s->gzindex]);
                   s->gzindex++;
               }
               if (s->gzhead->hcrc && s->pending > beg)
                   strm->adler = z_crc32(strm->adler, s->pending_buf + beg,
                                       s->pending - beg);
               if (s->gzindex == s->gzhead->extra_len) {
                   s->gzindex = 0;
                   s->status = NAME_STATE;
               }
           }
           else
               s->status = NAME_STATE;
       }
       if (s->status == NAME_STATE) {
           if (s->gzhead->name != NULL) {
               uInt beg = s->pending;  /* start of bytes to update crc */
               int val;
   
               do {
                   if (s->pending == s->pending_buf_size) {
                       if (s->gzhead->hcrc && s->pending > beg)
                           strm->adler = z_crc32(strm->adler, s->pending_buf + beg,
                                               s->pending - beg);
                       flush_pending(strm);
                       beg = s->pending;
                       if (s->pending == s->pending_buf_size) {
                           val = 1;
                           break;
                       }
                   }
                   val = s->gzhead->name[s->gzindex++];
                   put_byte(s, val);
               } while (val != 0);
               if (s->gzhead->hcrc && s->pending > beg)
                   strm->adler = z_crc32(strm->adler, s->pending_buf + beg,
                                       s->pending - beg);
               if (val == 0) {
                   s->gzindex = 0;
                   s->status = COMMENT_STATE;
               }
           }
           else
               s->status = COMMENT_STATE;
       }
       if (s->status == COMMENT_STATE) {
           if (s->gzhead->comment != NULL) {
               uInt beg = s->pending;  /* start of bytes to update crc */
               int val;
   
               do {
                   if (s->pending == s->pending_buf_size) {
                       if (s->gzhead->hcrc && s->pending > beg)
                           strm->adler = z_crc32(strm->adler, s->pending_buf + beg,
                                               s->pending - beg);
                       flush_pending(strm);
                       beg = s->pending;
                       if (s->pending == s->pending_buf_size) {
                           val = 1;
                           break;
                       }
                   }
                   val = s->gzhead->comment[s->gzindex++];
                   put_byte(s, val);
               } while (val != 0);
               if (s->gzhead->hcrc && s->pending > beg)
                   strm->adler = z_crc32(strm->adler, s->pending_buf + beg,
                                       s->pending - beg);
               if (val == 0)
                   s->status = HCRC_STATE;
           }
           else
               s->status = HCRC_STATE;
       }
       if (s->status == HCRC_STATE) {
           if (s->gzhead->hcrc) {
               if (s->pending + 2 > s->pending_buf_size)
                   flush_pending(strm);
               if (s->pending + 2 <= s->pending_buf_size) {
                   put_byte(s, (Byte)(strm->adler & 0xff));
                   put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
                   strm->adler = z_crc32(0L, Z_NULL, 0);
                   s->status = BUSY_STATE;
               }
           }
           else
               s->status = BUSY_STATE;
       }
   #endif
   
       /* 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_BUF_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->wrap <= 0) return Z_STREAM_END;
   
       /* Write the trailer */
   #ifdef GZIP
       if (s->wrap == 2) {
           put_byte(s, (Byte)(strm->adler & 0xff));
           put_byte(s, (Byte)((strm->adler >> 8) & 0xff));
           put_byte(s, (Byte)((strm->adler >> 16) & 0xff));
           put_byte(s, (Byte)((strm->adler >> 24) & 0xff));
           put_byte(s, (Byte)(strm->total_in & 0xff));
           put_byte(s, (Byte)((strm->total_in >> 8) & 0xff));
           put_byte(s, (Byte)((strm->total_in >> 16) & 0xff));
           put_byte(s, (Byte)((strm->total_in >> 24) & 0xff));
       }
       else
   #endif
       {
           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.
        */
       if (s->wrap > 0) s->wrap = -s->wrap; /* 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 != EXTRA_STATE &&
           status != NAME_STATE &&
           status != COMMENT_STATE &&
           status != HCRC_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;
   
       zmemcpy(dest, source, sizeof(z_stream));
   
       ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
       if (ds == Z_NULL) return Z_MEM_ERROR;
       dest->state = (struct internal_state FAR *) ds;
       zmemcpy(ds, ss, sizeof(deflate_state));
       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 /* MAXSEG_64K */
   }
   
   /* ===========================================================================
    * 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->wrap == 1) {
           strm->adler = adler32(strm->adler, strm->next_in, len);
       }
  #ifdef GZIP
      else if (strm->state->wrap == 2) {
          strm->adler = z_crc32(strm->adler, strm->next_in, len);
      }
  #endif
      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;
  #ifndef FASTEST
  #ifdef ASMV
      match_init(); /* initialize the asm code */
  #endif
  #endif
  }
  
  #ifndef FASTEST
  /* ===========================================================================
   * 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.
   */
  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.  Note that the checks below
           * for insufficient lookahead only occur occasionally for performance
           * reasons.  Therefore uninitialized memory will be accessed, and
           * conditional jumps will be made that depend on those values.
           * However the length of the match is limited to the lookahead, so
           * the output of deflate is not affected by the uninitialized values.
           */
  #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;
  }
  #endif /* ASMV */
  #endif /* FASTEST */
  
  /* ---------------------------------------------------------------------------
   * Optimized version for level == 1 or strategy == Z_RLE only
   */
  local uInt longest_match_fast(s, cur_match)
      deflate_state *s;
      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 (uInt)len <= s->lookahead ? (uInt)len : s->lookahead;
  }
  
  #ifdef DEBUG
  /* ===========================================================================
   * Check that the match at match_start is indeed a match.
   */
  local void check_match(s, start, match, length)
      deflate_state *s;
      IPos start, 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 /* DEBUG */
  
  /* ===========================================================================
   * 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(s)
      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 (sizeof(int) <= 2) {
              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 && lookahead == 1 (input done a 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.
           */
          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.)
               */
              /* %%% avoid this when Z_RLE */
              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(s, flush)
      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(s, flush)
      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).
               */
  #ifdef FASTEST
              if ((s->strategy != Z_HUFFMAN_ONLY && s->strategy != Z_RLE) ||
                  (s->strategy == Z_RLE && s->strstart - hash_head == 1)) {
                  s->match_length = longest_match_fast (s, hash_head);
              }
  #else
              if (s->strategy != Z_HUFFMAN_ONLY && s->strategy != Z_RLE) {
                  s->match_length = longest_match (s, hash_head);
              } else if (s->strategy == Z_RLE && s->strstart - hash_head == 1) {
                  s->match_length = longest_match_fast (s, hash_head);
              }
  #endif
              /* longest_match() or longest_match_fast() 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 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;
  }
  
  #ifndef FASTEST
  /* ===========================================================================
   * 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(s, flush)
      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->strategy != Z_RLE) {
                  s->match_length = longest_match (s, hash_head);
              } else if (s->strategy == Z_RLE && s->strstart - hash_head == 1) {
                  s->match_length = longest_match_fast (s, hash_head);
              }
              /* longest_match() or longest_match_fast() sets match_start */
  
              if (s->match_length <= 5 && (s->strategy == Z_FILTERED
  #if TOO_FAR <= 32767
                  || (s->match_length == MIN_MATCH &&
                      s->strstart - s->match_start > TOO_FAR)
  #endif
                  )) {
  
                  /* 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;
  }
  #endif /* FASTEST */
  
  #if 0
  /* ===========================================================================
   * For Z_RLE, simply look for runs of bytes, generate matches only of distance
   * one.  Do not maintain a hash table.  (It will be regenerated if this run of
   * deflate switches away from Z_RLE.)
   */
  local block_state deflate_rle(s, flush)
      deflate_state *s;
      int flush;
  {
      int bflush;         /* set if current block must be flushed */
      uInt run;           /* length of run */
      uInt max;           /* maximum length of run */
      uInt prev;          /* byte at distance one to match */
      Bytef *scan;        /* scan for end of run */
  
      for (;;) {
          /* Make sure that we always have enough lookahead, except
           * at the end of the input file. We need MAX_MATCH bytes
           * for the longest encodable run.
           */
          if (s->lookahead < MAX_MATCH) {
              fill_window(s);
              if (s->lookahead < MAX_MATCH && flush == Z_NO_FLUSH) {
                  return need_more;
              }
              if (s->lookahead == 0) break; /* flush the current block */
          }
  
          /* See how many times the previous byte repeats */
          run = 0;
          if (s->strstart > 0) {      /* if there is a previous byte, that is */
              max = s->lookahead < MAX_MATCH ? s->lookahead : MAX_MATCH;
              scan = s->window + s->strstart - 1;
              prev = *scan++;
              do {
                  if (*scan++ != prev)
                      break;
              } while (++run < max);
          }
  
          /* Emit match if have run of MIN_MATCH or longer, else emit literal */
          if (run >= MIN_MATCH) {
              check_match(s, s->strstart, s->strstart - 1, run);
              _tr_tally_dist(s, 1, run - MIN_MATCH, bflush);
              s->lookahead -= run;
              s->strstart += run;
          } 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;
  }
  #endif

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