zdftrees.cpp

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// $Id: zdftrees.cpp 817 2006-04-14 16:34:09Z alex $
/* @@tag:xara-cn@@ DO NOT MODIFY THIS LINE
================================XARAHEADERSTART===========================
 
               Xara LX, a vector drawing and manipulation program.
                    Copyright (C) 1993-2006 Xara Group Ltd.
       Copyright on certain contributions may be held in joint with their
              respective authors. See AUTHORS file for details.

LICENSE TO USE AND MODIFY SOFTWARE
----------------------------------

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Xara LX is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License version 2 as published
by the Free Software Foundation.

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Franklin St, Fifth Floor, Boston, MA  02110-1301 USA


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-----------------

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----------------

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=================================XARAHEADEREND============================
 */
//
// A file which encapsulates the zipped file streaming routines and data.
// Used to compress/uncompress the native files.

/*
*/

#include "camtypes.h"
#include "zdeflate.h"

// This is not compulsory, but you may as well put it in so that the correct version
// of your file can be registered in the .exe
DECLARE_SOURCE("$Revision: 817 $");

// This will get Camelot to display the filename and linenumber of any memory allocations
// that are not released at program exit
#define new CAM_DEBUG_NEW

// Comes from Zlib file trees.c
//
/*
 *  ALGORITHM
 *
 *      The "deflation" process uses several Huffman trees. The more
 *      common source values are represented by shorter bit sequences.
 *
 *      Each code tree is stored in a compressed form which is itself
 * a Huffman encoding of the lengths of all the code strings (in
 * ascending order by source values).  The actual code strings are
 * reconstructed from the lengths in the inflate process, as described
 * in the deflate specification.
 *
 *  REFERENCES
 *
 *      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
 *      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
 *
 *      Storer, James A.
 *          Data Compression:  Methods and Theory, pp. 49-50.
 *          Computer Science Press, 1988.  ISBN 0-7167-8156-5.
 *
 *      Sedgewick, R.
 *          Algorithms, p290.
 *          Addison-Wesley, 1983. ISBN 0-201-06672-6.
 */

// Used to be in zdeflate.h but too dangerous and clashes with something in paths.h
#define Freq fc.freq
#define Code fc.code
#define Dad  dl.dad
#define Len  dl.len

/* ===========================================================================
 * Constants
 */

#define MAX_BL_BITS 7
/* Bit length codes must not exceed MAX_BL_BITS bits */

#define END_BLOCK 256
/* end of block literal code */

#define REP_3_6      16
/* repeat previous bit length 3-6 times (2 bits of repeat count) */

#define REPZ_3_10    17
/* repeat a zero length 3-10 times  (3 bits of repeat count) */

#define REPZ_11_138  18
/* repeat a zero length 11-138 times  (7 bits of repeat count) */

INT32 extra_lbits[LENGTH_CODES] /* extra bits for each length code */
   = {0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0};

INT32 extra_dbits[D_CODES] /* extra bits for each distance code */
   = {0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13};

INT32 extra_blbits[BL_CODES]/* extra bits for each bit length code */
   = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};

uch bl_order[BL_CODES]
   = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
/* The lengths of the bit length codes are sent in order of decreasing
 * probability, to avoid transmitting the lengths for unused bit length codes.
 */

#define Buf_size (8 * 2*sizeof(char))
/* Number of bits used within bi_buf. (bi_buf might be implemented on
 * more than 16 bits on some systems.)
 */


/* ===========================================================================
 * Local data. These are initialized only once.
 */

ct_data static_ltree[L_CODES+2];
/* The static literal tree. Since the bit lengths are imposed, there is no
 * need for the L_CODES extra codes used during heap construction. However
 * The codes 286 and 287 are needed to build a canonical tree (see _tr_init
 * below).
 */

ct_data static_dtree[D_CODES];
/* The static distance tree. (Actually a trivial tree since all codes use
 * 5 bits.)
 */

uch dist_code[512];
/* distance codes. The first 256 values correspond to the distances
 * 3 .. 258, the last 256 values correspond to the top 8 bits of
 * the 15 bit distances.
 */

uch length_code[MAX_MATCH-MIN_MATCH+1];
/* length code for each normalized match length (0 == MIN_MATCH) */

INT32 base_length[LENGTH_CODES];
/* First normalized length for each code (0 = MIN_MATCH) */

INT32 base_dist[D_CODES];
/* First normalized distance for each code (0 = distance of 1) */

struct static_tree_desc_s {
    ct_data *static_tree;        /* static tree or NULL */
    intf    *extra_bits;         /* extra bits for each code or NULL */
    INT32     extra_base;          /* base index for extra_bits */
    INT32     elems;               /* max number of elements in the tree */
    INT32     max_length;          /* max bit length for the codes */
};

static_tree_desc  static_l_desc =
{static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};

static_tree_desc  static_d_desc =
{static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};

static_tree_desc  static_bl_desc =
{(ct_data *)0, extra_blbits, 0,      BL_CODES, MAX_BL_BITS};

/* ===========================================================================
 * Local (static) routines in this file.
 */

#ifndef DEBUG
#  define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)
   /* Send a code of the given tree. c and tree must not have side effects */

#else /* DEBUG */
#  define send_code(s, c, tree) \
     { if (verbose>1) _ftprintf(stderr,"\ncd %3d ",(c)); \
       send_bits(s, tree[c].Code, tree[c].Len); }
#endif

#define d_code(dist) \
   ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
/* Mapping from a distance to a distance code. dist is the distance - 1 and
 * must not have side effects. dist_code[256] and dist_code[257] are never
 * used.
 */

/* ===========================================================================
 * Output a short LSB first on the stream.
 * IN assertion: there is enough room in pendingBuf.
 */
#define put_short(s, w) { \
    put_byte(s, (uch)((w) & 0xff)); \
    put_byte(s, (uch)((ush)(w) >> 8)); \
}

/* ===========================================================================
 * Send a value on a given number of bits.
 * IN assertion: length <= 16 and value fits in length bits.
 */
#ifdef DEBUG
//    value     /* value to send */
//    length    /* number of bits */

void ZipDeflate::send_bits(DeflateState *s, INT32 value, INT32 length)
{
    Tracevv((stderr," l %2d v %4x ", length, value));
    Assert(length > 0 && length <= 15, "invalid length");
    s->bits_sent += (ulg)length;

    /* If not enough room in bi_buf, use (valid) bits from bi_buf and
     * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
     * unused bits in value.
     */
    if (s->bi_valid > (INT32)Buf_size - length) {
        s->bi_buf |= (value << s->bi_valid);
        put_short(s, s->bi_buf);
        s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
        s->bi_valid += length - Buf_size;
    } else {
        s->bi_buf |= value << s->bi_valid;
        s->bi_valid += length;
    }
}
#else /* !DEBUG */

#define send_bits(s, value, length) \
{ INT32 len = length;\
  if (s->bi_valid > (INT32)Buf_size - len) {\
    INT32 val = value;\
    s->bi_buf |= (val << s->bi_valid);\
    put_short(s, s->bi_buf);\
    s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\
    s->bi_valid += len - Buf_size;\
  } else {\
    s->bi_buf |= (value) << s->bi_valid;\
    s->bi_valid += len;\
  }\
}
#endif /* DEBUG */


#define MAX(a,b) (a >= b ? a : b)
/* the arguments must not have side effects */

/********************************************************************************************

>   void ZipDeflate::ct_static_init()

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Purpose:    Initialize the various 'constant' tables.
                To do: do this at compile time.

********************************************************************************************/

void ZipDeflate::tr_static_init()
{
    static BOOL static_init_done = 0;
    INT32 n;        /* iterates over tree elements */
    INT32 bits;     /* bit counter */
    INT32 length;   /* length value */
    INT32 code;     /* code value */
    INT32 dist;     /* distance index */
    ush bl_count[MAX_BITS+1];
    /* number of codes at each bit length for an optimal tree */

    if (static_init_done) return;

    /* Initialize the mapping length (0..255) -> length code (0..28) */
    length = 0;
    for (code = 0; code < LENGTH_CODES-1; code++) {
        base_length[code] = length;
        for (n = 0; n < (1<<extra_lbits[code]); n++) {
            length_code[length++] = (uch)code;
        }
    }
    Assert (length == 256, "tr_static_init: length != 256");
    /* Note that the length 255 (match length 258) can be represented
     * in two different ways: code 284 + 5 bits or code 285, so we
     * overwrite length_code[255] to use the best encoding:
     */
    length_code[length-1] = (uch)code;

    /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
    dist = 0;
    for (code = 0 ; code < 16; code++) {
        base_dist[code] = dist;
        for (n = 0; n < (1<<extra_dbits[code]); n++) {
            dist_code[dist++] = (uch)code;
        }
    }
    Assert (dist == 256, "tr_static_init: dist != 256");
    dist >>= 7; /* from now on, all distances are divided by 128 */
    for ( ; code < D_CODES; code++) {
        base_dist[code] = dist << 7;
        for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
            dist_code[256 + dist++] = (uch)code;
        }
    }
    Assert (dist == 256, "tr_static_init: 256+dist != 512");

    /* Construct the codes of the static literal tree */
    for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
    n = 0;
    while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
    while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
    while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
    while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
    /* Codes 286 and 287 do not exist, but we must include them in the
     * tree construction to get a canonical Huffman tree (longest code
     * all ones)
     */
    gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);

    /* The static distance tree is trivial: */
    for (n = 0; n < D_CODES; n++) {
        static_dtree[n].Len = 5;
        static_dtree[n].Code = bi_reverse((unsigned)n, 5);
    }
    static_init_done = 1;
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Purpose:    Initialize the tree data structures for a new zlib stream.

********************************************************************************************/

void ZipDeflate::_tr_init( DeflateState *s)
{
    tr_static_init();

    s->compressed_len = 0L;

    s->l_desc.dyn_tree = s->dyn_ltree;
    s->l_desc.stat_desc = &static_l_desc;

    s->d_desc.dyn_tree = s->dyn_dtree;
    s->d_desc.stat_desc = &static_d_desc;

    s->bl_desc.dyn_tree = s->bl_tree;
    s->bl_desc.stat_desc = &static_bl_desc;

    s->bi_buf = 0;
    s->bi_valid = 0;
    s->last_eob_len = 8; /* enough lookahead for inflate */
#ifdef DEBUG
    s->bits_sent = 0L;
#endif

    /* Initialize the first block of the first file: */
    init_block(s);
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Purpose:    Initialize a new block.

********************************************************************************************/

void ZipDeflate::init_block( DeflateState *s)
{
    INT32 n; /* iterates over tree elements */

    /* Initialize the trees. */
    for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
    for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
    for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;

    s->dyn_ltree[END_BLOCK].Freq = 1;
    s->opt_len = s->static_len = 0L;
    s->last_lit = s->matches = 0;
}

/********************************************************************************************
********************************************************************************************/

#define SMALLEST 1
/* Index within the heap array of least frequent node in the Huffman tree */


/* ===========================================================================
 * Remove the smallest element from the heap and recreate the heap with
 * one less element. Updates heap and heap_len.
 */
#define pqremove(s, tree, top) \
{\
    top = s->heap[SMALLEST]; \
    s->heap[SMALLEST] = s->heap[s->heap_len--]; \
    pqdownheap(s, tree, SMALLEST); \
}

/* ===========================================================================
 * Compares to subtrees, using the tree depth as tie breaker when
 * the subtrees have equal frequency. This minimizes the worst case length.
 */
#define smaller(tree, n, m, depth) \
   (tree[n].Freq < tree[m].Freq || \
   (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))


/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s       current deflate state
                tree    the tree to restore
                k       node to move down 
    Purpose:    Restore the heap property by moving down the tree starting at node k,
                exchanging a node with the smallest of its two sons if necessary, stopping
                when the heap property is re-established (each father smaller than its
                two sons).

********************************************************************************************/

void ZipDeflate::pqdownheap( DeflateState *s, ct_data *tree, INT32 k)
{
    INT32 v = s->heap[k];
    INT32 j = k << 1;  /* left son of k */
    while (j <= s->heap_len) {
        /* Set j to the smallest of the two sons: */
        if (j < s->heap_len &&
            smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
            j++;
        }
        /* Exit if v is smaller than both sons */
        if (smaller(tree, v, s->heap[j], s->depth)) break;

        /* Exchange v with the smallest son */
        s->heap[k] = s->heap[j];  k = j;

        /* And continue down the tree, setting j to the left son of k */
        j <<= 1;
    }
    s->heap[k] = v;
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s       current deflate state
                desc    the tree descriptor
    Purpose:    Compute the optimal bit lengths for a tree and update the total bit length
                for the current block.
                IN assertion: the fields freq and dad are set, heap[heap_max] and
                   above are the tree nodes sorted by increasing frequency.
                OUT assertions: the field len is set to the optimal bit length, the
                    array bl_count contains the frequencies for each bit length.
                    The length opt_len is updated; static_len is also updated if stree is
                    not null.
    

********************************************************************************************/

void ZipDeflate::gen_bitlen( DeflateState *s, tree_desc *desc)
{
    ct_data *tree  = desc->dyn_tree;
    INT32 max_code   = desc->max_code;
    ct_data *stree = desc->stat_desc->static_tree;
    intf *extra    = desc->stat_desc->extra_bits;
    INT32 base       = desc->stat_desc->extra_base;
    INT32 max_length = desc->stat_desc->max_length;
    INT32 h;              /* heap index */
    INT32 n, m;           /* iterate over the tree elements */
    INT32 bits;           /* bit length */
    INT32 xbits;          /* extra bits */
    ush f;              /* frequency */
    INT32 overflow = 0;   /* number of elements with bit length too large */

    for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;

    /* In a first pass, compute the optimal bit lengths (which may
     * overflow in the case of the bit length tree).
     */
    tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */

    for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
        n = s->heap[h];
        bits = tree[tree[n].Dad].Len + 1;
        if (bits > max_length) bits = max_length, overflow++;
        tree[n].Len = (ush)bits;
        /* We overwrite tree[n].Dad which is no longer needed */

        if (n > max_code) continue; /* not a leaf node */

        s->bl_count[bits]++;
        xbits = 0;
        if (n >= base) xbits = extra[n-base];
        f = tree[n].Freq;
        s->opt_len += (ulg)f * (bits + xbits);
        if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
    }
    if (overflow == 0) return;

    Trace((stderr,"\nbit length overflow\n"));
    /* This happens for example on obj2 and pic of the Calgary corpus */

    /* Find the first bit length which could increase: */
    do {
        bits = max_length-1;
        while (s->bl_count[bits] == 0) bits--;
        s->bl_count[bits]--;      /* move one leaf down the tree */
        s->bl_count[bits+1] += 2; /* move one overflow item as its brother */
        s->bl_count[max_length]--;
        /* The brother of the overflow item also moves one step up,
         * but this does not affect bl_count[max_length]
         */
        overflow -= 2;
    } while (overflow > 0);

    /* Now recompute all bit lengths, scanning in increasing frequency.
     * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
     * lengths instead of fixing only the wrong ones. This idea is taken
     * from 'ar' written by Haruhiko Okumura.)
     */
    for (bits = max_length; bits != 0; bits--) {
        n = s->bl_count[bits];
        while (n != 0) {
            m = s->heap[--h];
            if (m > max_code) continue;
            if (tree[m].Len != (unsigned) bits) {
                Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
                s->opt_len += ((INT32)bits - (INT32)tree[m].Len)
                              *(INT32)tree[m].Freq;
                tree[m].Len = (ush)bits;
            }
            n--;
        }
    }
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     tree        the tree to decorate
                max_code    largest code with non zero frequency
                bl_count[]  number of codes at each bit length
    Purpose:    Generate the codes for a given tree and bit counts (which need not be optimal).
                IN assertion: the array bl_count contains the bit length statistics for
                the given tree and the field len is set for all tree elements.
                OUT assertion: the field code is set for all tree elements of non
                    zero code length.

********************************************************************************************/

void ZipDeflate::gen_codes(ct_data *tree, INT32 max_code, ushf bl_count[])
{
    ush next_code[MAX_BITS+1]; /* next code value for each bit length */
    ush code = 0;              /* running code value */
    INT32 bits;                  /* bit index */
    INT32 n;                     /* code index */

    /* The distribution counts are first used to generate the code values
     * without bit reversal.
     */
    for (bits = 1; bits <= MAX_BITS; bits++) {
        next_code[bits] = code = (code + bl_count[bits-1]) << 1;
    }
    /* Check that the bit counts in bl_count are consistent. The last code
     * must be all ones.
     */
    Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
            "inconsistent bit counts");
    Tracev((stderr,"\ngen_codes: max_code %d ", max_code));

    for (n = 0;  n <= max_code; n++) {
        INT32 len = tree[n].Len;
        if (len == 0) continue;
        /* Now reverse the bits */
        tree[n].Code = bi_reverse(next_code[len]++, len);

        Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
             n, (_istgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
    }
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s       current deflate state
                desc    the tree descriptor
    Purpose:    Construct one Huffman tree and assigns the code bit strings and lengths.
                Update the total bit length for the current block.
                IN assertion: the field freq is set for all tree elements.
                OUT assertions: the fields len and code are set to the optimal bit length
                    and corresponding code. The length opt_len is updated; static_len is
                    also updated if stree is not null. The field max_code is set.

********************************************************************************************/

void ZipDeflate::build_tree( DeflateState *s, tree_desc *desc)
{
    ct_data *tree   = desc->dyn_tree;
    ct_data *stree  = desc->stat_desc->static_tree;
    INT32 elems       = desc->stat_desc->elems;
    INT32 n, m;          /* iterate over heap elements */
    INT32 max_code = -1; /* largest code with non zero frequency */
    INT32 node;          /* new node being created */

    /* Construct the initial heap, with least frequent element in
     * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
     * heap[0] is not used.
     */
    s->heap_len = 0, s->heap_max = HEAP_SIZE;

    for (n = 0; n < elems; n++) {
        if (tree[n].Freq != 0) {
            s->heap[++(s->heap_len)] = max_code = n;
            s->depth[n] = 0;
        } else {
            tree[n].Len = 0;
        }
    }

    /* The pkzip format requires that at least one distance code exists,
     * and that at least one bit should be sent even if there is only one
     * possible code. So to avoid special checks later on we force at least
     * two codes of non zero frequency.
     */
    while (s->heap_len < 2) {
        node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0);
        tree[node].Freq = 1;
        s->depth[node] = 0;
        s->opt_len--; if (stree) s->static_len -= stree[node].Len;
        /* node is 0 or 1 so it does not have extra bits */
    }
    desc->max_code = max_code;

    /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
     * establish sub-heaps of increasing lengths:
     */
    for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n);

    /* Construct the Huffman tree by repeatedly combining the least two
     * frequent nodes.
     */
    node = elems;              /* next internal node of the tree */
    do {
        pqremove(s, tree, n);  /* n = node of least frequency */
        m = s->heap[SMALLEST]; /* m = node of next least frequency */

        s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
        s->heap[--(s->heap_max)] = m;

        /* Create a new node father of n and m */
        tree[node].Freq = tree[n].Freq + tree[m].Freq;
        s->depth[node] = (uch) (MAX(s->depth[n], s->depth[m]) + 1);
        tree[n].Dad = tree[m].Dad = (ush)node;
#ifdef DUMP_BL_TREE
        if (tree == s->bl_tree) {
            _ftprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
                    node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
        }
#endif
        /* and insert the new node in the heap */
        s->heap[SMALLEST] = node++;
        pqdownheap(s, tree, SMALLEST);

    } while (s->heap_len >= 2);

    s->heap[--(s->heap_max)] = s->heap[SMALLEST];

    /* At this point, the fields freq and dad are set. We can now
     * generate the bit lengths.
     */
    gen_bitlen(s, (tree_desc *)desc);

    /* The field len is now set, we can generate the bit codes */
    gen_codes ((ct_data *)tree, max_code, s->bl_count);
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s           the current deflate state
                tree        the tree to be scanned
                max_code    and its largest code of non zero frequency
    
    Purpose:    Scan a literal or distance tree to determine the frequencies of the codes
                in the bit length tree.

********************************************************************************************/

void ZipDeflate::scan_tree( DeflateState *s, ct_data *tree, INT32 max_code)
{
    INT32 n;                     /* iterates over all tree elements */
    INT32 prevlen = -1;          /* last emitted length */
    INT32 curlen;                /* length of current code */
    INT32 nextlen = tree[0].Len; /* length of next code */
    INT32 count = 0;             /* repeat count of the current code */
    INT32 max_count = 7;         /* max repeat count */
    INT32 min_count = 4;         /* min repeat count */

    if (nextlen == 0) max_count = 138, min_count = 3;
    tree[max_code+1].Len = (ush)0xffff; /* guard */

    for (n = 0; n <= max_code; n++) {
        curlen = nextlen; nextlen = tree[n+1].Len;
        if (++count < max_count && curlen == nextlen) {
            continue;
        } else if (count < min_count) {
            s->bl_tree[curlen].Freq += count;
        } else if (curlen != 0) {
            if (curlen != prevlen) s->bl_tree[curlen].Freq++;
            s->bl_tree[REP_3_6].Freq++;
        } else if (count <= 10) {
            s->bl_tree[REPZ_3_10].Freq++;
        } else {
            s->bl_tree[REPZ_11_138].Freq++;
        }
        count = 0; prevlen = curlen;
        if (nextlen == 0) {
            max_count = 138, min_count = 3;
        } else if (curlen == nextlen) {
            max_count = 6, min_count = 3;
        } else {
            max_count = 7, min_count = 4;
        }
    }
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s           the current deflate state
                tree        the tree to be scanned
                max_code    and its largest code of non zero frequency
    Purpose:    Send a literal or distance tree in compressed form, using the codes in
                bl_tree

********************************************************************************************/

void ZipDeflate::send_tree( DeflateState *s, ct_data *tree, INT32 max_code)
{
    INT32 n;                     /* iterates over all tree elements */
    INT32 prevlen = -1;          /* last emitted length */
    INT32 curlen;                /* length of current code */
    INT32 nextlen = tree[0].Len; /* length of next code */
    INT32 count = 0;             /* repeat count of the current code */
    INT32 max_count = 7;         /* max repeat count */
    INT32 min_count = 4;         /* min repeat count */

    /* tree[max_code+1].Len = -1; */  /* guard already set */
    if (nextlen == 0) max_count = 138, min_count = 3;

    for (n = 0; n <= max_code; n++) {
        curlen = nextlen; nextlen = tree[n+1].Len;
        if (++count < max_count && curlen == nextlen) {
            continue;
        } else if (count < min_count) {
            do { send_code(s, curlen, s->bl_tree); } while (--count != 0);

        } else if (curlen != 0) {
            if (curlen != prevlen) {
                send_code(s, curlen, s->bl_tree); count--;
            }
            Assert(count >= 3 && count <= 6, " 3_6?");
            send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2);

        } else if (count <= 10) {
            send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3);

        } else {
            send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7);
        }
        count = 0; prevlen = curlen;
        if (nextlen == 0) {
            max_count = 138, min_count = 3;
        } else if (curlen == nextlen) {
            max_count = 6, min_count = 3;
        } else {
            max_count = 7, min_count = 4;
        }
    }
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s           the current deflate state
    Purpose:    Construct the Huffman tree for the bit lengths and return the index in
                bl_order of the last bit length code to send.

********************************************************************************************/

INT32 ZipDeflate::build_bl_tree( DeflateState *s)
{
    INT32 max_blindex;  /* index of last bit length code of non zero freq */

    /* Determine the bit length frequencies for literal and distance trees */
    scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code);
    scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code);

    /* Build the bit length tree: */
    build_tree(s, (tree_desc *)(&(s->bl_desc)));
    /* opt_len now includes the length of the tree representations, except
     * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
     */

    /* Determine the number of bit length codes to send. The pkzip format
     * requires that at least 4 bit length codes be sent. (appnote.txt says
     * 3 but the actual value used is 4.)
     */
    for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
        if (s->bl_tree[bl_order[max_blindex]].Len != 0) break;
    }
    /* Update opt_len to include the bit length tree and counts */
    s->opt_len += 3*(max_blindex+1) + 5+5+4;
    Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
            s->opt_len, s->static_len));

    return max_blindex;
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s                               the current deflate state
                lcodes, dcodes, blcodes         number of codes for each tree 
    Purpose:    Send the header for a block using dynamic Huffman trees: the counts, the
                lengths of the bit length codes, the literal tree and the distance tree.
                IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.

********************************************************************************************/

void ZipDeflate::send_all_trees( DeflateState *s, INT32 lcodes, INT32 dcodes, INT32 blcodes)
{
    INT32 rank;                    /* index in bl_order */

    Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
    Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
            "too many codes");
    Tracev((stderr, "\nbl counts: "));
    send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */
    send_bits(s, dcodes-1,   5);
    send_bits(s, blcodes-4,  4); /* not -3 as stated in appnote.txt */
    for (rank = 0; rank < blcodes; rank++) {
        Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
        send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
    }
    Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent));

    send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */
    Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent));

    send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */
    Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent));
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s           the current deflate state
                buf         input block
                stored_len  length of input block
                eof         true if this is the last block for a file
    Purpose:    Send a stored block

********************************************************************************************/

void ZipDeflate::_tr_stored_block( DeflateState *s, char *buf, ulg stored_len, INT32 eof)
{
    send_bits(s, (STORED_BLOCK<<1)+eof, 3);  /* send block type */
    s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
    s->compressed_len += (stored_len + 4) << 3;

    copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
}

// New version 0.99
/* ===========================================================================
 * Send one empty static block to give enough lookahead for inflate.
 * This takes 10 bits, of which 7 may remain in the bit buffer.
 * The current inflate code requires 9 bits of lookahead. If the
 * last two codes for the previous block (real code plus EOB) were coded
 * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
 * the last real code. In this case we send two empty static blocks instead
 * of one. (There are no problems if the previous block is stored or fixed.)
 * To simplify the code, we assume the worst case of last real code encoded
 * on one bit only.
 */
void ZipDeflate::_tr_align(DeflateState* s)
{
    send_bits(s, STATIC_TREES<<1, 3);
    send_code(s, END_BLOCK, static_ltree);
    s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
    bi_flush(s);
    /* Of the 10 bits for the empty block, we have already sent
     * (10 - bi_valid) bits. The lookahead for the last real code (before
     * the EOB of the previous block) was thus at least one plus the length
     * of the EOB plus what we have just sent of the empty static block.
     */
    if (1 + s->last_eob_len + 10 - s->bi_valid < 9) {
        send_bits(s, STATIC_TREES<<1, 3);
        send_code(s, END_BLOCK, static_ltree);
        s->compressed_len += 10L;
        bi_flush(s);
    }
    s->last_eob_len = 7;
}


/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s           the current deflate state
                buf         input block, or NULL if too old
                stored_len  length of input block
                eof         true if this is the last block for a file
    Purpose:    Determine the best encoding for the current block: dynamic trees, static
                trees or store, and output the encoded block to the zip file. This function
                returns the total compressed length for the file so far.

********************************************************************************************/

ulg ZipDeflate::_tr_flush_block( DeflateState *s, char *buf, ulg stored_len, INT32 eof)
{
    ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
    INT32 max_blindex = 0;  /* index of last bit length code of non zero freq */

    /* Build the Huffman trees unless a stored block is forced */
    if (s->level > 0) {

     /* Check if the file is ascii or binary */
    if (s->data_type == Z_UNKNOWN) set_data_type(s);

    /* Construct the literal and distance trees */
    build_tree(s, (tree_desc *)(&(s->l_desc)));
    Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
        s->static_len));

    build_tree(s, (tree_desc *)(&(s->d_desc)));
    Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
        s->static_len));
    /* At this point, opt_len and static_len are the total bit lengths of
     * the compressed block data, excluding the tree representations.
     */

    /* Build the bit length tree for the above two trees, and get the index
     * in bl_order of the last bit length code to send.
     */
    max_blindex = build_bl_tree(s);

    /* Determine the best encoding. Compute first the block length in bytes*/
    opt_lenb = (s->opt_len+3+7)>>3;
    static_lenb = (s->static_len+3+7)>>3;

    Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
        opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
        s->last_lit));

    if (static_lenb <= opt_lenb) opt_lenb = static_lenb;

    } else {
        Assert(buf != (char*)0, "lost buf");
    opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
    }

    /* If compression failed and this is the first and last block,
     * and if the .zip file can be seeked (to rewrite the local header),
     * the whole file is transformed into a stored file:
     */
#ifdef STORED_FILE_OK
#  ifdef FORCE_STORED_FILE
    if (eof && s->compressed_len == 0L) { /* force stored file */
#  else
    if (stored_len <= opt_lenb && eof && s->compressed_len==0L && seekable()) {
#  endif
        /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
        if (buf == (charf*)0) error ("block vanished");

        copy_block(buf, (unsigned)stored_len, 0); /* without header */
        s->compressed_len = stored_len << 3;
        s->method = STORED;
    } else
#endif /* STORED_FILE_OK */

#ifdef FORCE_STORED
    if (buf != (char*)0) { /* force stored block */
#else
    if (stored_len+4 <= opt_lenb && buf != (char*)0) {
                       /* 4: two words for the lengths */
#endif
        /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
         * Otherwise we can't have processed more than WSIZE input bytes since
         * the last block flush, because compression would have been
         * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
         * transform a block into a stored block.
         */
        _tr_stored_block(s, buf, stored_len, eof);

#ifdef FORCE_STATIC
    } else if (static_lenb >= 0) { /* force static trees */
#else
    } else if (static_lenb == opt_lenb) {
#endif
        send_bits(s, (STATIC_TREES<<1)+eof, 3);
        compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
        s->compressed_len += 3 + s->static_len;
    } else {
        send_bits(s, (DYN_TREES<<1)+eof, 3);
        send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
                       max_blindex+1);
        compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
        s->compressed_len += 3 + s->opt_len;
    }
    Assert (s->compressed_len == s->bits_sent, "bad compressed size");
    init_block(s);

    if (eof) {
        bi_windup(s);
        s->compressed_len += 7;  /* align on byte boundary */
    }
    Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
           s->compressed_len-7*eof));

    return s->compressed_len >> 3;
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s           the current deflate state
                dist        distance of matched string
                lc          match length-MIN_MATCH or unmatched char (if dist==0)
    Purpose:    Save the match info and tally the frequency counts. Return true if
                the current block must be flushed.

********************************************************************************************/

INT32 ZipDeflate::_tr_tally( DeflateState *s, unsigned dist, unsigned lc)
{
    s->d_buf[s->last_lit] = (ush)dist;
    s->l_buf[s->last_lit++] = (uch)lc;
    if (dist == 0) {
        /* lc is the unmatched char */
        s->dyn_ltree[lc].Freq++;
    } else {
        s->matches++;
        /* Here, lc is the match length - MIN_MATCH */
        dist--;             /* dist = match distance - 1 */
        Assert((ush)dist < (ush)MAX_DIST(s) &&
               (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
               (ush)d_code(dist) < (ush)D_CODES,  "_tr_tally: bad match");

        s->dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
        s->dyn_dtree[d_code(dist)].Freq++;
    }

    /* Try to guess if it is profitable to stop the current block here */
    if (s->level > 2 && (s->last_lit & 0xfff) == 0) {
        /* Compute an upper bound for the compressed length */
        ulg out_length = (ulg)s->last_lit*8L;
        ulg in_length = (ulg)((INT32)s->strstart - s->block_start);
        INT32 dcode;
        for (dcode = 0; dcode < D_CODES; dcode++) {
            out_length += (ulg)s->dyn_dtree[dcode].Freq *
                (5L+extra_dbits[dcode]);
        }
        out_length >>= 3;
        Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
               s->last_lit, in_length, out_length,
               100L - out_length*100L/in_length));
        if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
    }
    return (s->last_lit == s->lit_bufsize-1);
    /* We avoid equality with lit_bufsize because of wraparound at 64K
     * on 16 bit machines and because stored blocks are restricted to
     * 64K-1 bytes.
     */
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s       the current deflate state
                ltree   literal tree
                dtree   distance tree
    Purpose:    Send the block data compressed using the given Huffman trees

********************************************************************************************/

void ZipDeflate::compress_block( DeflateState *s, ct_data *ltree, ct_data * dtree)
{
    unsigned dist;      /* distance of matched string */
    INT32 lc;             /* match length or unmatched char (if dist == 0) */
    UINT32 lx = 0;      /* running index in l_buf */
    unsigned code;      /* the code to send */
    INT32 extra;          /* number of extra bits to send */

    if (s->last_lit != 0) do {
        dist = s->d_buf[lx];
        lc = s->l_buf[lx++];
        if (dist == 0) {
            send_code(s, lc, ltree); /* send a literal byte */
            Tracecv(_istgraph(lc), (stderr," '%c' ", lc));
        } else {
            /* Here, lc is the match length - MIN_MATCH */
            code = length_code[lc];
            send_code(s, code+LITERALS+1, ltree); /* send the length code */
            extra = extra_lbits[code];
            if (extra != 0) {
                lc -= base_length[code];
                send_bits(s, lc, extra);       /* send the extra length bits */
            }
            dist--; /* dist is now the match distance - 1 */
            code = d_code(dist);
            Assert (code < D_CODES, "bad d_code");

            send_code(s, code, dtree);       /* send the distance code */
            extra = extra_dbits[code];
            if (extra != 0) {
                dist -= base_dist[code];
                send_bits(s, dist, extra);   /* send the extra distance bits */
            }
        } /* literal or match pair ? */

        /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
        Assert(s->pending < ( INT32 ) ( s->lit_bufsize + ( 2 * lx ) ), "pendingBuf overflow");

    } while (lx < s->last_lit);

    send_code(s, END_BLOCK, ltree);
    s->last_eob_len = ltree[END_BLOCK].Len;
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s       the current deflate state
    Purpose:    Set the data type to ASCII or BINARY, using a crude approximation:
                binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
                IN assertion: the fields freq of dyn_ltree are set and the total of all
                frequencies does not exceed 64K (to fit in an INT32 on 16 bit machines).

********************************************************************************************/

void ZipDeflate::set_data_type( DeflateState *s)
{
    INT32 n = 0;
    unsigned ascii_freq = 0;
    unsigned bin_freq = 0;
    while (n < 7)        bin_freq += s->dyn_ltree[n++].Freq;
    while (n < 128)    ascii_freq += s->dyn_ltree[n++].Freq;
    while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq;
    s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII);
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s       the current deflate state
                value   value to send
                length  number of bits
    Purpose:    Send a value on a given number of bits.
                IN assertion: length <= 16 and value fits in length bits.

********************************************************************************************/
#if 0
void ZipDeflate::send_bits( DeflateState *s, INT32 value, INT32 length)
{
#ifdef DEBUG
    Tracev((stderr," l %2d v %4x ", length, value));
    Assert(length > 0 && length <= 15, "invalid length");
    s->bits_sent += (ulg)length;
#endif
    /* If not enough room in bi_buf, use (valid) bits from bi_buf and
     * (16 - bi_valid) bits from value, leaving (width - (16-bi_valid))
     * unused bits in value.
     */
     if (s->bi_valid > (INT32)Buf_size - length) {
        s->bi_buf |= (value << s->bi_valid);
        put_short(s, s->bi_buf);
        s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);
        s->bi_valid += length - Buf_size;
    } else {
        s->bi_buf |= value << s->bi_valid;
        s->bi_valid += length;
    }
} 
#endif

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     code        the value to invert
                len         its bit length
    Purpose:    Reverse the first len bits of a code, using straightforward code (a faster
                method would use a table)
                IN assertion: 1 <= len <= 15

********************************************************************************************/

unsigned ZipDeflate::bi_reverse(unsigned code, INT32 len)
{
    register unsigned res = 0;
    do {
        res |= code & 1;
        code >>= 1, res <<= 1;
    } while (--len > 0);
    return res >> 1;
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s       the current deflate state
    Purpose:    Flush the bit buffer, keeping at most 7 bits in it.
                New Version 0.99

********************************************************************************************/
 
void ZipDeflate::bi_flush(DeflateState *s)
{
    if (s->bi_valid == 16) {
        put_short(s, s->bi_buf);
        s->bi_buf = 0;
        s->bi_valid = 0;
    } else if (s->bi_valid >= 8) {
        put_byte(s, (Byte)s->bi_buf);
        s->bi_buf >>= 8;
        s->bi_valid -= 8;
    }
}

/********************************************************************************************

>   

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s       the current deflate state
    Purpose:    Write out any remaining bits in an incomplete byte.
                Flush the bit buffer and align the output on a byte boundary

********************************************************************************************/

void ZipDeflate::bi_windup( DeflateState *s)
{
    if (s->bi_valid > 8) {
        put_short(s, s->bi_buf);
    } else if (s->bi_valid > 0) {
        put_byte(s, (Byte)s->bi_buf);
    }
    s->bi_buf = 0;
    s->bi_valid = 0;
#ifdef DEBUG
    s->bits_sent = (s->bits_sent+7) & ~7;
#endif
}

/********************************************************************************************

>   void ZipDeflate::copy_block( DeflateState *s, char *buf, unsigned len, INT32 header)

    Author:     Neville_Humphrys (Xara Group Ltd) <camelotdev@xara.com>
    Created:    24/05/95
    Inputs:     s       the current deflate state
                buf     the input data
                len     its length
                header  true if block header must be written
    Purpose:    Copy a stored block, storing first the length and its
                one's complement if requested.

********************************************************************************************/

void ZipDeflate::copy_block( DeflateState *s, char *buf, unsigned len, INT32 header)
{
    bi_windup(s);        /* align on byte boundary */
    s->last_eob_len = 8; /* enough lookahead for inflate */

    if (header) {
        put_short(s, (ush)len);   
        put_short(s, (ush)~len);
#ifdef DEBUG
        s->bits_sent += 2*16;
#endif
    }
#ifdef DEBUG
    s->bits_sent += (ulg)len<<3;
#endif
    while (len--) {
        put_byte(s, *buf++);
    }
}

---