    /* trees.c -- output deflated data using Huffman coding
     * Copyright (C) 1995-2012 Jean-loup Gailly
     * detect_data_type() function provided freely by Cosmin Truta, 2006
     * For conditions of distribution and use, see copyright notice in zlib.h
     */

    /*
     *  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.
     */

    /* @(#) $Id$ */

    /* #define GEN_TREES_H */

    #include "deflate.h"

    #ifdef DEBUG
    #  include <ctype.h>
    #endif

    /* ===========================================================================
     * 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) */

    local const int 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};

    local const int 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};

    local const int 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};

    local const 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.
     */

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

    #define DIST_CODE_LEN  512 /* see definition of array dist_code below */

    #if defined(GEN_TREES_H) || !defined(STDC)
    /* non ANSI compilers may not accept trees.h */

    local 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).
     */

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

    uch _dist_code[DIST_CODE_LEN];
    /* 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) */

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

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

    #else
    #  include "trees.h"
    #endif /* GEN_TREES_H */

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

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

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

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

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

    local void tr_static_init OF((void));
    local void init_block     OF((deflate_state *s));
    local void pqdownheap     OF((deflate_state *s, ct_data *tree, int k));
    local void gen_bitlen     OF((deflate_state *s, tree_desc *desc));
    local void gen_codes      OF((ct_data *tree, int max_code, ushf *bl_count));
    local void build_tree     OF((deflate_state *s, tree_desc *desc));
    local void scan_tree      OF((deflate_state *s, ct_data *tree, int max_code));
    local void send_tree      OF((deflate_state *s, ct_data *tree, int max_code));
    local int  build_bl_tree  OF((deflate_state *s));
    local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
                                  int blcodes));
    local void compress_block OF((deflate_state *s, const ct_data *ltree,
                                  const ct_data *dtree));
    local int  detect_data_type OF((deflate_state *s));
    local unsigned bi_reverse OF((unsigned value, int length));
    local void bi_windup      OF((deflate_state *s));
    local void bi_flush       OF((deflate_state *s));
    local void copy_block     OF((deflate_state *s, charf *buf, unsigned len,
                                  int header));

    #ifdef GEN_TREES_H
    local void gen_trees_header OF((void));
    #endif

    #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 (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
           send_bits(s, tree[c].Code, tree[c].Len); }
    #endif

    /* ===========================================================================
     * 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
    local void send_bits      OF((deflate_state *s, int value, int length));

    local void send_bits(s, value, length)
        deflate_state *s;
        int value;  /* value to send */
        int length; /* number of bits */
    {
        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 > (int)Buf_size - length) {
            s->bi_buf |= (ush)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 |= (ush)value << s->bi_valid;
            s->bi_valid += length;
        }
    }
    #else /* !DEBUG */

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

    /* the arguments must not have side effects */

    /* ===========================================================================
     * Initialize the various 'constant' tables.
     */
    local void tr_static_init()
    {
    #if defined(GEN_TREES_H) || !defined(STDC)
        static int static_init_done = 0;
        int n;        /* iterates over tree elements */
        int bits;     /* bit counter */
        int length;   /* length value */
        int code;     /* code value */
        int 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;

        /* For some embedded targets, global variables are not initialized: */
    #ifdef NO_INIT_GLOBAL_POINTERS
        static_l_desc.static_tree = static_ltree;
        static_l_desc.extra_bits = extra_lbits;
        static_d_desc.static_tree = static_dtree;
        static_d_desc.extra_bits = extra_dbits;
        static_bl_desc.extra_bits = extra_blbits;
    #endif

        /* 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;

    #  ifdef GEN_TREES_H
        gen_trees_header();
    #  endif
    #endif /* defined(GEN_TREES_H) || !defined(STDC) */
    }

    /* ===========================================================================
     * Genererate the file trees.h describing the static trees.
     */
    #ifdef GEN_TREES_H
    #  ifndef DEBUG
    #    include <stdio.h>
    #  endif

    #  define SEPARATOR(i, last, width) \
          ((i) == (last)? "\n};\n\n" :    \
           ((i) % (width) == (width)-1 ? ",\n" : ", "))

    void gen_trees_header()
    {
        FILE *header = fopen("trees.h", "w");
        int i;

        Assert (header != NULL, "Can't open trees.h");
        fprintf(header,
                "/* header created automatically with -DGEN_TREES_H */\n\n");

        fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");
        for (i = 0; i < L_CODES+2; i++) {
            fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,
                    static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));
        }

        fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");
        for (i = 0; i < D_CODES; i++) {
            fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,
                    static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));
        }

        fprintf(header, "const uch ZLIB_INTERNAL _dist_code[DIST_CODE_LEN] = {\n");
        for (i = 0; i < DIST_CODE_LEN; i++) {
            fprintf(header, "%2u%s", _dist_code[i],
                    SEPARATOR(i, DIST_CODE_LEN-1, 20));
        }

        fprintf(header,
            "const uch ZLIB_INTERNAL _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");
        for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {
            fprintf(header, "%2u%s", _length_code[i],
                    SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));
        }

        fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");
        for (i = 0; i < LENGTH_CODES; i++) {
            fprintf(header, "%1u%s", base_length[i],
                    SEPARATOR(i, LENGTH_CODES-1, 20));
        }

        fprintf(header, "local const int base_dist[D_CODES] = {\n");
        for (i = 0; i < D_CODES; i++) {
            fprintf(header, "%5u%s", base_dist[i],
                    SEPARATOR(i, D_CODES-1, 10));
        }

        fclose(header);
    }
    #endif /* GEN_TREES_H */

    /* ===========================================================================
     * Initialize the tree data structures for a new zlib stream.
     */
    void ZLIB_INTERNAL _tr_init(s)
        deflate_state *s;
    {
        tr_static_init();

        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;
    #ifdef DEBUG
        s->compressed_len = 0L;
        s->bits_sent = 0L;
    #endif

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

    /* ===========================================================================
     * Initialize a new block.
     */
    local void init_block(s)
        deflate_state *s;
    {
        int 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]))

    /* ===========================================================================
     * 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).
     */
    local void pqdownheap(s, tree, k)
        deflate_state *s;
        ct_data *tree;  /* the tree to restore */
        int k;               /* node to move down */
    {
        int v = s->heap[k];
        int 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;
    }

    /* ===========================================================================
     * 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.
     */
    local void gen_bitlen(s, desc)
        deflate_state *s;
        tree_desc *desc;    /* the tree descriptor */
    {
        ct_data *tree        = desc->dyn_tree;
        int max_code         = desc->max_code;
        const ct_data *stree = desc->stat_desc->static_tree;
        const intf *extra    = desc->stat_desc->extra_bits;
        int base             = desc->stat_desc->extra_base;
        int max_length       = desc->stat_desc->max_length;
        int h;              /* heap index */
        int n, m;           /* iterate over the tree elements */
        int bits;           /* bit length */
        int xbits;          /* extra bits */
        ush f;              /* frequency */
        int 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 ((unsigned) tree[m].Len != (unsigned) bits) {
                    Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
                    s->opt_len += ((long)bits - (long)tree[m].Len)
                                  *(long)tree[m].Freq;
                    tree[m].Len = (ush)bits;
                }
                n--;
            }
        }
    }

    /* ===========================================================================
     * 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.
     */
    local void gen_codes (tree, max_code, bl_count)
        ct_data *tree;             /* the tree to decorate */
        int max_code;              /* largest code with non zero frequency */
        ushf *bl_count;            /* number of codes at each bit length */
    {
        ush next_code[MAX_BITS+1]; /* next code value for each bit length */
        ush code = 0;              /* running code value */
        int bits;                  /* bit index */
        int 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++) {
            int 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, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
        }
    }

    /* ===========================================================================
     * 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.
     */
    local void build_tree(s, desc)
        deflate_state *s;
        tree_desc *desc; /* the tree descriptor */
    {
        ct_data *tree         = desc->dyn_tree;
        const ct_data *stree  = desc->stat_desc->static_tree;
        int elems             = desc->stat_desc->elems;
        int n, m;          /* iterate over heap elements */
        int max_code = -1; /* largest code with non zero frequency */
        int 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)((s->depth[n] >= s->depth[m] ?
                                    s->depth[n] : s->depth[m]) + 1);
            tree[n].Dad = tree[m].Dad = (ush)node;
    #ifdef DUMP_BL_TREE
            if (tree == s->bl_tree) {
                fprintf(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);
    }

    /* ===========================================================================
     * Scan a literal or distance tree to determine the frequencies of the codes
     * in the bit length tree.
     */
    local void scan_tree (s, tree, max_code)
        deflate_state *s;
        ct_data *tree;   /* the tree to be scanned */
        int max_code;    /* and its largest code of non zero frequency */
    {
        int n;                     /* iterates over all tree elements */
        int prevlen = -1;          /* last emitted length */
        int curlen;                /* length of current code */
        int nextlen = tree[0].Len; /* length of next code */
        int count = 0;             /* repeat count of the current code */
        int max_count = 7;         /* max repeat count */
        int 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;
            }
        }
    }

    /* ===========================================================================
     * Send a literal or distance tree in compressed form, using the codes in
     * bl_tree.
     */
    local void send_tree (s, tree, max_code)
        deflate_state *s;
        ct_data *tree; /* the tree to be scanned */
        int max_code;       /* and its largest code of non zero frequency */
    {
        int n;                     /* iterates over all tree elements */
        int prevlen = -1;          /* last emitted length */
        int curlen;                /* length of current code */
        int nextlen = tree[0].Len; /* length of next code */
        int count = 0;             /* repeat count of the current code */
        int max_count = 7;         /* max repeat count */
        int 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;
            }
        }
    }

    /* ===========================================================================
     * Construct the Huffman tree for the bit lengths and return the index in
     * bl_order of the last bit length code to send.
     */
    local int build_bl_tree(s)
        deflate_state *s;
    {
        int 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;
    }

    /* ===========================================================================
     * 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.
     */
    local void send_all_trees(s, lcodes, dcodes, blcodes)
        deflate_state *s;
        int lcodes, dcodes, blcodes; /* number of codes for each tree */
    {
        int 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));
    }

    /* ===========================================================================
     * Send a stored block
     */
    void ZLIB_INTERNAL _tr_stored_block(s, buf, stored_len, last)
        deflate_state *s;
        charf *buf;       /* input block */
        ulg stored_len;   /* length of input block */
        int last;         /* one if this is the last block for a file */
    {
        send_bits(s, (STORED_BLOCK<<1)+last, 3);    /* send block type */
    #ifdef DEBUG
        s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;
        s->compressed_len += (stored_len + 4) << 3;
    #endif
        copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
    }

    /* ===========================================================================
     * Flush the bits in the bit buffer to pending output (leaves at most 7 bits)
     */
    void ZLIB_INTERNAL _tr_flush_bits(s)
        deflate_state *s;
    {
        bi_flush(s);
    }

    /* ===========================================================================
     * Send one empty static block to give enough lookahead for inflate.
     * This takes 10 bits, of which 7 may remain in the bit buffer.
     */
    void ZLIB_INTERNAL _tr_align(s)
        deflate_state *s;
    {
        send_bits(s, STATIC_TREES<<1, 3);
        send_code(s, END_BLOCK, static_ltree);
    #ifdef DEBUG
        s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
    #endif
        bi_flush(s);
    }

    /* ===========================================================================
     * Determine the best encoding for the current block: dynamic trees, static
     * trees or store, and output the encoded block to the zip file.
     */
    void ZLIB_INTERNAL _tr_flush_block(s, buf, stored_len, last)
        deflate_state *s;
        charf *buf;       /* input block, or NULL if too old */
        ulg stored_len;   /* length of input block */
        int last;         /* one if this is the last block for a file */
    {
        ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
        int 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 binary or text */
            if (s->strm->data_type == Z_UNKNOWN)
                s->strm->data_type = detect_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 the block lengths 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 */
        }

    #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, last);

    #ifdef FORCE_STATIC
        } else if (static_lenb >= 0) { /* force static trees */
    #else
        } else if (s->strategy == Z_FIXED || static_lenb == opt_lenb) {
    #endif
            send_bits(s, (STATIC_TREES<<1)+last, 3);
            compress_block(s, (const ct_data *)static_ltree,
                           (const ct_data *)static_dtree);
    #ifdef DEBUG
            s->compressed_len += 3 + s->static_len;
    #endif
        } else {
            send_bits(s, (DYN_TREES<<1)+last, 3);
            send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
                           max_blindex+1);
            compress_block(s, (const ct_data *)s->dyn_ltree,
                           (const ct_data *)s->dyn_dtree);
    #ifdef DEBUG
            s->compressed_len += 3 + s->opt_len;
    #endif
        }
        Assert (s->compressed_len == s->bits_sent, "bad compressed size");
        /* The above check is made mod 2^32, for files larger than 512 MB
         * and uLong implemented on 32 bits.
         */
        init_block(s);

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

    /* ===========================================================================
     * Save the match info and tally the frequency counts. Return true if
     * the current block must be flushed.
     */
    int ZLIB_INTERNAL _tr_tally (s, dist, lc)
        deflate_state *s;
        unsigned dist;  /* distance of matched string */
        unsigned lc;    /* match length-MIN_MATCH or unmatched char (if dist==0) */
    {
        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++;
        }

    #ifdef TRUNCATE_BLOCK
        /* Try to guess if it is profitable to stop the current block here */
        if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
            /* Compute an upper bound for the compressed length */
            ulg out_length = (ulg)s->last_lit*8L;
            ulg in_length = (ulg)((long)s->strstart - s->block_start);
            int 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;
        }
    #endif
        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.
         */
    }

    /* ===========================================================================
     * Send the block data compressed using the given Huffman trees
     */
    local void compress_block(s, ltree, dtree)
        deflate_state *s;
        const ct_data *ltree; /* literal tree */
        const ct_data *dtree; /* distance tree */
    {
        unsigned dist;      /* distance of matched string */
        int lc;             /* match length or unmatched char (if dist == 0) */
        unsigned lx = 0;    /* running index in l_buf */
        unsigned code;      /* the code to send */
        int 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(isgraph(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((uInt)(s->pending) < s->lit_bufsize + 2*lx,
                   "pendingBuf overflow");

        } while (lx < s->last_lit);

        send_code(s, END_BLOCK, ltree);
    }

    /* ===========================================================================
     * Check if the data type is TEXT or BINARY, using the following algorithm:
     * - TEXT if the two conditions below are satisfied:
     *    a) There are no non-portable control characters belonging to the
     *       "black list" (0..6, 14..25, 28..31).
     *    b) There is at least one printable character belonging to the
     *       "white list" (9 {TAB}, 10 {LF}, 13 {CR}, 32..255).
     * - BINARY otherwise.
     * - The following partially-portable control characters form a
     *   "gray list" that is ignored in this detection algorithm:
     *   (7 {BEL}, 8 {BS}, 11 {VT}, 12 {FF}, 26 {SUB}, 27 {ESC}).
     * IN assertion: the fields Freq of dyn_ltree are set.
     */
    local int detect_data_type(s)
        deflate_state *s;
    {
        /* black_mask is the bit mask of black-listed bytes
         * set bits 0..6, 14..25, and 28..31
         * 0xf3ffc07f = binary 11110011111111111100000001111111
         */
        unsigned long black_mask = 0xf3ffc07fUL;
        int n;

        /* Check for non-textual ("black-listed") bytes. */
        for (n = 0; n <= 31; n++, black_mask >>= 1)
            if ((black_mask & 1) && (s->dyn_ltree[n].Freq != 0))
                return Z_BINARY;

        /* Check for textual ("white-listed") bytes. */
        if (s->dyn_ltree[9].Freq != 0 || s->dyn_ltree[10].Freq != 0
                || s->dyn_ltree[13].Freq != 0)
            return Z_TEXT;
        for (n = 32; n < LITERALS; n++)
            if (s->dyn_ltree[n].Freq != 0)
                return Z_TEXT;

        /* There are no "black-listed" or "white-listed" bytes:
         * this stream either is empty or has tolerated ("gray-listed") bytes only.
         */
        return Z_BINARY;
    }

    /* ===========================================================================
     * Reverse the first len bits of a code, using straightforward code (a faster
     * method would use a table)
     * IN assertion: 1 <= len <= 15
     */
    local unsigned bi_reverse(code, len)
        unsigned code; /* the value to invert */
        int len;       /* its bit length */
    {
        register unsigned res = 0;
        do {
            res |= code & 1;
            code >>= 1, res <<= 1;
        } while (--len > 0);
        return res >> 1;
    }

    /* ===========================================================================
     * Flush the bit buffer, keeping at most 7 bits in it.
     */
    local void bi_flush(s)
        deflate_state *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;
        }
    }

    /* ===========================================================================
     * Flush the bit buffer and align the output on a byte boundary
     */
    local void bi_windup(s)
        deflate_state *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
    }

    /* ===========================================================================
     * Copy a stored block, storing first the length and its
     * one's complement if requested.
     */
    local void copy_block(s, buf, len, header)
        deflate_state *s;
        charf    *buf;    /* the input data */
        unsigned len;     /* its length */
        int      header;  /* true if block header must be written */
    {
        bi_windup(s);        /* align on byte boundary */

        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++);
        }
    }