/* trees.c -- output deflated data using Huffman coding

 * Copyright (C) 1995-2017 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.

 */

#include "zbuild.h"

#include "deflate.h"

#include "trees.h"

#include "trees_emit.h"

#include "trees_tbl.h"

/* 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.

 */

struct static_tree_desc_s {

    const ct_data *static_tree; /* static tree or NULL */

    const int     *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 */

    unsigned int   max_length;  /* max bit length for the codes */

};

static const static_tree_desc  static_l_desc =

{static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};

static const static_tree_desc  static_d_desc =

{static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};

static const static_tree_desc  static_bl_desc =

{(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};

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

 * Local (static) routines in this file.

 */

static void init_block       (deflate_state *s);

static void pqdownheap       (deflate_state *s, ct_data *tree, int k);

static void gen_bitlen       (deflate_state *s, tree_desc *desc);

static void build_tree       (deflate_state *s, tree_desc *desc);

static void scan_tree        (deflate_state *s, ct_data *tree, int max_code);

static void send_tree        (deflate_state *s, ct_data *tree, int max_code);

static int  build_bl_tree    (deflate_state *s);

static void send_all_trees   (deflate_state *s, int lcodes, int dcodes, int blcodes);

static void compress_block   (deflate_state *s, const ct_data *ltree, const ct_data *dtree);

static int  detect_data_type (deflate_state *s);

static void bi_flush         (deflate_state *s);

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

 * Initialize the tree data structures for a new zlib stream.

 */

void Z_INTERNAL zng_tr_init(deflate_state *s) {

    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 ZLIB_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.

 */

static void init_block(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->sym_next = 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).

 */

static void pqdownheap(deflate_state *s, ct_data *tree, int k) {

    /* tree: the tree to restore */

    /* 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.

 */

static void gen_bitlen(deflate_state *s, tree_desc *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 int *extra        = desc->stat_desc->extra_bits;

    int base                = desc->stat_desc->extra_base;

    unsigned int max_length = desc->stat_desc->max_length;

    int h;              /* heap index */

    int n, m;           /* iterate over the tree elements */

    unsigned int bits;  /* bit length */

    int xbits;          /* extra bits */

    uint16_t 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 + 1u;

        if (bits > max_length){

            bits = max_length;

            overflow++;

        }

        tree[n].Len = (uint16_t)bits;

        /* We overwrite tree[n].Dad which is no longer needed */

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

            continue;

        s->bl_count[bits]++;

        xbits = 0;

        if (n >= base)

            xbits = extra[n-base];

        f = tree[n].Freq;

        s->opt_len += (unsigned long)f * (unsigned int)(bits + xbits);

        if (stree)

            s->static_len += (unsigned long)f * (unsigned int)(stree[n].Len + xbits);

    }

    if (overflow == 0)

        return;

    Tracev((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] += 2u; /* 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 != bits) {

                Tracev((stderr, "code %d bits %d->%u\n", m, tree[m].Len, bits));

                s->opt_len += (unsigned long)(bits * tree[m].Freq);

                s->opt_len -= (unsigned long)(tree[m].Len * tree[m].Freq);

                tree[m].Len = (uint16_t)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.

 */

Z_INTERNAL void gen_codes(ct_data *tree, int max_code, uint16_t *bl_count) {

    /* tree: the tree to decorate */

    /* max_code: largest code with non zero frequency */

    /* bl_count: number of codes at each bit length */

    uint16_t next_code[MAX_BITS+1];  /* next code value for each bit length */

    unsigned int 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++) {

        code = (code + bl_count[bits-1]) << 1;

        next_code[bits] = (uint16_t)code;

    }

    /* 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 = (uint16_t)bi_reverse(next_code[len]++, len);

        Tracecv(tree != static_ltree, (stderr, "\nn %3d %c l %2d c %4x (%x) ",

             n, (isgraph(n & 0xff) ? 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.

 */

static void build_tree(deflate_state *s, tree_desc *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] = (unsigned char)((s->depth[n] >= s->depth[m] ?

                                          s->depth[n] : s->depth[m]) + 1);

        tree[n].Dad = tree[m].Dad = (uint16_t)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.

 */

static void scan_tree(deflate_state *s, ct_data *tree, int max_code) {

    /* tree: the tree to be scanned */

    /* 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 */

    uint16_t count = 0;        /* repeat count of the current code */

    uint16_t max_count = 7;    /* max repeat count */

    uint16_t min_count = 4;    /* min repeat count */

    if (nextlen == 0)

        max_count = 138, min_count = 3;

    tree[max_code+1].Len = (uint16_t)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.

 */

static void send_tree(deflate_state *s, ct_data *tree, int max_code) {

    /* tree: the tree to be scanned */

    /* 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;

    // Temp local variables

    uint32_t bi_valid = s->bi_valid;

    uint64_t bi_buf = s->bi_buf;

    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, bi_buf, bi_valid);

            } while (--count != 0);

        } else if (curlen != 0) {

            if (curlen != prevlen) {

                send_code(s, curlen, s->bl_tree, bi_buf, bi_valid);

                count--;

            }

            Assert(count >= 3 && count <= 6, " 3_6?");

            send_code(s, REP_3_6, s->bl_tree, bi_buf, bi_valid);

            send_bits(s, count-3, 2, bi_buf, bi_valid);

        } else if (count <= 10) {

            send_code(s, REPZ_3_10, s->bl_tree, bi_buf, bi_valid);

            send_bits(s, count-3, 3, bi_buf, bi_valid);

        } else {

            send_code(s, REPZ_11_138, s->bl_tree, bi_buf, bi_valid);

            send_bits(s, count-11, 7, bi_buf, bi_valid);

        }

        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;

        }

    }

    // Store back temp variables

    s->bi_buf = bi_buf;

    s->bi_valid = bi_valid;

}

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

 * Construct the Huffman tree for the bit lengths and return the index in

 * bl_order of the last bit length code to send.

 */

static int build_bl_tree(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*((unsigned long)max_blindex+1) + 5+5+4;

    Tracev((stderr, "\ndyn trees: dyn %lu, stat %lu", 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.

 */

static void send_all_trees(deflate_state *s, int lcodes, int dcodes, int blcodes) {

    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");

    // Temp local variables

    uint32_t bi_valid = s->bi_valid;

    uint64_t bi_buf = s->bi_buf;

    Tracev((stderr, "\nbl counts: "));

    send_bits(s, lcodes-257, 5, bi_buf, bi_valid); /* not +255 as stated in appnote.txt */

    send_bits(s, dcodes-1,   5, bi_buf, bi_valid);

    send_bits(s, blcodes-4,  4, bi_buf, bi_valid); /* not -3 as stated in appnote.txt */

    for (rank = 0; rank < blcodes; rank++) {

        Tracev((stderr, "\nbl code %2u ", bl_order[rank]));

        send_bits(s, s->bl_tree[bl_order[rank]].Len, 3, bi_buf, bi_valid);

    }

    Tracev((stderr, "\nbl tree: sent %lu", s->bits_sent));

    // Store back temp variables

    s->bi_buf = bi_buf;

    s->bi_valid = bi_valid;

    send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */

    Tracev((stderr, "\nlit tree: sent %lu", s->bits_sent));

    send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */

    Tracev((stderr, "\ndist tree: sent %lu", s->bits_sent));

}

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

 * Send a stored block

 */

void Z_INTERNAL zng_tr_stored_block(deflate_state *s, char *buf, uint32_t stored_len, int last) {

    /* buf: input block */

    /* stored_len: length of input block */

    /* last: one if this is the last block for a file */

    zng_tr_emit_tree(s, STORED_BLOCK, last); /* send block type */

    zng_tr_emit_align(s);                    /* align on byte boundary */

    cmpr_bits_align(s);

    put_short(s, (uint16_t)stored_len);

    put_short(s, (uint16_t)~stored_len);

    cmpr_bits_add(s, 32);

    sent_bits_add(s, 32);

    if (stored_len) {

        memcpy(s->pending_buf + s->pending, (unsigned char *)buf, stored_len);

        s->pending += stored_len;

        cmpr_bits_add(s, stored_len << 3);

        sent_bits_add(s, stored_len << 3);

    }

}

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

 * Flush the bits in the bit buffer to pending output (leaves at most 7 bits)

 */

void Z_INTERNAL zng_tr_flush_bits(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 Z_INTERNAL zng_tr_align(deflate_state *s) {

    zng_tr_emit_tree(s, STATIC_TREES, 0);

    zng_tr_emit_end_block(s, static_ltree, 0);

    bi_flush(s);

}

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

 * Determine the best encoding for the current block: dynamic trees, static

 * trees or store, and write out the encoded block.

 */

void Z_INTERNAL zng_tr_flush_block(deflate_state *s, char *buf, uint32_t stored_len, int last) {

    /* buf: input block, or NULL if too old */

    /* stored_len: length of input block */

    /* last: one if this is the last block for a file */

    unsigned long 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 (UNLIKELY(s->sym_next == 0)) {

        /* Emit an empty static tree block with no codes */

        opt_lenb = static_lenb = 0;

        s->static_len = 7;

    } else 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 %lu, stat %lu", s->opt_len, s->static_len));

        build_tree(s, (tree_desc *)(&(s->d_desc)));

        Tracev((stderr, "\ndist data: dyn %lu, stat %lu", 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 %u lit %u ",

                opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,

                s->sym_next / 3));

        if (static_lenb <= opt_lenb || s->strategy == Z_FIXED)

            opt_lenb = static_lenb;

    } else {

        Assert(buf != NULL, "lost buf");

        opt_lenb = static_lenb = stored_len + 5; /* force a stored block */

    }

    if (stored_len+4 <= opt_lenb && buf != NULL) {

        /* 4: two words for the lengths

         * 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.

         */

        zng_tr_stored_block(s, buf, stored_len, last);

    } else if (static_lenb == opt_lenb) {

        zng_tr_emit_tree(s, STATIC_TREES, last);

        compress_block(s, (const ct_data *)static_ltree, (const ct_data *)static_dtree);

        cmpr_bits_add(s, s->static_len);

    } else {

        zng_tr_emit_tree(s, DYN_TREES, last);

        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);

        cmpr_bits_add(s, s->opt_len);

    }

    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 unsigned long implemented on 32 bits.

     */

    init_block(s);

    if (last) {

        zng_tr_emit_align(s);

    }

    Tracev((stderr, "\ncomprlen %lu(%lu) ", s->compressed_len>>3, s->compressed_len-7*last));

}

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

 * Send the block data compressed using the given Huffman trees

 */

static void compress_block(deflate_state *s, const ct_data *ltree, const ct_data *dtree) {

    /* ltree: literal tree */

    /* dtree: distance tree */

    unsigned dist;      /* distance of matched string */

    int lc;             /* match length or unmatched char (if dist == 0) */

    unsigned sx = 0;    /* running index in sym_buf */

    if (s->sym_next != 0) {

        do {

            dist = s->sym_buf[sx++] & 0xff;

            dist += (unsigned)(s->sym_buf[sx++] & 0xff) << 8;

            lc = s->sym_buf[sx++];

            if (dist == 0) {

                zng_emit_lit(s, ltree, lc);

            } else {

                zng_emit_dist(s, ltree, dtree, lc, dist);

            } /* literal or match pair ? */

            /* Check that the overlay between pending_buf and sym_buf is ok: */

            Assert(s->pending < s->lit_bufsize + sx, "pending_buf overflow");

        } while (sx < s->sym_next);

    }

    zng_emit_end_block(s, ltree, 0);

}

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

 * 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.

 */

static int detect_data_type(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;

}

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

 * Flush the bit buffer, keeping at most 7 bits in it.

 */

static void bi_flush(deflate_state *s) {

    if (s->bi_valid == 64) {

        put_uint64(s, s->bi_buf);

        s->bi_buf = 0;

        s->bi_valid = 0;

    } else {

        if (s->bi_valid >= 32) {

            put_uint32(s, (uint32_t)s->bi_buf);

            s->bi_buf >>= 32;

            s->bi_valid -= 32;

        }

        if (s->bi_valid >= 16) {

            put_short(s, (uint16_t)s->bi_buf);

            s->bi_buf >>= 16;

            s->bi_valid -= 16;

        }

        if (s->bi_valid >= 8) {

            put_byte(s, s->bi_buf);

            s->bi_buf >>= 8;

            s->bi_valid -= 8;

        }

    }

}

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

 * Reverse the first len bits of a code, using straightforward code (a faster

 * method would use a table)

 * IN assertion: 1 <= len <= 15

 */

Z_INTERNAL unsigned bi_reverse(unsigned code, int len) {

    /* code: the value to invert */

    /* len: its bit length */

    Z_REGISTER unsigned res = 0;

    do {

        res |= code & 1;

        code >>= 1, res <<= 1;

    } while (--len > 0);

    return res >> 1;

}