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

 * Copyright (C) 1995-2026 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 "deflate_p.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 pq_radix_pass    (const uint32_t *src, uint32_t *dst, int n, int shift, uint16_t *count);

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

static void gen_bitlen       (deflate_state *s, tree_desc *desc, const uint32_t *sorted, int nleaves, int root);

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);

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

 * 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;

    s->bi_used = 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 = 0;

    s->sym_next = 0;

}

/* Queue entries pack freq above the node index, so a single 32-bit compare orders nodes by

 * frequency, breaking ties by node index: leaves first, then internal nodes in creation order,

 * which keeps the worst-case code length small. */

#define PQ_NODE_BITS 10

#define pq_pack(freq, node) (((uint32_t)(freq) << PQ_NODE_BITS) | (unsigned)(node))

#define pq_node(e)  ((int)((e) & ((1u << PQ_NODE_BITS) - 1)))

#define pq_freq(e)  ((e) >> PQ_NODE_BITS)

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

 * One stable counting-sort pass over an 8-bit digit of the packed entries.

 * count holds the digit histogram at offset +1, accumulated during the leaf

 * scan, and is turned into running start positions here. Used by build_tree().

 */

static void pq_radix_pass(const uint32_t *src, uint32_t *dst, int n, int shift, uint16_t *count) {

    int i;

    for (i = 1; i <= 256; i++)

        count[i] = (uint16_t)(count[i] + count[i-1]);

    for (i = 0; i < n; i++)

        dst[count[(src[i] >> shift) & 0xFF]++] = src[i];

}

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

 * Take the smaller of the two queue heads: the next unused leaf, or the next

 * created internal node. Used by build_tree().

 */

static inline uint32_t pq_take(const uint32_t *leaves, int *li, int nleaves,

                               const uint32_t *internals, int *ihead, int itail) {

    if (*li < nleaves && (*ihead == itail || leaves[*li] < internals[*ihead]))

        return leaves[(*li)++];

    return internals[(*ihead)++];

}

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

 * 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 */

    int nleaves = 0;

    int li = 0, ihead = 0, itail = 0;  /* queue positions for leaves and internal nodes */

    int merges;

    uint32_t *leaves = s->pq_leaves;   /* packed leaf entries, sorted by frequency */

    uint32_t *scratch = s->pq_scratch; /* radix buffer, then FIFO of created internal nodes */

    uint32_t *sorted = leaves;         /* sorted leaves, in scratch after a single pass */

    uint32_t *internals = scratch;     /* internal node FIFO, in whichever buffer is free */

    uint16_t count_lo[257];            /* histogram of the low frequency byte, at offset +1 */

    uint16_t count_hi[257];            /* histogram of the high frequency byte, at offset +1 */

    memset(count_lo, 0, sizeof(count_lo));

    memset(count_hi, 0, sizeof(count_hi));

    for (n = 0; n < elems; n++) {

        const uint16_t freq = tree[n].Freq;

        if (freq != 0) {

            leaves[nleaves++] = pq_pack(freq, n);

            count_lo[(freq & 0xFF) + 1]++;

            count_hi[(freq >> 8) + 1]++;

            max_code = n;

        } 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 (nleaves < 2) {

        node = (max_code < 2 ? ++max_code : 0);

        leaves[nleaves++] = pq_pack(1, node);

        tree[node].Freq = 1;

        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;

    /* Sort the leaves by packed entry. The scan above appended them in node order, which is

     * ascending in the node bits, so two stable passes over the freq bytes finish the sort.

     * A forced node can arrive out of node order, but then there are exactly two leaves,

     * so the radix path only ever sorts entries the histograms counted. */

    if (nleaves == 2) {

        if (leaves[0] > leaves[1]) {

            const uint32_t t = leaves[0];

            leaves[0] = leaves[1];

            leaves[1] = t;

        }

    } else if ((int)count_hi[1] == nleaves) {

        /* Every frequency fits in one byte, so the first pass already produces the final

         * order. The sorted entries then live in scratch, so the internal-node FIFO takes

         * over the leaves buffer instead. */

        pq_radix_pass(leaves, scratch, nleaves, PQ_NODE_BITS, count_lo);

        sorted = scratch;

        internals = leaves;

    } else {

        /* Sort by the low then high frequency byte, ending back in leaves. */

        pq_radix_pass(leaves, scratch, nleaves, PQ_NODE_BITS, count_lo);

        pq_radix_pass(scratch, leaves, nleaves, PQ_NODE_BITS + 8, count_hi);

    }

    /* Construct the Huffman tree by repeatedly combining the least two frequent nodes.

     * Sorted leaves and the FIFO of created nodes are each ascending, because merge sums

     * never decrease, so the two smallest nodes are always at the queue heads.

     */

    node = elems;              /* next internal node of the tree */

    for (merges = nleaves - 1; merges > 0; merges--) {

        /* en = entry of least frequency, em = entry of next least frequency */

        const uint32_t en = pq_take(sorted, &li, nleaves, internals, &ihead, itail);

        const uint32_t em = pq_take(sorted, &li, nleaves, internals, &ihead, itail);

        n = pq_node(en);

        m = pq_node(em);

        /* Create a new node father of n and m. Freq wraps the same way the uint16_t

         * state field did. */

        const uint16_t f = (uint16_t)(pq_freq(en) + pq_freq(em));

        tree[node].Freq = f;

        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 append the new node to the internal queue */

        internals[itail++] = pq_pack(f, node);

        node++;

    }

    /* At this point, the fields freq and dad are set. We can now

     * generate the bit lengths.

     */

    gen_bitlen(s, (tree_desc *)desc, sorted, nleaves, node - 1);

    /* The field len is now set, we can generate the bit codes */

    gen_codes((ct_data *)tree, max_code, s->bl_count);

}

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

 * 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, sorted holds the leaves by

 *    increasing frequency, and root is the last created node.

 * 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. Used by build_tree().

 */

static void gen_bitlen(deflate_state *s, tree_desc *desc, const uint32_t *sorted, int nleaves, int root) {

    /* desc: the tree descriptor */

    ct_data *tree           = desc->dyn_tree;

    int elems               = desc->stat_desc->elems;

    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 i;              /* index into sorted */

    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[root].Len = 0; /* root of the tree */

    /* Dads are created after their sons, so a descending walk visits each dad first */

    for (n = root - 1; n >= elems; n--) {

        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 */

    }

    for (i = 0; i < nleaves; i++) {

        n = pq_node(sorted[i]);

        bits = tree[tree[n].Dad].Len + 1u;

        if (bits > max_length){

            bits = max_length;

            overflow++;

        }

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

        s->bl_count[bits]++;

        xbits = 0;

        if (n >= base)

            xbits = extra[n-base];

        f = tree[n].Freq;

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

        if (stree)

            s->static_len += (unsigned int)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.

     * (It is simpler to reconstruct all lengths instead of fixing only

     * the wrong ones. This idea is taken from 'ar' written by Haruhiko Okumura.)

     */

    i = 0;

    for (bits = max_length; bits != 0; bits--) {

        n = s->bl_count[bits];

        while (n != 0) {

            m = pq_node(sorted[i++]);

            if (tree[m].Len != bits) {

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

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

                s->opt_len -= (unsigned int)(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. Used by build_tree().

 */

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 */

    uint16_t 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] = 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 = 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));

    }

}

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

 * 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 int)max_blindex+1) + 5+5+4;

    Tracev((stderr, "\ndyn trees: dyn %u, stat %u", 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, unsigned 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, buf, stored_len);

        s->pending += stored_len;

        cmpr_bits_add(s, stored_len << 3);

        sent_bits_add(s, stored_len << 3);

    }

}

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

 * 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);

    zng_tr_flush_bits(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, unsigned 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 int 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 %u, stat %u", s->opt_len, s->static_len));

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

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

 */

#if !defined(LIT_MEM) && OPTIMAL_CMP >= 64

/* One 64-bit little-endian load at sx spans the next two symbols' dist fields

 * (bits 0..15, 24..39) and literals (bits 16..23, 40..47). The second symbol's dist

 * field alone separates a one-literal run from a two-literal one. */

#define LIT3_DIST1_MASK 0x000000FFFF000000ULL

#endif

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 symbol buffers */

    /* Local pointers to avoid indirection */

    const unsigned int sym_next = s->sym_next;

#ifdef LIT_MEM

    uint16_t *d_buf = s->d_buf;

    unsigned char *l_buf = s->l_buf;

#else

    unsigned char *sym_buf = s->sym_buf;

#endif

    /* Keep the bit writer state in registers across the entire loop */

    uint64_t bi_buf = s->bi_buf;

    uint32_t bi_valid = s->bi_valid;

    uint32_t pending = s->pending;

    if (sym_next != 0) {

        do {

            send_bits_flush(s, bi_buf, bi_valid, pending);

#ifdef LIT_MEM

            dist = d_buf[sx];

            lc = l_buf[sx++];

#else

#  if OPTIMAL_CMP >= 32

            uint32_t dist_lc = Z_U32_FROM_LE(zng_memread_4(&sym_buf[sx]));

            dist = dist_lc & 0xffff;

            lc = (dist_lc >> 16) & 0xff;

#  else

            dist = sym_buf[sx] + ((unsigned)sym_buf[sx + 1] << 8);

            lc = sym_buf[sx + 2];

#  endif

            sx += 3;

#endif

            if (dist == 0) {

                uint64_t bits = 0;

                uint32_t nbits = 0;

                send_code_merge(s, lc, ltree, bits, nbits);

#if !defined(LIT_MEM) && OPTIMAL_CMP >= 64

                /* Accumulate up to 2 more consecutive literals into the same merge. Their

                 * codes are at most 15 bits each, so all three fit alongside the at most

                 * 7 bits the flush above leaves behind. */

                if (sx + 8 <= sym_next) {

                    uint64_t next_syms = Z_U64_FROM_LE(zng_memread_8(&sym_buf[sx]));

                    /* A dist field is zero exactly when that symbol is a literal */

                    if ((uint16_t)next_syms == 0) {

                        send_code_merge(s, (unsigned)((next_syms >> 16) & 0xff), ltree, bits, nbits);

                        sx += 3;

                        if ((next_syms & LIT3_DIST1_MASK) == 0) {

                            send_code_merge(s, (unsigned)((next_syms >> 40) & 0xff), ltree, bits, nbits);

                            sx += 3;

                        }

                    }

                }

#endif

                /* The codes were traced and counted as they accumulated */

                Assert(bi_valid + nbits <= 64, "bit buffer overflow");

                bi_buf |= bits << bi_valid;

                bi_valid += nbits;

            } else {

                uint32_t match_bits_len;

                uint64_t match_bits = zng_assemble_dist(ltree, dtree, lc, dist, &match_bits_len);

                send_bits_merge(s, match_bits, match_bits_len, bi_buf, bi_valid);

            } /* literal or match pair ? */

            /* Check for no overlay of pending_buf on needed symbols */

#ifdef LIT_MEM

            Assert(pending < 2 * (s->lit_bufsize + sx), "pending_buf overflow");

#else

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

#endif

        } while (sx < sym_next);

    }

    s->pending = pending;

    zng_emit_end_block(s, ltree, 0, &bi_buf, &bi_valid);

    /* Write back to state */

    s->bi_buf = bi_buf;

    s->bi_valid = bi_valid;

}

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

 * 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

 *       "block list" (0..6, 14..25, 28..31).

 *    b) There is at least one printable character belonging to the

 *       "allow 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) {

    /* block_mask is the bit mask of block-listed bytes

     * set bits 0..6, 14..25, and 28..31

     * 0xf3ffc07f = binary 11110011111111111100000001111111

     */

    unsigned long block_mask = 0xf3ffc07fUL;

    int n;

    /* Check for non-textual ("block-listed") bytes. */

    for (n = 0; n <= 31; n++, block_mask >>= 1)

        if ((block_mask & 1) && (s->dyn_ltree[n].Freq != 0))

            return Z_BINARY;

    /* Check for textual ("allow-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 "block-listed" or "allow-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.

 */

void Z_INTERNAL zng_tr_flush_bits(deflate_state *s) {

    if (s->bi_valid >= 48) {

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

        put_short(s, (uint16_t)(s->bi_buf >> 32));

        s->bi_buf >>= 48;

        s->bi_valid -= 48;

    } 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;

    }

}