/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=4 sts=4 sw=4 fenc=utf-8                                :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 1995-2017 Jean-loup Gailly                                         │
│ Use of this source code is governed by the BSD-style licenses that can       │
│ be found in the third_party/zlib/LICENSE file.                               │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/stdio/stdio.h"
#include "libc/str/str.h"
#include "third_party/zlib/deflate.h"
#include "third_party/zlib/internal.h"

asm(".ident\t\"\\n\\n\
zlib (zlib License)\\n\
Copyright 1995-2017 Jean-loup Gailly and Mark Adler\"");
asm(".include \"libc/disclaimer.inc\"");

/**
 * @fileoverview output deflated data using Huffman coding
 *
 *  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.
 */

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

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

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

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

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

static 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};

static 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};

static 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};

static const uint8_t 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.
 */

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 */
};

static const static_tree_desc static_l_desc = {kZlibStaticLtree, extra_lbits,
                                               LITERALS + 1, L_CODES, MAX_BITS};

static const static_tree_desc static_d_desc = {kZlibStaticDtree, 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 tr_static_init(void);
static void init_block(struct DeflateState *s);
static void pqdownheap(struct DeflateState *s, ct_data *tree, int k);
static void gen_bitlen(struct DeflateState *s, tree_desc *desc);
static void gen_codes(ct_data *tree, int max_code, uint16_t *bl_count);
static void build_tree(struct DeflateState *s, tree_desc *desc);
static void scan_tree(struct DeflateState *s, ct_data *tree, int max_code);
static void send_tree(struct DeflateState *s, ct_data *tree, int max_code);
static int build_bl_tree(struct DeflateState *s);
static void send_all_trees(struct DeflateState *s, int lcodes, int dcodes,
                           int blcodes);
static void compress_block(struct DeflateState *s, const ct_data *ltree,
                           const ct_data *dtree);
static int detect_data_type(struct DeflateState *s);
static unsigned bi_reverse(unsigned value, int length);
static void bi_windup(struct DeflateState *s);
static void bi_flush(struct DeflateState *s);

#ifdef GEN_TREES_H
static void gen_trees_header(void);
#endif

#ifndef ZLIB_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 /* !ZLIB_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, (uint8_t)((w)&0xff));           \
    put_byte(s, (uint8_t)((uint16_t)(w) >> 8)); \
  }

/**
 * Send a value on a given number of bits.
 * IN assertion: length <= 16 and value fits in length bits.
 */
#ifdef ZLIB_DEBUG
static void send_bits(struct DeflateState *s, int value, int length) {
  Tracevv((stderr, " l %2d v %4x ", length, value));
  Assert(length > 0 && length <= 15, "invalid length");
  s->bits_sent += (uint64_t)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 |= (uint16_t)value << s->bi_valid;
    put_short(s, s->bi_buf);
    s->bi_buf = (uint16_t)value >> (Buf_size - s->bi_valid);
    s->bi_valid += length - Buf_size;
  } else {
    s->bi_buf |= (uint16_t)value << s->bi_valid;
    s->bi_valid += length;
  }
}
#else /* !ZLIB_DEBUG */
#define send_bits(s, value, length)                          \
  {                                                          \
    int len = length;                                        \
    if (s->bi_valid > (int)Buf_size - len) {                 \
      int val = (int)value;                                  \
      s->bi_buf |= (uint16_t)val << s->bi_valid;             \
      put_short(s, s->bi_buf);                               \
      s->bi_buf = (uint16_t)val >> (Buf_size - s->bi_valid); \
      s->bi_valid += len - Buf_size;                         \
    } else {                                                 \
      s->bi_buf |= (uint16_t)(value) << s->bi_valid;         \
      s->bi_valid += len;                                    \
    }                                                        \
  }
#endif /* ZLIB_DEBUG */

/* the arguments must not have side effects */

/**
 * Initialize the various 'constant' tables.
 */
static void tr_static_init(void) {
#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 */
  uint16_t 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 = kZlibStaticLtree;
  static_l_desc.extra_bits = extra_lbits;
  static_d_desc.static_tree = kZlibStaticDtree;
  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++) {
    kZlibBaseLength[code] = length;
    for (n = 0; n < (1u << extra_lbits[code]); n++) {
      kZlibLengthCode[length++] = (uint8_t)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:
   */
  kZlibLengthCode[length - 1] = (uint8_t)code;

  /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
  dist = 0;
  for (code = 0; code < 16; code++) {
    kZlibBaseDist[code] = dist;
    for (n = 0; n < (1u << extra_dbits[code]); n++) {
      kZlibDistCode[dist++] = (uint8_t)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++) {
    kZlibBaseDist[code] = dist << 7;
    for (n = 0; n < (1 << (extra_dbits[code] - 7)); n++) {
      kZlibDistCode[256 + dist++] = (uint8_t)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) kZlibStaticLtree[n++].Len = 8, bl_count[8]++;
  while (n <= 255) kZlibStaticLtree[n++].Len = 9, bl_count[9]++;
  while (n <= 279) kZlibStaticLtree[n++].Len = 7, bl_count[7]++;
  while (n <= 287) kZlibStaticLtree[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 *)kZlibStaticLtree, L_CODES + 1, bl_count);

  /* The static distance tree is trivial: */
  for (n = 0; n < D_CODES; n++) {
    kZlibStaticDtree[n].Len = 5;
    kZlibStaticDtree[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

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

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

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

  fprintf(header, "const uint8_t kZlibDistCode[DIST_CODE_LEN] = {\n");
  for (i = 0; i < DIST_CODE_LEN; i++) {
    fprintf(header, "%2u%s", kZlibDistCode[i],
            SEPARATOR(i, DIST_CODE_LEN - 1, 20));
  }

  fprintf(header, "const uint8_t kZlibLengthCode[MAX_MATCH-MIN_MATCH+1]= {\n");
  for (i = 0; i < MAX_MATCH - MIN_MATCH + 1; i++) {
    fprintf(header, "%2u%s", kZlibLengthCode[i],
            SEPARATOR(i, MAX_MATCH - MIN_MATCH, 20));
  }

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

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

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

/**
 * Initialize the tree data structures for a new zlib stream.
 */
void _tr_init(struct DeflateState *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 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(struct DeflateState *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).
 * @param tree is tree to restore
 * @param k is node to move down
 */
static void pqdownheap(struct DeflateState *s, ct_data *tree, int k) {
  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(struct DeflateState *s, tree_desc *desc) {
  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 */
  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 + 1;
    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) 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 += (uint64_t)f * (unsigned)(bits + xbits);
    if (stree) s->static_len += (uint64_t)f * (unsigned)(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] += 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) {
        Tracev((stderr, "code %d bits %d->%d\n", m, tree[m].Len, bits));
        s->opt_len += ((uint64_t)bits - tree[m].Len) * tree[m].Freq;
        tree[m].Len = (uint16_t)bits;
      }
      n--;
    }
  }
}

/**
 * Generates codes for given tree and bit counts (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.
 *
 * @param max_code is largest code with non zero frequency
 * @param bl_count is number of codes at each bit length
 */
static void gen_codes(ct_data *tree, int max_code, uint16_t *bl_count) {
  uint16_t next_code[MAX_BITS + 1]; /* next code value for each bit length */
  unsigned 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 != kZlibStaticLtree,
            (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.
 */
static void build_tree(struct DeflateState *s, tree_desc *desc) {
  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] =
        (uint8_t)((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.
 *
 * @param tree is tree to be scanned
 * @param max_code is its largest code of non zero frequency
 */
static void scan_tree(struct DeflateState *s, ct_data *tree, int max_code) {
  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 = (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.
 *
 * @param tree is tree to be scanned
 * @param max_code is its largest code of non zero frequency
 */
static void send_tree(struct DeflateState *s, ct_data *tree, int max_code) {
  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.
 */
static int build_bl_tree(struct DeflateState *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 * ((uint64_t)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.
 */
static void send_all_trees(struct DeflateState *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");
  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));
}

/**
 * Sends stored block.
 * @param last is one if this is the last block of file
 */
void _tr_stored_block(struct DeflateState *s, charf *buf, uint64_t stored_len,
                      int last) {
  send_bits(s, (STORED_BLOCK << 1) + last, 3); /* send block type */
  bi_windup(s);                                /* align on byte boundary */
  put_short(s, (uint16_t)stored_len);
  put_short(s, (uint16_t)~stored_len);
  memcpy(s->pending_buf + s->pending, (Bytef *)buf, stored_len);
  s->pending += stored_len;
#ifdef ZLIB_DEBUG
  s->compressed_len = (s->compressed_len + 3 + 7) & (uint64_t)~7L;
  s->compressed_len += (stored_len + 4) << 3;
  s->bits_sent += 2 * 16;
  s->bits_sent += stored_len << 3;
#endif
}

/**
 * Flushes bits in bit buffer to pending output (leaves at most 7 bits)
 */
void _tr_flush_bits(struct DeflateState *s) { bi_flush(s); }

/**
 * Sends one empty static block to give enough lookahead for inflate.
 * This takes 10 bits, of which 7 may remain in the bit buffer.
 */
void _tr_align(struct DeflateState *s) {
  send_bits(s, STATIC_TREES << 1, 3);
  send_code(s, END_BLOCK, kZlibStaticLtree);
#ifdef ZLIB_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 write out the encoded block.
 *
 * @param last is one if this is the last block of file
 */
void _tr_flush_block(struct DeflateState *s, charf *buf, uint64_t stored_len,
                     int last) {
  uint64_t 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->sym_next / 3));

    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 *)kZlibStaticLtree,
                   (const ct_data *)kZlibStaticDtree);
#ifdef ZLIB_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 ZLIB_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 ZLIB_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.
 *
 * @param dist is distance of matched string
 * @param lc is match length-MIN_MATCH or unmatched char (if dist==0)
 */
int _tr_tally(struct DeflateState *s, unsigned dist, unsigned lc) {
  s->sym_buf[s->sym_next++] = dist;
  s->sym_buf[s->sym_next++] = dist >> 8;
  s->sym_buf[s->sym_next++] = 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((uint16_t)dist < (uint16_t)MAX_DIST(s) &&
               (uint16_t)lc <= (uint16_t)(MAX_MATCH - MIN_MATCH) &&
               (uint16_t)d_code(dist) < (uint16_t)D_CODES,
           "_tr_tally: bad match");

    s->dyn_ltree[kZlibLengthCode[lc] + LITERALS + 1].Freq++;
    s->dyn_dtree[d_code(dist)].Freq++;
  }
  return (s->sym_next == s->sym_end);
}

/**
 * Send the block data compressed using the given Huffman trees
 */
static void compress_block(struct DeflateState *s, const ct_data *ltree,
                           const ct_data *dtree) {
  unsigned dist;   /* distance of matched string */
  int lc;          /* match length or unmatched char (if dist == 0) */
  unsigned sx = 0; /* running index in sym_buf */
  unsigned code;   /* the code to send */
  int extra;       /* number of extra bits to send */

  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) {
        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 = kZlibLengthCode[lc];
        send_code(s, code + LITERALS + 1, ltree); /* send the length code */
        extra = extra_lbits[code];
        if (extra != 0) {
          lc -= kZlibBaseLength[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 -= (unsigned)kZlibBaseDist[code];
          send_bits(s, dist, extra); /* send the extra distance bits */
        }
      } /* literal or match pair ? */

      /* Check that the overlay between pending_buf and sym_buf is ok: */
      Assert(s->pending < s->lit_bufsize + sx, "pendingBuf overflow");

    } while (sx < s->sym_next);

  send_code(s, END_BLOCK, ltree);
}

/**
 * Checks if data type is TEXT or BINARY.
 *
 * This uses 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(struct DeflateState *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
 *
 * @param code is value to invert
 * @param len is in bits
 */
static unsigned bi_reverse(unsigned code, int len) {
  register unsigned res = 0;
  do {
    res |= code & 1;
    code >>= 1, res <<= 1;
  } while (--len > 0);
  return res >> 1;
}

/**
 * Flushes bit buffer, keeping at most 7 bits in it.
 */
static void bi_flush(struct DeflateState *s) {
  if (s->bi_valid == 16) {
    put_short(s, s->bi_buf);
    s->bi_buf = 0;
    s->bi_valid = 0;
  } else if (s->bi_valid >= 8) {
    put_byte(s, (Byte)s->bi_buf);
    s->bi_buf >>= 8;
    s->bi_valid -= 8;
  }
}

/**
 * Flushes bit buffer and align the output on a byte boundary
 */
static void bi_windup(struct DeflateState *s) {
  if (s->bi_valid > 8) {
    put_short(s, s->bi_buf);
  } else if (s->bi_valid > 0) {
    put_byte(s, (Byte)s->bi_buf);
  }
  s->bi_buf = 0;
  s->bi_valid = 0;
#ifdef ZLIB_DEBUG
  s->bits_sent = (s->bits_sent + 7) & ~7;
#endif
}