trees.c

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation. Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/* trees.c -- output deflated data using Huffman coding
 * Copyright (C) 1995-2024 Jean-loup Gailly
 * detect_data_type() function provided freely by Cosmin Truta, 2006
 * For conditions of distribution and use, see copyright notice in zlib.h
 */

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

/* @(#) $Id$ */

/* #define GEN_TREES_H */

#include"deflate.h"

#ifdefZLIB_DEBUG
# include<ctype.h>
#endif

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

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

#defineEND_BLOCK 256
/* end of block literal code */

#defineREP_3_6 16
/* repeat previous bit length 3-6 times (2 bits of repeat count) */

#defineREPZ_3_10 17
/* repeat a zero length 3-10 times (3 bits of repeat count) */

#defineREPZ_11_138 18
/* repeat a zero length 11-138 times (7 bits of repeat count) */

localconstintextra_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};

localconstintextra_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};

localconstintextra_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};

localconstuchbl_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.
 */

#defineDIST_CODE_LEN 512 /* see definition of array dist_code below */

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

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

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

uch_dist_code[DIST_CODE_LEN];
/* Distance codes. The first 256 values correspond to the distances
 * 3 .. 258, the last 256 values correspond to the top 8 bits of
 * the 15 bit distances.
 */

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

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

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

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

structstatic_tree_desc_s {
constct_data*static_tree; /* static tree or NULL */
constintf*extra_bits; /* extra bits for each code or NULL */
intextra_base; /* base index for extra_bits */
intelems; /* max number of elements in the tree */
intmax_length; /* max bit length for the codes */
};

#ifdefNO_INIT_GLOBAL_POINTERS
# defineTCONST
#else
# defineTCONST const
#endif

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

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

localTCONSTstatic_tree_descstatic_bl_desc=
{(constct_data*)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS};

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

/* ===========================================================================
 * Reverse the first len bits of a code, using straightforward code (a faster
 * method would use a table)
 * IN assertion: 1 <= len <= 15
 */
local unsignedbi_reverse(unsignedcode, intlen) {
 register unsignedres=0;
do {
res |= code&1;
code >>= 1, res <<= 1;
 } while (--len>0);
returnres >> 1;
}

/* ===========================================================================
 * Flush the bit buffer, keeping at most 7 bits in it.
 */
localvoidbi_flush(deflate_state*s) {
if (s->bi_valid==16) {
put_short(s, s->bi_buf);
s->bi_buf=0;
s->bi_valid=0;
 } elseif (s->bi_valid >= 8) {
put_byte(s, (Byte)s->bi_buf);
s->bi_buf >>= 8;
s->bi_valid-=8;
 }
}

/* ===========================================================================
 * Flush the bit buffer and align the output on a byte boundary
 */
localvoidbi_windup(deflate_state*s) {
if (s->bi_valid>8) {
put_short(s, s->bi_buf);
 } elseif (s->bi_valid>0) {
put_byte(s, (Byte)s->bi_buf);
 }
s->bi_buf=0;
s->bi_valid=0;
#ifdefZLIB_DEBUG
s->bits_sent= (s->bits_sent+7) & ~7;
#endif
}

/* ===========================================================================
 * 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.
 */
localvoidgen_codes(ct_data*tree, intmax_code, ushf*bl_count) {
ushnext_code[MAX_BITS+1]; /* next code value for each bit length */
unsignedcode=0; /* running code value */
intbits; /* bit index */
intn; /* 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] = (ush)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++) {
intlen=tree[n].Len;
if (len==0) continue;
/* Now reverse the bits */
tree[n].Code= (ush)bi_reverse(next_code[len]++, len);

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

#ifdefGEN_TREES_H
localvoidgen_trees_header(void);
#endif

#ifndefZLIB_DEBUG
# definesend_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 */
# definesend_code(s, c, tree) \
 { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \
 send_bits(s, tree[c].Code, tree[c].Len); }
#endif

/* ===========================================================================
 * Send a value on a given number of bits.
 * IN assertion: length <= 16 and value fits in length bits.
 */
#ifdefZLIB_DEBUG
localvoidsend_bits(deflate_state*s, intvalue, intlength) {
Tracevv((stderr," l %2d v %4x ", length, value));
Assert(length>0&&length <= 15, "invalid length");
s->bits_sent+= (ulg)length;

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

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


/* the arguments must not have side effects */

/* ===========================================================================
 * Initialize the various 'constant' tables.
 */
localvoidtr_static_init(void) {
#if defined(GEN_TREES_H) || !defined(STDC)
staticintstatic_init_done=0;
intn; /* iterates over tree elements */
intbits; /* bit counter */
intlength; /* length value */
intcode; /* code value */
intdist; /* distance index */
ushbl_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: */
#ifdefNO_INIT_GLOBAL_POINTERS
static_l_desc.static_tree=static_ltree;
static_l_desc.extra_bits=extra_lbits;
static_d_desc.static_tree=static_dtree;
static_d_desc.extra_bits=extra_dbits;
static_bl_desc.extra_bits=extra_blbits;
#endif

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

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

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

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

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

/* ===========================================================================
 * Generate the file trees.h describing the static trees.
 */
#ifdefGEN_TREES_H
# ifndefZLIB_DEBUG
# include<stdio.h>
# endif

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

voidgen_trees_header(void) {
FILE*header=fopen("trees.h", "w");
inti;

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

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

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

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

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

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

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

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

/* ===========================================================================
 * Initialize a new block.
 */
localvoidinit_block(deflate_state*s) {
intn; /* 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;
}

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

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

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

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

s->bi_buf=0;
s->bi_valid=0;
#ifdefZLIB_DEBUG
s->compressed_len=0L;
s->bits_sent=0L;
#endif

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

#defineSMALLEST 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.
 */
#definepqremove(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.
 */
#definesmaller(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).
 */
localvoidpqdownheap(deflate_state*s, ct_data*tree, intk) {
intv=s->heap[k];
intj=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.
 */
localvoidgen_bitlen(deflate_state*s, tree_desc*desc) {
ct_data*tree=desc->dyn_tree;
intmax_code=desc->max_code;
constct_data*stree=desc->stat_desc->static_tree;
constintf*extra=desc->stat_desc->extra_bits;
intbase=desc->stat_desc->extra_base;
intmax_length=desc->stat_desc->max_length;
inth; /* heap index */
intn, m; /* iterate over the tree elements */
intbits; /* bit length */
intxbits; /* extra bits */
ushf; /* frequency */
intoverflow=0; /* number of elements with bit length too large */

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

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

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

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

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

#ifdefDUMP_BL_TREE
# include<stdio.h>
#endif

/* ===========================================================================
 * 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.
 */
localvoidbuild_tree(deflate_state*s, tree_desc*desc) {
ct_data*tree=desc->dyn_tree;
constct_data*stree=desc->stat_desc->static_tree;
intelems=desc->stat_desc->elems;
intn, m; /* iterate over heap elements */
intmax_code=-1; /* largest code with non zero frequency */
intnode; /* new node being created */

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

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

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

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

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

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

/* Create a new node father of n and m */
tree[node].Freq=tree[n].Freq+tree[m].Freq;
s->depth[node] = (uch)((s->depth[n] >= s->depth[m] ?
s->depth[n] : s->depth[m]) +1);
tree[n].Dad=tree[m].Dad= (ush)node;
#ifdefDUMP_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.
 */
localvoidscan_tree(deflate_state*s, ct_data*tree, intmax_code) {
intn; /* iterates over all tree elements */
intprevlen=-1; /* last emitted length */
intcurlen; /* length of current code */
intnextlen=tree[0].Len; /* length of next code */
intcount=0; /* repeat count of the current code */
intmax_count=7; /* max repeat count */
intmin_count=4; /* min repeat count */

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

for (n=0; n <= max_code; n++) {
curlen=nextlen; nextlen=tree[n+1].Len;
if (++count<max_count&&curlen==nextlen) {
continue;
 } elseif (count<min_count) {
s->bl_tree[curlen].Freq+=count;
 } elseif (curlen!=0) {
if (curlen!=prevlen) s->bl_tree[curlen].Freq++;
s->bl_tree[REP_3_6].Freq++;
 } elseif (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;
 } elseif (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.
 */
localvoidsend_tree(deflate_state*s, ct_data*tree, intmax_code) {
intn; /* iterates over all tree elements */
intprevlen=-1; /* last emitted length */
intcurlen; /* length of current code */
intnextlen=tree[0].Len; /* length of next code */
intcount=0; /* repeat count of the current code */
intmax_count=7; /* max repeat count */
intmin_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;
 } elseif (count<min_count) {
do { send_code(s, curlen, s->bl_tree); } while (--count!=0);

 } elseif (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);

 } elseif (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;
 } elseif (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.
 */
localintbuild_bl_tree(deflate_state*s) {
intmax_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*((ulg)max_blindex+1) +5+5+4;
Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
s->opt_len, s->static_len));

returnmax_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.
 */
localvoidsend_all_trees(deflate_state*s, intlcodes, intdcodes,
intblcodes) {
intrank; /* index in bl_order */

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

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

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

/* ===========================================================================
 * Send a stored block
 */
voidZLIB_INTERNAL_tr_stored_block(deflate_state*s, charf*buf,
ulgstored_len, intlast) {
send_bits(s, (STORED_BLOCK<<1) +last, 3); /* send block type */
bi_windup(s); /* align on byte boundary */
put_short(s, (ush)stored_len);
put_short(s, (ush)~stored_len);
if (stored_len)
zmemcpy(s->pending_buf+s->pending, (Bytef*)buf, stored_len);
s->pending+=stored_len;
#ifdefZLIB_DEBUG
s->compressed_len= (s->compressed_len+3+7) & (ulg)~7L;
s->compressed_len+= (stored_len+4) << 3;
s->bits_sent+=2*16;
s->bits_sent+=stored_len << 3;
#endif
}

/* ===========================================================================
 * Flush the bits in the bit buffer to pending output (leaves at most 7 bits)
 */
voidZLIB_INTERNAL_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.
 */
voidZLIB_INTERNAL_tr_align(deflate_state*s) {
send_bits(s, STATIC_TREES<<1, 3);
send_code(s, END_BLOCK, static_ltree);
#ifdefZLIB_DEBUG
s->compressed_len+=10L; /* 3 for block type, 7 for EOB */
#endif
bi_flush(s);
}

/* ===========================================================================
 * Send the block data compressed using the given Huffman trees
 */
localvoidcompress_block(deflate_state*s, constct_data*ltree,
constct_data*dtree) {
unsigneddist; /* distance of matched string */
intlc; /* match length or unmatched char (if dist == 0) */
unsignedsx=0; /* running index in symbol buffers */
unsignedcode; /* the code to send */
intextra; /* number of extra bits to send */

if (s->sym_next!=0) do {
#ifdefLIT_MEM
dist=s->d_buf[sx];
lc=s->l_buf[sx++];
#else
dist=s->sym_buf[sx++] &0xff;
dist+= (unsigned)(s->sym_buf[sx++] &0xff) << 8;
lc=s->sym_buf[sx++];
#endif
if (dist==0) {
send_code(s, lc, ltree); /* send a literal byte */
Tracecv(isgraph(lc), (stderr," '%c' ", lc));
 } else {
/* Here, lc is the match length - MIN_MATCH */
code=_length_code[lc];
send_code(s, code+LITERALS+1, ltree); /* send length code */
extra=extra_lbits[code];
if (extra!=0) {
lc-=base_length[code];
send_bits(s, lc, extra); /* send the extra length bits */
 }
dist--; /* dist is now the match distance - 1 */
code=d_code(dist);
Assert (code<D_CODES, "bad d_code");

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

/* Check for no overlay of pending_buf on needed symbols */
#ifdefLIT_MEM
Assert(s->pending<2* (s->lit_bufsize+sx), "pendingBuf overflow");
#else
Assert(s->pending<s->lit_bufsize+sx, "pendingBuf overflow");
#endif

 } while (sx<s->sym_next);

send_code(s, END_BLOCK, ltree);
}

/* ===========================================================================
 * Check if the data type is TEXT or BINARY, using the following algorithm:
 * - TEXT if the two conditions below are satisfied:
 * a) There are no non-portable control characters belonging to the
 * "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.
 */
localintdetect_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 longblock_mask=0xf3ffc07fUL;
intn;

/* 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))
returnZ_BINARY;