trees.c File Reference

#include "deflate.h"

Classes
struct	static_tree_desc_s

Macros
#define	MAX_BL_BITS   7
#define	END_BLOCK   256
#define	REP_3_6   16
#define	REPZ_3_10   17
#define	REPZ_11_138   18
#define	DIST_CODE_LEN   512 /* see definition of array dist_code below */
#define	send_code(s, c, tree)   send_bits(s, tree[c].Code, tree[c].Len)
#define	put_short(s, w)
#define	send_bits(s, value, length)
#define	SMALLEST   1
#define	pqremove(s, tree, top)
#define	smaller(tree, n, m, depth)

Functions
void tr_static_init	OF ((void))
void init_block	OF ((deflate_state *s))
void pqdownheap	OF ((deflate_state *s, ct_data *tree, int k))
void gen_bitlen	OF ((deflate_state *s, tree_desc *desc))
void gen_codes	OF ((ct_data *tree, int max_code, ushf *bl_count))
void scan_tree	OF ((deflate_state *s, ct_data *tree, int max_code))
void send_all_trees	OF ((deflate_state *s, int lcodes, int dcodes, int blcodes))
void compress_block	OF ((deflate_state *s, const ct_data *ltree, const ct_data *dtree))
unsigned bi_reverse	OF ((unsigned value, int length))
void	tr_static_init ()
void ZLIB_INTERNAL	_tr_init (deflate_state *s)
void	init_block (deflate_state *s)
void	pqdownheap (deflate_state *s, ct_data *tree, int k)
void	gen_bitlen (deflate_state *s, tree_desc *desc)
void	gen_codes (ct_data *tree, int max_code, ushf *bl_count)
void	build_tree (deflate_state *s, tree_desc *desc)
void	scan_tree (deflate_state *s, ct_data *tree, int max_code)
void	send_tree (deflate_state *s, ct_data *tree, int max_code)
int	build_bl_tree (deflate_state *s)
void	send_all_trees (deflate_state *s, int lcodes, int dcodes, int blcodes)
void ZLIB_INTERNAL	_tr_stored_block (deflate_state *s, charf *buf, ulg stored_len, int last)
void ZLIB_INTERNAL	_tr_flush_bits (deflate_state *s)
void ZLIB_INTERNAL	_tr_align (deflate_state *s)
void ZLIB_INTERNAL	_tr_flush_block (deflate_state *s, charf *buf, ulg stored_len, int last)
int ZLIB_INTERNAL	_tr_tally (deflate_state *s, unsigned dist, unsigned lc)
void	compress_block (deflate_state *s, const ct_data *ltree, const ct_data *dtree)
int	detect_data_type (deflate_state *s)
unsigned	bi_reverse (unsigned code, int len)
void	bi_flush (deflate_state *s)
void	bi_windup (deflate_state *s)

Variables
const int	extra_lbits [LENGTH_CODES] = {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}
const int	extra_dbits [D_CODES] = {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}
const int	extra_blbits [BL_CODES] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7}
const uch	bl_order [BL_CODES] = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15}
ct_data	static_ltree [L_CODES+2]
ct_data	static_dtree [D_CODES]
uch	_dist_code [DIST_CODE_LEN]
uch	_length_code [MAX_MATCH-MIN_MATCH+1]
int	base_length [LENGTH_CODES]
int	base_dist [D_CODES]
const static_tree_desc	static_l_desc
const static_tree_desc	static_d_desc
const static_tree_desc	static_bl_desc

Macro Definition Documentation

MAX_BL_BITS

#define MAX_BL_BITS   7

END_BLOCK

#define END_BLOCK   256

REP_3_6

#define REP_3_6   16

REPZ_3_10

#define REPZ_3_10   17

REPZ_11_138

#define REPZ_11_138   18

DIST_CODE_LEN

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

send_code

#define send_code	(		s,
			c,
			tree
	)		send_bits(s, tree[c].Code, tree[c].Len)

put_short

#define put_short	(		s,
			w
	)

Value:

{ \
    put_byte(s, (uch)((w) & 0xff)); \
    put_byte(s, (uch)((ush)(w) >> 8)); \
}

send_bits

#define send_bits	(		s,
			value,
			length
	)

Value:

{ 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;\
  }\
}

SMALLEST

#define SMALLEST   1

pqremove

#define pqremove	(		s,
			tree,
			top
	)

Value:

{\
    top = s->heap[SMALLEST]; \
    s->heap[SMALLEST] = s->heap[s->heap_len--]; \
    pqdownheap(s, tree, SMALLEST); \
}

smaller

#define smaller	(		tree,
			n,
			m,
			depth
	)

Value:

(tree[n].Freq < tree[m].Freq || \
   (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))

Function Documentation

OF() [1/9]

void tr_static_init OF

(

(void)

)

OF() [2/9]

void init_block OF

(

(deflate_state *s)

)

OF() [3/9]

void pqdownheap OF

(

(deflate_state *s, ct_data *tree, int k)

)

OF() [4/9]

void gen_bitlen OF

(

(deflate_state *s, tree_desc *desc)

)

OF() [5/9]

void gen_codes OF

(

(ct_data *tree, int max_code, ushf *bl_count)

)

OF() [6/9]

void scan_tree OF

(

(deflate_state *s, ct_data *tree, int max_code)

)

OF() [7/9]

void send_all_trees OF

(

(deflate_state *s, int lcodes, int dcodes, int blcodes)

)

OF() [8/9]

void compress_block OF

(

(deflate_state *s, const ct_data *ltree, const ct_data *dtree)

)

OF() [9/9]

unsigned bi_reverse OF

(

(unsigned value, int length)

)

tr_static_init()

void tr_static_init

(

)

{
#if defined(GEN_TREES_H) || !defined(STDC)
    static int static_init_done = 0;
    int n;        /* iterates over tree elements */
    int bits;     /* bit counter */
    int length;   /* length value */
    int code;     /* code value */
    int dist;     /* distance index */
    ush bl_count[MAX_BITS+1];
    /* number of codes at each bit length for an optimal tree */
 
    if (static_init_done) return;
 
    /* For some embedded targets, global variables are not initialized: */
#ifdef NO_INIT_GLOBAL_POINTERS
    static_l_desc.static_tree = static_ltree;
    static_l_desc.extra_bits = extra_lbits;
    static_d_desc.static_tree = static_dtree;
    static_d_desc.extra_bits = extra_dbits;
    static_bl_desc.extra_bits = extra_blbits;
#endif
 
    /* Initialize the mapping length (0..255) -> length code (0..28) */
    length = 0;
    for (code = 0; code < LENGTH_CODES-1; code++) {
        base_length[code] = length;
        for (n = 0; n < (1<<extra_lbits[code]); n++) {
            _length_code[length++] = (uch)code;
        }
    }
    Assert (length == 256, "tr_static_init: length != 256");
    /* Note that the length 255 (match length 258) can be represented
     * in two different ways: code 284 + 5 bits or code 285, so we
     * overwrite length_code[255] to use the best encoding:
     */
    _length_code[length-1] = (uch)code;
 
    /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
    dist = 0;
    for (code = 0 ; code < 16; code++) {
        base_dist[code] = dist;
        for (n = 0; n < (1<<extra_dbits[code]); n++) {
            _dist_code[dist++] = (uch)code;
        }
    }
    Assert (dist == 256, "tr_static_init: dist != 256");
    dist >>= 7; /* from now on, all distances are divided by 128 */
    for ( ; code < D_CODES; code++) {
        base_dist[code] = dist << 7;
        for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
            _dist_code[256 + dist++] = (uch)code;
        }
    }
    Assert (dist == 256, "tr_static_init: 256+dist != 512");
 
    /* Construct the codes of the static literal tree */
    for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
    n = 0;
    while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
    while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
    while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
    while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
    /* Codes 286 and 287 do not exist, but we must include them in the
     * tree construction to get a canonical Huffman tree (longest code
     * all ones)
     */
    gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);
 
    /* The static distance tree is trivial: */
    for (n = 0; n < D_CODES; n++) {
        static_dtree[n].Len = 5;
        static_dtree[n].Code = bi_reverse((unsigned)n, 5);
    }
    static_init_done = 1;
 
#  ifdef GEN_TREES_H
    gen_trees_header();
#  endif
#endif /* defined(GEN_TREES_H) || !defined(STDC) */
}

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_tr_init()

void ZLIB_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;
#ifdef ZLIB_DEBUG
    s->compressed_len = 0L;
    s->bits_sent = 0L;
#endif
 
    /* Initialize the first block of the first file: */
    init_block(s);
}

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init_block()

void init_block

(

deflate_state *

s

)

{
    int n; /* iterates over tree elements */
 
    /* Initialize the trees. */
    for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;
    for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;
    for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;
 
    s->dyn_ltree[END_BLOCK].Freq = 1;
    s->opt_len = s->static_len = 0L;
    s->last_lit = s->matches = 0;
}

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pqdownheap()

void pqdownheap	(	deflate_state *	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;
}

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gen_bitlen()

void gen_bitlen	(	deflate_state *	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 */
    ush f;              /* frequency */
    int overflow = 0;   /* number of elements with bit length too large */
 
    for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0;
 
    /* In a first pass, compute the optimal bit lengths (which may
     * overflow in the case of the bit length tree).
     */
    tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */
 
    for (h = s->heap_max+1; h < HEAP_SIZE; h++) {
        n = s->heap[h];
        bits = tree[tree[n].Dad].Len + 1;
        if (bits > max_length) bits = max_length, overflow++;
        tree[n].Len = (ush)bits;
        /* We overwrite tree[n].Dad which is no longer needed */
 
        if (n > max_code) continue; /* not a leaf node */
 
        s->bl_count[bits]++;
        xbits = 0;
        if (n >= base) xbits = extra[n-base];
        f = tree[n].Freq;
        s->opt_len += (ulg)f * (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--;
        }
    }
}

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gen_codes()

void gen_codes	(	ct_data *	tree,
		int	max_code,
		ushf *	bl_count
	)

{
    ush 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] = (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++) {
        int len = 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));
    }
}

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build_tree()

void build_tree	(	deflate_state *	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] = (uch)((s->depth[n] >= s->depth[m] ?
                                s->depth[n] : s->depth[m]) + 1);
        tree[n].Dad = tree[m].Dad = (ush)node;
#ifdef DUMP_BL_TREE
        if (tree == s->bl_tree) {
            fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
                    node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
        }
#endif
        /* and insert the new node in the heap */
        s->heap[SMALLEST] = node++;
        pqdownheap(s, tree, SMALLEST);
 
    } while (s->heap_len >= 2);
 
    s->heap[--(s->heap_max)] = s->heap[SMALLEST];
 
    /* At this point, the fields freq and dad are set. We can now
     * generate the bit lengths.
     */
    gen_bitlen(s, (tree_desc *)desc);
 
    /* The field len is now set, we can generate the bit codes */
    gen_codes ((ct_data *)tree, max_code, s->bl_count);
}

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scan_tree()

void scan_tree	(	deflate_state *	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 = (ush)0xffff; /* guard */
 
    for (n = 0; n <= max_code; n++) {
        curlen = nextlen; nextlen = tree[n+1].Len;
        if (++count < max_count && curlen == nextlen) {
            continue;
        } else if (count < min_count) {
            s->bl_tree[curlen].Freq += count;
        } else if (curlen != 0) {
            if (curlen != prevlen) s->bl_tree[curlen].Freq++;
            s->bl_tree[REP_3_6].Freq++;
        } else if (count <= 10) {
            s->bl_tree[REPZ_3_10].Freq++;
        } else {
            s->bl_tree[REPZ_11_138].Freq++;
        }
        count = 0; prevlen = curlen;
        if (nextlen == 0) {
            max_count = 138, min_count = 3;
        } else if (curlen == nextlen) {
            max_count = 6, min_count = 3;
        } else {
            max_count = 7, min_count = 4;
        }
    }
}

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send_tree()

void send_tree	(	deflate_state *	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;
        }
    }
}

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build_bl_tree()

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*((ulg)max_blindex+1) + 5+5+4;
    Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld",
            s->opt_len, s->static_len));
 
    return max_blindex;
}

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send_all_trees()

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");
    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));
}

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_tr_stored_block()

void ZLIB_INTERNAL _tr_stored_block	(	deflate_state *	s,
		charf *	buf,
		ulg	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, (ush)stored_len);
    put_short(s, (ush)~stored_len);
    zmemcpy(s->pending_buf + s->pending, (Bytef *)buf, stored_len);
    s->pending += stored_len;
#ifdef ZLIB_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
}

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_tr_flush_bits()

void ZLIB_INTERNAL _tr_flush_bits

(

deflate_state *

s

)

{
    bi_flush(s);
}

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_tr_align()

void ZLIB_INTERNAL _tr_align

(

deflate_state *

s

)

{
    send_bits(s, STATIC_TREES<<1, 3);
    send_code(s, END_BLOCK, static_ltree);
#ifdef ZLIB_DEBUG
    s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
#endif
    bi_flush(s);
}

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_tr_flush_block()

void ZLIB_INTERNAL _tr_flush_block	(	deflate_state *	s,
		charf *	buf,
		ulg	stored_len,
		int	last
	)

{
    ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
    int max_blindex = 0;  /* index of last bit length code of non zero freq */
 
    /* Build the Huffman trees unless a stored block is forced */
    if (s->level > 0) {
 
        /* Check if the file is binary or text */
        if (s->strm->data_type == Z_UNKNOWN)
            s->strm->data_type = detect_data_type(s);
 
        /* Construct the literal and distance trees */
        build_tree(s, (tree_desc *)(&(s->l_desc)));
        Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len,
                s->static_len));
 
        build_tree(s, (tree_desc *)(&(s->d_desc)));
        Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len,
                s->static_len));
        /* At this point, opt_len and static_len are the total bit lengths of
         * the compressed block data, excluding the tree representations.
         */
 
        /* Build the bit length tree for the above two trees, and get the index
         * in bl_order of the last bit length code to send.
         */
        max_blindex = build_bl_tree(s);
 
        /* Determine the best encoding. Compute the block lengths in bytes. */
        opt_lenb = (s->opt_len+3+7)>>3;
        static_lenb = (s->static_len+3+7)>>3;
 
        Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
                opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
                s->last_lit));
 
        if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
 
    } else {
        Assert(buf != (char*)0, "lost buf");
        opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
    }
 
#ifdef FORCE_STORED
    if (buf != (char*)0) { /* force stored block */
#else
    if (stored_len+4 <= opt_lenb && buf != (char*)0) {
                       /* 4: two words for the lengths */
#endif
        /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
         * Otherwise we can't have processed more than WSIZE input bytes since
         * the last block flush, because compression would have been
         * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
         * transform a block into a stored block.
         */
        _tr_stored_block(s, buf, stored_len, last);
 
#ifdef FORCE_STATIC
    } else if (static_lenb >= 0) { /* force static trees */
#else
    } else if (s->strategy == Z_FIXED || static_lenb == opt_lenb) {
#endif
        send_bits(s, (STATIC_TREES<<1)+last, 3);
        compress_block(s, (const ct_data *)static_ltree,
                       (const ct_data *)static_dtree);
#ifdef 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));
}

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_tr_tally()

int ZLIB_INTERNAL _tr_tally	(	deflate_state *	s,
		unsigned	dist,
		unsigned	lc
	)

{
    s->d_buf[s->last_lit] = (ush)dist;
    s->l_buf[s->last_lit++] = (uch)lc;
    if (dist == 0) {
        /* lc is the unmatched char */
        s->dyn_ltree[lc].Freq++;
    } else {
        s->matches++;
        /* Here, lc is the match length - MIN_MATCH */
        dist--;             /* dist = match distance - 1 */
        Assert((ush)dist < (ush)MAX_DIST(s) &&
               (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
               (ush)d_code(dist) < (ush)D_CODES,  "_tr_tally: bad match");
 
        s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
        s->dyn_dtree[d_code(dist)].Freq++;
    }
 
#ifdef TRUNCATE_BLOCK
    /* Try to guess if it is profitable to stop the current block here */
    if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
        /* Compute an upper bound for the compressed length */
        ulg out_length = (ulg)s->last_lit*8L;
        ulg in_length = (ulg)((long)s->strstart - s->block_start);
        int dcode;
        for (dcode = 0; dcode < D_CODES; dcode++) {
            out_length += (ulg)s->dyn_dtree[dcode].Freq *
                (5L+extra_dbits[dcode]);
        }
        out_length >>= 3;
        Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
               s->last_lit, in_length, out_length,
               100L - out_length*100L/in_length));
        if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
    }
#endif
    return (s->last_lit == s->lit_bufsize-1);
    /* We avoid equality with lit_bufsize because of wraparound at 64K
     * on 16 bit machines and because stored blocks are restricted to
     * 64K-1 bytes.
     */
}

compress_block()

void compress_block	(	deflate_state *	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 lx = 0;    /* running index in l_buf */
    unsigned code;      /* the code to send */
    int extra;          /* number of extra bits to send */
 
    if (s->last_lit != 0) do {
        dist = s->d_buf[lx];
        lc = s->l_buf[lx++];
        if (dist == 0) {
            send_code(s, lc, ltree); /* send a literal byte */
            Tracecv(isgraph(lc), (stderr," '%c' ", lc));
        } else {
            /* Here, lc is the match length - MIN_MATCH */
            code = _length_code[lc];
            send_code(s, code+LITERALS+1, ltree); /* send the length code */
            extra = extra_lbits[code];
            if (extra != 0) {
                lc -= base_length[code];
                send_bits(s, lc, extra);       /* send the extra length bits */
            }
            dist--; /* dist is now the match distance - 1 */
            code = d_code(dist);
            Assert (code < D_CODES, "bad d_code");
 
            send_code(s, code, dtree);       /* send the distance code */
            extra = extra_dbits[code];
            if (extra != 0) {
                dist -= (unsigned)base_dist[code];
                send_bits(s, dist, extra);   /* send the extra distance bits */
            }
        } /* literal or match pair ? */
 
        /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
        Assert((uInt)(s->pending) < s->lit_bufsize + 2*lx,
               "pendingBuf overflow");
 
    } while (lx < s->last_lit);
 
    send_code(s, END_BLOCK, ltree);
}

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detect_data_type()

int detect_data_type

(

deflate_state *

s

)

{
    /* black_mask is the bit mask of black-listed bytes
     * set bits 0..6, 14..25, and 28..31
     * 0xf3ffc07f = binary 11110011111111111100000001111111
     */
    unsigned long black_mask = 0xf3ffc07fUL;
    int n;
 
    /* Check for non-textual ("black-listed") bytes. */
    for (n = 0; n <= 31; n++, black_mask >>= 1)
        if ((black_mask & 1) && (s->dyn_ltree[n].Freq != 0))
            return Z_BINARY;
 
    /* Check for textual ("white-listed") bytes. */
    if (s->dyn_ltree[9].Freq != 0 || s->dyn_ltree[10].Freq != 0
            || s->dyn_ltree[13].Freq != 0)
        return Z_TEXT;
    for (n = 32; n < LITERALS; n++)
        if (s->dyn_ltree[n].Freq != 0)
            return Z_TEXT;
 
    /* There are no "black-listed" or "white-listed" bytes:
     * this stream either is empty or has tolerated ("gray-listed") bytes only.
     */
    return Z_BINARY;
}

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bi_reverse()

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;
}

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bi_flush()

void bi_flush

(

deflate_state *

s

)

{
    if (s->bi_valid == 16) {
        put_short(s, s->bi_buf);
        s->bi_buf = 0;
        s->bi_valid = 0;
    } else if (s->bi_valid >= 8) {
        put_byte(s, (Byte)s->bi_buf);
        s->bi_buf >>= 8;
        s->bi_valid -= 8;
    }
}

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bi_windup()

void bi_windup

(

deflate_state *

s

)

{
    if (s->bi_valid > 8) {
        put_short(s, s->bi_buf);
    } else if (s->bi_valid > 0) {
        put_byte(s, (Byte)s->bi_buf);
    }
    s->bi_buf = 0;
    s->bi_valid = 0;
#ifdef ZLIB_DEBUG
    s->bits_sent = (s->bits_sent+7) & ~7;
#endif
}

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Variable Documentation

extra_lbits

const int extra_lbits[LENGTH_CODES] = {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}

extra_dbits

const int extra_dbits[D_CODES] = {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}

extra_blbits

const int extra_blbits[BL_CODES] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7}

bl_order

const uch bl_order[BL_CODES] = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15}

static_ltree

ct_data static_ltree[L_CODES+2]

static_dtree

ct_data static_dtree[D_CODES]

_dist_code

uch _dist_code[DIST_CODE_LEN]

_length_code

uch _length_code[MAX_MATCH-MIN_MATCH+1]

base_length

int base_length[LENGTH_CODES]

base_dist

int base_dist[D_CODES]

static_l_desc

const static_tree_desc static_l_desc

Initial value:

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

static_d_desc

const static_tree_desc static_d_desc

Initial value:

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

static_bl_desc

const static_tree_desc static_bl_desc

Initial value:

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