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zlib/trees.c

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/* trees.c -- output deflated data using Huffman coding
* Copyright (C) 1995 Jean-loup Gailly
* 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: trees.c,v 1.5 1995/05/03 17:27:12 jloup Exp $ */
#include "deflate.h"
#ifdef DEBUG
# include <ctype.h>
#endif
/* ===========================================================================
* Constants
*/
#define MAX_BL_BITS 7
/* Bit length codes must not exceed MAX_BL_BITS bits */
#define END_BLOCK 256
/* end of block literal code */
#define REP_3_6 16
/* repeat previous bit length 3-6 times (2 bits of repeat count) */
#define REPZ_3_10 17
/* repeat a zero length 3-10 times (3 bits of repeat count) */
#define REPZ_11_138 18
/* repeat a zero length 11-138 times (7 bits of repeat count) */
local 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};
local 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};
local 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};
local uch 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.
*/
#define Buf_size (8 * 2*sizeof(char))
/* Number of bits used within bi_buf. (bi_buf might be implemented on
* more than 16 bits on some systems.)
*/
/* ===========================================================================
* Local data. These are initialized only once.
* To do: initialize at compile time to be completely reentrant. ???
*/
local ct_data static_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 ct_init
* below).
*/
local ct_data static_dtree[D_CODES];
/* The static distance tree. (Actually a trivial tree since all codes use
* 5 bits.)
*/
local uch dist_code[512];
/* 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.
*/
local uch length_code[MAX_MATCH-MIN_MATCH+1];
/* length code for each normalized match length (0 == MIN_MATCH) */
local int base_length[LENGTH_CODES];
/* First normalized length for each code (0 = MIN_MATCH) */
local int base_dist[D_CODES];
/* First normalized distance for each code (0 = distance of 1) */
struct static_tree_desc_s {
ct_data *static_tree; /* static tree or NULL */
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 */
};
local static_tree_desc static_l_desc =
{static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};
local static_tree_desc static_d_desc =
{static_dtree, extra_dbits, 0, D_CODES, MAX_BITS};
local static_tree_desc static_bl_desc =
{(ct_data *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS};
/* ===========================================================================
* Local (static) routines in this file.
*/
local void ct_static_init OF((void));
local void init_block OF((deflate_state *s));
local void pqdownheap OF((deflate_state *s, ct_data *tree, int k));
local void gen_bitlen OF((deflate_state *s, tree_desc *desc));
local void gen_codes OF((ct_data *tree, int max_code, ushf *bl_count));
local void build_tree OF((deflate_state *s, tree_desc *desc));
local void scan_tree OF((deflate_state *s, ct_data *tree, int max_code));
local void send_tree OF((deflate_state *s, ct_data *tree, int max_code));
local int build_bl_tree OF((deflate_state *s));
local void send_all_trees OF((deflate_state *s, int lcodes, int dcodes,
int blcodes));
local void compress_block OF((deflate_state *s, ct_data *ltree,
ct_data *dtree));
local void set_data_type OF((deflate_state *s));
local unsigned bi_reverse OF((unsigned value, int length));
local void bi_windup OF((deflate_state *s));
local void bi_flush OF((deflate_state *s));
local void copy_block OF((deflate_state *s, charf *buf, unsigned len,
int header));
#ifndef 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 /* DEBUG */
# define send_code(s, c, tree) \
{ if (verbose>1) fprintf(stderr,"\ncd %3d ",(c)); \
send_bits(s, tree[c].Code, tree[c].Len); }
#endif
#define d_code(dist) \
((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
/* Mapping from a distance to a distance code. dist is the distance - 1 and
* must not have side effects. dist_code[256] and dist_code[257] are never
* used.
*/
/* ===========================================================================
* Output a short LSB first on the stream.
* IN assertion: there is enough room in pendingBuf.
*/
#define put_short(s, w) { \
put_byte(s, (uch)((w) & 0xff)); \
put_byte(s, (uch)((ush)(w) >> 8)); \
}
/* ===========================================================================
* Send a value on a given number of bits.
* IN assertion: length <= 16 and value fits in length bits.
*/
#ifdef DEBUG
local void send_bits OF((deflate_state *s, int value, int length));
local void send_bits(s, value, length)
deflate_state *s;
int value; /* value to send */
int length; /* number of bits */
{
Tracev((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 |= (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 |= value << s->bi_valid;
s->bi_valid += length;
}
}
#else /* !DEBUG */
#define send_bits(s, value, length) \
{ int len = length;\
if (s->bi_valid > (int)Buf_size - len) {\
int val = value;\
s->bi_buf |= (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 |= (value) << s->bi_valid;\
s->bi_valid += len;\
}\
}
#endif /* DEBUG */
#define MAX(a,b) (a >= b ? a : b)
/* the arguments must not have side effects */
/* ===========================================================================
* Initialize the various 'constant' tables.
* To do: do this at compile time.
*/
local void ct_static_init()
{
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 */
/* 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, "ct_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, "ct_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, "ct_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(n, 5);
}
}
/* ===========================================================================
* Initialize the tree data structures for a new zlib stream.
*/
void ct_init(s)
deflate_state *s;
{
if (static_dtree[0].Len == 0) {
ct_static_init(); /* To do: at compile time */
}
s->compressed_len = 0L;
s->l_desc.dyn_tree = s->dyn_ltree;
s->l_desc.stat_desc = &static_l_desc;
s->d_desc.dyn_tree = s->dyn_dtree;
s->d_desc.stat_desc = &static_d_desc;
s->bl_desc.dyn_tree = s->bl_tree;
s->bl_desc.stat_desc = &static_bl_desc;
s->bi_buf = 0;
s->bi_valid = 0;
s->last_eob_len = 8; /* enough lookahead for inflate */
#ifdef DEBUG
s->bits_sent = 0L;
#endif
/* Initialize the first block of the first file: */
init_block(s);
}
/* ===========================================================================
* Initialize a new block.
*/
local void init_block(s)
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;
}
#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).
*/
local void pqdownheap(s, tree, k)
deflate_state *s;
ct_data *tree; /* the tree to restore */
int k; /* node to move down */
{
int v = s->heap[k];
int j = k << 1; /* left son of k */
while (j <= s->heap_len) {
/* Set j to the smallest of the two sons: */
if (j < s->heap_len &&
smaller(tree, s->heap[j+1], s->heap[j], s->depth)) {
j++;
}
/* Exit if v is smaller than both sons */
if (smaller(tree, v, s->heap[j], s->depth)) break;
/* Exchange v with the smallest son */
s->heap[k] = s->heap[j]; k = j;
/* And continue down the tree, setting j to the left son of k */
j <<= 1;
}
s->heap[k] = v;
}
/* ===========================================================================
* Compute the optimal bit lengths for a tree and update the total bit length
* for the current block.
* IN assertion: the fields freq and dad are set, heap[heap_max] and
* above are the tree nodes sorted by increasing frequency.
* OUT assertions: the field len is set to the optimal bit length, the
* array bl_count contains the frequencies for each bit length.
* The length opt_len is updated; static_len is also updated if stree is
* not null.
*/
local void gen_bitlen(s, desc)
deflate_state *s;
tree_desc *desc; /* the tree descriptor */
{
ct_data *tree = desc->dyn_tree;
int max_code = desc->max_code;
ct_data *stree = desc->stat_desc->static_tree;
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 * (bits + xbits);
if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits);
}
if (overflow == 0) return;
Trace((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 (tree[m].Len != (unsigned) bits) {
Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
s->opt_len += ((long)bits - (long)tree[m].Len)
*(long)tree[m].Freq;
tree[m].Len = (ush)bits;
}
n--;
}
}
}
/* ===========================================================================
* Generate the codes for a given tree and bit counts (which need not be
* optimal).
* IN assertion: the array bl_count contains the bit length statistics for
* the given tree and the field len is set for all tree elements.
* OUT assertion: the field code is set for all tree elements of non
* zero code length.
*/
local void gen_codes (tree, max_code, bl_count)
ct_data *tree; /* the tree to decorate */
int max_code; /* largest code with non zero frequency */
ushf *bl_count; /* number of codes at each bit length */
{
ush next_code[MAX_BITS+1]; /* next code value for each bit length */
ush 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++) {
next_code[bits] = code = (code + bl_count[bits-1]) << 1;
}
/* Check that the bit counts in bl_count are consistent. The last code
* must be all ones.
*/
Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
"inconsistent bit counts");
Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
for (n = 0; n <= max_code; n++) {
int len = tree[n].Len;
if (len == 0) continue;
/* Now reverse the bits */
tree[n].Code = bi_reverse(next_code[len]++, len);
Tracec(tree != static_ltree, (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.
*/
local void build_tree(s, desc)
deflate_state *s;
tree_desc *desc; /* the tree descriptor */
{
ct_data *tree = desc->dyn_tree;
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) (MAX(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);
}
/* ===========================================================================
* Scan a literal or distance tree to determine the frequencies of the codes
* in the bit length tree.
*/
local void scan_tree (s, tree, max_code)
deflate_state *s;
ct_data *tree; /* the tree to be scanned */
int max_code; /* and its largest code of non zero frequency */
{
int n; /* iterates over all tree elements */
int prevlen = -1; /* last emitted length */
int curlen; /* length of current code */
int nextlen = tree[0].Len; /* length of next code */
int count = 0; /* repeat count of the current code */
int max_count = 7; /* max repeat count */
int min_count = 4; /* min repeat count */
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;
}
}
}
/* ===========================================================================
* Send a literal or distance tree in compressed form, using the codes in
* bl_tree.
*/
local void send_tree (s, tree, max_code)
deflate_state *s;
ct_data *tree; /* the tree to be scanned */
int max_code; /* and its largest code of non zero frequency */
{
int n; /* iterates over all tree elements */
int prevlen = -1; /* last emitted length */
int curlen; /* length of current code */
int nextlen = tree[0].Len; /* length of next code */
int count = 0; /* repeat count of the current code */
int max_count = 7; /* max repeat count */
int min_count = 4; /* min repeat count */
/* tree[max_code+1].Len = -1; */ /* guard already set */
if (nextlen == 0) max_count = 138, min_count = 3;
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.
*/
local int build_bl_tree(s)
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*(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.
*/
local void send_all_trees(s, lcodes, dcodes, blcodes)
deflate_state *s;
int lcodes, dcodes, blcodes; /* number of codes for each tree */
{
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));
}
/* ===========================================================================
* Send a stored block
*/
void ct_stored_block(s, buf, stored_len, eof)
deflate_state *s;
charf *buf; /* input block */
ulg stored_len; /* length of input block */
int eof; /* true if this is the last block for a file */
{
send_bits(s, (STORED_BLOCK<<1)+eof, 3); /* send block type */
s->compressed_len = (s->compressed_len + 3 + 7) & ~7L;
s->compressed_len += (stored_len + 4) << 3;
copy_block(s, buf, (unsigned)stored_len, 1); /* with header */
}
/* ===========================================================================
* Send one empty static block to give enough lookahead for inflate.
* This takes 10 bits, of which 7 may remain in the bit buffer.
* The current inflate code requires 9 bits of lookahead. If the EOB
* code for the previous block was coded on 5 bits or less, inflate
* may have only 5+3 bits of lookahead to decode this EOB.
* (There are no problems if the previous block is stored or fixed.)
*/
void ct_align(s)
deflate_state *s;
{
send_bits(s, STATIC_TREES<<1, 3);
send_code(s, END_BLOCK, static_ltree);
s->compressed_len += 10L; /* 3 for block type, 7 for EOB */
bi_flush(s);
/* Of the 10 bits for the empty block, we have already sent
* (10 - bi_valid) bits. The lookahead for the EOB of the previous
* block was thus its length plus what we have just sent.
*/
if (s->last_eob_len + 10 - s->bi_valid < 9) {
send_bits(s, STATIC_TREES<<1, 3);
send_code(s, END_BLOCK, static_ltree);
s->compressed_len += 10L;
bi_flush(s);
}
s->last_eob_len = 7;
}
/* ===========================================================================
* Determine the best encoding for the current block: dynamic trees, static
* trees or store, and output the encoded block to the zip file. This function
* returns the total compressed length for the file so far.
*/
ulg ct_flush_block(s, buf, stored_len, eof)
deflate_state *s;
charf *buf; /* input block, or NULL if too old */
ulg stored_len; /* length of input block */
int eof; /* true if this is the last block for a file */
{
ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
int max_blindex; /* index of last bit length code of non zero freq */
/* Check if the file is ascii or binary */
if (s->data_type == UNKNOWN) set_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 first the block length 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;
/* If compression failed and this is the first and last block,
* and if the .zip file can be seeked (to rewrite the local header),
* the whole file is transformed into a stored file:
*/
#ifdef STORED_FILE_OK
# ifdef FORCE_STORED_FILE
if (eof && compressed_len == 0L) { /* force stored file */
# else
if (stored_len <= opt_lenb && eof && s->compressed_len==0L && seekable()) {
# endif
/* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
if (buf == (charf*)0) error ("block vanished");
copy_block(buf, (unsigned)stored_len, 0); /* without header */
s->compressed_len = stored_len << 3;
s->method = STORED;
} else
#endif /* STORED_FILE_OK */
#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.
*/
ct_stored_block(s, buf, stored_len, eof);
#ifdef FORCE_STATIC
} else if (static_lenb >= 0) { /* force static trees */
#else
} else if (static_lenb == opt_lenb) {
#endif
send_bits(s, (STATIC_TREES<<1)+eof, 3);
compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree);
s->compressed_len += 3 + s->static_len;
} else {
send_bits(s, (DYN_TREES<<1)+eof, 3);
send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1,
max_blindex+1);
compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree);
s->compressed_len += 3 + s->opt_len;
}
Assert (s->compressed_len == s->bits_sent, "bad compressed size");
init_block(s);
if (eof) {
bi_windup(s);
s->compressed_len += 7; /* align on byte boundary */
}
Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3,
s->compressed_len-7*eof));
return s->compressed_len >> 3;
}
/* ===========================================================================
* Save the match info and tally the frequency counts. Return true if
* the current block must be flushed.
*/
int ct_tally (s, dist, lc)
deflate_state *s;
int dist; /* distance of matched string */
int lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */
{
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, "ct_tally: bad match");
s->dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
s->dyn_dtree[d_code(dist)].Freq++;
}
/* Try to guess if it is profitable to stop the current block here */
if (s->level > 2 && (s->last_lit & 0xfff) == 0) {
/* Compute an upper bound for the compressed length */
ulg out_length = (ulg)s->last_lit*8L;
ulg in_length = (ulg)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;
}
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.
*/
}
/* ===========================================================================
* Send the block data compressed using the given Huffman trees
*/
local void compress_block(s, ltree, dtree)
deflate_state *s;
ct_data *ltree; /* literal tree */
ct_data *dtree; /* distance tree */
{
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 -= 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(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow");
} while (lx < s->last_lit);
send_code(s, END_BLOCK, ltree);
s->last_eob_len = ltree[END_BLOCK].Len;
}
/* ===========================================================================
* Set the data type to ASCII or BINARY, using a crude approximation:
* binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
* IN assertion: the fields freq of dyn_ltree are set and the total of all
* frequencies does not exceed 64K (to fit in an int on 16 bit machines).
*/
local void set_data_type(s)
deflate_state *s;
{
int n = 0;
unsigned ascii_freq = 0;
unsigned bin_freq = 0;
while (n < 7) bin_freq += s->dyn_ltree[n++].Freq;
while (n < 128) ascii_freq += s->dyn_ltree[n++].Freq;
while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq;
s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? BINARY : ASCII);
}
/* ===========================================================================
* Reverse the first len bits of a code, using straightforward code (a faster
* method would use a table)
* IN assertion: 1 <= len <= 15
*/
local unsigned bi_reverse(code, len)
unsigned code; /* the value to invert */
int len; /* its bit length */
{
register unsigned res = 0;
do {
res |= code & 1;
code >>= 1, res <<= 1;
} while (--len > 0);
return res >> 1;
}
/* ===========================================================================
* Flush the bit buffer, keeping at most 7 bits in it.
*/
local void bi_flush(s)
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;
}
}
/* ===========================================================================
* Flush the bit buffer and align the output on a byte boundary
*/
local void bi_windup(s)
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 DEBUG
s->bits_sent = (s->bits_sent+7) & ~7;
#endif
}
/* ===========================================================================
* Copy a stored block, storing first the length and its
* one's complement if requested.
*/
local void copy_block(s, buf, len, header)
deflate_state *s;
charf *buf; /* the input data */
unsigned len; /* its length */
int header; /* true if block header must be written */
{
bi_windup(s); /* align on byte boundary */
s->last_eob_len = 8; /* enough lookahead for inflate */
if (header) {
put_short(s, (ush)len);
put_short(s, (ush)~len);
#ifdef DEBUG
s->bits_sent += 2*16;
#endif
}
#ifdef DEBUG
s->bits_sent += (ulg)len<<3;
#endif
while (len--) {
put_byte(s, *buf++);
}
}