mirror/freebsd
1
0
Fork 0
mirror of https://git.FreeBSD.org/src.git synced 2024-12-11 09:50:12 +00:00
Code Issues Releases Activity
040f100044
freebsd/gnu/usr.bin/gzip/trees.c

1076 lines
40 KiB
C
Raw Blame History

/* trees.c -- output deflated data using Huffman coding
* Copyright (C) 1992-1993 Jean-loup Gailly
* This is free software; you can redistribute it and/or modify it under the
* terms of the GNU General Public License, see the file COPYING.
*/
/*
* PURPOSE
*
* Encode various sets of source values using variable-length
* binary code trees.
*
* DISCUSSION
*
* The PKZIP "deflation" process uses several Huffman trees. The more
* common source values are represented by shorter bit sequences.
*
* Each code tree is stored in the ZIP file 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 UNZIP process, as described in the "application note"
* (APPNOTE.TXT) distributed as part of PKWARE's PKZIP program.
*
* REFERENCES
*
* Lynch, Thomas J.
* Data Compression: Techniques and Applications, pp. 53-55.
* Lifetime Learning Publications, 1985. ISBN 0-534-03418-7.
*
* 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.
*
* INTERFACE
*
* void ct_init (ush *attr, int *methodp)
* Allocate the match buffer, initialize the various tables and save
* the location of the internal file attribute (ascii/binary) and
* method (DEFLATE/STORE)
*
* void ct_tally (int dist, int lc);
* Save the match info and tally the frequency counts.
*
* long flush_block (char *buf, ulg stored_len, int eof)
* Determine the best encoding for the current block: dynamic trees,
* static trees or store, and output the encoded block to the zip
* file. Returns the total compressed length for the file so far.
*
*/
#include <ctype.h>
#include "tailor.h"
#include "gzip.h"
#ifdef RCSID
static char rcsid[] = "$Id: trees.c,v 0.12 1993/06/10 13:27:54 jloup Exp $";
#endif
/* ===========================================================================
* Constants
*/
#define MAX_BITS 15
/* All codes must not exceed MAX_BITS bits */
#define MAX_BL_BITS 7
/* Bit length codes must not exceed MAX_BL_BITS bits */
#define LENGTH_CODES 29
/* number of length codes, not counting the special END_BLOCK code */
#define LITERALS 256
/* number of literal bytes 0..255 */
#define END_BLOCK 256
/* end of block literal code */
#define L_CODES (LITERALS+1+LENGTH_CODES)
/* number of Literal or Length codes, including the END_BLOCK code */
#define D_CODES 30
/* number of distance codes */
#define BL_CODES 19
/* number of codes used to transfer the bit lengths */
local int near 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 near 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 near 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};
#define STORED_BLOCK 0
#define STATIC_TREES 1
#define DYN_TREES 2
/* The three kinds of block type */
#ifndef LIT_BUFSIZE
# ifdef SMALL_MEM
# define LIT_BUFSIZE 0x2000
# else
# ifdef MEDIUM_MEM
# define LIT_BUFSIZE 0x4000
# else
# define LIT_BUFSIZE 0x8000
# endif
# endif
#endif
#ifndef DIST_BUFSIZE
# define DIST_BUFSIZE LIT_BUFSIZE
#endif
/* Sizes of match buffers for literals/lengths and distances. There are
* 4 reasons for limiting LIT_BUFSIZE to 64K:
* - frequencies can be kept in 16 bit counters
* - if compression is not successful for the first block, all input data is
* still in the window so we can still emit a stored block even when input
* comes from standard input. (This can also be done for all blocks if
* LIT_BUFSIZE is not greater than 32K.)
* - if compression is not successful for a file smaller than 64K, we can
* even emit a stored file instead of a stored block (saving 5 bytes).
* - creating new Huffman trees less frequently may not provide fast
* adaptation to changes in the input data statistics. (Take for
* example a binary file with poorly compressible code followed by
* a highly compressible string table.) Smaller buffer sizes give
* fast adaptation but have of course the overhead of transmitting trees
* more frequently.
* - I can't count above 4
* The current code is general and allows DIST_BUFSIZE < LIT_BUFSIZE (to save
* memory at the expense of compression). Some optimizations would be possible
* if we rely on DIST_BUFSIZE == LIT_BUFSIZE.
*/
#if LIT_BUFSIZE > INBUFSIZ
error cannot overlay l_buf and inbuf
#endif
#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 data
*/
/* Data structure describing a single value and its code string. */
typedef struct ct_data {
union {
ush freq; /* frequency count */
ush code; /* bit string */
} fc;
union {
ush dad; /* father node in Huffman tree */
ush len; /* length of bit string */
} dl;
} ct_data;
#define Freq fc.freq
#define Code fc.code
#define Dad dl.dad
#define Len dl.len
#define HEAP_SIZE (2*L_CODES+1)
/* maximum heap size */
local ct_data near dyn_ltree[HEAP_SIZE]; /* literal and length tree */
local ct_data near dyn_dtree[2*D_CODES+1]; /* distance tree */
local ct_data near 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 near static_dtree[D_CODES];
/* The static distance tree. (Actually a trivial tree since all codes use
* 5 bits.)
*/
local ct_data near bl_tree[2*BL_CODES+1];
/* Huffman tree for the bit lengths */
typedef struct tree_desc {
ct_data near *dyn_tree; /* the dynamic tree */
ct_data near *static_tree; /* corresponding static tree or NULL */
int near *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 */
int max_code; /* largest code with non zero frequency */
} tree_desc;
local tree_desc near l_desc =
{dyn_ltree, static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS, 0};
local tree_desc near d_desc =
{dyn_dtree, static_dtree, extra_dbits, 0, D_CODES, MAX_BITS, 0};
local tree_desc near bl_desc =
{bl_tree, (ct_data near *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS, 0};
local ush near bl_count[MAX_BITS+1];
/* number of codes at each bit length for an optimal tree */
local uch near bl_order[BL_CODES]
= {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
/* The lengths of the bit length codes are sent in order of decreasing
* probability, to avoid transmitting the lengths for unused bit length codes.
*/
local int near heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
local int heap_len; /* number of elements in the heap */
local int heap_max; /* element of largest frequency */
/* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
* The same heap array is used to build all trees.
*/
local uch near depth[2*L_CODES+1];
/* Depth of each subtree used as tie breaker for trees of equal frequency */
local uch length_code[MAX_MATCH-MIN_MATCH+1];
/* length code for each normalized match length (0 == MIN_MATCH) */
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 int near base_length[LENGTH_CODES];
/* First normalized length for each code (0 = MIN_MATCH) */
local int near base_dist[D_CODES];
/* First normalized distance for each code (0 = distance of 1) */
#define l_buf inbuf
/* DECLARE(uch, l_buf, LIT_BUFSIZE); buffer for literals or lengths */
/* DECLARE(ush, d_buf, DIST_BUFSIZE); buffer for distances */
local uch near flag_buf[(LIT_BUFSIZE/8)];
/* flag_buf is a bit array distinguishing literals from lengths in
* l_buf, thus indicating the presence or absence of a distance.
*/
local unsigned last_lit; /* running index in l_buf */
local unsigned last_dist; /* running index in d_buf */
local unsigned last_flags; /* running index in flag_buf */
local uch flags; /* current flags not yet saved in flag_buf */
local uch flag_bit; /* current bit used in flags */
/* bits are filled in flags starting at bit 0 (least significant).
* Note: these flags are overkill in the current code since we don't
* take advantage of DIST_BUFSIZE == LIT_BUFSIZE.
*/
local ulg opt_len; /* bit length of current block with optimal trees */
local ulg static_len; /* bit length of current block with static trees */
local ulg compressed_len; /* total bit length of compressed file */
local ulg input_len; /* total byte length of input file */
/* input_len is for debugging only since we can get it by other means. */
ush *file_type; /* pointer to UNKNOWN, BINARY or ASCII */
int *file_method; /* pointer to DEFLATE or STORE */
#ifdef DEBUG
extern ulg bits_sent; /* bit length of the compressed data */
extern long isize; /* byte length of input file */
#endif
extern long block_start; /* window offset of current block */
extern unsigned near strstart; /* window offset of current string */
/* ===========================================================================
* Local (static) routines in this file.
*/
local void init_block OF((void));
local void pqdownheap OF((ct_data near *tree, int k));
local void gen_bitlen OF((tree_desc near *desc));
local void gen_codes OF((ct_data near *tree, int max_code));
local void build_tree OF((tree_desc near *desc));
local void scan_tree OF((ct_data near *tree, int max_code));
local void send_tree OF((ct_data near *tree, int max_code));
local int build_bl_tree OF((void));
local void send_all_trees OF((int lcodes, int dcodes, int blcodes));
local void compress_block OF((ct_data near *ltree, ct_data near *dtree));
local void set_file_type OF((void));
#ifndef DEBUG
# define send_code(c, tree) send_bits(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(c, tree) \
{ if (verbose>1) fprintf(stderr,"\ncd %3d ",(c)); \
send_bits(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.
*/
#define MAX(a,b) (a >= b ? a : b)
/* the arguments must not have side effects */
/* ===========================================================================
* Allocate the match buffer, initialize the various tables and save the
* location of the internal file attribute (ascii/binary) and method
* (DEFLATE/STORE).
*/
void ct_init(attr, methodp)
ush *attr; /* pointer to internal file attribute */
int *methodp; /* pointer to compression method */
{
int n; /* iterates over tree elements */
int bits; /* bit counter */
int length; /* length value */
int code; /* code value */
int dist; /* distance index */
file_type = attr;
file_method = methodp;
compressed_len = input_len = 0L;
if (static_dtree[0].Len != 0) return; /* ct_init already called */
/* 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_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_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_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 near *)static_ltree, L_CODES+1);
/* 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 first block of the first file: */
init_block();
}
/* ===========================================================================
* Initialize a new block.
*/
local void init_block()
{
int n; /* iterates over tree elements */
/* Initialize the trees. */
for (n = 0; n < L_CODES; n++) dyn_ltree[n].Freq = 0;
for (n = 0; n < D_CODES; n++) dyn_dtree[n].Freq = 0;
for (n = 0; n < BL_CODES; n++) bl_tree[n].Freq = 0;
dyn_ltree[END_BLOCK].Freq = 1;
opt_len = static_len = 0L;
last_lit = last_dist = last_flags = 0;
flags = 0; flag_bit = 1;
}
#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(tree, top) \
{\
top = heap[SMALLEST]; \
heap[SMALLEST] = heap[heap_len--]; \
pqdownheap(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) \
(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(tree, k)
ct_data near *tree; /* the tree to restore */
int k; /* node to move down */
{
int v = heap[k];
int j = k << 1; /* left son of k */
while (j <= heap_len) {
/* Set j to the smallest of the two sons: */
if (j < heap_len && smaller(tree, heap[j+1], heap[j])) j++;
/* Exit if v is smaller than both sons */
if (smaller(tree, v, heap[j])) break;
/* Exchange v with the smallest son */
heap[k] = heap[j]; k = j;
/* And continue down the tree, setting j to the left son of k */
j <<= 1;
}
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(desc)
tree_desc near *desc; /* the tree descriptor */
{
ct_data near *tree = desc->dyn_tree;
int near *extra = desc->extra_bits;
int base = desc->extra_base;
int max_code = desc->max_code;
int max_length = desc->max_length;
ct_data near *stree = desc->static_tree;
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++) 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[heap[heap_max]].Len = 0; /* root of the heap */
for (h = heap_max+1; h < HEAP_SIZE; h++) {
n = 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 */
bl_count[bits]++;
xbits = 0;
if (n >= base) xbits = extra[n-base];
f = tree[n].Freq;
opt_len += (ulg)f * (bits + xbits);
if (stree) 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 (bl_count[bits] == 0) bits--;
bl_count[bits]--; /* move one leaf down the tree */
bl_count[bits+1] += 2; /* move one overflow item as its brother */
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 = bl_count[bits];
while (n != 0) {
m = 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));
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)
ct_data near *tree; /* the tree to decorate */
int max_code; /* largest code with non zero frequency */
{
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(desc)
tree_desc near *desc; /* the tree descriptor */
{
ct_data near *tree = desc->dyn_tree;
ct_data near *stree = desc->static_tree;
int elems = desc->elems;
int n, m; /* iterate over heap elements */
int max_code = -1; /* largest code with non zero frequency */
int node = elems; /* next internal node of the tree */
/* 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.
*/
heap_len = 0, heap_max = HEAP_SIZE;
for (n = 0; n < elems; n++) {
if (tree[n].Freq != 0) {
heap[++heap_len] = max_code = n;
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 (heap_len < 2) {
int new = heap[++heap_len] = (max_code < 2 ? ++max_code : 0);
tree[new].Freq = 1;
depth[new] = 0;
opt_len--; if (stree) static_len -= stree[new].Len;
/* new 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 = heap_len/2; n >= 1; n--) pqdownheap(tree, n);
/* Construct the Huffman tree by repeatedly combining the least two
* frequent nodes.
*/
do {
pqremove(tree, n); /* n = node of least frequency */
m = heap[SMALLEST]; /* m = node of next least frequency */
heap[--heap_max] = n; /* keep the nodes sorted by frequency */
heap[--heap_max] = m;
/* Create a new node father of n and m */
tree[node].Freq = tree[n].Freq + tree[m].Freq;
depth[node] = (uch) (MAX(depth[n], depth[m]) + 1);
tree[n].Dad = tree[m].Dad = (ush)node;
#ifdef DUMP_BL_TREE
if (tree == 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 */
heap[SMALLEST] = node++;
pqdownheap(tree, SMALLEST);
} while (heap_len >= 2);
heap[--heap_max] = heap[SMALLEST];
/* At this point, the fields freq and dad are set. We can now
* generate the bit lengths.
*/
gen_bitlen((tree_desc near *)desc);
/* The field len is now set, we can generate the bit codes */
gen_codes ((ct_data near *)tree, max_code);
}
/* ===========================================================================
* Scan a literal or distance tree to determine the frequencies of the codes
* in the bit length tree. Updates opt_len to take into account the repeat
* counts. (The contribution of the bit length codes will be added later
* during the construction of bl_tree.)
*/
local void scan_tree (tree, max_code)
ct_data near *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) {
bl_tree[curlen].Freq += count;
} else if (curlen != 0) {
if (curlen != prevlen) bl_tree[curlen].Freq++;
bl_tree[REP_3_6].Freq++;
} else if (count <= 10) {
bl_tree[REPZ_3_10].Freq++;
} else {
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 (tree, max_code)
ct_data near *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(curlen, bl_tree); } while (--count != 0);
} else if (curlen != 0) {
if (curlen != prevlen) {
send_code(curlen, bl_tree); count--;
}
Assert(count >= 3 && count <= 6, " 3_6?");
send_code(REP_3_6, bl_tree); send_bits(count-3, 2);
} else if (count <= 10) {
send_code(REPZ_3_10, bl_tree); send_bits(count-3, 3);
} else {
send_code(REPZ_11_138, bl_tree); send_bits(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()
{
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((ct_data near *)dyn_ltree, l_desc.max_code);
scan_tree((ct_data near *)dyn_dtree, d_desc.max_code);
/* Build the bit length tree: */
build_tree((tree_desc near *)(&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 (bl_tree[bl_order[max_blindex]].Len != 0) break;
}
/* Update opt_len to include the bit length tree and counts */
opt_len += 3*(max_blindex+1) + 5+5+4;
Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld", opt_len, 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(lcodes, dcodes, blcodes)
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(lcodes-257, 5); /* not +255 as stated in appnote.txt */
send_bits(dcodes-1, 5);
send_bits(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(bl_tree[bl_order[rank]].Len, 3);
}
Tracev((stderr, "\nbl tree: sent %ld", bits_sent));
send_tree((ct_data near *)dyn_ltree, lcodes-1); /* send the literal tree */
Tracev((stderr, "\nlit tree: sent %ld", bits_sent));
send_tree((ct_data near *)dyn_dtree, dcodes-1); /* send the distance tree */
Tracev((stderr, "\ndist tree: sent %ld", bits_sent));
}
/* ===========================================================================
* 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 flush_block(buf, stored_len, eof)
char *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 */
flag_buf[last_flags] = flags; /* Save the flags for the last 8 items */
/* Check if the file is ascii or binary */
if (*file_type == (ush)UNKNOWN) set_file_type();
/* Construct the literal and distance trees */
build_tree((tree_desc near *)(&l_desc));
Tracev((stderr, "\nlit data: dyn %ld, stat %ld", opt_len, static_len));
build_tree((tree_desc near *)(&d_desc));
Tracev((stderr, "\ndist data: dyn %ld, stat %ld", opt_len, 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();
/* Determine the best encoding. Compute first the block length in bytes */
opt_lenb = (opt_len+3+7)>>3;
static_lenb = (static_len+3+7)>>3;
input_len += stored_len; /* for debugging only */
Trace((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u dist %u ",
opt_lenb, opt_len, static_lenb, static_len, stored_len,
last_lit, last_dist));
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 FORCE_METHOD
if (level == 1 && eof && compressed_len == 0L) { /* force stored file */
#else
if (stored_len <= opt_lenb && eof && compressed_len == 0L && seekable()) {
#endif
/* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
if (buf == (char*)0) error ("block vanished");
copy_block(buf, (unsigned)stored_len, 0); /* without header */
compressed_len = stored_len << 3;
*file_method = STORED;
#ifdef FORCE_METHOD
} else if (level == 2 && buf != (char*)0) { /* force stored block */
#else
} 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.
*/
send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */
compressed_len = (compressed_len + 3 + 7) & ~7L;
compressed_len += (stored_len + 4) << 3;
copy_block(buf, (unsigned)stored_len, 1); /* with header */
#ifdef FORCE_METHOD
} else if (level == 3) { /* force static trees */
#else
} else if (static_lenb == opt_lenb) {
#endif
send_bits((STATIC_TREES<<1)+eof, 3);
compress_block((ct_data near *)static_ltree, (ct_data near *)static_dtree);
compressed_len += 3 + static_len;
} else {
send_bits((DYN_TREES<<1)+eof, 3);
send_all_trees(l_desc.max_code+1, d_desc.max_code+1, max_blindex+1);
compress_block((ct_data near *)dyn_ltree, (ct_data near *)dyn_dtree);
compressed_len += 3 + opt_len;
}
Assert (compressed_len == bits_sent, "bad compressed size");
init_block();
if (eof) {
Assert (input_len == isize, "bad input size");
bi_windup();
compressed_len += 7; /* align on byte boundary */
}
Tracev((stderr,"\ncomprlen %lu(%lu) ", compressed_len>>3,
compressed_len-7*eof));
return compressed_len >> 3;
}
/* ===========================================================================
* Save the match info and tally the frequency counts. Return true if
* the current block must be flushed.
*/
int ct_tally (dist, lc)
int dist; /* distance of matched string */
int lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */
{
l_buf[last_lit++] = (uch)lc;
if (dist == 0) {
/* lc is the unmatched char */
dyn_ltree[lc].Freq++;
} else {
/* Here, lc is the match length - MIN_MATCH */
dist--; /* dist = match distance - 1 */
Assert((ush)dist < (ush)MAX_DIST &&
(ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
(ush)d_code(dist) < (ush)D_CODES, "ct_tally: bad match");
dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
dyn_dtree[d_code(dist)].Freq++;
d_buf[last_dist++] = (ush)dist;
flags |= flag_bit;
}
flag_bit <<= 1;
/* Output the flags if they fill a byte: */
if ((last_lit & 7) == 0) {
flag_buf[last_flags++] = flags;
flags = 0, flag_bit = 1;
}
/* Try to guess if it is profitable to stop the current block here */
if (level > 2 && (last_lit & 0xfff) == 0) {
/* Compute an upper bound for the compressed length */
ulg out_length = (ulg)last_lit*8L;
ulg in_length = (ulg)strstart-block_start;
int dcode;
for (dcode = 0; dcode < D_CODES; dcode++) {
out_length += (ulg)dyn_dtree[dcode].Freq*(5L+extra_dbits[dcode]);
}
out_length >>= 3;
Trace((stderr,"\nlast_lit %u, last_dist %u, in %ld, out ~%ld(%ld%%) ",
last_lit, last_dist, in_length, out_length,
100L - out_length*100L/in_length));
if (last_dist < last_lit/2 && out_length < in_length/2) return 1;
}
return (last_lit == LIT_BUFSIZE-1 || last_dist == DIST_BUFSIZE);
/* 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(ltree, dtree)
ct_data near *ltree; /* literal tree */
ct_data near *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 dx = 0; /* running index in d_buf */
unsigned fx = 0; /* running index in flag_buf */
uch flag = 0; /* current flags */
unsigned code; /* the code to send */
int extra; /* number of extra bits to send */
if (last_lit != 0) do {
if ((lx & 7) == 0) flag = flag_buf[fx++];
lc = l_buf[lx++];
if ((flag & 1) == 0) {
send_code(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(code+LITERALS+1, ltree); /* send the length code */
extra = extra_lbits[code];
if (extra != 0) {
lc -= base_length[code];
send_bits(lc, extra); /* send the extra length bits */
}
dist = d_buf[dx++];
/* Here, dist is the match distance - 1 */
code = d_code(dist);
Assert (code < D_CODES, "bad d_code");
send_code(code, dtree); /* send the distance code */
extra = extra_dbits[code];
if (extra != 0) {
dist -= base_dist[code];
send_bits(dist, extra); /* send the extra distance bits */
}
} /* literal or match pair ? */
flag >>= 1;
} while (lx < last_lit);
send_code(END_BLOCK, ltree);
}
/* ===========================================================================
* Set the file 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_file_type()
{
int n = 0;
unsigned ascii_freq = 0;
unsigned bin_freq = 0;
while (n < 7) bin_freq += dyn_ltree[n++].Freq;
while (n < 128) ascii_freq += dyn_ltree[n++].Freq;
while (n < LITERALS) bin_freq += dyn_ltree[n++].Freq;
*file_type = bin_freq > (ascii_freq >> 2) ? BINARY : ASCII;
if (*file_type == BINARY && translate_eol) {
warn("-l used on binary file", "");
}
}
Reference in New Issue View Git Blame Copy Permalink