FGFS-4.1/simgear
4
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
9b4fe7d92d
simgear/zlib/deflate.c
curt 39521df546 Version 1.1.3
1998-07-24 21:35:29 +00:00

1351 lines
48 KiB
C
Raw Blame History

/* deflate.c -- compress data using the deflation algorithm
* Copyright (C) 1995-1998 Jean-loup Gailly.
* For conditions of distribution and use, see copyright notice in zlib.h
*/
/*
* ALGORITHM
*
* The "deflation" process depends on being able to identify portions
* of the input text which are identical to earlier input (within a
* sliding window trailing behind the input currently being processed).
*
* The most straightforward technique turns out to be the fastest for
* most input files: try all possible matches and select the longest.
* The key feature of this algorithm is that insertions into the string
* dictionary are very simple and thus fast, and deletions are avoided
* completely. Insertions are performed at each input character, whereas
* string matches are performed only when the previous match ends. So it
* is preferable to spend more time in matches to allow very fast string
* insertions and avoid deletions. The matching algorithm for small
* strings is inspired from that of Rabin & Karp. A brute force approach
* is used to find longer strings when a small match has been found.
* A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
* (by Leonid Broukhis).
* A previous version of this file used a more sophisticated algorithm
* (by Fiala and Greene) which is guaranteed to run in linear amortized
* time, but has a larger average cost, uses more memory and is patented.
* However the F&G algorithm may be faster for some highly redundant
* files if the parameter max_chain_length (described below) is too large.
*
* ACKNOWLEDGEMENTS
*
* The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
* I found it in 'freeze' written by Leonid Broukhis.
* Thanks to many people for bug reports and testing.
*
* REFERENCES
*
* Deutsch, L.P.,"DEFLATE Compressed Data Format Specification".
* Available in ftp://ds.internic.net/rfc/rfc1951.txt
*
* A description of the Rabin and Karp algorithm is given in the book
* "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
*
* Fiala,E.R., and Greene,D.H.
* Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595
*
*/
/* @(#) $Id$ */
#include "deflate.h"
const char deflate_copyright[] =
" deflate 1.1.3 Copyright 1995-1998 Jean-loup Gailly ";
/*
If you use the zlib library in a product, an acknowledgment is welcome
in the documentation of your product. If for some reason you cannot
include such an acknowledgment, I would appreciate that you keep this
copyright string in the executable of your product.
*/
/* ===========================================================================
* Function prototypes.
*/
typedef enum {
need_more, /* block not completed, need more input or more output */
block_done, /* block flush performed */
finish_started, /* finish started, need only more output at next deflate */
finish_done /* finish done, accept no more input or output */
} block_state;
typedef block_state (*compress_func) OF((deflate_state *s, int flush));
/* Compression function. Returns the block state after the call. */
local void fill_window OF((deflate_state *s));
local block_state deflate_stored OF((deflate_state *s, int flush));
local block_state deflate_fast OF((deflate_state *s, int flush));
local block_state deflate_slow OF((deflate_state *s, int flush));
local void lm_init OF((deflate_state *s));
local void putShortMSB OF((deflate_state *s, uInt b));
local void flush_pending OF((z_streamp strm));
local int read_buf OF((z_streamp strm, Bytef *buf, unsigned size));
#ifdef ASMV
void match_init OF((void)); /* asm code initialization */
uInt longest_match OF((deflate_state *s, IPos cur_match));
#else
local uInt longest_match OF((deflate_state *s, IPos cur_match));
#endif
#ifdef DEBUG
local void check_match OF((deflate_state *s, IPos start, IPos match,
int length));
#endif
/* ===========================================================================
* Local data
*/
#define NIL 0
/* Tail of hash chains */
#ifndef TOO_FAR
# define TOO_FAR 4096
#endif
/* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
#define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
/* Minimum amount of lookahead, except at the end of the input file.
* See deflate.c for comments about the MIN_MATCH+1.
*/
/* Values for max_lazy_match, good_match and max_chain_length, depending on
* the desired pack level (0..9). The values given below have been tuned to
* exclude worst case performance for pathological files. Better values may be
* found for specific files.
*/
typedef struct config_s {
ush good_length; /* reduce lazy search above this match length */
ush max_lazy; /* do not perform lazy search above this match length */
ush nice_length; /* quit search above this match length */
ush max_chain;
compress_func func;
} config;
local const config configuration_table[10] = {
/* good lazy nice chain */
/* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */
/* 1 */ {4, 4, 8, 4, deflate_fast}, /* maximum speed, no lazy matches */
/* 2 */ {4, 5, 16, 8, deflate_fast},
/* 3 */ {4, 6, 32, 32, deflate_fast},
/* 4 */ {4, 4, 16, 16, deflate_slow}, /* lazy matches */
/* 5 */ {8, 16, 32, 32, deflate_slow},
/* 6 */ {8, 16, 128, 128, deflate_slow},
/* 7 */ {8, 32, 128, 256, deflate_slow},
/* 8 */ {32, 128, 258, 1024, deflate_slow},
/* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* maximum compression */
/* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
* For deflate_fast() (levels <= 3) good is ignored and lazy has a different
* meaning.
*/
#define EQUAL 0
/* result of memcmp for equal strings */
struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
/* ===========================================================================
* Update a hash value with the given input byte
* IN assertion: all calls to to UPDATE_HASH are made with consecutive
* input characters, so that a running hash key can be computed from the
* previous key instead of complete recalculation each time.
*/
#define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
/* ===========================================================================
* Insert string str in the dictionary and set match_head to the previous head
* of the hash chain (the most recent string with same hash key). Return
* the previous length of the hash chain.
* If this file is compiled with -DFASTEST, the compression level is forced
* to 1, and no hash chains are maintained.
* IN assertion: all calls to to INSERT_STRING are made with consecutive
* input characters and the first MIN_MATCH bytes of str are valid
* (except for the last MIN_MATCH-1 bytes of the input file).
*/
#ifdef FASTEST
#define INSERT_STRING(s, str, match_head) \
(UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
match_head = s->head[s->ins_h], \
s->head[s->ins_h] = (Pos)(str))
#else
#define INSERT_STRING(s, str, match_head) \
(UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
s->prev[(str) & s->w_mask] = match_head = s->head[s->ins_h], \
s->head[s->ins_h] = (Pos)(str))
#endif
/* ===========================================================================
* Initialize the hash table (avoiding 64K overflow for 16 bit systems).
* prev[] will be initialized on the fly.
*/
#define CLEAR_HASH(s) \
s->head[s->hash_size-1] = NIL; \
zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
/* ========================================================================= */
int ZEXPORT deflateInit_(strm, level, version, stream_size)
z_streamp strm;
int level;
const char *version;
int stream_size;
{
return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL,
Z_DEFAULT_STRATEGY, version, stream_size);
/* To do: ignore strm->next_in if we use it as window */
}
/* ========================================================================= */
int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
version, stream_size)
z_streamp strm;
int level;
int method;
int windowBits;
int memLevel;
int strategy;
const char *version;
int stream_size;
{
deflate_state *s;
int noheader = 0;
static const char* my_version = ZLIB_VERSION;
ushf *overlay;
/* We overlay pending_buf and d_buf+l_buf. This works since the average
* output size for (length,distance) codes is <= 24 bits.
*/
if (version == Z_NULL || version[0] != my_version[0] ||
stream_size != sizeof(z_stream)) {
return Z_VERSION_ERROR;
}
if (strm == Z_NULL) return Z_STREAM_ERROR;
strm->msg = Z_NULL;
if (strm->zalloc == Z_NULL) {
strm->zalloc = zcalloc;
strm->opaque = (voidpf)0;
}
if (strm->zfree == Z_NULL) strm->zfree = zcfree;
if (level == Z_DEFAULT_COMPRESSION) level = 6;
#ifdef FASTEST
level = 1;
#endif
if (windowBits < 0) { /* undocumented feature: suppress zlib header */
noheader = 1;
windowBits = -windowBits;
}
if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
strategy < 0 || strategy > Z_HUFFMAN_ONLY) {
return Z_STREAM_ERROR;
}
s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state));
if (s == Z_NULL) return Z_MEM_ERROR;
strm->state = (struct internal_state FAR *)s;
s->strm = strm;
s->noheader = noheader;
s->w_bits = windowBits;
s->w_size = 1 << s->w_bits;
s->w_mask = s->w_size - 1;
s->hash_bits = memLevel + 7;
s->hash_size = 1 << s->hash_bits;
s->hash_mask = s->hash_size - 1;
s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH);
s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte));
s->prev = (Posf *) ZALLOC(strm, s->w_size, sizeof(Pos));
s->head = (Posf *) ZALLOC(strm, s->hash_size, sizeof(Pos));
s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */
overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
s->pending_buf = (uchf *) overlay;
s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
s->pending_buf == Z_NULL) {
strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);
deflateEnd (strm);
return Z_MEM_ERROR;
}
s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
s->level = level;
s->strategy = strategy;
s->method = (Byte)method;
return deflateReset(strm);
}
/* ========================================================================= */
int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
z_streamp strm;
const Bytef *dictionary;
uInt dictLength;
{
deflate_state *s;
uInt length = dictLength;
uInt n;
IPos hash_head = 0;
if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL ||
strm->state->status != INIT_STATE) return Z_STREAM_ERROR;
s = strm->state;
strm->adler = adler32(strm->adler, dictionary, dictLength);
if (length < MIN_MATCH) return Z_OK;
if (length > MAX_DIST(s)) {
length = MAX_DIST(s);
#ifndef USE_DICT_HEAD
dictionary += dictLength - length; /* use the tail of the dictionary */
#endif
}
zmemcpy(s->window, dictionary, length);
s->strstart = length;
s->block_start = (long)length;
/* Insert all strings in the hash table (except for the last two bytes).
* s->lookahead stays null, so s->ins_h will be recomputed at the next
* call of fill_window.
*/
s->ins_h = s->window[0];
UPDATE_HASH(s, s->ins_h, s->window[1]);
for (n = 0; n <= length - MIN_MATCH; n++) {
INSERT_STRING(s, n, hash_head);
}
if (hash_head) hash_head = 0; /* to make compiler happy */
return Z_OK;
}
/* ========================================================================= */
int ZEXPORT deflateReset (strm)
z_streamp strm;
{
deflate_state *s;
if (strm == Z_NULL || strm->state == Z_NULL ||
strm->zalloc == Z_NULL || strm->zfree == Z_NULL) return Z_STREAM_ERROR;
strm->total_in = strm->total_out = 0;
strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */
strm->data_type = Z_UNKNOWN;
s = (deflate_state *)strm->state;
s->pending = 0;
s->pending_out = s->pending_buf;
if (s->noheader < 0) {
s->noheader = 0; /* was set to -1 by deflate(..., Z_FINISH); */
}
s->status = s->noheader ? BUSY_STATE : INIT_STATE;
strm->adler = 1;
s->last_flush = Z_NO_FLUSH;
_tr_init(s);
lm_init(s);
return Z_OK;
}
/* ========================================================================= */
int ZEXPORT deflateParams(strm, level, strategy)
z_streamp strm;
int level;
int strategy;
{
deflate_state *s;
compress_func func;
int err = Z_OK;
if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
s = strm->state;
if (level == Z_DEFAULT_COMPRESSION) {
level = 6;
}
if (level < 0 || level > 9 || strategy < 0 || strategy > Z_HUFFMAN_ONLY) {
return Z_STREAM_ERROR;
}
func = configuration_table[s->level].func;
if (func != configuration_table[level].func && strm->total_in != 0) {
/* Flush the last buffer: */
err = deflate(strm, Z_PARTIAL_FLUSH);
}
if (s->level != level) {
s->level = level;
s->max_lazy_match = configuration_table[level].max_lazy;
s->good_match = configuration_table[level].good_length;
s->nice_match = configuration_table[level].nice_length;
s->max_chain_length = configuration_table[level].max_chain;
}
s->strategy = strategy;
return err;
}
/* =========================================================================
* Put a short in the pending buffer. The 16-bit value is put in MSB order.
* IN assertion: the stream state is correct and there is enough room in
* pending_buf.
*/
local void putShortMSB (s, b)
deflate_state *s;
uInt b;
{
put_byte(s, (Byte)(b >> 8));
put_byte(s, (Byte)(b & 0xff));
}
/* =========================================================================
* Flush as much pending output as possible. All deflate() output goes
* through this function so some applications may wish to modify it
* to avoid allocating a large strm->next_out buffer and copying into it.
* (See also read_buf()).
*/
local void flush_pending(strm)
z_streamp strm;
{
unsigned len = strm->state->pending;
if (len > strm->avail_out) len = strm->avail_out;
if (len == 0) return;
zmemcpy(strm->next_out, strm->state->pending_out, len);
strm->next_out += len;
strm->state->pending_out += len;
strm->total_out += len;
strm->avail_out -= len;
strm->state->pending -= len;
if (strm->state->pending == 0) {
strm->state->pending_out = strm->state->pending_buf;
}
}
/* ========================================================================= */
int ZEXPORT deflate (strm, flush)
z_streamp strm;
int flush;
{
int old_flush; /* value of flush param for previous deflate call */
deflate_state *s;
if (strm == Z_NULL || strm->state == Z_NULL ||
flush > Z_FINISH || flush < 0) {
return Z_STREAM_ERROR;
}
s = strm->state;
if (strm->next_out == Z_NULL ||
(strm->next_in == Z_NULL && strm->avail_in != 0) ||
(s->status == FINISH_STATE && flush != Z_FINISH)) {
ERR_RETURN(strm, Z_STREAM_ERROR);
}
if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR);
s->strm = strm; /* just in case */
old_flush = s->last_flush;
s->last_flush = flush;
/* Write the zlib header */
if (s->status == INIT_STATE) {
uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8;
uInt level_flags = (s->level-1) >> 1;
if (level_flags > 3) level_flags = 3;
header |= (level_flags << 6);
if (s->strstart != 0) header |= PRESET_DICT;
header += 31 - (header % 31);
s->status = BUSY_STATE;
putShortMSB(s, header);
/* Save the adler32 of the preset dictionary: */
if (s->strstart != 0) {
putShortMSB(s, (uInt)(strm->adler >> 16));
putShortMSB(s, (uInt)(strm->adler & 0xffff));
}
strm->adler = 1L;
}
/* Flush as much pending output as possible */
if (s->pending != 0) {
flush_pending(strm);
if (strm->avail_out == 0) {
/* Since avail_out is 0, deflate will be called again with
* more output space, but possibly with both pending and
* avail_in equal to zero. There won't be anything to do,
* but this is not an error situation so make sure we
* return OK instead of BUF_ERROR at next call of deflate:
*/
s->last_flush = -1;
return Z_OK;
}
/* Make sure there is something to do and avoid duplicate consecutive
* flushes. For repeated and useless calls with Z_FINISH, we keep
* returning Z_STREAM_END instead of Z_BUFF_ERROR.
*/
} else if (strm->avail_in == 0 && flush <= old_flush &&
flush != Z_FINISH) {
ERR_RETURN(strm, Z_BUF_ERROR);
}
/* User must not provide more input after the first FINISH: */
if (s->status == FINISH_STATE && strm->avail_in != 0) {
ERR_RETURN(strm, Z_BUF_ERROR);
}
/* Start a new block or continue the current one.
*/
if (strm->avail_in != 0 || s->lookahead != 0 ||
(flush != Z_NO_FLUSH && s->status != FINISH_STATE)) {
block_state bstate;
bstate = (*(configuration_table[s->level].func))(s, flush);
if (bstate == finish_started || bstate == finish_done) {
s->status = FINISH_STATE;
}
if (bstate == need_more || bstate == finish_started) {
if (strm->avail_out == 0) {
s->last_flush = -1; /* avoid BUF_ERROR next call, see above */
}
return Z_OK;
/* If flush != Z_NO_FLUSH && avail_out == 0, the next call
* of deflate should use the same flush parameter to make sure
* that the flush is complete. So we don't have to output an
* empty block here, this will be done at next call. This also
* ensures that for a very small output buffer, we emit at most
* one empty block.
*/
}
if (bstate == block_done) {
if (flush == Z_PARTIAL_FLUSH) {
_tr_align(s);
} else { /* FULL_FLUSH or SYNC_FLUSH */
_tr_stored_block(s, (char*)0, 0L, 0);
/* For a full flush, this empty block will be recognized
* as a special marker by inflate_sync().
*/
if (flush == Z_FULL_FLUSH) {
CLEAR_HASH(s); /* forget history */
}
}
flush_pending(strm);
if (strm->avail_out == 0) {
s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */
return Z_OK;
}
}
}
Assert(strm->avail_out > 0, "bug2");
if (flush != Z_FINISH) return Z_OK;
if (s->noheader) return Z_STREAM_END;
/* Write the zlib trailer (adler32) */
putShortMSB(s, (uInt)(strm->adler >> 16));
putShortMSB(s, (uInt)(strm->adler & 0xffff));
flush_pending(strm);
/* If avail_out is zero, the application will call deflate again
* to flush the rest.
*/
s->noheader = -1; /* write the trailer only once! */
return s->pending != 0 ? Z_OK : Z_STREAM_END;
}
/* ========================================================================= */
int ZEXPORT deflateEnd (strm)
z_streamp strm;
{
int status;
if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
status = strm->state->status;
if (status != INIT_STATE && status != BUSY_STATE &&
status != FINISH_STATE) {
return Z_STREAM_ERROR;
}
/* Deallocate in reverse order of allocations: */
TRY_FREE(strm, strm->state->pending_buf);
TRY_FREE(strm, strm->state->head);
TRY_FREE(strm, strm->state->prev);
TRY_FREE(strm, strm->state->window);
ZFREE(strm, strm->state);
strm->state = Z_NULL;
return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK;
}
/* =========================================================================
* Copy the source state to the destination state.
* To simplify the source, this is not supported for 16-bit MSDOS (which
* doesn't have enough memory anyway to duplicate compression states).
*/
int ZEXPORT deflateCopy (dest, source)
z_streamp dest;
z_streamp source;
{
#ifdef MAXSEG_64K
return Z_STREAM_ERROR;
#else
deflate_state *ds;
deflate_state *ss;
ushf *overlay;
if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
return Z_STREAM_ERROR;
}
ss = source->state;
*dest = *source;
ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state));
if (ds == Z_NULL) return Z_MEM_ERROR;
dest->state = (struct internal_state FAR *) ds;
*ds = *ss;
ds->strm = dest;
ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
ds->prev = (Posf *) ZALLOC(dest, ds->w_size, sizeof(Pos));
ds->head = (Posf *) ZALLOC(dest, ds->hash_size, sizeof(Pos));
overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
ds->pending_buf = (uchf *) overlay;
if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
ds->pending_buf == Z_NULL) {
deflateEnd (dest);
return Z_MEM_ERROR;
}
/* following zmemcpy do not work for 16-bit MSDOS */
zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos));
zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos));
zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
ds->l_desc.dyn_tree = ds->dyn_ltree;
ds->d_desc.dyn_tree = ds->dyn_dtree;
ds->bl_desc.dyn_tree = ds->bl_tree;
return Z_OK;
#endif
}
/* ===========================================================================
* Read a new buffer from the current input stream, update the adler32
* and total number of bytes read. All deflate() input goes through
* this function so some applications may wish to modify it to avoid
* allocating a large strm->next_in buffer and copying from it.
* (See also flush_pending()).
*/
local int read_buf(strm, buf, size)
z_streamp strm;
Bytef *buf;
unsigned size;
{
unsigned len = strm->avail_in;
if (len > size) len = size;
if (len == 0) return 0;
strm->avail_in -= len;
if (!strm->state->noheader) {
strm->adler = adler32(strm->adler, strm->next_in, len);
}
zmemcpy(buf, strm->next_in, len);
strm->next_in += len;
strm->total_in += len;
return (int)len;
}
/* ===========================================================================
* Initialize the "longest match" routines for a new zlib stream
*/
local void lm_init (s)
deflate_state *s;
{
s->window_size = (ulg)2L*s->w_size;
CLEAR_HASH(s);
/* Set the default configuration parameters:
*/
s->max_lazy_match = configuration_table[s->level].max_lazy;
s->good_match = configuration_table[s->level].good_length;
s->nice_match = configuration_table[s->level].nice_length;
s->max_chain_length = configuration_table[s->level].max_chain;
s->strstart = 0;
s->block_start = 0L;
s->lookahead = 0;
s->match_length = s->prev_length = MIN_MATCH-1;
s->match_available = 0;
s->ins_h = 0;
#ifdef ASMV
match_init(); /* initialize the asm code */
#endif
}
/* ===========================================================================
* Set match_start to the longest match starting at the given string and
* return its length. Matches shorter or equal to prev_length are discarded,
* in which case the result is equal to prev_length and match_start is
* garbage.
* IN assertions: cur_match is the head of the hash chain for the current
* string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
* OUT assertion: the match length is not greater than s->lookahead.
*/
#ifndef ASMV
/* For 80x86 and 680x0, an optimized version will be provided in match.asm or
* match.S. The code will be functionally equivalent.
*/
#ifndef FASTEST
local uInt longest_match(s, cur_match)
deflate_state *s;
IPos cur_match; /* current match */
{
unsigned chain_length = s->max_chain_length;/* max hash chain length */
register Bytef *scan = s->window + s->strstart; /* current string */
register Bytef *match; /* matched string */
register int len; /* length of current match */
int best_len = s->prev_length; /* best match length so far */
int nice_match = s->nice_match; /* stop if match long enough */
IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
s->strstart - (IPos)MAX_DIST(s) : NIL;
/* Stop when cur_match becomes <= limit. To simplify the code,
* we prevent matches with the string of window index 0.
*/
Posf *prev = s->prev;
uInt wmask = s->w_mask;
#ifdef UNALIGNED_OK
/* Compare two bytes at a time. Note: this is not always beneficial.
* Try with and without -DUNALIGNED_OK to check.
*/
register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1;
register ush scan_start = *(ushf*)scan;
register ush scan_end = *(ushf*)(scan+best_len-1);
#else
register Bytef *strend = s->window + s->strstart + MAX_MATCH;
register Byte scan_end1 = scan[best_len-1];
register Byte scan_end = scan[best_len];
#endif
/* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
* It is easy to get rid of this optimization if necessary.
*/
Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
/* Do not waste too much time if we already have a good match: */
if (s->prev_length >= s->good_match) {
chain_length >>= 2;
}
/* Do not look for matches beyond the end of the input. This is necessary
* to make deflate deterministic.
*/
if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
do {
Assert(cur_match < s->strstart, "no future");
match = s->window + cur_match;
/* Skip to next match if the match length cannot increase
* or if the match length is less than 2:
*/
#if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
/* This code assumes sizeof(unsigned short) == 2. Do not use
* UNALIGNED_OK if your compiler uses a different size.
*/
if (*(ushf*)(match+best_len-1) != scan_end ||
*(ushf*)match != scan_start) continue;
/* It is not necessary to compare scan[2] and match[2] since they are
* always equal when the other bytes match, given that the hash keys
* are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
* strstart+3, +5, ... up to strstart+257. We check for insufficient
* lookahead only every 4th comparison; the 128th check will be made
* at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
* necessary to put more guard bytes at the end of the window, or
* to check more often for insufficient lookahead.
*/
Assert(scan[2] == match[2], "scan[2]?");
scan++, match++;
do {
} while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
*(ushf*)(scan+=2) == *(ushf*)(match+=2) &&
scan < strend);
/* The funny "do {}" generates better code on most compilers */
/* Here, scan <= window+strstart+257 */
Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
if (*scan == *match) scan++;
len = (MAX_MATCH - 1) - (int)(strend-scan);
scan = strend - (MAX_MATCH-1);
#else /* UNALIGNED_OK */
if (match[best_len] != scan_end ||
match[best_len-1] != scan_end1 ||
*match != *scan ||
*++match != scan[1]) continue;
/* The check at best_len-1 can be removed because it will be made
* again later. (This heuristic is not always a win.)
* It is not necessary to compare scan[2] and match[2] since they
* are always equal when the other bytes match, given that
* the hash keys are equal and that HASH_BITS >= 8.
*/
scan += 2, match++;
Assert(*scan == *match, "match[2]?");
/* We check for insufficient lookahead only every 8th comparison;
* the 256th check will be made at strstart+258.
*/
do {
} while (*++scan == *++match && *++scan == *++match &&
*++scan == *++match && *++scan == *++match &&
*++scan == *++match && *++scan == *++match &&
*++scan == *++match && *++scan == *++match &&
scan < strend);
Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
len = MAX_MATCH - (int)(strend - scan);
scan = strend - MAX_MATCH;
#endif /* UNALIGNED_OK */
if (len > best_len) {
s->match_start = cur_match;
best_len = len;
if (len >= nice_match) break;
#ifdef UNALIGNED_OK
scan_end = *(ushf*)(scan+best_len-1);
#else
scan_end1 = scan[best_len-1];
scan_end = scan[best_len];
#endif
}
} while ((cur_match = prev[cur_match & wmask]) > limit
&& --chain_length != 0);
if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
return s->lookahead;
}
#else /* FASTEST */
/* ---------------------------------------------------------------------------
* Optimized version for level == 1 only
*/
local uInt longest_match(s, cur_match)
deflate_state *s;
IPos cur_match; /* current match */
{
register Bytef *scan = s->window + s->strstart; /* current string */
register Bytef *match; /* matched string */
register int len; /* length of current match */
register Bytef *strend = s->window + s->strstart + MAX_MATCH;
/* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
* It is easy to get rid of this optimization if necessary.
*/
Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever");
Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
Assert(cur_match < s->strstart, "no future");
match = s->window + cur_match;
/* Return failure if the match length is less than 2:
*/
if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1;
/* The check at best_len-1 can be removed because it will be made
* again later. (This heuristic is not always a win.)
* It is not necessary to compare scan[2] and match[2] since they
* are always equal when the other bytes match, given that
* the hash keys are equal and that HASH_BITS >= 8.
*/
scan += 2, match += 2;
Assert(*scan == *match, "match[2]?");
/* We check for insufficient lookahead only every 8th comparison;
* the 256th check will be made at strstart+258.
*/
do {
} while (*++scan == *++match && *++scan == *++match &&
*++scan == *++match && *++scan == *++match &&
*++scan == *++match && *++scan == *++match &&
*++scan == *++match && *++scan == *++match &&
scan < strend);
Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan");
len = MAX_MATCH - (int)(strend - scan);
if (len < MIN_MATCH) return MIN_MATCH - 1;
s->match_start = cur_match;
return len <= s->lookahead ? len : s->lookahead;
}
#endif /* FASTEST */
#endif /* ASMV */
#ifdef DEBUG
/* ===========================================================================
* Check that the match at match_start is indeed a match.
*/
local void check_match(s, start, match, length)
deflate_state *s;
IPos start, match;
int length;
{
/* check that the match is indeed a match */
if (zmemcmp(s->window + match,
s->window + start, length) != EQUAL) {
fprintf(stderr, " start %u, match %u, length %d\n",
start, match, length);
do {
fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
} while (--length != 0);
z_error("invalid match");
}
if (z_verbose > 1) {
fprintf(stderr,"\\[%d,%d]", start-match, length);
do { putc(s->window[start++], stderr); } while (--length != 0);
}
}
#else
# define check_match(s, start, match, length)
#endif
/* ===========================================================================
* Fill the window when the lookahead becomes insufficient.
* Updates strstart and lookahead.
*
* IN assertion: lookahead < MIN_LOOKAHEAD
* OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
* At least one byte has been read, or avail_in == 0; reads are
* performed for at least two bytes (required for the zip translate_eol
* option -- not supported here).
*/
local void fill_window(s)
deflate_state *s;
{
register unsigned n, m;
register Posf *p;
unsigned more; /* Amount of free space at the end of the window. */
uInt wsize = s->w_size;
do {
more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart);
/* Deal with !@#$% 64K limit: */
if (more == 0 && s->strstart == 0 && s->lookahead == 0) {
more = wsize;
} else if (more == (unsigned)(-1)) {
/* Very unlikely, but possible on 16 bit machine if strstart == 0
* and lookahead == 1 (input done one byte at time)
*/
more--;
/* If the window is almost full and there is insufficient lookahead,
* move the upper half to the lower one to make room in the upper half.
*/
} else if (s->strstart >= wsize+MAX_DIST(s)) {
zmemcpy(s->window, s->window+wsize, (unsigned)wsize);
s->match_start -= wsize;
s->strstart -= wsize; /* we now have strstart >= MAX_DIST */
s->block_start -= (long) wsize;
/* Slide the hash table (could be avoided with 32 bit values
at the expense of memory usage). We slide even when level == 0
to keep the hash table consistent if we switch back to level > 0
later. (Using level 0 permanently is not an optimal usage of
zlib, so we don't care about this pathological case.)
*/
n = s->hash_size;
p = &s->head[n];
do {
m = *--p;
*p = (Pos)(m >= wsize ? m-wsize : NIL);
} while (--n);
n = wsize;
#ifndef FASTEST
p = &s->prev[n];
do {
m = *--p;
*p = (Pos)(m >= wsize ? m-wsize : NIL);
/* If n is not on any hash chain, prev[n] is garbage but
* its value will never be used.
*/
} while (--n);
#endif
more += wsize;
}
if (s->strm->avail_in == 0) return;
/* If there was no sliding:
* strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
* more == window_size - lookahead - strstart
* => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
* => more >= window_size - 2*WSIZE + 2
* In the BIG_MEM or MMAP case (not yet supported),
* window_size == input_size + MIN_LOOKAHEAD &&
* strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
* Otherwise, window_size == 2*WSIZE so more >= 2.
* If there was sliding, more >= WSIZE. So in all cases, more >= 2.
*/
Assert(more >= 2, "more < 2");
n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more);
s->lookahead += n;
/* Initialize the hash value now that we have some input: */
if (s->lookahead >= MIN_MATCH) {
s->ins_h = s->window[s->strstart];
UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
#if MIN_MATCH != 3
Call UPDATE_HASH() MIN_MATCH-3 more times
#endif
}
/* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
* but this is not important since only literal bytes will be emitted.
*/
} while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0);
}
/* ===========================================================================
* Flush the current block, with given end-of-file flag.
* IN assertion: strstart is set to the end of the current match.
*/
#define FLUSH_BLOCK_ONLY(s, eof) { \
_tr_flush_block(s, (s->block_start >= 0L ? \
(charf *)&s->window[(unsigned)s->block_start] : \
(charf *)Z_NULL), \
(ulg)((long)s->strstart - s->block_start), \
(eof)); \
s->block_start = s->strstart; \
flush_pending(s->strm); \
Tracev((stderr,"[FLUSH]")); \
}
/* Same but force premature exit if necessary. */
#define FLUSH_BLOCK(s, eof) { \
FLUSH_BLOCK_ONLY(s, eof); \
if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \
}
/* ===========================================================================
* Copy without compression as much as possible from the input stream, return
* the current block state.
* This function does not insert new strings in the dictionary since
* uncompressible data is probably not useful. This function is used
* only for the level=0 compression option.
* NOTE: this function should be optimized to avoid extra copying from
* window to pending_buf.
*/
local block_state deflate_stored(s, flush)
deflate_state *s;
int flush;
{
/* Stored blocks are limited to 0xffff bytes, pending_buf is limited
* to pending_buf_size, and each stored block has a 5 byte header:
*/
ulg max_block_size = 0xffff;
ulg max_start;
if (max_block_size > s->pending_buf_size - 5) {
max_block_size = s->pending_buf_size - 5;
}
/* Copy as much as possible from input to output: */
for (;;) {
/* Fill the window as much as possible: */
if (s->lookahead <= 1) {
Assert(s->strstart < s->w_size+MAX_DIST(s) ||
s->block_start >= (long)s->w_size, "slide too late");
fill_window(s);
if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more;
if (s->lookahead == 0) break; /* flush the current block */
}
Assert(s->block_start >= 0L, "block gone");
s->strstart += s->lookahead;
s->lookahead = 0;
/* Emit a stored block if pending_buf will be full: */
max_start = s->block_start + max_block_size;
if (s->strstart == 0 || (ulg)s->strstart >= max_start) {
/* strstart == 0 is possible when wraparound on 16-bit machine */
s->lookahead = (uInt)(s->strstart - max_start);
s->strstart = (uInt)max_start;
FLUSH_BLOCK(s, 0);
}
/* Flush if we may have to slide, otherwise block_start may become
* negative and the data will be gone:
*/
if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) {
FLUSH_BLOCK(s, 0);
}
}
FLUSH_BLOCK(s, flush == Z_FINISH);
return flush == Z_FINISH ? finish_done : block_done;
}
/* ===========================================================================
* Compress as much as possible from the input stream, return the current
* block state.
* This function does not perform lazy evaluation of matches and inserts
* new strings in the dictionary only for unmatched strings or for short
* matches. It is used only for the fast compression options.
*/
local block_state deflate_fast(s, flush)
deflate_state *s;
int flush;
{
IPos hash_head = NIL; /* head of the hash chain */
int bflush; /* set if current block must be flushed */
for (;;) {
/* Make sure that we always have enough lookahead, except
* at the end of the input file. We need MAX_MATCH bytes
* for the next match, plus MIN_MATCH bytes to insert the
* string following the next match.
*/
if (s->lookahead < MIN_LOOKAHEAD) {
fill_window(s);
if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
return need_more;
}
if (s->lookahead == 0) break; /* flush the current block */
}
/* Insert the string window[strstart .. strstart+2] in the
* dictionary, and set hash_head to the head of the hash chain:
*/
if (s->lookahead >= MIN_MATCH) {
INSERT_STRING(s, s->strstart, hash_head);
}
/* Find the longest match, discarding those <= prev_length.
* At this point we have always match_length < MIN_MATCH
*/
if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) {
/* To simplify the code, we prevent matches with the string
* of window index 0 (in particular we have to avoid a match
* of the string with itself at the start of the input file).
*/
if (s->strategy != Z_HUFFMAN_ONLY) {
s->match_length = longest_match (s, hash_head);
}
/* longest_match() sets match_start */
}
if (s->match_length >= MIN_MATCH) {
check_match(s, s->strstart, s->match_start, s->match_length);
_tr_tally_dist(s, s->strstart - s->match_start,
s->match_length - MIN_MATCH, bflush);
s->lookahead -= s->match_length;
/* Insert new strings in the hash table only if the match length
* is not too large. This saves time but degrades compression.
*/
#ifndef FASTEST
if (s->match_length <= s->max_insert_length &&
s->lookahead >= MIN_MATCH) {
s->match_length--; /* string at strstart already in hash table */
do {
s->strstart++;
INSERT_STRING(s, s->strstart, hash_head);
/* strstart never exceeds WSIZE-MAX_MATCH, so there are
* always MIN_MATCH bytes ahead.
*/
} while (--s->match_length != 0);
s->strstart++;
} else
#endif
{
s->strstart += s->match_length;
s->match_length = 0;
s->ins_h = s->window[s->strstart];
UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]);
#if MIN_MATCH != 3
Call UPDATE_HASH() MIN_MATCH-3 more times
#endif
/* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
* matter since it will be recomputed at next deflate call.
*/
}
} else {
/* No match, output a literal byte */
Tracevv((stderr,"%c", s->window[s->strstart]));
_tr_tally_lit (s, s->window[s->strstart], bflush);
s->lookahead--;
s->strstart++;
}
if (bflush) FLUSH_BLOCK(s, 0);
}
FLUSH_BLOCK(s, flush == Z_FINISH);
return flush == Z_FINISH ? finish_done : block_done;
}
/* ===========================================================================
* Same as above, but achieves better compression. We use a lazy
* evaluation for matches: a match is finally adopted only if there is
* no better match at the next window position.
*/
local block_state deflate_slow(s, flush)
deflate_state *s;
int flush;
{
IPos hash_head = NIL; /* head of hash chain */
int bflush; /* set if current block must be flushed */
/* Process the input block. */
for (;;) {
/* Make sure that we always have enough lookahead, except
* at the end of the input file. We need MAX_MATCH bytes
* for the next match, plus MIN_MATCH bytes to insert the
* string following the next match.
*/
if (s->lookahead < MIN_LOOKAHEAD) {
fill_window(s);
if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) {
return need_more;
}
if (s->lookahead == 0) break; /* flush the current block */
}
/* Insert the string window[strstart .. strstart+2] in the
* dictionary, and set hash_head to the head of the hash chain:
*/
if (s->lookahead >= MIN_MATCH) {
INSERT_STRING(s, s->strstart, hash_head);
}
/* Find the longest match, discarding those <= prev_length.
*/
s->prev_length = s->match_length, s->prev_match = s->match_start;
s->match_length = MIN_MATCH-1;
if (hash_head != NIL && s->prev_length < s->max_lazy_match &&
s->strstart - hash_head <= MAX_DIST(s)) {
/* To simplify the code, we prevent matches with the string
* of window index 0 (in particular we have to avoid a match
* of the string with itself at the start of the input file).
*/
if (s->strategy != Z_HUFFMAN_ONLY) {
s->match_length = longest_match (s, hash_head);
}
/* longest_match() sets match_start */
if (s->match_length <= 5 && (s->strategy == Z_FILTERED ||
(s->match_length == MIN_MATCH &&
s->strstart - s->match_start > TOO_FAR))) {
/* If prev_match is also MIN_MATCH, match_start is garbage
* but we will ignore the current match anyway.
*/
s->match_length = MIN_MATCH-1;
}
}
/* If there was a match at the previous step and the current
* match is not better, output the previous match:
*/
if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) {
uInt max_insert = s->strstart + s->lookahead - MIN_MATCH;
/* Do not insert strings in hash table beyond this. */
check_match(s, s->strstart-1, s->prev_match, s->prev_length);
_tr_tally_dist(s, s->strstart -1 - s->prev_match,
s->prev_length - MIN_MATCH, bflush);
/* Insert in hash table all strings up to the end of the match.
* strstart-1 and strstart are already inserted. If there is not
* enough lookahead, the last two strings are not inserted in
* the hash table.
*/
s->lookahead -= s->prev_length-1;
s->prev_length -= 2;
do {
if (++s->strstart <= max_insert) {
INSERT_STRING(s, s->strstart, hash_head);
}
} while (--s->prev_length != 0);
s->match_available = 0;
s->match_length = MIN_MATCH-1;
s->strstart++;
if (bflush) FLUSH_BLOCK(s, 0);
} else if (s->match_available) {
/* If there was no match at the previous position, output a
* single literal. If there was a match but the current match
* is longer, truncate the previous match to a single literal.
*/
Tracevv((stderr,"%c", s->window[s->strstart-1]));
_tr_tally_lit(s, s->window[s->strstart-1], bflush);
if (bflush) {
FLUSH_BLOCK_ONLY(s, 0);
}
s->strstart++;
s->lookahead--;
if (s->strm->avail_out == 0) return need_more;
} else {
/* There is no previous match to compare with, wait for
* the next step to decide.
*/
s->match_available = 1;
s->strstart++;
s->lookahead--;
}
}
Assert (flush != Z_NO_FLUSH, "no flush?");
if (s->match_available) {
Tracevv((stderr,"%c", s->window[s->strstart-1]));
_tr_tally_lit(s, s->window[s->strstart-1], bflush);
s->match_available = 0;
}
FLUSH_BLOCK(s, flush == Z_FINISH);
return flush == Z_FINISH ? finish_done : block_done;
}
Reference in New Issue View Git Blame Copy Permalink