1 /* deflate.c -- compress data using the deflation algorithm
2 * Copyright (C) 1995-2002 Jean-loup Gailly.
3 * For conditions of distribution and use, see copyright notice in zlib.h
9 * The "deflation" process depends on being able to identify portions
10 * of the input text which are identical to earlier input (within a
11 * sliding window trailing behind the input currently being processed).
13 * The most straightforward technique turns out to be the fastest for
14 * most input files: try all possible matches and select the longest.
15 * The key feature of this algorithm is that insertions into the string
16 * dictionary are very simple and thus fast, and deletions are avoided
17 * completely. Insertions are performed at each input character, whereas
18 * string matches are performed only when the previous match ends. So it
19 * is preferable to spend more time in matches to allow very fast string
20 * insertions and avoid deletions. The matching algorithm for small
21 * strings is inspired from that of Rabin & Karp. A brute force approach
22 * is used to find longer strings when a small match has been found.
23 * A similar algorithm is used in comic (by Jan-Mark Wams) and freeze
24 * (by Leonid Broukhis).
25 * A previous version of this file used a more sophisticated algorithm
26 * (by Fiala and Greene) which is guaranteed to run in linear amortized
27 * time, but has a larger average cost, uses more memory and is patented.
28 * However the F&G algorithm may be faster for some highly redundant
29 * files if the parameter max_chain_length (described below) is too large.
33 * The idea of lazy evaluation of matches is due to Jan-Mark Wams, and
34 * I found it in 'freeze' written by Leonid Broukhis.
35 * Thanks to many people for bug reports and testing.
39 * Deutsch, L.P.,"DEFLATE Compressed Data Format Specification".
40 * Available in ftp://ds.internic.net/rfc/rfc1951.txt
42 * A description of the Rabin and Karp algorithm is given in the book
43 * "Algorithms" by R. Sedgewick, Addison-Wesley, p252.
45 * Fiala,E.R., and Greene,D.H.
46 * Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595
50 /* @(#) $Id: deflate.c 119 2004-10-05 20:38:42Z oyvind $ */
54 const char deflate_copyright
[] =
55 " deflate 1.1.4 Copyright 1995-2002 Jean-loup Gailly ";
57 If you use the zlib library in a product, an acknowledgment is welcome
58 in the documentation of your product. If for some reason you cannot
59 include such an acknowledgment, I would appreciate that you keep this
60 copyright string in the executable of your product.
63 /* ===========================================================================
64 * Function prototypes.
67 need_more
, /* block not completed, need more input or more output */
68 block_done
, /* block flush performed */
69 finish_started
, /* finish started, need only more output at next deflate */
70 finish_done
/* finish done, accept no more input or output */
73 typedef block_state (*compress_func
) OF((deflate_state
*s
, int flush
));
74 /* Compression function. Returns the block state after the call. */
76 local
void fill_window
OF((deflate_state
*s
));
77 local block_state deflate_stored
OF((deflate_state
*s
, int flush
));
78 local block_state deflate_fast
OF((deflate_state
*s
, int flush
));
79 local block_state deflate_slow
OF((deflate_state
*s
, int flush
));
80 local
void lm_init
OF((deflate_state
*s
));
81 local
void putShortMSB
OF((deflate_state
*s
, uInt b
));
82 local
void flush_pending
OF((z_streamp strm
));
83 local
int read_buf
OF((z_streamp strm
, Bytef
*buf
, unsigned size
));
85 void match_init
OF((void)); /* asm code initialization */
86 uInt longest_match
OF((deflate_state
*s
, IPos cur_match
));
88 local uInt longest_match
OF((deflate_state
*s
, IPos cur_match
));
92 local
void check_match
OF((deflate_state
*s
, IPos start
, IPos match
,
96 /* ===========================================================================
101 /* Tail of hash chains */
104 # define TOO_FAR 4096
106 /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
108 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
109 /* Minimum amount of lookahead, except at the end of the input file.
110 * See deflate.c for comments about the MIN_MATCH+1.
113 /* Values for max_lazy_match, good_match and max_chain_length, depending on
114 * the desired pack level (0..9). The values given below have been tuned to
115 * exclude worst case performance for pathological files. Better values may be
116 * found for specific files.
118 typedef struct config_s
{
119 ush good_length
; /* reduce lazy search above this match length */
120 ush max_lazy
; /* do not perform lazy search above this match length */
121 ush nice_length
; /* quit search above this match length */
126 local
const config configuration_table
[10] = {
127 /* good lazy nice chain */
128 /* 0 */ {0, 0, 0, 0, deflate_stored
}, /* store only */
129 /* 1 */ {4, 4, 8, 4, deflate_fast
}, /* maximum speed, no lazy matches */
130 /* 2 */ {4, 5, 16, 8, deflate_fast
},
131 /* 3 */ {4, 6, 32, 32, deflate_fast
},
133 /* 4 */ {4, 4, 16, 16, deflate_slow
}, /* lazy matches */
134 /* 5 */ {8, 16, 32, 32, deflate_slow
},
135 /* 6 */ {8, 16, 128, 128, deflate_slow
},
136 /* 7 */ {8, 32, 128, 256, deflate_slow
},
137 /* 8 */ {32, 128, 258, 1024, deflate_slow
},
138 /* 9 */ {32, 258, 258, 4096, deflate_slow
}}; /* maximum compression */
140 /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
141 * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
146 /* result of memcmp for equal strings */
148 struct static_tree_desc_s
{int dummy
;}; /* for buggy compilers */
150 /* ===========================================================================
151 * Update a hash value with the given input byte
152 * IN assertion: all calls to to UPDATE_HASH are made with consecutive
153 * input characters, so that a running hash key can be computed from the
154 * previous key instead of complete recalculation each time.
156 #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
159 /* ===========================================================================
160 * Insert string str in the dictionary and set match_head to the previous head
161 * of the hash chain (the most recent string with same hash key). Return
162 * the previous length of the hash chain.
163 * If this file is compiled with -DFASTEST, the compression level is forced
164 * to 1, and no hash chains are maintained.
165 * IN assertion: all calls to to INSERT_STRING are made with consecutive
166 * input characters and the first MIN_MATCH bytes of str are valid
167 * (except for the last MIN_MATCH-1 bytes of the input file).
170 #define INSERT_STRING(s, str, match_head) \
171 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
172 match_head = s->head[s->ins_h], \
173 s->head[s->ins_h] = (Pos)(str))
175 #define INSERT_STRING(s, str, match_head) \
176 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
177 s->prev[(str) & s->w_mask] = match_head = s->head[s->ins_h], \
178 s->head[s->ins_h] = (Pos)(str))
181 /* ===========================================================================
182 * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
183 * prev[] will be initialized on the fly.
185 #define CLEAR_HASH(s) \
186 s->head[s->hash_size-1] = NIL; \
187 zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
189 /* ========================================================================= */
190 int ZEXPORT
deflateInit_(strm
, level
, version
, stream_size
)
196 return deflateInit2_(strm
, level
, Z_DEFLATED
, MAX_WBITS
, DEF_MEM_LEVEL
,
197 Z_DEFAULT_STRATEGY
, version
, stream_size
);
198 /* To do: ignore strm->next_in if we use it as window */
201 /* ========================================================================= */
202 int ZEXPORT
deflateInit2_(strm
, level
, method
, windowBits
, memLevel
, strategy
,
203 version
, stream_size
)
215 static const char* my_version
= ZLIB_VERSION
;
218 /* We overlay pending_buf and d_buf+l_buf. This works since the average
219 * output size for (length,distance) codes is <= 24 bits.
222 if (version
== Z_NULL
|| version
[0] != my_version
[0] ||
223 stream_size
!= sizeof(z_stream
)) {
224 return Z_VERSION_ERROR
;
226 if (strm
== Z_NULL
) return Z_STREAM_ERROR
;
229 if (strm
->zalloc
== Z_NULL
) {
230 strm
->zalloc
= zcalloc
;
231 strm
->opaque
= (voidpf
)0;
233 if (strm
->zfree
== Z_NULL
) strm
->zfree
= zcfree
;
235 if (level
== Z_DEFAULT_COMPRESSION
) level
= 6;
240 if (windowBits
< 0) { /* undocumented feature: suppress zlib header */
242 windowBits
= -windowBits
;
244 if (memLevel
< 1 || memLevel
> MAX_MEM_LEVEL
|| method
!= Z_DEFLATED
||
245 windowBits
< 9 || windowBits
> 15 || level
< 0 || level
> 9 ||
246 strategy
< 0 || strategy
> Z_HUFFMAN_ONLY
) {
247 return Z_STREAM_ERROR
;
249 s
= (deflate_state
*) ZALLOC(strm
, 1, sizeof(deflate_state
));
250 if (s
== Z_NULL
) return Z_MEM_ERROR
;
251 strm
->state
= (struct internal_state FAR
*)s
;
254 s
->noheader
= noheader
;
255 s
->w_bits
= windowBits
;
256 s
->w_size
= 1 << s
->w_bits
;
257 s
->w_mask
= s
->w_size
- 1;
259 s
->hash_bits
= memLevel
+ 7;
260 s
->hash_size
= 1 << s
->hash_bits
;
261 s
->hash_mask
= s
->hash_size
- 1;
262 s
->hash_shift
= ((s
->hash_bits
+MIN_MATCH
-1)/MIN_MATCH
);
264 s
->window
= (Bytef
*) ZALLOC(strm
, s
->w_size
, 2*sizeof(Byte
));
265 s
->prev
= (Posf
*) ZALLOC(strm
, s
->w_size
, sizeof(Pos
));
266 s
->head
= (Posf
*) ZALLOC(strm
, s
->hash_size
, sizeof(Pos
));
268 s
->lit_bufsize
= 1 << (memLevel
+ 6); /* 16K elements by default */
270 overlay
= (ushf
*) ZALLOC(strm
, s
->lit_bufsize
, sizeof(ush
)+2);
271 s
->pending_buf
= (uchf
*) overlay
;
272 s
->pending_buf_size
= (ulg
)s
->lit_bufsize
* (sizeof(ush
)+2L);
274 if (s
->window
== Z_NULL
|| s
->prev
== Z_NULL
|| s
->head
== Z_NULL
||
275 s
->pending_buf
== Z_NULL
) {
276 strm
->msg
= (char*)ERR_MSG(Z_MEM_ERROR
);
280 s
->d_buf
= overlay
+ s
->lit_bufsize
/sizeof(ush
);
281 s
->l_buf
= s
->pending_buf
+ (1+sizeof(ush
))*s
->lit_bufsize
;
284 s
->strategy
= strategy
;
285 s
->method
= (Byte
)method
;
287 return deflateReset(strm
);
290 /* ========================================================================= */
291 int ZEXPORT
deflateSetDictionary (strm
, dictionary
, dictLength
)
293 const Bytef
*dictionary
;
297 uInt length
= dictLength
;
301 if (strm
== Z_NULL
|| strm
->state
== Z_NULL
|| dictionary
== Z_NULL
||
302 strm
->state
->status
!= INIT_STATE
) return Z_STREAM_ERROR
;
305 strm
->adler
= adler32(strm
->adler
, dictionary
, dictLength
);
307 if (length
< MIN_MATCH
) return Z_OK
;
308 if (length
> MAX_DIST(s
)) {
309 length
= MAX_DIST(s
);
310 #ifndef USE_DICT_HEAD
311 dictionary
+= dictLength
- length
; /* use the tail of the dictionary */
314 zmemcpy(s
->window
, dictionary
, length
);
315 s
->strstart
= length
;
316 s
->block_start
= (long)length
;
318 /* Insert all strings in the hash table (except for the last two bytes).
319 * s->lookahead stays null, so s->ins_h will be recomputed at the next
320 * call of fill_window.
322 s
->ins_h
= s
->window
[0];
323 UPDATE_HASH(s
, s
->ins_h
, s
->window
[1]);
324 for (n
= 0; n
<= length
- MIN_MATCH
; n
++) {
325 INSERT_STRING(s
, n
, hash_head
);
327 if (hash_head
) hash_head
= 0; /* to make compiler happy */
331 /* ========================================================================= */
332 int ZEXPORT
deflateReset (strm
)
337 if (strm
== Z_NULL
|| strm
->state
== Z_NULL
||
338 strm
->zalloc
== Z_NULL
|| strm
->zfree
== Z_NULL
) return Z_STREAM_ERROR
;
340 strm
->total_in
= strm
->total_out
= 0;
341 strm
->msg
= Z_NULL
; /* use zfree if we ever allocate msg dynamically */
342 strm
->data_type
= Z_UNKNOWN
;
344 s
= (deflate_state
*)strm
->state
;
346 s
->pending_out
= s
->pending_buf
;
348 if (s
->noheader
< 0) {
349 s
->noheader
= 0; /* was set to -1 by deflate(..., Z_FINISH); */
351 s
->status
= s
->noheader
? BUSY_STATE
: INIT_STATE
;
353 s
->last_flush
= Z_NO_FLUSH
;
361 /* ========================================================================= */
362 int ZEXPORT
deflateParams(strm
, level
, strategy
)
371 if (strm
== Z_NULL
|| strm
->state
== Z_NULL
) return Z_STREAM_ERROR
;
374 if (level
== Z_DEFAULT_COMPRESSION
) {
377 if (level
< 0 || level
> 9 || strategy
< 0 || strategy
> Z_HUFFMAN_ONLY
) {
378 return Z_STREAM_ERROR
;
380 func
= configuration_table
[s
->level
].func
;
382 if (func
!= configuration_table
[level
].func
&& strm
->total_in
!= 0) {
383 /* Flush the last buffer: */
384 err
= deflate(strm
, Z_PARTIAL_FLUSH
);
386 if (s
->level
!= level
) {
388 s
->max_lazy_match
= configuration_table
[level
].max_lazy
;
389 s
->good_match
= configuration_table
[level
].good_length
;
390 s
->nice_match
= configuration_table
[level
].nice_length
;
391 s
->max_chain_length
= configuration_table
[level
].max_chain
;
393 s
->strategy
= strategy
;
397 /* =========================================================================
398 * Put a short in the pending buffer. The 16-bit value is put in MSB order.
399 * IN assertion: the stream state is correct and there is enough room in
402 local
void putShortMSB (s
, b
)
406 put_byte(s
, (Byte
)(b
>> 8));
407 put_byte(s
, (Byte
)(b
& 0xff));
410 /* =========================================================================
411 * Flush as much pending output as possible. All deflate() output goes
412 * through this function so some applications may wish to modify it
413 * to avoid allocating a large strm->next_out buffer and copying into it.
414 * (See also read_buf()).
416 local
void flush_pending(strm
)
419 unsigned len
= strm
->state
->pending
;
421 if (len
> strm
->avail_out
) len
= strm
->avail_out
;
422 if (len
== 0) return;
424 zmemcpy(strm
->next_out
, strm
->state
->pending_out
, len
);
425 strm
->next_out
+= len
;
426 strm
->state
->pending_out
+= len
;
427 strm
->total_out
+= len
;
428 strm
->avail_out
-= len
;
429 strm
->state
->pending
-= len
;
430 if (strm
->state
->pending
== 0) {
431 strm
->state
->pending_out
= strm
->state
->pending_buf
;
435 /* ========================================================================= */
436 int ZEXPORT
deflate (strm
, flush
)
440 int old_flush
; /* value of flush param for previous deflate call */
443 if (strm
== Z_NULL
|| strm
->state
== Z_NULL
||
444 flush
> Z_FINISH
|| flush
< 0) {
445 return Z_STREAM_ERROR
;
449 if (strm
->next_out
== Z_NULL
||
450 (strm
->next_in
== Z_NULL
&& strm
->avail_in
!= 0) ||
451 (s
->status
== FINISH_STATE
&& flush
!= Z_FINISH
)) {
452 ERR_RETURN(strm
, Z_STREAM_ERROR
);
454 if (strm
->avail_out
== 0) ERR_RETURN(strm
, Z_BUF_ERROR
);
456 s
->strm
= strm
; /* just in case */
457 old_flush
= s
->last_flush
;
458 s
->last_flush
= flush
;
460 /* Write the zlib header */
461 if (s
->status
== INIT_STATE
) {
463 uInt header
= (Z_DEFLATED
+ ((s
->w_bits
-8)<<4)) << 8;
464 uInt level_flags
= (s
->level
-1) >> 1;
466 if (level_flags
> 3) level_flags
= 3;
467 header
|= (level_flags
<< 6);
468 if (s
->strstart
!= 0) header
|= PRESET_DICT
;
469 header
+= 31 - (header
% 31);
471 s
->status
= BUSY_STATE
;
472 putShortMSB(s
, header
);
474 /* Save the adler32 of the preset dictionary: */
475 if (s
->strstart
!= 0) {
476 putShortMSB(s
, (uInt
)(strm
->adler
>> 16));
477 putShortMSB(s
, (uInt
)(strm
->adler
& 0xffff));
482 /* Flush as much pending output as possible */
483 if (s
->pending
!= 0) {
485 if (strm
->avail_out
== 0) {
486 /* Since avail_out is 0, deflate will be called again with
487 * more output space, but possibly with both pending and
488 * avail_in equal to zero. There won't be anything to do,
489 * but this is not an error situation so make sure we
490 * return OK instead of BUF_ERROR at next call of deflate:
496 /* Make sure there is something to do and avoid duplicate consecutive
497 * flushes. For repeated and useless calls with Z_FINISH, we keep
498 * returning Z_STREAM_END instead of Z_BUFF_ERROR.
500 } else if (strm
->avail_in
== 0 && flush
<= old_flush
&&
502 ERR_RETURN(strm
, Z_BUF_ERROR
);
505 /* User must not provide more input after the first FINISH: */
506 if (s
->status
== FINISH_STATE
&& strm
->avail_in
!= 0) {
507 ERR_RETURN(strm
, Z_BUF_ERROR
);
510 /* Start a new block or continue the current one.
512 if (strm
->avail_in
!= 0 || s
->lookahead
!= 0 ||
513 (flush
!= Z_NO_FLUSH
&& s
->status
!= FINISH_STATE
)) {
516 bstate
= (*(configuration_table
[s
->level
].func
))(s
, flush
);
518 if (bstate
== finish_started
|| bstate
== finish_done
) {
519 s
->status
= FINISH_STATE
;
521 if (bstate
== need_more
|| bstate
== finish_started
) {
522 if (strm
->avail_out
== 0) {
523 s
->last_flush
= -1; /* avoid BUF_ERROR next call, see above */
526 /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
527 * of deflate should use the same flush parameter to make sure
528 * that the flush is complete. So we don't have to output an
529 * empty block here, this will be done at next call. This also
530 * ensures that for a very small output buffer, we emit at most
534 if (bstate
== block_done
) {
535 if (flush
== Z_PARTIAL_FLUSH
) {
537 } else { /* FULL_FLUSH or SYNC_FLUSH */
538 _tr_stored_block(s
, (char*)0, 0L, 0);
539 /* For a full flush, this empty block will be recognized
540 * as a special marker by inflate_sync().
542 if (flush
== Z_FULL_FLUSH
) {
543 CLEAR_HASH(s
); /* forget history */
547 if (strm
->avail_out
== 0) {
548 s
->last_flush
= -1; /* avoid BUF_ERROR at next call, see above */
553 Assert(strm
->avail_out
> 0, "bug2");
555 if (flush
!= Z_FINISH
) return Z_OK
;
556 if (s
->noheader
) return Z_STREAM_END
;
558 /* Write the zlib trailer (adler32) */
559 putShortMSB(s
, (uInt
)(strm
->adler
>> 16));
560 putShortMSB(s
, (uInt
)(strm
->adler
& 0xffff));
562 /* If avail_out is zero, the application will call deflate again
565 s
->noheader
= -1; /* write the trailer only once! */
566 return s
->pending
!= 0 ? Z_OK
: Z_STREAM_END
;
569 /* ========================================================================= */
570 int ZEXPORT
deflateEnd (strm
)
575 if (strm
== Z_NULL
|| strm
->state
== Z_NULL
) return Z_STREAM_ERROR
;
577 status
= strm
->state
->status
;
578 if (status
!= INIT_STATE
&& status
!= BUSY_STATE
&&
579 status
!= FINISH_STATE
) {
580 return Z_STREAM_ERROR
;
583 /* Deallocate in reverse order of allocations: */
584 TRY_FREE(strm
, strm
->state
->pending_buf
);
585 TRY_FREE(strm
, strm
->state
->head
);
586 TRY_FREE(strm
, strm
->state
->prev
);
587 TRY_FREE(strm
, strm
->state
->window
);
589 ZFREE(strm
, strm
->state
);
590 strm
->state
= Z_NULL
;
592 return status
== BUSY_STATE
? Z_DATA_ERROR
: Z_OK
;
595 /* =========================================================================
596 * Copy the source state to the destination state.
597 * To simplify the source, this is not supported for 16-bit MSDOS (which
598 * doesn't have enough memory anyway to duplicate compression states).
600 int ZEXPORT
deflateCopy (dest
, source
)
605 return Z_STREAM_ERROR
;
612 if (source
== Z_NULL
|| dest
== Z_NULL
|| source
->state
== Z_NULL
) {
613 return Z_STREAM_ERROR
;
620 ds
= (deflate_state
*) ZALLOC(dest
, 1, sizeof(deflate_state
));
621 if (ds
== Z_NULL
) return Z_MEM_ERROR
;
622 dest
->state
= (struct internal_state FAR
*) ds
;
626 ds
->window
= (Bytef
*) ZALLOC(dest
, ds
->w_size
, 2*sizeof(Byte
));
627 ds
->prev
= (Posf
*) ZALLOC(dest
, ds
->w_size
, sizeof(Pos
));
628 ds
->head
= (Posf
*) ZALLOC(dest
, ds
->hash_size
, sizeof(Pos
));
629 overlay
= (ushf
*) ZALLOC(dest
, ds
->lit_bufsize
, sizeof(ush
)+2);
630 ds
->pending_buf
= (uchf
*) overlay
;
632 if (ds
->window
== Z_NULL
|| ds
->prev
== Z_NULL
|| ds
->head
== Z_NULL
||
633 ds
->pending_buf
== Z_NULL
) {
637 /* following zmemcpy do not work for 16-bit MSDOS */
638 zmemcpy(ds
->window
, ss
->window
, ds
->w_size
* 2 * sizeof(Byte
));
639 zmemcpy(ds
->prev
, ss
->prev
, ds
->w_size
* sizeof(Pos
));
640 zmemcpy(ds
->head
, ss
->head
, ds
->hash_size
* sizeof(Pos
));
641 zmemcpy(ds
->pending_buf
, ss
->pending_buf
, (uInt
)ds
->pending_buf_size
);
643 ds
->pending_out
= ds
->pending_buf
+ (ss
->pending_out
- ss
->pending_buf
);
644 ds
->d_buf
= overlay
+ ds
->lit_bufsize
/sizeof(ush
);
645 ds
->l_buf
= ds
->pending_buf
+ (1+sizeof(ush
))*ds
->lit_bufsize
;
647 ds
->l_desc
.dyn_tree
= ds
->dyn_ltree
;
648 ds
->d_desc
.dyn_tree
= ds
->dyn_dtree
;
649 ds
->bl_desc
.dyn_tree
= ds
->bl_tree
;
655 /* ===========================================================================
656 * Read a new buffer from the current input stream, update the adler32
657 * and total number of bytes read. All deflate() input goes through
658 * this function so some applications may wish to modify it to avoid
659 * allocating a large strm->next_in buffer and copying from it.
660 * (See also flush_pending()).
662 local
int read_buf(strm
, buf
, size
)
667 unsigned len
= strm
->avail_in
;
669 if (len
> size
) len
= size
;
670 if (len
== 0) return 0;
672 strm
->avail_in
-= len
;
674 if (!strm
->state
->noheader
) {
675 strm
->adler
= adler32(strm
->adler
, strm
->next_in
, len
);
677 zmemcpy(buf
, strm
->next_in
, len
);
678 strm
->next_in
+= len
;
679 strm
->total_in
+= len
;
684 /* ===========================================================================
685 * Initialize the "longest match" routines for a new zlib stream
687 local
void lm_init (s
)
690 s
->window_size
= (ulg
)2L*s
->w_size
;
694 /* Set the default configuration parameters:
696 s
->max_lazy_match
= configuration_table
[s
->level
].max_lazy
;
697 s
->good_match
= configuration_table
[s
->level
].good_length
;
698 s
->nice_match
= configuration_table
[s
->level
].nice_length
;
699 s
->max_chain_length
= configuration_table
[s
->level
].max_chain
;
704 s
->match_length
= s
->prev_length
= MIN_MATCH
-1;
705 s
->match_available
= 0;
708 match_init(); /* initialize the asm code */
712 /* ===========================================================================
713 * Set match_start to the longest match starting at the given string and
714 * return its length. Matches shorter or equal to prev_length are discarded,
715 * in which case the result is equal to prev_length and match_start is
717 * IN assertions: cur_match is the head of the hash chain for the current
718 * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
719 * OUT assertion: the match length is not greater than s->lookahead.
722 /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
723 * match.S. The code will be functionally equivalent.
726 local uInt
longest_match(s
, cur_match
)
728 IPos cur_match
; /* current match */
730 unsigned chain_length
= s
->max_chain_length
;/* max hash chain length */
731 register Bytef
*scan
= s
->window
+ s
->strstart
; /* current string */
732 register Bytef
*match
; /* matched string */
733 register int len
; /* length of current match */
734 int best_len
= s
->prev_length
; /* best match length so far */
735 int nice_match
= s
->nice_match
; /* stop if match long enough */
736 IPos limit
= s
->strstart
> (IPos
)MAX_DIST(s
) ?
737 s
->strstart
- (IPos
)MAX_DIST(s
) : NIL
;
738 /* Stop when cur_match becomes <= limit. To simplify the code,
739 * we prevent matches with the string of window index 0.
741 Posf
*prev
= s
->prev
;
742 uInt wmask
= s
->w_mask
;
745 /* Compare two bytes at a time. Note: this is not always beneficial.
746 * Try with and without -DUNALIGNED_OK to check.
748 register Bytef
*strend
= s
->window
+ s
->strstart
+ MAX_MATCH
- 1;
749 register ush scan_start
= *(ushf
*)scan
;
750 register ush scan_end
= *(ushf
*)(scan
+best_len
-1);
752 register Bytef
*strend
= s
->window
+ s
->strstart
+ MAX_MATCH
;
753 register Byte scan_end1
= scan
[best_len
-1];
754 register Byte scan_end
= scan
[best_len
];
757 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
758 * It is easy to get rid of this optimization if necessary.
760 Assert(s
->hash_bits
>= 8 && MAX_MATCH
== 258, "Code too clever");
762 /* Do not waste too much time if we already have a good match: */
763 if (s
->prev_length
>= s
->good_match
) {
766 /* Do not look for matches beyond the end of the input. This is necessary
767 * to make deflate deterministic.
769 if ((uInt
)nice_match
> s
->lookahead
) nice_match
= s
->lookahead
;
771 Assert((ulg
)s
->strstart
<= s
->window_size
-MIN_LOOKAHEAD
, "need lookahead");
774 Assert(cur_match
< s
->strstart
, "no future");
775 match
= s
->window
+ cur_match
;
777 /* Skip to next match if the match length cannot increase
778 * or if the match length is less than 2:
780 #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
781 /* This code assumes sizeof(unsigned short) == 2. Do not use
782 * UNALIGNED_OK if your compiler uses a different size.
784 if (*(ushf
*)(match
+best_len
-1) != scan_end
||
785 *(ushf
*)match
!= scan_start
) continue;
787 /* It is not necessary to compare scan[2] and match[2] since they are
788 * always equal when the other bytes match, given that the hash keys
789 * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
790 * strstart+3, +5, ... up to strstart+257. We check for insufficient
791 * lookahead only every 4th comparison; the 128th check will be made
792 * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
793 * necessary to put more guard bytes at the end of the window, or
794 * to check more often for insufficient lookahead.
796 Assert(scan
[2] == match
[2], "scan[2]?");
799 } while (*(ushf
*)(scan
+=2) == *(ushf
*)(match
+=2) &&
800 *(ushf
*)(scan
+=2) == *(ushf
*)(match
+=2) &&
801 *(ushf
*)(scan
+=2) == *(ushf
*)(match
+=2) &&
802 *(ushf
*)(scan
+=2) == *(ushf
*)(match
+=2) &&
804 /* The funny "do {}" generates better code on most compilers */
806 /* Here, scan <= window+strstart+257 */
807 Assert(scan
<= s
->window
+(unsigned)(s
->window_size
-1), "wild scan");
808 if (*scan
== *match
) scan
++;
810 len
= (MAX_MATCH
- 1) - (int)(strend
-scan
);
811 scan
= strend
- (MAX_MATCH
-1);
813 #else /* UNALIGNED_OK */
815 if (match
[best_len
] != scan_end
||
816 match
[best_len
-1] != scan_end1
||
818 *++match
!= scan
[1]) continue;
820 /* The check at best_len-1 can be removed because it will be made
821 * again later. (This heuristic is not always a win.)
822 * It is not necessary to compare scan[2] and match[2] since they
823 * are always equal when the other bytes match, given that
824 * the hash keys are equal and that HASH_BITS >= 8.
827 Assert(*scan
== *match
, "match[2]?");
829 /* We check for insufficient lookahead only every 8th comparison;
830 * the 256th check will be made at strstart+258.
833 } while (*++scan
== *++match
&& *++scan
== *++match
&&
834 *++scan
== *++match
&& *++scan
== *++match
&&
835 *++scan
== *++match
&& *++scan
== *++match
&&
836 *++scan
== *++match
&& *++scan
== *++match
&&
839 Assert(scan
<= s
->window
+(unsigned)(s
->window_size
-1), "wild scan");
841 len
= MAX_MATCH
- (int)(strend
- scan
);
842 scan
= strend
- MAX_MATCH
;
844 #endif /* UNALIGNED_OK */
846 if (len
> best_len
) {
847 s
->match_start
= cur_match
;
849 if (len
>= nice_match
) break;
851 scan_end
= *(ushf
*)(scan
+best_len
-1);
853 scan_end1
= scan
[best_len
-1];
854 scan_end
= scan
[best_len
];
857 } while ((cur_match
= prev
[cur_match
& wmask
]) > limit
858 && --chain_length
!= 0);
860 if ((uInt
)best_len
<= s
->lookahead
) return (uInt
)best_len
;
865 /* ---------------------------------------------------------------------------
866 * Optimized version for level == 1 only
868 local uInt
longest_match(s
, cur_match
)
870 IPos cur_match
; /* current match */
872 register Bytef
*scan
= s
->window
+ s
->strstart
; /* current string */
873 register Bytef
*match
; /* matched string */
874 register int len
; /* length of current match */
875 register Bytef
*strend
= s
->window
+ s
->strstart
+ MAX_MATCH
;
877 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
878 * It is easy to get rid of this optimization if necessary.
880 Assert(s
->hash_bits
>= 8 && MAX_MATCH
== 258, "Code too clever");
882 Assert((ulg
)s
->strstart
<= s
->window_size
-MIN_LOOKAHEAD
, "need lookahead");
884 Assert(cur_match
< s
->strstart
, "no future");
886 match
= s
->window
+ cur_match
;
888 /* Return failure if the match length is less than 2:
890 if (match
[0] != scan
[0] || match
[1] != scan
[1]) return MIN_MATCH
-1;
892 /* The check at best_len-1 can be removed because it will be made
893 * again later. (This heuristic is not always a win.)
894 * It is not necessary to compare scan[2] and match[2] since they
895 * are always equal when the other bytes match, given that
896 * the hash keys are equal and that HASH_BITS >= 8.
898 scan
+= 2, match
+= 2;
899 Assert(*scan
== *match
, "match[2]?");
901 /* We check for insufficient lookahead only every 8th comparison;
902 * the 256th check will be made at strstart+258.
905 } while (*++scan
== *++match
&& *++scan
== *++match
&&
906 *++scan
== *++match
&& *++scan
== *++match
&&
907 *++scan
== *++match
&& *++scan
== *++match
&&
908 *++scan
== *++match
&& *++scan
== *++match
&&
911 Assert(scan
<= s
->window
+(unsigned)(s
->window_size
-1), "wild scan");
913 len
= MAX_MATCH
- (int)(strend
- scan
);
915 if (len
< MIN_MATCH
) return MIN_MATCH
- 1;
917 s
->match_start
= cur_match
;
918 return len
<= s
->lookahead
? len
: s
->lookahead
;
924 /* ===========================================================================
925 * Check that the match at match_start is indeed a match.
927 local
void check_match(s
, start
, match
, length
)
932 /* check that the match is indeed a match */
933 if (zmemcmp(s
->window
+ match
,
934 s
->window
+ start
, length
) != EQUAL
) {
935 fprintf(stderr
, " start %u, match %u, length %d\n",
936 start
, match
, length
);
938 fprintf(stderr
, "%c%c", s
->window
[match
++], s
->window
[start
++]);
939 } while (--length
!= 0);
940 z_error("invalid match");
943 fprintf(stderr
,"\\[%d,%d]", start
-match
, length
);
944 do { putc(s
->window
[start
++], stderr
); } while (--length
!= 0);
948 # define check_match(s, start, match, length)
951 /* ===========================================================================
952 * Fill the window when the lookahead becomes insufficient.
953 * Updates strstart and lookahead.
955 * IN assertion: lookahead < MIN_LOOKAHEAD
956 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
957 * At least one byte has been read, or avail_in == 0; reads are
958 * performed for at least two bytes (required for the zip translate_eol
959 * option -- not supported here).
961 local
void fill_window(s
)
964 register unsigned n
, m
;
966 unsigned more
; /* Amount of free space at the end of the window. */
967 uInt wsize
= s
->w_size
;
970 more
= (unsigned)(s
->window_size
-(ulg
)s
->lookahead
-(ulg
)s
->strstart
);
972 /* Deal with !@#$% 64K limit: */
973 if (more
== 0 && s
->strstart
== 0 && s
->lookahead
== 0) {
976 } else if (more
== (unsigned)(-1)) {
977 /* Very unlikely, but possible on 16 bit machine if strstart == 0
978 * and lookahead == 1 (input done one byte at time)
982 /* If the window is almost full and there is insufficient lookahead,
983 * move the upper half to the lower one to make room in the upper half.
985 } else if (s
->strstart
>= wsize
+MAX_DIST(s
)) {
987 zmemcpy(s
->window
, s
->window
+wsize
, (unsigned)wsize
);
988 s
->match_start
-= wsize
;
989 s
->strstart
-= wsize
; /* we now have strstart >= MAX_DIST */
990 s
->block_start
-= (long) wsize
;
992 /* Slide the hash table (could be avoided with 32 bit values
993 at the expense of memory usage). We slide even when level == 0
994 to keep the hash table consistent if we switch back to level > 0
995 later. (Using level 0 permanently is not an optimal usage of
996 zlib, so we don't care about this pathological case.)
1002 *p
= (Pos
)(m
>= wsize
? m
-wsize
: NIL
);
1010 *p
= (Pos
)(m
>= wsize
? m
-wsize
: NIL
);
1011 /* If n is not on any hash chain, prev[n] is garbage but
1012 * its value will never be used.
1018 if (s
->strm
->avail_in
== 0) return;
1020 /* If there was no sliding:
1021 * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
1022 * more == window_size - lookahead - strstart
1023 * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
1024 * => more >= window_size - 2*WSIZE + 2
1025 * In the BIG_MEM or MMAP case (not yet supported),
1026 * window_size == input_size + MIN_LOOKAHEAD &&
1027 * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
1028 * Otherwise, window_size == 2*WSIZE so more >= 2.
1029 * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
1031 Assert(more
>= 2, "more < 2");
1033 n
= read_buf(s
->strm
, s
->window
+ s
->strstart
+ s
->lookahead
, more
);
1036 /* Initialize the hash value now that we have some input: */
1037 if (s
->lookahead
>= MIN_MATCH
) {
1038 s
->ins_h
= s
->window
[s
->strstart
];
1039 UPDATE_HASH(s
, s
->ins_h
, s
->window
[s
->strstart
+1]);
1041 Call
UPDATE_HASH() MIN_MATCH
-3 more times
1044 /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
1045 * but this is not important since only literal bytes will be emitted.
1048 } while (s
->lookahead
< MIN_LOOKAHEAD
&& s
->strm
->avail_in
!= 0);
1051 /* ===========================================================================
1052 * Flush the current block, with given end-of-file flag.
1053 * IN assertion: strstart is set to the end of the current match.
1055 #define FLUSH_BLOCK_ONLY(s, eof) { \
1056 _tr_flush_block(s, (s->block_start >= 0L ? \
1057 (charf *)&s->window[(unsigned)s->block_start] : \
1059 (ulg)((long)s->strstart - s->block_start), \
1061 s->block_start = s->strstart; \
1062 flush_pending(s->strm); \
1063 Tracev((stderr,"[FLUSH]")); \
1066 /* Same but force premature exit if necessary. */
1067 #define FLUSH_BLOCK(s, eof) { \
1068 FLUSH_BLOCK_ONLY(s, eof); \
1069 if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \
1072 /* ===========================================================================
1073 * Copy without compression as much as possible from the input stream, return
1074 * the current block state.
1075 * This function does not insert new strings in the dictionary since
1076 * uncompressible data is probably not useful. This function is used
1077 * only for the level=0 compression option.
1078 * NOTE: this function should be optimized to avoid extra copying from
1079 * window to pending_buf.
1081 local block_state
deflate_stored(s
, flush
)
1085 /* Stored blocks are limited to 0xffff bytes, pending_buf is limited
1086 * to pending_buf_size, and each stored block has a 5 byte header:
1088 ulg max_block_size
= 0xffff;
1091 if (max_block_size
> s
->pending_buf_size
- 5) {
1092 max_block_size
= s
->pending_buf_size
- 5;
1095 /* Copy as much as possible from input to output: */
1097 /* Fill the window as much as possible: */
1098 if (s
->lookahead
<= 1) {
1100 Assert(s
->strstart
< s
->w_size
+MAX_DIST(s
) ||
1101 s
->block_start
>= (long)s
->w_size
, "slide too late");
1104 if (s
->lookahead
== 0 && flush
== Z_NO_FLUSH
) return need_more
;
1106 if (s
->lookahead
== 0) break; /* flush the current block */
1108 Assert(s
->block_start
>= 0L, "block gone");
1110 s
->strstart
+= s
->lookahead
;
1113 /* Emit a stored block if pending_buf will be full: */
1114 max_start
= s
->block_start
+ max_block_size
;
1115 if (s
->strstart
== 0 || (ulg
)s
->strstart
>= max_start
) {
1116 /* strstart == 0 is possible when wraparound on 16-bit machine */
1117 s
->lookahead
= (uInt
)(s
->strstart
- max_start
);
1118 s
->strstart
= (uInt
)max_start
;
1121 /* Flush if we may have to slide, otherwise block_start may become
1122 * negative and the data will be gone:
1124 if (s
->strstart
- (uInt
)s
->block_start
>= MAX_DIST(s
)) {
1128 FLUSH_BLOCK(s
, flush
== Z_FINISH
);
1129 return flush
== Z_FINISH
? finish_done
: block_done
;
1132 /* ===========================================================================
1133 * Compress as much as possible from the input stream, return the current
1135 * This function does not perform lazy evaluation of matches and inserts
1136 * new strings in the dictionary only for unmatched strings or for short
1137 * matches. It is used only for the fast compression options.
1139 local block_state
deflate_fast(s
, flush
)
1143 IPos hash_head
= NIL
; /* head of the hash chain */
1144 int bflush
; /* set if current block must be flushed */
1147 /* Make sure that we always have enough lookahead, except
1148 * at the end of the input file. We need MAX_MATCH bytes
1149 * for the next match, plus MIN_MATCH bytes to insert the
1150 * string following the next match.
1152 if (s
->lookahead
< MIN_LOOKAHEAD
) {
1154 if (s
->lookahead
< MIN_LOOKAHEAD
&& flush
== Z_NO_FLUSH
) {
1157 if (s
->lookahead
== 0) break; /* flush the current block */
1160 /* Insert the string window[strstart .. strstart+2] in the
1161 * dictionary, and set hash_head to the head of the hash chain:
1163 if (s
->lookahead
>= MIN_MATCH
) {
1164 INSERT_STRING(s
, s
->strstart
, hash_head
);
1167 /* Find the longest match, discarding those <= prev_length.
1168 * At this point we have always match_length < MIN_MATCH
1170 if (hash_head
!= NIL
&& s
->strstart
- hash_head
<= MAX_DIST(s
)) {
1171 /* To simplify the code, we prevent matches with the string
1172 * of window index 0 (in particular we have to avoid a match
1173 * of the string with itself at the start of the input file).
1175 if (s
->strategy
!= Z_HUFFMAN_ONLY
) {
1176 s
->match_length
= longest_match (s
, hash_head
);
1178 /* longest_match() sets match_start */
1180 if (s
->match_length
>= MIN_MATCH
) {
1181 check_match(s
, s
->strstart
, s
->match_start
, s
->match_length
);
1183 _tr_tally_dist(s
, s
->strstart
- s
->match_start
,
1184 s
->match_length
- MIN_MATCH
, bflush
);
1186 s
->lookahead
-= s
->match_length
;
1188 /* Insert new strings in the hash table only if the match length
1189 * is not too large. This saves time but degrades compression.
1192 if (s
->match_length
<= s
->max_insert_length
&&
1193 s
->lookahead
>= MIN_MATCH
) {
1194 s
->match_length
--; /* string at strstart already in hash table */
1197 INSERT_STRING(s
, s
->strstart
, hash_head
);
1198 /* strstart never exceeds WSIZE-MAX_MATCH, so there are
1199 * always MIN_MATCH bytes ahead.
1201 } while (--s
->match_length
!= 0);
1206 s
->strstart
+= s
->match_length
;
1207 s
->match_length
= 0;
1208 s
->ins_h
= s
->window
[s
->strstart
];
1209 UPDATE_HASH(s
, s
->ins_h
, s
->window
[s
->strstart
+1]);
1211 Call
UPDATE_HASH() MIN_MATCH
-3 more times
1213 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not
1214 * matter since it will be recomputed at next deflate call.
1218 /* No match, output a literal byte */
1219 Tracevv((stderr
,"%c", s
->window
[s
->strstart
]));
1220 _tr_tally_lit (s
, s
->window
[s
->strstart
], bflush
);
1224 if (bflush
) FLUSH_BLOCK(s
, 0);
1226 FLUSH_BLOCK(s
, flush
== Z_FINISH
);
1227 return flush
== Z_FINISH
? finish_done
: block_done
;
1230 /* ===========================================================================
1231 * Same as above, but achieves better compression. We use a lazy
1232 * evaluation for matches: a match is finally adopted only if there is
1233 * no better match at the next window position.
1235 local block_state
deflate_slow(s
, flush
)
1239 IPos hash_head
= NIL
; /* head of hash chain */
1240 int bflush
; /* set if current block must be flushed */
1242 /* Process the input block. */
1244 /* Make sure that we always have enough lookahead, except
1245 * at the end of the input file. We need MAX_MATCH bytes
1246 * for the next match, plus MIN_MATCH bytes to insert the
1247 * string following the next match.
1249 if (s
->lookahead
< MIN_LOOKAHEAD
) {
1251 if (s
->lookahead
< MIN_LOOKAHEAD
&& flush
== Z_NO_FLUSH
) {
1254 if (s
->lookahead
== 0) break; /* flush the current block */
1257 /* Insert the string window[strstart .. strstart+2] in the
1258 * dictionary, and set hash_head to the head of the hash chain:
1260 if (s
->lookahead
>= MIN_MATCH
) {
1261 INSERT_STRING(s
, s
->strstart
, hash_head
);
1264 /* Find the longest match, discarding those <= prev_length.
1266 s
->prev_length
= s
->match_length
, s
->prev_match
= s
->match_start
;
1267 s
->match_length
= MIN_MATCH
-1;
1269 if (hash_head
!= NIL
&& s
->prev_length
< s
->max_lazy_match
&&
1270 s
->strstart
- hash_head
<= MAX_DIST(s
)) {
1271 /* To simplify the code, we prevent matches with the string
1272 * of window index 0 (in particular we have to avoid a match
1273 * of the string with itself at the start of the input file).
1275 if (s
->strategy
!= Z_HUFFMAN_ONLY
) {
1276 s
->match_length
= longest_match (s
, hash_head
);
1278 /* longest_match() sets match_start */
1280 if (s
->match_length
<= 5 && (s
->strategy
== Z_FILTERED
||
1281 (s
->match_length
== MIN_MATCH
&&
1282 s
->strstart
- s
->match_start
> TOO_FAR
))) {
1284 /* If prev_match is also MIN_MATCH, match_start is garbage
1285 * but we will ignore the current match anyway.
1287 s
->match_length
= MIN_MATCH
-1;
1290 /* If there was a match at the previous step and the current
1291 * match is not better, output the previous match:
1293 if (s
->prev_length
>= MIN_MATCH
&& s
->match_length
<= s
->prev_length
) {
1294 uInt max_insert
= s
->strstart
+ s
->lookahead
- MIN_MATCH
;
1295 /* Do not insert strings in hash table beyond this. */
1297 check_match(s
, s
->strstart
-1, s
->prev_match
, s
->prev_length
);
1299 _tr_tally_dist(s
, s
->strstart
-1 - s
->prev_match
,
1300 s
->prev_length
- MIN_MATCH
, bflush
);
1302 /* Insert in hash table all strings up to the end of the match.
1303 * strstart-1 and strstart are already inserted. If there is not
1304 * enough lookahead, the last two strings are not inserted in
1307 s
->lookahead
-= s
->prev_length
-1;
1308 s
->prev_length
-= 2;
1310 if (++s
->strstart
<= max_insert
) {
1311 INSERT_STRING(s
, s
->strstart
, hash_head
);
1313 } while (--s
->prev_length
!= 0);
1314 s
->match_available
= 0;
1315 s
->match_length
= MIN_MATCH
-1;
1318 if (bflush
) FLUSH_BLOCK(s
, 0);
1320 } else if (s
->match_available
) {
1321 /* If there was no match at the previous position, output a
1322 * single literal. If there was a match but the current match
1323 * is longer, truncate the previous match to a single literal.
1325 Tracevv((stderr
,"%c", s
->window
[s
->strstart
-1]));
1326 _tr_tally_lit(s
, s
->window
[s
->strstart
-1], bflush
);
1328 FLUSH_BLOCK_ONLY(s
, 0);
1332 if (s
->strm
->avail_out
== 0) return need_more
;
1334 /* There is no previous match to compare with, wait for
1335 * the next step to decide.
1337 s
->match_available
= 1;
1342 Assert (flush
!= Z_NO_FLUSH
, "no flush?");
1343 if (s
->match_available
) {
1344 Tracevv((stderr
,"%c", s
->window
[s
->strstart
-1]));
1345 _tr_tally_lit(s
, s
->window
[s
->strstart
-1], bflush
);
1346 s
->match_available
= 0;
1348 FLUSH_BLOCK(s
, flush
== Z_FINISH
);
1349 return flush
== Z_FINISH
? finish_done
: block_done
;