1 /* deflate.c -- compress data using the deflation algorithm
2 * Copyright (C) 1995-2013 Jean-loup Gailly and Mark Adler
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 http://tools.ietf.org/html/rfc1951
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
52 #include "hammer2_zlib_deflate.h"
53 #include "../hammer2.h"
54 #include <sys/malloc.h> //for malloc macros
56 MALLOC_DECLARE(C_ZLIB_BUFFER_DEFLATE
);
57 MALLOC_DEFINE(C_ZLIB_BUFFER_DEFLATE
, "compzlibbufferdeflate",
58 "A private buffer used by zlib library for deflate function.");
60 const char deflate_copyright
[] =
61 " deflate 1.2.8 Copyright 1995-2013 Jean-loup Gailly and Mark Adler ";
63 If you use the zlib library in a product, an acknowledgment is welcome
64 in the documentation of your product. If for some reason you cannot
65 include such an acknowledgment, I would appreciate that you keep this
66 copyright string in the executable of your product.
69 /* ===========================================================================
70 * Function prototypes.
73 need_more
, /* block not completed, need more input or more output */
74 block_done
, /* block flush performed */
75 finish_started
, /* finish started, need only more output at next deflate */
76 finish_done
/* finish done, accept no more input or output */
79 typedef block_state (*compress_func
)(deflate_state
*s
, int flush
);
80 /* Compression function. Returns the block state after the call. */
82 local
void fill_window (deflate_state
*s
);
84 local block_state
deflate_slow(deflate_state
*s
, int flush
);
86 local block_state
deflate_rle(deflate_state
*s
, int flush
);
87 local block_state
deflate_huff(deflate_state
*s
, int flush
);
88 local
void lm_init(deflate_state
*s
);
89 local
void putShortMSB(deflate_state
*s
, uInt b
);
90 local
void flush_pending(z_streamp strm
);
91 local
int read_buf(z_streamp strm
, Bytef
*buf
, unsigned size
);
93 void match_init(void); /* asm code initialization */
94 uInt
longest_match(deflate_state
*s
, IPos cur_match
);
96 local uInt
longest_match(deflate_state
*s
, IPos cur_match
);
100 local
void check_match(deflate_state
*s
, IPos start
, IPos match
,
104 int deflateInit2_(z_streamp strm
, int level
, int method
, int windowBits
,
105 int memLevel
, int strategy
, const char *version
,
107 int deflateReset (z_streamp strm
);
108 int deflateResetKeep (z_streamp strm
);
110 /* ===========================================================================
115 /* Tail of hash chains */
118 # define TOO_FAR 4096
120 /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */
122 /* Values for max_lazy_match, good_match and max_chain_length, depending on
123 * the desired pack level (0..9). The values given below have been tuned to
124 * exclude worst case performance for pathological files. Better values may be
125 * found for specific files.
127 typedef struct config_s
{
128 ush good_length
; /* reduce lazy search above this match length */
129 ush max_lazy
; /* do not perform lazy search above this match length */
130 ush nice_length
; /* quit search above this match length */
135 local
const config configuration_table
[10] = {
136 /* good lazy nice chain */
137 /* 0 */ {0, 0, 0, 0, deflate_slow
/*deflate_stored*/}, /* store only */
138 /* 1 */ {4, 4, 8, 4, deflate_slow
/*deflate_fast*/}, /* max speed, no lazy matches */
139 /* 2 */ {4, 5, 16, 8, deflate_slow
/*deflate_fast*/},
140 /* 3 */ {4, 6, 32, 32, deflate_slow
/*deflate_fast*/},
142 /* 4 */ {4, 4, 16, 16, deflate_slow
}, /* lazy matches */
143 /* 5 */ {8, 16, 32, 32, deflate_slow
},
144 /* 6 */ {8, 16, 128, 128, deflate_slow
},
145 /* 7 */ {8, 32, 128, 256, deflate_slow
},
146 /* 8 */ {32, 128, 258, 1024, deflate_slow
},
147 /* 9 */ {32, 258, 258, 4096, deflate_slow
}}; /* max compression */
149 /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4
150 * For deflate_fast() (levels <= 3) good is ignored and lazy has a different
155 /* result of memcmp for equal strings */
157 #ifndef NO_DUMMY_DECL
158 struct static_tree_desc_s
{int dummy
;}; /* for buggy compilers */
161 /* rank Z_BLOCK between Z_NO_FLUSH and Z_PARTIAL_FLUSH */
162 #define RANK(f) (((f) << 1) - ((f) > 4 ? 9 : 0))
164 /* ===========================================================================
165 * Update a hash value with the given input byte
166 * IN assertion: all calls to to UPDATE_HASH are made with consecutive
167 * input characters, so that a running hash key can be computed from the
168 * previous key instead of complete recalculation each time.
170 #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask)
173 /* ===========================================================================
174 * Insert string str in the dictionary and set match_head to the previous head
175 * of the hash chain (the most recent string with same hash key). Return
176 * the previous length of the hash chain.
177 * If this file is compiled with -DFASTEST, the compression level is forced
178 * to 1, and no hash chains are maintained.
179 * IN assertion: all calls to to INSERT_STRING are made with consecutive
180 * input characters and the first MIN_MATCH bytes of str are valid
181 * (except for the last MIN_MATCH-1 bytes of the input file).
183 #define INSERT_STRING(s, str, match_head) \
184 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \
185 match_head = s->prev[(str) & s->w_mask] = s->head[s->ins_h], \
186 s->head[s->ins_h] = (Pos)(str))
188 /* ===========================================================================
189 * Initialize the hash table (avoiding 64K overflow for 16 bit systems).
190 * prev[] will be initialized on the fly.
192 #define CLEAR_HASH(s) \
193 s->head[s->hash_size-1] = NIL; \
194 zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head));
196 /* ========================================================================= */
198 deflateInit_(z_streamp strm
, int level
, const char *version
, int stream_size
)
200 return deflateInit2_(strm
, level
, Z_DEFLATED
, MAX_WBITS
, DEF_MEM_LEVEL
,
201 Z_DEFAULT_STRATEGY
, version
, stream_size
);
202 /* To do: ignore strm->next_in if we use it as window */
205 /* ========================================================================= */
207 deflateInit2_(z_streamp strm
, int level
, int method
, int windowBits
,
208 int memLevel
, int strategy
, const char *version
, int stream_size
)
212 static const char my_version
[] = ZLIB_VERSION
;
215 /* We overlay pending_buf and d_buf+l_buf. This works since the average
216 * output size for (length,distance) codes is <= 24 bits.
219 if (version
== Z_NULL
|| version
[0] != my_version
[0] ||
220 stream_size
!= sizeof(z_stream
)) {
221 return Z_VERSION_ERROR
;
223 if (strm
== Z_NULL
) return Z_STREAM_ERROR
;
227 if (level
== Z_DEFAULT_COMPRESSION
) level
= 6;
229 if (windowBits
< 0) { /* suppress zlib wrapper */
231 windowBits
= -windowBits
;
233 if (memLevel
< 1 || memLevel
> MAX_MEM_LEVEL
|| method
!= Z_DEFLATED
||
234 windowBits
< 8 || windowBits
> 15 || level
< 0 || level
> 9 ||
235 strategy
< 0 || strategy
> Z_FIXED
) {
236 return Z_STREAM_ERROR
;
238 if (windowBits
== 8) windowBits
= 9; /* until 256-byte window bug fixed */
239 s
= (deflate_state
*) kmalloc(sizeof(*s
), C_ZLIB_BUFFER_DEFLATE
, M_INTWAIT
);
240 if (s
== Z_NULL
) return Z_MEM_ERROR
;
241 strm
->state
= (struct internal_state FAR
*)s
;
245 s
->w_bits
= windowBits
;
246 s
->w_size
= 1 << s
->w_bits
;
247 s
->w_mask
= s
->w_size
- 1;
249 s
->hash_bits
= memLevel
+ 7;
250 s
->hash_size
= 1 << s
->hash_bits
;
251 s
->hash_mask
= s
->hash_size
- 1;
252 s
->hash_shift
= ((s
->hash_bits
+MIN_MATCH
-1)/MIN_MATCH
);
254 s
->window
= (Bytef
*) kmalloc((s
->w_size
)*2*sizeof(Byte
), C_ZLIB_BUFFER_DEFLATE
, M_INTWAIT
);
255 s
->prev
= (Posf
*) kmalloc((s
->w_size
)*sizeof(Pos
), C_ZLIB_BUFFER_DEFLATE
, M_INTWAIT
);
256 s
->head
= (Posf
*) kmalloc((s
->hash_size
)*sizeof(Pos
), C_ZLIB_BUFFER_DEFLATE
, M_INTWAIT
);
258 s
->high_water
= 0; /* nothing written to s->window yet */
260 s
->lit_bufsize
= 1 << (memLevel
+ 6); /* 16K elements by default */
262 overlay
= (ushf
*) kmalloc((s
->lit_bufsize
)*(sizeof(ush
)+2), C_ZLIB_BUFFER_DEFLATE
, M_INTWAIT
);
263 s
->pending_buf
= (uchf
*) overlay
;
264 s
->pending_buf_size
= (ulg
)s
->lit_bufsize
* (sizeof(ush
)+2L);
266 if (s
->window
== Z_NULL
|| s
->prev
== Z_NULL
|| s
->head
== Z_NULL
||
267 s
->pending_buf
== Z_NULL
) {
268 s
->status
= FINISH_STATE
;
269 strm
->msg
= ERR_MSG(Z_MEM_ERROR
);
273 s
->d_buf
= overlay
+ s
->lit_bufsize
/sizeof(ush
);
274 s
->l_buf
= s
->pending_buf
+ (1+sizeof(ush
))*s
->lit_bufsize
;
277 s
->strategy
= strategy
;
278 s
->method
= (Byte
)method
;
280 return deflateReset(strm
);
283 /* ========================================================================= */
285 deflateResetKeep (z_streamp strm
)
289 if (strm
== Z_NULL
|| strm
->state
== Z_NULL
) {
290 return Z_STREAM_ERROR
;
293 strm
->total_in
= strm
->total_out
= 0;
294 strm
->msg
= Z_NULL
; /* use zfree if we ever allocate msg dynamically */
295 strm
->data_type
= Z_UNKNOWN
;
297 s
= (deflate_state
*)strm
->state
;
299 s
->pending_out
= s
->pending_buf
;
302 s
->wrap
= -s
->wrap
; /* was made negative by deflate(..., Z_FINISH); */
304 s
->status
= s
->wrap
? INIT_STATE
: BUSY_STATE
;
305 strm
->adler
= adler32(0L, Z_NULL
, 0);
306 s
->last_flush
= Z_NO_FLUSH
;
313 /* ========================================================================= */
315 deflateReset (z_streamp strm
)
319 ret
= deflateResetKeep(strm
);
321 lm_init(strm
->state
);
325 /* =========================================================================
326 * Put a short in the pending buffer. The 16-bit value is put in MSB order.
327 * IN assertion: the stream state is correct and there is enough room in
332 putShortMSB (deflate_state
*s
, uInt b
)
334 put_byte(s
, (Byte
)(b
>> 8));
335 put_byte(s
, (Byte
)(b
& 0xff));
338 /* =========================================================================
339 * Flush as much pending output as possible. All deflate() output goes
340 * through this function so some applications may wish to modify it
341 * to avoid allocating a large strm->next_out buffer and copying into it.
342 * (See also read_buf()).
346 flush_pending(z_streamp strm
)
349 deflate_state
*s
= strm
->state
;
353 if (len
> strm
->avail_out
) len
= strm
->avail_out
;
354 if (len
== 0) return;
356 zmemcpy(strm
->next_out
, s
->pending_out
, len
);
357 strm
->next_out
+= len
;
358 s
->pending_out
+= len
;
359 strm
->total_out
+= len
;
360 strm
->avail_out
-= len
;
362 if (s
->pending
== 0) {
363 s
->pending_out
= s
->pending_buf
;
367 /* ========================================================================= */
369 deflate (z_streamp strm
, int flush
)
371 int old_flush
; /* value of flush param for previous deflate call */
374 if (strm
== Z_NULL
|| strm
->state
== Z_NULL
||
375 flush
> Z_BLOCK
|| flush
< 0) {
376 return Z_STREAM_ERROR
;
380 if (strm
->next_out
== Z_NULL
||
381 (strm
->next_in
== Z_NULL
&& strm
->avail_in
!= 0) ||
382 (s
->status
== FINISH_STATE
&& flush
!= Z_FINISH
)) {
383 ERR_RETURN(strm
, Z_STREAM_ERROR
);
385 if (strm
->avail_out
== 0) ERR_RETURN(strm
, Z_BUF_ERROR
);
387 s
->strm
= strm
; /* just in case */
388 old_flush
= s
->last_flush
;
389 s
->last_flush
= flush
;
391 /* Write the header */
392 uInt header
= (Z_DEFLATED
+ ((s
->w_bits
-8)<<4)) << 8;
395 if (s
->strategy
>= Z_HUFFMAN_ONLY
|| s
->level
< 2)
397 else if (s
->level
< 6)
399 else if (s
->level
== 6)
403 header
|= (level_flags
<< 6);
404 if (s
->strstart
!= 0) header
|= PRESET_DICT
;
405 header
+= 31 - (header
% 31);
407 s
->status
= BUSY_STATE
;
408 putShortMSB(s
, header
);
410 /* Save the adler32 of the preset dictionary: */
411 if (s
->strstart
!= 0) {
412 putShortMSB(s
, (uInt
)(strm
->adler
>> 16));
413 putShortMSB(s
, (uInt
)(strm
->adler
& 0xffff));
415 strm
->adler
= adler32(0L, Z_NULL
, 0);
417 /* Flush as much pending output as possible */
418 if (s
->pending
!= 0) {
420 if (strm
->avail_out
== 0) {
421 /* Since avail_out is 0, deflate will be called again with
422 * more output space, but possibly with both pending and
423 * avail_in equal to zero. There won't be anything to do,
424 * but this is not an error situation so make sure we
425 * return OK instead of BUF_ERROR at next call of deflate:
431 /* Make sure there is something to do and avoid duplicate consecutive
432 * flushes. For repeated and useless calls with Z_FINISH, we keep
433 * returning Z_STREAM_END instead of Z_BUF_ERROR.
435 } else if (strm
->avail_in
== 0 && RANK(flush
) <= RANK(old_flush
) &&
437 ERR_RETURN(strm
, Z_BUF_ERROR
);
440 /* User must not provide more input after the first FINISH: */
441 if (s
->status
== FINISH_STATE
&& strm
->avail_in
!= 0) {
442 ERR_RETURN(strm
, Z_BUF_ERROR
);
445 /* Start a new block or continue the current one.
447 if (strm
->avail_in
!= 0 || s
->lookahead
!= 0 ||
448 (flush
!= Z_NO_FLUSH
&& s
->status
!= FINISH_STATE
)) {
451 bstate
= s
->strategy
== Z_HUFFMAN_ONLY
? deflate_huff(s
, flush
) :
452 (s
->strategy
== Z_RLE
? deflate_rle(s
, flush
) :
453 (*(configuration_table
[s
->level
].func
))(s
, flush
));
455 if (bstate
== finish_started
|| bstate
== finish_done
) {
456 s
->status
= FINISH_STATE
;
458 if (bstate
== need_more
|| bstate
== finish_started
) {
459 if (strm
->avail_out
== 0) {
460 s
->last_flush
= -1; /* avoid BUF_ERROR next call, see above */
463 /* If flush != Z_NO_FLUSH && avail_out == 0, the next call
464 * of deflate should use the same flush parameter to make sure
465 * that the flush is complete. So we don't have to output an
466 * empty block here, this will be done at next call. This also
467 * ensures that for a very small output buffer, we emit at most
471 if (bstate
== block_done
) {
472 if (flush
== Z_PARTIAL_FLUSH
) {
474 } else if (flush
!= Z_BLOCK
) { /* FULL_FLUSH or SYNC_FLUSH */
475 _tr_stored_block(s
, (char*)0, 0L, 0);
476 /* For a full flush, this empty block will be recognized
477 * as a special marker by inflate_sync().
479 if (flush
== Z_FULL_FLUSH
) {
480 CLEAR_HASH(s
); /* forget history */
481 if (s
->lookahead
== 0) {
489 if (strm
->avail_out
== 0) {
490 s
->last_flush
= -1; /* avoid BUF_ERROR at next call, see above */
495 Assert(strm
->avail_out
> 0, "bug2");
497 if (flush
!= Z_FINISH
) return Z_OK
;
498 if (s
->wrap
<= 0) return Z_STREAM_END
;
500 /* Write the trailer */
501 putShortMSB(s
, (uInt
)(strm
->adler
>> 16));
502 putShortMSB(s
, (uInt
)(strm
->adler
& 0xffff));
505 /* If avail_out is zero, the application will call deflate again
508 if (s
->wrap
> 0) s
->wrap
= -s
->wrap
; /* write the trailer only once! */
509 return s
->pending
!= 0 ? Z_OK
: Z_STREAM_END
;
512 /* ========================================================================= */
514 deflateEnd (z_streamp strm
)
518 if (strm
== Z_NULL
|| strm
->state
== Z_NULL
) return Z_STREAM_ERROR
;
520 status
= strm
->state
->status
;
521 if (status
!= INIT_STATE
&&
522 status
!= EXTRA_STATE
&&
523 status
!= NAME_STATE
&&
524 status
!= COMMENT_STATE
&&
525 status
!= HCRC_STATE
&&
526 status
!= BUSY_STATE
&&
527 status
!= FINISH_STATE
) {
528 return Z_STREAM_ERROR
;
531 /* Deallocate in reverse order of allocations: */
532 kfree(strm
->state
->pending_buf
, C_ZLIB_BUFFER_DEFLATE
);
533 kfree(strm
->state
->head
, C_ZLIB_BUFFER_DEFLATE
);
534 kfree(strm
->state
->prev
, C_ZLIB_BUFFER_DEFLATE
);
535 kfree(strm
->state
->window
, C_ZLIB_BUFFER_DEFLATE
);
537 kfree(strm
->state
, C_ZLIB_BUFFER_DEFLATE
);
538 strm
->state
= Z_NULL
;
540 return status
== BUSY_STATE
? Z_DATA_ERROR
: Z_OK
;
543 /* ===========================================================================
544 * Read a new buffer from the current input stream, update the adler32
545 * and total number of bytes read. All deflate() input goes through
546 * this function so some applications may wish to modify it to avoid
547 * allocating a large strm->next_in buffer and copying from it.
548 * (See also flush_pending()).
552 read_buf(z_streamp strm
, Bytef
*buf
, unsigned size
)
554 unsigned len
= strm
->avail_in
;
556 if (len
> size
) len
= size
;
557 if (len
== 0) return 0;
559 strm
->avail_in
-= len
;
561 zmemcpy(buf
, strm
->next_in
, len
);
562 if (strm
->state
->wrap
== 1) {
563 strm
->adler
= adler32(strm
->adler
, buf
, len
);
566 strm
->next_in
+= len
;
567 strm
->total_in
+= len
;
572 /* ===========================================================================
573 * Initialize the "longest match" routines for a new zlib stream
577 lm_init (deflate_state
*s
)
579 s
->window_size
= (ulg
)2L*s
->w_size
;
583 /* Set the default configuration parameters:
585 s
->max_lazy_match
= configuration_table
[s
->level
].max_lazy
;
586 s
->good_match
= configuration_table
[s
->level
].good_length
;
587 s
->nice_match
= configuration_table
[s
->level
].nice_length
;
588 s
->max_chain_length
= configuration_table
[s
->level
].max_chain
;
594 s
->match_length
= s
->prev_length
= MIN_MATCH
-1;
595 s
->match_available
= 0;
599 match_init(); /* initialize the asm code */
605 /* ===========================================================================
606 * Set match_start to the longest match starting at the given string and
607 * return its length. Matches shorter or equal to prev_length are discarded,
608 * in which case the result is equal to prev_length and match_start is
610 * IN assertions: cur_match is the head of the hash chain for the current
611 * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1
612 * OUT assertion: the match length is not greater than s->lookahead.
615 /* For 80x86 and 680x0, an optimized version will be provided in match.asm or
616 * match.S. The code will be functionally equivalent.
620 longest_match(deflate_state
*s
, IPos cur_match
) /* cur_match = current match */
622 unsigned chain_length
= s
->max_chain_length
;/* max hash chain length */
623 register Bytef
*scan
= s
->window
+ s
->strstart
; /* current string */
624 register Bytef
*match
; /* matched string */
625 register int len
; /* length of current match */
626 int best_len
= s
->prev_length
; /* best match length so far */
627 int nice_match
= s
->nice_match
; /* stop if match long enough */
628 IPos limit
= s
->strstart
> (IPos
)MAX_DIST(s
) ?
629 s
->strstart
- (IPos
)MAX_DIST(s
) : NIL
;
630 /* Stop when cur_match becomes <= limit. To simplify the code,
631 * we prevent matches with the string of window index 0.
633 Posf
*prev
= s
->prev
;
634 uInt wmask
= s
->w_mask
;
637 /* Compare two bytes at a time. Note: this is not always beneficial.
638 * Try with and without -DUNALIGNED_OK to check.
640 register Bytef
*strend
= s
->window
+ s
->strstart
+ MAX_MATCH
- 1;
641 register ush scan_start
= *(ushf
*)scan
;
642 register ush scan_end
= *(ushf
*)(scan
+best_len
-1);
644 register Bytef
*strend
= s
->window
+ s
->strstart
+ MAX_MATCH
;
645 register Byte scan_end1
= scan
[best_len
-1];
646 register Byte scan_end
= scan
[best_len
];
649 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
650 * It is easy to get rid of this optimization if necessary.
652 Assert(s
->hash_bits
>= 8 && MAX_MATCH
== 258, "Code too clever");
654 /* Do not waste too much time if we already have a good match: */
655 if (s
->prev_length
>= s
->good_match
) {
658 /* Do not look for matches beyond the end of the input. This is necessary
659 * to make deflate deterministic.
661 if ((uInt
)nice_match
> s
->lookahead
) nice_match
= s
->lookahead
;
663 Assert((ulg
)s
->strstart
<= s
->window_size
-MIN_LOOKAHEAD
, "need lookahead");
666 Assert(cur_match
< s
->strstart
, "no future");
667 match
= s
->window
+ cur_match
;
669 /* Skip to next match if the match length cannot increase
670 * or if the match length is less than 2. Note that the checks below
671 * for insufficient lookahead only occur occasionally for performance
672 * reasons. Therefore uninitialized memory will be accessed, and
673 * conditional jumps will be made that depend on those values.
674 * However the length of the match is limited to the lookahead, so
675 * the output of deflate is not affected by the uninitialized values.
677 #if (defined(UNALIGNED_OK) && MAX_MATCH == 258)
678 /* This code assumes sizeof(unsigned short) == 2. Do not use
679 * UNALIGNED_OK if your compiler uses a different size.
681 if (*(ushf
*)(match
+best_len
-1) != scan_end
||
682 *(ushf
*)match
!= scan_start
) continue;
684 /* It is not necessary to compare scan[2] and match[2] since they are
685 * always equal when the other bytes match, given that the hash keys
686 * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at
687 * strstart+3, +5, ... up to strstart+257. We check for insufficient
688 * lookahead only every 4th comparison; the 128th check will be made
689 * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is
690 * necessary to put more guard bytes at the end of the window, or
691 * to check more often for insufficient lookahead.
693 Assert(scan
[2] == match
[2], "scan[2]?");
696 } while (*(ushf
*)(scan
+=2) == *(ushf
*)(match
+=2) &&
697 *(ushf
*)(scan
+=2) == *(ushf
*)(match
+=2) &&
698 *(ushf
*)(scan
+=2) == *(ushf
*)(match
+=2) &&
699 *(ushf
*)(scan
+=2) == *(ushf
*)(match
+=2) &&
701 /* The funny "do {}" generates better code on most compilers */
703 /* Here, scan <= window+strstart+257 */
704 Assert(scan
<= s
->window
+(unsigned)(s
->window_size
-1), "wild scan");
705 if (*scan
== *match
) scan
++;
707 len
= (MAX_MATCH
- 1) - (int)(strend
-scan
);
708 scan
= strend
- (MAX_MATCH
-1);
710 #else /* UNALIGNED_OK */
712 if (match
[best_len
] != scan_end
||
713 match
[best_len
-1] != scan_end1
||
715 *++match
!= scan
[1]) continue;
717 /* The check at best_len-1 can be removed because it will be made
718 * again later. (This heuristic is not always a win.)
719 * It is not necessary to compare scan[2] and match[2] since they
720 * are always equal when the other bytes match, given that
721 * the hash keys are equal and that HASH_BITS >= 8.
724 Assert(*scan
== *match
, "match[2]?");
726 /* We check for insufficient lookahead only every 8th comparison;
727 * the 256th check will be made at strstart+258.
730 } while (*++scan
== *++match
&& *++scan
== *++match
&&
731 *++scan
== *++match
&& *++scan
== *++match
&&
732 *++scan
== *++match
&& *++scan
== *++match
&&
733 *++scan
== *++match
&& *++scan
== *++match
&&
736 Assert(scan
<= s
->window
+(unsigned)(s
->window_size
-1), "wild scan");
738 len
= MAX_MATCH
- (int)(strend
- scan
);
739 scan
= strend
- MAX_MATCH
;
741 #endif /* UNALIGNED_OK */
743 if (len
> best_len
) {
744 s
->match_start
= cur_match
;
746 if (len
>= nice_match
) break;
748 scan_end
= *(ushf
*)(scan
+best_len
-1);
750 scan_end1
= scan
[best_len
-1];
751 scan_end
= scan
[best_len
];
754 } while ((cur_match
= prev
[cur_match
& wmask
]) > limit
755 && --chain_length
!= 0);
757 if ((uInt
)best_len
<= s
->lookahead
) return (uInt
)best_len
;
765 /* ===========================================================================
766 * Check that the match at match_start is indeed a match.
770 check_match(deflate_state
*s
, IPos start
, IPos match
, int length
)
772 /* check that the match is indeed a match */
773 if (zmemcmp(s
->window
+ match
,
774 s
->window
+ start
, length
) != EQUAL
) {
775 fprintf(stderr
, " start %u, match %u, length %d\n",
776 start
, match
, length
);
778 fprintf(stderr
, "%c%c", s
->window
[match
++], s
->window
[start
++]);
779 } while (--length
!= 0);
780 z_error("invalid match");
783 fprintf(stderr
,"\\[%d,%d]", start
-match
, length
);
784 do { putc(s
->window
[start
++], stderr
); } while (--length
!= 0);
788 # define check_match(s, start, match, length)
791 /* ===========================================================================
792 * Fill the window when the lookahead becomes insufficient.
793 * Updates strstart and lookahead.
795 * IN assertion: lookahead < MIN_LOOKAHEAD
796 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD
797 * At least one byte has been read, or avail_in == 0; reads are
798 * performed for at least two bytes (required for the zip translate_eol
799 * option -- not supported here).
803 fill_window(deflate_state
*s
)
805 register unsigned n
, m
;
807 unsigned more
; /* Amount of free space at the end of the window. */
808 uInt wsize
= s
->w_size
;
810 Assert(s
->lookahead
< MIN_LOOKAHEAD
, "already enough lookahead");
813 more
= (unsigned)(s
->window_size
-(ulg
)s
->lookahead
-(ulg
)s
->strstart
);
815 /* Deal with !@#$% 64K limit: */
816 if (sizeof(int) <= 2) {
817 if (more
== 0 && s
->strstart
== 0 && s
->lookahead
== 0) {
820 } else if (more
== (unsigned)(-1)) {
821 /* Very unlikely, but possible on 16 bit machine if
822 * strstart == 0 && lookahead == 1 (input done a byte at time)
828 /* If the window is almost full and there is insufficient lookahead,
829 * move the upper half to the lower one to make room in the upper half.
831 if (s
->strstart
>= wsize
+MAX_DIST(s
)) {
833 zmemcpy(s
->window
, s
->window
+wsize
, (unsigned)wsize
);
834 s
->match_start
-= wsize
;
835 s
->strstart
-= wsize
; /* we now have strstart >= MAX_DIST */
836 s
->block_start
-= (long) wsize
;
838 /* Slide the hash table (could be avoided with 32 bit values
839 at the expense of memory usage). We slide even when level == 0
840 to keep the hash table consistent if we switch back to level > 0
841 later. (Using level 0 permanently is not an optimal usage of
842 zlib, so we don't care about this pathological case.)
848 *p
= (Pos
)(m
>= wsize
? m
-wsize
: NIL
);
856 *p
= (Pos
)(m
>= wsize
? m
-wsize
: NIL
);
857 /* If n is not on any hash chain, prev[n] is garbage but
858 * its value will never be used.
864 if (s
->strm
->avail_in
== 0) break;
866 /* If there was no sliding:
867 * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 &&
868 * more == window_size - lookahead - strstart
869 * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1)
870 * => more >= window_size - 2*WSIZE + 2
871 * In the BIG_MEM or MMAP case (not yet supported),
872 * window_size == input_size + MIN_LOOKAHEAD &&
873 * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD.
874 * Otherwise, window_size == 2*WSIZE so more >= 2.
875 * If there was sliding, more >= WSIZE. So in all cases, more >= 2.
877 Assert(more
>= 2, "more < 2");
879 n
= read_buf(s
->strm
, s
->window
+ s
->strstart
+ s
->lookahead
, more
);
882 /* Initialize the hash value now that we have some input: */
883 if (s
->lookahead
+ s
->insert
>= MIN_MATCH
) {
884 uInt str
= s
->strstart
- s
->insert
;
885 s
->ins_h
= s
->window
[str
];
886 UPDATE_HASH(s
, s
->ins_h
, s
->window
[str
+ 1]);
888 Call
UPDATE_HASH() MIN_MATCH
-3 more times
891 UPDATE_HASH(s
, s
->ins_h
, s
->window
[str
+ MIN_MATCH
-1]);
893 s
->prev
[str
& s
->w_mask
] = s
->head
[s
->ins_h
];
895 s
->head
[s
->ins_h
] = (Pos
)str
;
898 if (s
->lookahead
+ s
->insert
< MIN_MATCH
)
902 /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage,
903 * but this is not important since only literal bytes will be emitted.
906 } while (s
->lookahead
< MIN_LOOKAHEAD
&& s
->strm
->avail_in
!= 0);
908 /* If the WIN_INIT bytes after the end of the current data have never been
909 * written, then zero those bytes in order to avoid memory check reports of
910 * the use of uninitialized (or uninitialised as Julian writes) bytes by
911 * the longest match routines. Update the high water mark for the next
912 * time through here. WIN_INIT is set to MAX_MATCH since the longest match
913 * routines allow scanning to strstart + MAX_MATCH, ignoring lookahead.
915 if (s
->high_water
< s
->window_size
) {
916 ulg curr
= s
->strstart
+ (ulg
)(s
->lookahead
);
919 if (s
->high_water
< curr
) {
920 /* Previous high water mark below current data -- zero WIN_INIT
921 * bytes or up to end of window, whichever is less.
923 init
= s
->window_size
- curr
;
926 zmemzero(s
->window
+ curr
, (unsigned)init
);
927 s
->high_water
= curr
+ init
;
929 else if (s
->high_water
< (ulg
)curr
+ WIN_INIT
) {
930 /* High water mark at or above current data, but below current data
931 * plus WIN_INIT -- zero out to current data plus WIN_INIT, or up
932 * to end of window, whichever is less.
934 init
= (ulg
)curr
+ WIN_INIT
- s
->high_water
;
935 if (init
> s
->window_size
- s
->high_water
)
936 init
= s
->window_size
- s
->high_water
;
937 zmemzero(s
->window
+ s
->high_water
, (unsigned)init
);
938 s
->high_water
+= init
;
942 Assert((ulg
)s
->strstart
<= s
->window_size
- MIN_LOOKAHEAD
,
943 "not enough room for search");
946 /* ===========================================================================
947 * Flush the current block, with given end-of-file flag.
948 * IN assertion: strstart is set to the end of the current match.
950 #define FLUSH_BLOCK_ONLY(s, last) { \
951 _tr_flush_block(s, (s->block_start >= 0L ? \
952 (charf *)&s->window[(unsigned)s->block_start] : \
954 (ulg)((long)s->strstart - s->block_start), \
956 s->block_start = s->strstart; \
957 flush_pending(s->strm); \
958 Tracev((stderr,"[FLUSH]")); \
961 /* Same but force premature exit if necessary. */
962 #define FLUSH_BLOCK(s, last) { \
963 FLUSH_BLOCK_ONLY(s, last); \
964 if (s->strm->avail_out == 0) return (last) ? finish_started : need_more; \
968 /* ===========================================================================
969 * Same as above, but achieves better compression. We use a lazy
970 * evaluation for matches: a match is finally adopted only if there is
971 * no better match at the next window position.
975 deflate_slow(deflate_state
*s
, int flush
)
977 IPos hash_head
; /* head of hash chain */
978 int bflush
; /* set if current block must be flushed */
980 /* Process the input block. */
982 /* Make sure that we always have enough lookahead, except
983 * at the end of the input file. We need MAX_MATCH bytes
984 * for the next match, plus MIN_MATCH bytes to insert the
985 * string following the next match.
987 if (s
->lookahead
< MIN_LOOKAHEAD
) {
989 if (s
->lookahead
< MIN_LOOKAHEAD
&& flush
== Z_NO_FLUSH
) {
992 if (s
->lookahead
== 0) break; /* flush the current block */
995 /* Insert the string window[strstart .. strstart+2] in the
996 * dictionary, and set hash_head to the head of the hash chain:
999 if (s
->lookahead
>= MIN_MATCH
) {
1000 INSERT_STRING(s
, s
->strstart
, hash_head
);
1003 /* Find the longest match, discarding those <= prev_length.
1005 s
->prev_length
= s
->match_length
, s
->prev_match
= s
->match_start
;
1006 s
->match_length
= MIN_MATCH
-1;
1008 if (hash_head
!= NIL
&& s
->prev_length
< s
->max_lazy_match
&&
1009 s
->strstart
- hash_head
<= MAX_DIST(s
)) {
1010 /* To simplify the code, we prevent matches with the string
1011 * of window index 0 (in particular we have to avoid a match
1012 * of the string with itself at the start of the input file).
1014 s
->match_length
= longest_match (s
, hash_head
);
1015 /* longest_match() sets match_start */
1017 if (s
->match_length
<= 5 && (s
->strategy
== Z_FILTERED
1018 #if TOO_FAR <= 32767
1019 || (s
->match_length
== MIN_MATCH
&&
1020 s
->strstart
- s
->match_start
> TOO_FAR
)
1024 /* If prev_match is also MIN_MATCH, match_start is garbage
1025 * but we will ignore the current match anyway.
1027 s
->match_length
= MIN_MATCH
-1;
1030 /* If there was a match at the previous step and the current
1031 * match is not better, output the previous match:
1033 if (s
->prev_length
>= MIN_MATCH
&& s
->match_length
<= s
->prev_length
) {
1034 uInt max_insert
= s
->strstart
+ s
->lookahead
- MIN_MATCH
;
1035 /* Do not insert strings in hash table beyond this. */
1037 check_match(s
, s
->strstart
-1, s
->prev_match
, s
->prev_length
);
1039 _tr_tally_dist(s
, s
->strstart
-1 - s
->prev_match
,
1040 s
->prev_length
- MIN_MATCH
, bflush
);
1042 /* Insert in hash table all strings up to the end of the match.
1043 * strstart-1 and strstart are already inserted. If there is not
1044 * enough lookahead, the last two strings are not inserted in
1047 s
->lookahead
-= s
->prev_length
-1;
1048 s
->prev_length
-= 2;
1050 if (++s
->strstart
<= max_insert
) {
1051 INSERT_STRING(s
, s
->strstart
, hash_head
);
1053 } while (--s
->prev_length
!= 0);
1054 s
->match_available
= 0;
1055 s
->match_length
= MIN_MATCH
-1;
1058 if (bflush
) FLUSH_BLOCK(s
, 0);
1060 } else if (s
->match_available
) {
1061 /* If there was no match at the previous position, output a
1062 * single literal. If there was a match but the current match
1063 * is longer, truncate the previous match to a single literal.
1065 Tracevv((stderr
,"%c", s
->window
[s
->strstart
-1]));
1066 _tr_tally_lit(s
, s
->window
[s
->strstart
-1], bflush
);
1068 FLUSH_BLOCK_ONLY(s
, 0);
1072 if (s
->strm
->avail_out
== 0) return need_more
;
1074 /* There is no previous match to compare with, wait for
1075 * the next step to decide.
1077 s
->match_available
= 1;
1082 Assert (flush
!= Z_NO_FLUSH
, "no flush?");
1083 if (s
->match_available
) {
1084 Tracevv((stderr
,"%c", s
->window
[s
->strstart
-1]));
1085 _tr_tally_lit(s
, s
->window
[s
->strstart
-1], bflush
);
1086 s
->match_available
= 0;
1088 s
->insert
= s
->strstart
< MIN_MATCH
-1 ? s
->strstart
: MIN_MATCH
-1;
1089 if (flush
== Z_FINISH
) {
1097 #endif /* FASTEST */
1099 /* ===========================================================================
1100 * For Z_RLE, simply look for runs of bytes, generate matches only of distance
1101 * one. Do not maintain a hash table. (It will be regenerated if this run of
1102 * deflate switches away from Z_RLE.)
1106 deflate_rle(deflate_state
*s
, int flush
)
1108 int bflush
; /* set if current block must be flushed */
1109 uInt prev
; /* byte at distance one to match */
1110 Bytef
*scan
, *strend
; /* scan goes up to strend for length of run */
1113 /* Make sure that we always have enough lookahead, except
1114 * at the end of the input file. We need MAX_MATCH bytes
1115 * for the longest run, plus one for the unrolled loop.
1117 if (s
->lookahead
<= MAX_MATCH
) {
1119 if (s
->lookahead
<= MAX_MATCH
&& flush
== Z_NO_FLUSH
) {
1122 if (s
->lookahead
== 0) break; /* flush the current block */
1125 /* See how many times the previous byte repeats */
1126 s
->match_length
= 0;
1127 if (s
->lookahead
>= MIN_MATCH
&& s
->strstart
> 0) {
1128 scan
= s
->window
+ s
->strstart
- 1;
1130 if (prev
== *++scan
&& prev
== *++scan
&& prev
== *++scan
) {
1131 strend
= s
->window
+ s
->strstart
+ MAX_MATCH
;
1133 } while (prev
== *++scan
&& prev
== *++scan
&&
1134 prev
== *++scan
&& prev
== *++scan
&&
1135 prev
== *++scan
&& prev
== *++scan
&&
1136 prev
== *++scan
&& prev
== *++scan
&&
1138 s
->match_length
= MAX_MATCH
- (int)(strend
- scan
);
1139 if (s
->match_length
> s
->lookahead
)
1140 s
->match_length
= s
->lookahead
;
1142 Assert(scan
<= s
->window
+(uInt
)(s
->window_size
-1), "wild scan");
1145 /* Emit match if have run of MIN_MATCH or longer, else emit literal */
1146 if (s
->match_length
>= MIN_MATCH
) {
1147 check_match(s
, s
->strstart
, s
->strstart
- 1, s
->match_length
);
1149 _tr_tally_dist(s
, 1, s
->match_length
- MIN_MATCH
, bflush
);
1151 s
->lookahead
-= s
->match_length
;
1152 s
->strstart
+= s
->match_length
;
1153 s
->match_length
= 0;
1155 /* No match, output a literal byte */
1156 Tracevv((stderr
,"%c", s
->window
[s
->strstart
]));
1157 _tr_tally_lit (s
, s
->window
[s
->strstart
], bflush
);
1161 if (bflush
) FLUSH_BLOCK(s
, 0);
1164 if (flush
== Z_FINISH
) {
1173 /* ===========================================================================
1174 * For Z_HUFFMAN_ONLY, do not look for matches. Do not maintain a hash table.
1175 * (It will be regenerated if this run of deflate switches away from Huffman.)
1179 deflate_huff(deflate_state
*s
, int flush
)
1181 int bflush
; /* set if current block must be flushed */
1184 /* Make sure that we have a literal to write. */
1185 if (s
->lookahead
== 0) {
1187 if (s
->lookahead
== 0) {
1188 if (flush
== Z_NO_FLUSH
)
1190 break; /* flush the current block */
1194 /* Output a literal byte */
1195 s
->match_length
= 0;
1196 Tracevv((stderr
,"%c", s
->window
[s
->strstart
]));
1197 _tr_tally_lit (s
, s
->window
[s
->strstart
], bflush
);
1200 if (bflush
) FLUSH_BLOCK(s
, 0);
1203 if (flush
== Z_FINISH
) {