forked from sztupy/adbputty
-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy pathSSHZLIB.C
1385 lines (1249 loc) · 37.8 KB
/
SSHZLIB.C
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/*
* Zlib (RFC1950 / RFC1951) compression for PuTTY.
*
* There will no doubt be criticism of my decision to reimplement
* Zlib compression from scratch instead of using the existing zlib
* code. People will cry `reinventing the wheel'; they'll claim
* that the `fundamental basis of OSS' is code reuse; they'll want
* to see a really good reason for me having chosen not to use the
* existing code.
*
* Well, here are my reasons. Firstly, I don't want to link the
* whole of zlib into the PuTTY binary; PuTTY is justifiably proud
* of its small size and I think zlib contains a lot of unnecessary
* baggage for the kind of compression that SSH requires.
*
* Secondly, I also don't like the alternative of using zlib.dll.
* Another thing PuTTY is justifiably proud of is its ease of
* installation, and the last thing I want to do is to start
* mandating DLLs. Not only that, but there are two _kinds_ of
* zlib.dll kicking around, one with C calling conventions on the
* exported functions and another with WINAPI conventions, and
* there would be a significant danger of getting the wrong one.
*
* Thirdly, there seems to be a difference of opinion on the IETF
* secsh mailing list about the correct way to round off a
* compressed packet and start the next. In particular, there's
* some talk of switching to a mechanism zlib isn't currently
* capable of supporting (see below for an explanation). Given that
* sort of uncertainty, I thought it might be better to have code
* that will support even the zlib-incompatible worst case.
*
* Fourthly, it's a _second implementation_. Second implementations
* are fundamentally a Good Thing in standardisation efforts. The
* difference of opinion mentioned above has arisen _precisely_
* because there has been only one zlib implementation and
* everybody has used it. I don't intend that this should happen
* again.
*/
#include <stdlib.h>
#include <assert.h>
#ifdef ZLIB_STANDALONE
/*
* This module also makes a handy zlib decoding tool for when
* you're picking apart Zip files or PDFs or PNGs. If you compile
* it with ZLIB_STANDALONE defined, it builds on its own and
* becomes a command-line utility.
*
* Therefore, here I provide a self-contained implementation of the
* macros required from the rest of the PuTTY sources.
*/
#define snew(type) ( (type *) malloc(sizeof(type)) )
#define snewn(n, type) ( (type *) malloc((n) * sizeof(type)) )
#define sresize(x, n, type) ( (type *) realloc((x), (n) * sizeof(type)) )
#define sfree(x) ( free((x)) )
#else
#include "ssh.h"
#endif
#ifndef FALSE
#define FALSE 0
#define TRUE (!FALSE)
#endif
/* ----------------------------------------------------------------------
* Basic LZ77 code. This bit is designed modularly, so it could be
* ripped out and used in a different LZ77 compressor. Go to it,
* and good luck :-)
*/
struct LZ77InternalContext;
struct LZ77Context {
struct LZ77InternalContext *ictx;
void *userdata;
void (*literal) (struct LZ77Context * ctx, unsigned char c);
void (*match) (struct LZ77Context * ctx, int distance, int len);
};
/*
* Initialise the private fields of an LZ77Context. It's up to the
* user to initialise the public fields.
*/
static int lz77_init(struct LZ77Context *ctx);
/*
* Supply data to be compressed. Will update the private fields of
* the LZ77Context, and will call literal() and match() to output.
* If `compress' is FALSE, it will never emit a match, but will
* instead call literal() for everything.
*/
static void lz77_compress(struct LZ77Context *ctx,
unsigned char *data, int len, int compress);
/*
* Modifiable parameters.
*/
#define WINSIZE 32768 /* window size. Must be power of 2! */
#define HASHMAX 2039 /* one more than max hash value */
#define MAXMATCH 32 /* how many matches we track */
#define HASHCHARS 3 /* how many chars make a hash */
/*
* This compressor takes a less slapdash approach than the
* gzip/zlib one. Rather than allowing our hash chains to fall into
* disuse near the far end, we keep them doubly linked so we can
* _find_ the far end, and then every time we add a new byte to the
* window (thus rolling round by one and removing the previous
* byte), we can carefully remove the hash chain entry.
*/
#define INVALID -1 /* invalid hash _and_ invalid offset */
struct WindowEntry {
short next, prev; /* array indices within the window */
short hashval;
};
struct HashEntry {
short first; /* window index of first in chain */
};
struct Match {
int distance, len;
};
struct LZ77InternalContext {
struct WindowEntry win[WINSIZE];
unsigned char data[WINSIZE];
int winpos;
struct HashEntry hashtab[HASHMAX];
unsigned char pending[HASHCHARS];
int npending;
};
static int lz77_hash(unsigned char *data)
{
return (257 * data[0] + 263 * data[1] + 269 * data[2]) % HASHMAX;
}
static int lz77_init(struct LZ77Context *ctx)
{
struct LZ77InternalContext *st;
int i;
st = snew(struct LZ77InternalContext);
if (!st)
return 0;
ctx->ictx = st;
for (i = 0; i < WINSIZE; i++)
st->win[i].next = st->win[i].prev = st->win[i].hashval = INVALID;
for (i = 0; i < HASHMAX; i++)
st->hashtab[i].first = INVALID;
st->winpos = 0;
st->npending = 0;
return 1;
}
static void lz77_advance(struct LZ77InternalContext *st,
unsigned char c, int hash)
{
int off;
/*
* Remove the hash entry at winpos from the tail of its chain,
* or empty the chain if it's the only thing on the chain.
*/
if (st->win[st->winpos].prev != INVALID) {
st->win[st->win[st->winpos].prev].next = INVALID;
} else if (st->win[st->winpos].hashval != INVALID) {
st->hashtab[st->win[st->winpos].hashval].first = INVALID;
}
/*
* Create a new entry at winpos and add it to the head of its
* hash chain.
*/
st->win[st->winpos].hashval = hash;
st->win[st->winpos].prev = INVALID;
off = st->win[st->winpos].next = st->hashtab[hash].first;
st->hashtab[hash].first = st->winpos;
if (off != INVALID)
st->win[off].prev = st->winpos;
st->data[st->winpos] = c;
/*
* Advance the window pointer.
*/
st->winpos = (st->winpos + 1) & (WINSIZE - 1);
}
#define CHARAT(k) ( (k)<0 ? st->data[(st->winpos+k)&(WINSIZE-1)] : data[k] )
static void lz77_compress(struct LZ77Context *ctx,
unsigned char *data, int len, int compress)
{
struct LZ77InternalContext *st = ctx->ictx;
int i, hash, distance, off, nmatch, matchlen, advance;
struct Match defermatch, matches[MAXMATCH];
int deferchr;
/*
* Add any pending characters from last time to the window. (We
* might not be able to.)
*/
for (i = 0; i < st->npending; i++) {
unsigned char foo[HASHCHARS];
int j;
if (len + st->npending - i < HASHCHARS) {
/* Update the pending array. */
for (j = i; j < st->npending; j++)
st->pending[j - i] = st->pending[j];
break;
}
for (j = 0; j < HASHCHARS; j++)
foo[j] = (i + j < st->npending ? st->pending[i + j] :
data[i + j - st->npending]);
lz77_advance(st, foo[0], lz77_hash(foo));
}
st->npending -= i;
defermatch.distance = 0; /* appease compiler */
defermatch.len = 0;
deferchr = '\0';
while (len > 0) {
/* Don't even look for a match, if we're not compressing. */
if (compress && len >= HASHCHARS) {
/*
* Hash the next few characters.
*/
hash = lz77_hash(data);
/*
* Look the hash up in the corresponding hash chain and see
* what we can find.
*/
nmatch = 0;
for (off = st->hashtab[hash].first;
off != INVALID; off = st->win[off].next) {
/* distance = 1 if off == st->winpos-1 */
/* distance = WINSIZE if off == st->winpos */
distance =
WINSIZE - (off + WINSIZE - st->winpos) % WINSIZE;
for (i = 0; i < HASHCHARS; i++)
if (CHARAT(i) != CHARAT(i - distance))
break;
if (i == HASHCHARS) {
matches[nmatch].distance = distance;
matches[nmatch].len = 3;
if (++nmatch >= MAXMATCH)
break;
}
}
} else {
nmatch = 0;
hash = INVALID;
}
if (nmatch > 0) {
/*
* We've now filled up matches[] with nmatch potential
* matches. Follow them down to find the longest. (We
* assume here that it's always worth favouring a
* longer match over a shorter one.)
*/
matchlen = HASHCHARS;
while (matchlen < len) {
int j;
for (i = j = 0; i < nmatch; i++) {
if (CHARAT(matchlen) ==
CHARAT(matchlen - matches[i].distance)) {
matches[j++] = matches[i];
}
}
if (j == 0)
break;
matchlen++;
nmatch = j;
}
/*
* We've now got all the longest matches. We favour the
* shorter distances, which means we go with matches[0].
* So see if we want to defer it or throw it away.
*/
matches[0].len = matchlen;
if (defermatch.len > 0) {
if (matches[0].len > defermatch.len + 1) {
/* We have a better match. Emit the deferred char,
* and defer this match. */
ctx->literal(ctx, (unsigned char) deferchr);
defermatch = matches[0];
deferchr = data[0];
advance = 1;
} else {
/* We don't have a better match. Do the deferred one. */
ctx->match(ctx, defermatch.distance, defermatch.len);
advance = defermatch.len - 1;
defermatch.len = 0;
}
} else {
/* There was no deferred match. Defer this one. */
defermatch = matches[0];
deferchr = data[0];
advance = 1;
}
} else {
/*
* We found no matches. Emit the deferred match, if
* any; otherwise emit a literal.
*/
if (defermatch.len > 0) {
ctx->match(ctx, defermatch.distance, defermatch.len);
advance = defermatch.len - 1;
defermatch.len = 0;
} else {
ctx->literal(ctx, data[0]);
advance = 1;
}
}
/*
* Now advance the position by `advance' characters,
* keeping the window and hash chains consistent.
*/
while (advance > 0) {
if (len >= HASHCHARS) {
lz77_advance(st, *data, lz77_hash(data));
} else {
st->pending[st->npending++] = *data;
}
data++;
len--;
advance--;
}
}
}
/* ----------------------------------------------------------------------
* Zlib compression. We always use the static Huffman tree option.
* Mostly this is because it's hard to scan a block in advance to
* work out better trees; dynamic trees are great when you're
* compressing a large file under no significant time constraint,
* but when you're compressing little bits in real time, things get
* hairier.
*
* I suppose it's possible that I could compute Huffman trees based
* on the frequencies in the _previous_ block, as a sort of
* heuristic, but I'm not confident that the gain would balance out
* having to transmit the trees.
*/
struct Outbuf {
unsigned char *outbuf;
int outlen, outsize;
unsigned long outbits;
int noutbits;
int firstblock;
int comp_disabled;
};
static void outbits(struct Outbuf *out, unsigned long bits, int nbits)
{
assert(out->noutbits + nbits <= 32);
out->outbits |= bits << out->noutbits;
out->noutbits += nbits;
while (out->noutbits >= 8) {
if (out->outlen >= out->outsize) {
out->outsize = out->outlen + 64;
out->outbuf = sresize(out->outbuf, out->outsize, unsigned char);
}
out->outbuf[out->outlen++] = (unsigned char) (out->outbits & 0xFF);
out->outbits >>= 8;
out->noutbits -= 8;
}
}
static const unsigned char mirrorbytes[256] = {
0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0,
0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8,
0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,
0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4,
0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,
0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec,
0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,
0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2,
0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,
0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea,
0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,
0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6,
0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,
0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee,
0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,
0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1,
0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,
0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9,
0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,
0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5,
0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,
0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed,
0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3,
0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,
0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb,
0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,
0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7,
0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,
0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef,
0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff,
};
typedef struct {
short code, extrabits;
int min, max;
} coderecord;
static const coderecord lencodes[] = {
{257, 0, 3, 3},
{258, 0, 4, 4},
{259, 0, 5, 5},
{260, 0, 6, 6},
{261, 0, 7, 7},
{262, 0, 8, 8},
{263, 0, 9, 9},
{264, 0, 10, 10},
{265, 1, 11, 12},
{266, 1, 13, 14},
{267, 1, 15, 16},
{268, 1, 17, 18},
{269, 2, 19, 22},
{270, 2, 23, 26},
{271, 2, 27, 30},
{272, 2, 31, 34},
{273, 3, 35, 42},
{274, 3, 43, 50},
{275, 3, 51, 58},
{276, 3, 59, 66},
{277, 4, 67, 82},
{278, 4, 83, 98},
{279, 4, 99, 114},
{280, 4, 115, 130},
{281, 5, 131, 162},
{282, 5, 163, 194},
{283, 5, 195, 226},
{284, 5, 227, 257},
{285, 0, 258, 258},
};
static const coderecord distcodes[] = {
{0, 0, 1, 1},
{1, 0, 2, 2},
{2, 0, 3, 3},
{3, 0, 4, 4},
{4, 1, 5, 6},
{5, 1, 7, 8},
{6, 2, 9, 12},
{7, 2, 13, 16},
{8, 3, 17, 24},
{9, 3, 25, 32},
{10, 4, 33, 48},
{11, 4, 49, 64},
{12, 5, 65, 96},
{13, 5, 97, 128},
{14, 6, 129, 192},
{15, 6, 193, 256},
{16, 7, 257, 384},
{17, 7, 385, 512},
{18, 8, 513, 768},
{19, 8, 769, 1024},
{20, 9, 1025, 1536},
{21, 9, 1537, 2048},
{22, 10, 2049, 3072},
{23, 10, 3073, 4096},
{24, 11, 4097, 6144},
{25, 11, 6145, 8192},
{26, 12, 8193, 12288},
{27, 12, 12289, 16384},
{28, 13, 16385, 24576},
{29, 13, 24577, 32768},
};
static void zlib_literal(struct LZ77Context *ectx, unsigned char c)
{
struct Outbuf *out = (struct Outbuf *) ectx->userdata;
if (out->comp_disabled) {
/*
* We're in an uncompressed block, so just output the byte.
*/
outbits(out, c, 8);
return;
}
if (c <= 143) {
/* 0 through 143 are 8 bits long starting at 00110000. */
outbits(out, mirrorbytes[0x30 + c], 8);
} else {
/* 144 through 255 are 9 bits long starting at 110010000. */
outbits(out, 1 + 2 * mirrorbytes[0x90 - 144 + c], 9);
}
}
static void zlib_match(struct LZ77Context *ectx, int distance, int len)
{
const coderecord *d, *l;
int i, j, k;
struct Outbuf *out = (struct Outbuf *) ectx->userdata;
assert(!out->comp_disabled);
while (len > 0) {
int thislen;
/*
* We can transmit matches of lengths 3 through 258
* inclusive. So if len exceeds 258, we must transmit in
* several steps, with 258 or less in each step.
*
* Specifically: if len >= 261, we can transmit 258 and be
* sure of having at least 3 left for the next step. And if
* len <= 258, we can just transmit len. But if len == 259
* or 260, we must transmit len-3.
*/
thislen = (len > 260 ? 258 : len <= 258 ? len : len - 3);
len -= thislen;
/*
* Binary-search to find which length code we're
* transmitting.
*/
i = -1;
j = sizeof(lencodes) / sizeof(*lencodes);
while (1) {
assert(j - i >= 2);
k = (j + i) / 2;
if (thislen < lencodes[k].min)
j = k;
else if (thislen > lencodes[k].max)
i = k;
else {
l = &lencodes[k];
break; /* found it! */
}
}
/*
* Transmit the length code. 256-279 are seven bits
* starting at 0000000; 280-287 are eight bits starting at
* 11000000.
*/
if (l->code <= 279) {
outbits(out, mirrorbytes[(l->code - 256) * 2], 7);
} else {
outbits(out, mirrorbytes[0xc0 - 280 + l->code], 8);
}
/*
* Transmit the extra bits.
*/
if (l->extrabits)
outbits(out, thislen - l->min, l->extrabits);
/*
* Binary-search to find which distance code we're
* transmitting.
*/
i = -1;
j = sizeof(distcodes) / sizeof(*distcodes);
while (1) {
assert(j - i >= 2);
k = (j + i) / 2;
if (distance < distcodes[k].min)
j = k;
else if (distance > distcodes[k].max)
i = k;
else {
d = &distcodes[k];
break; /* found it! */
}
}
/*
* Transmit the distance code. Five bits starting at 00000.
*/
outbits(out, mirrorbytes[d->code * 8], 5);
/*
* Transmit the extra bits.
*/
if (d->extrabits)
outbits(out, distance - d->min, d->extrabits);
}
}
void *zlib_compress_init(void)
{
struct Outbuf *out;
struct LZ77Context *ectx = snew(struct LZ77Context);
lz77_init(ectx);
ectx->literal = zlib_literal;
ectx->match = zlib_match;
out = snew(struct Outbuf);
out->outbits = out->noutbits = 0;
out->firstblock = 1;
out->comp_disabled = FALSE;
ectx->userdata = out;
return ectx;
}
void zlib_compress_cleanup(void *handle)
{
struct LZ77Context *ectx = (struct LZ77Context *)handle;
sfree(ectx->userdata);
sfree(ectx->ictx);
sfree(ectx);
}
/*
* Turn off actual LZ77 analysis for one block, to facilitate
* construction of a precise-length IGNORE packet. Returns the
* length adjustment (which is only valid for packets < 65536
* bytes, but that seems reasonable enough).
*/
static int zlib_disable_compression(void *handle)
{
struct LZ77Context *ectx = (struct LZ77Context *)handle;
struct Outbuf *out = (struct Outbuf *) ectx->userdata;
int n;
out->comp_disabled = TRUE;
n = 0;
/*
* If this is the first block, we will start by outputting two
* header bytes, and then three bits to begin an uncompressed
* block. This will cost three bytes (because we will start on
* a byte boundary, this is certain).
*/
if (out->firstblock) {
n = 3;
} else {
/*
* Otherwise, we will output seven bits to close the
* previous static block, and _then_ three bits to begin an
* uncompressed block, and then flush the current byte.
* This may cost two bytes or three, depending on noutbits.
*/
n += (out->noutbits + 10) / 8;
}
/*
* Now we output four bytes for the length / ~length pair in
* the uncompressed block.
*/
n += 4;
return n;
}
int zlib_compress_block(void *handle, unsigned char *block, int len,
unsigned char **outblock, int *outlen)
{
struct LZ77Context *ectx = (struct LZ77Context *)handle;
struct Outbuf *out = (struct Outbuf *) ectx->userdata;
int in_block;
out->outbuf = NULL;
out->outlen = out->outsize = 0;
/*
* If this is the first block, output the Zlib (RFC1950) header
* bytes 78 9C. (Deflate compression, 32K window size, default
* algorithm.)
*/
if (out->firstblock) {
outbits(out, 0x9C78, 16);
out->firstblock = 0;
in_block = FALSE;
} else
in_block = TRUE;
if (out->comp_disabled) {
if (in_block)
outbits(out, 0, 7); /* close static block */
while (len > 0) {
int blen = (len < 65535 ? len : 65535);
/*
* Start a Deflate (RFC1951) uncompressed block. We
* transmit a zero bit (BFINAL=0), followed by two more
* zero bits (BTYPE=00). Of course these are in the
* wrong order (00 0), not that it matters.
*/
outbits(out, 0, 3);
/*
* Output zero bits to align to a byte boundary.
*/
if (out->noutbits)
outbits(out, 0, 8 - out->noutbits);
/*
* Output the block length, and then its one's
* complement. They're little-endian, so all we need to
* do is pass them straight to outbits() with bit count
* 16.
*/
outbits(out, blen, 16);
outbits(out, blen ^ 0xFFFF, 16);
/*
* Do the `compression': we need to pass the data to
* lz77_compress so that it will be taken into account
* for subsequent (distance,length) pairs. But
* lz77_compress is passed FALSE, which means it won't
* actually find (or even look for) any matches; so
* every character will be passed straight to
* zlib_literal which will spot out->comp_disabled and
* emit in the uncompressed format.
*/
lz77_compress(ectx, block, blen, FALSE);
len -= blen;
block += blen;
}
outbits(out, 2, 3); /* open new block */
} else {
if (!in_block) {
/*
* Start a Deflate (RFC1951) fixed-trees block. We
* transmit a zero bit (BFINAL=0), followed by a zero
* bit and a one bit (BTYPE=01). Of course these are in
* the wrong order (01 0).
*/
outbits(out, 2, 3);
}
/*
* Do the compression.
*/
lz77_compress(ectx, block, len, TRUE);
/*
* End the block (by transmitting code 256, which is
* 0000000 in fixed-tree mode), and transmit some empty
* blocks to ensure we have emitted the byte containing the
* last piece of genuine data. There are three ways we can
* do this:
*
* - Minimal flush. Output end-of-block and then open a
* new static block. This takes 9 bits, which is
* guaranteed to flush out the last genuine code in the
* closed block; but allegedly zlib can't handle it.
*
* - Zlib partial flush. Output EOB, open and close an
* empty static block, and _then_ open the new block.
* This is the best zlib can handle.
*
* - Zlib sync flush. Output EOB, then an empty
* _uncompressed_ block (000, then sync to byte
* boundary, then send bytes 00 00 FF FF). Then open the
* new block.
*
* For the moment, we will use Zlib partial flush.
*/
outbits(out, 0, 7); /* close block */
outbits(out, 2, 3 + 7); /* empty static block */
outbits(out, 2, 3); /* open new block */
}
out->comp_disabled = FALSE;
*outblock = out->outbuf;
*outlen = out->outlen;
return 1;
}
/* ----------------------------------------------------------------------
* Zlib decompression. Of course, even though our compressor always
* uses static trees, our _decompressor_ has to be capable of
* handling dynamic trees if it sees them.
*/
/*
* The way we work the Huffman decode is to have a table lookup on
* the first N bits of the input stream (in the order they arrive,
* of course, i.e. the first bit of the Huffman code is in bit 0).
* Each table entry lists the number of bits to consume, plus
* either an output code or a pointer to a secondary table.
*/
struct zlib_table;
struct zlib_tableentry;
struct zlib_tableentry {
unsigned char nbits;
short code;
struct zlib_table *nexttable;
};
struct zlib_table {
int mask; /* mask applied to input bit stream */
struct zlib_tableentry *table;
};
#define MAXCODELEN 16
#define MAXSYMS 288
/*
* Build a single-level decode table for elements
* [minlength,maxlength) of the provided code/length tables, and
* recurse to build subtables.
*/
static struct zlib_table *zlib_mkonetab(int *codes, unsigned char *lengths,
int nsyms,
int pfx, int pfxbits, int bits)
{
struct zlib_table *tab = snew(struct zlib_table);
int pfxmask = (1 << pfxbits) - 1;
int nbits, i, j, code;
tab->table = snewn(1 << bits, struct zlib_tableentry);
tab->mask = (1 << bits) - 1;
for (code = 0; code <= tab->mask; code++) {
tab->table[code].code = -1;
tab->table[code].nbits = 0;
tab->table[code].nexttable = NULL;
}
for (i = 0; i < nsyms; i++) {
if (lengths[i] <= pfxbits || (codes[i] & pfxmask) != pfx)
continue;
code = (codes[i] >> pfxbits) & tab->mask;
for (j = code; j <= tab->mask; j += 1 << (lengths[i] - pfxbits)) {
tab->table[j].code = i;
nbits = lengths[i] - pfxbits;
if (tab->table[j].nbits < nbits)
tab->table[j].nbits = nbits;
}
}
for (code = 0; code <= tab->mask; code++) {
if (tab->table[code].nbits <= bits)
continue;
/* Generate a subtable. */
tab->table[code].code = -1;
nbits = tab->table[code].nbits - bits;
if (nbits > 7)
nbits = 7;
tab->table[code].nbits = bits;
tab->table[code].nexttable = zlib_mkonetab(codes, lengths, nsyms,
pfx | (code << pfxbits),
pfxbits + bits, nbits);
}
return tab;
}
/*
* Build a decode table, given a set of Huffman tree lengths.
*/
static struct zlib_table *zlib_mktable(unsigned char *lengths,
int nlengths)
{
int count[MAXCODELEN], startcode[MAXCODELEN], codes[MAXSYMS];
int code, maxlen;
int i, j;
/* Count the codes of each length. */
maxlen = 0;
for (i = 1; i < MAXCODELEN; i++)
count[i] = 0;
for (i = 0; i < nlengths; i++) {
count[lengths[i]]++;
if (maxlen < lengths[i])
maxlen = lengths[i];
}
/* Determine the starting code for each length block. */
code = 0;
for (i = 1; i < MAXCODELEN; i++) {
startcode[i] = code;
code += count[i];
code <<= 1;
}
/* Determine the code for each symbol. Mirrored, of course. */
for (i = 0; i < nlengths; i++) {
code = startcode[lengths[i]]++;
codes[i] = 0;
for (j = 0; j < lengths[i]; j++) {
codes[i] = (codes[i] << 1) | (code & 1);
code >>= 1;
}
}
/*
* Now we have the complete list of Huffman codes. Build a
* table.
*/
return zlib_mkonetab(codes, lengths, nlengths, 0, 0,
maxlen < 9 ? maxlen : 9);
}
static int zlib_freetable(struct zlib_table **ztab)
{
struct zlib_table *tab;
int code;
if (ztab == NULL)
return -1;
if (*ztab == NULL)
return 0;
tab = *ztab;
for (code = 0; code <= tab->mask; code++)
if (tab->table[code].nexttable != NULL)
zlib_freetable(&tab->table[code].nexttable);
sfree(tab->table);
tab->table = NULL;
sfree(tab);
*ztab = NULL;
return (0);
}
struct zlib_decompress_ctx {
struct zlib_table *staticlentable, *staticdisttable;
struct zlib_table *currlentable, *currdisttable, *lenlentable;
enum {
START, OUTSIDEBLK,
TREES_HDR, TREES_LENLEN, TREES_LEN, TREES_LENREP,
INBLK, GOTLENSYM, GOTLEN, GOTDISTSYM,
UNCOMP_LEN, UNCOMP_NLEN, UNCOMP_DATA
} state;
int sym, hlit, hdist, hclen, lenptr, lenextrabits, lenaddon, len,
lenrep;
int uncomplen;
unsigned char lenlen[19];
unsigned char lengths[286 + 32];
unsigned long bits;
int nbits;
unsigned char window[WINSIZE];
int winpos;
unsigned char *outblk;
int outlen, outsize;
};
void *zlib_decompress_init(void)
{
struct zlib_decompress_ctx *dctx = snew(struct zlib_decompress_ctx);
unsigned char lengths[288];
memset(lengths, 8, 144);
memset(lengths + 144, 9, 256 - 144);
memset(lengths + 256, 7, 280 - 256);
memset(lengths + 280, 8, 288 - 280);
dctx->staticlentable = zlib_mktable(lengths, 288);
memset(lengths, 5, 32);
dctx->staticdisttable = zlib_mktable(lengths, 32);
dctx->state = START; /* even before header */
dctx->currlentable = dctx->currdisttable = dctx->lenlentable = NULL;
dctx->bits = 0;
dctx->nbits = 0;
dctx->winpos = 0;
return dctx;
}
void zlib_decompress_cleanup(void *handle)
{
struct zlib_decompress_ctx *dctx = (struct zlib_decompress_ctx *)handle;
if (dctx->currlentable && dctx->currlentable != dctx->staticlentable)
zlib_freetable(&dctx->currlentable);
if (dctx->currdisttable && dctx->currdisttable != dctx->staticdisttable)
zlib_freetable(&dctx->currdisttable);
if (dctx->lenlentable)
zlib_freetable(&dctx->lenlentable);
zlib_freetable(&dctx->staticlentable);
zlib_freetable(&dctx->staticdisttable);
sfree(dctx);
}
static int zlib_huflookup(unsigned long *bitsp, int *nbitsp,
struct zlib_table *tab)