summaryrefslogtreecommitdiff
path: root/ext/sdbm/_sdbm.c
blob: d4cf621ea50b559eff411e2160a9c8e17ccf1ba8 (plain)
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
/*
 * sdbm - ndbm work-alike hashed database library
 * based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
 * author: oz@nexus.yorku.ca
 * status: public domain.
 *
 * core routines
 */

#ifndef lint
/*char sdbm_rcsid[] = "$Id$";*/
#endif

#include "sdbm.h"
#include "config.h"

/*
 * sdbm - ndbm work-alike hashed database library
 * tuning and portability constructs [not nearly enough]
 * author: oz@nexus.yorku.ca
 */

#define BYTESIZ		8

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifdef BSD42
#define SEEK_SET	L_SET
#define	memset(s,c,n)	bzero(s, n)		/* only when c is zero */
#define	memcpy(s1,s2,n)	bcopy(s2, s1, n)
#define	memcmp(s1,s2,n)	bcmp(s1,s2,n)
#endif

/*
 * important tuning parms (hah)
 */

#define SEEDUPS		/* always detect duplicates */
#define BADMESS		/* generate a message for worst case:
			   cannot make room after SPLTMAX splits */
/*
 * misc
 */
#ifdef DEBUG
#define debug(x)	printf x
#else
#define debug(x)
#endif

#ifdef BIG_E
#define GET_SHORT(p, i)	(((unsigned)((unsigned char *)(p))[(i)*2] << 8) + (((unsigned char *)(p))[(i)*2 + 1]))
#define PUT_SHORT(p, i, s) (((unsigned char *)(p))[(i)*2] = (unsigned char)((s) >> 8), ((unsigned char *)(p))[(i)*2 + 1] = (unsigned char)(s))
#else
#define GET_SHORT(p, i)	((p)[i])
#define PUT_SHORT(p, i, s)	((p)[i] = (s))
#endif

/*#include "pair.h"*/
static int   fitpair proto((char *, int));
static void  putpair proto((char *, datum, datum));
static datum getpair proto((char *, datum));
static int   delpair proto((char *, datum));
static int   chkpage proto((char *));
static datum getnkey proto((char *, int));
static void  splpage proto((char *, char *, long));
#ifdef SEEDUPS
static int   duppair proto((char *, datum));
#endif

#include <stdio.h>
#include <stdlib.h>
#ifdef MSDOS
#include <io.h>
#endif
#include <sys/types.h>
#include <sys/stat.h>
#ifdef BSD42
#include <sys/file.h>
#else
#include <fcntl.h>
/*#include <memory.h>*/
#endif
#ifndef O_BINARY
#define O_BINARY	0
#endif

#include <errno.h>
#ifndef EPERM
#define EPERM	EACCES
#endif
#include <string.h>

#ifdef __STDC__
#include <stddef.h>
#endif

#ifndef NULL
#define NULL	0
#endif

/*
 * externals
 */
#if !defined sun && !defined MSDOS && !defined _WIN32 && !defined __CYGWIN__ && !defined(errno)
extern int errno;
#endif

/*
 * forward
 */
static int getdbit proto((DBM *, long));
static int setdbit proto((DBM *, long));
static int getpage proto((DBM *, long));
static datum getnext proto((DBM *));
static int makroom proto((DBM *, long, int));

/*
 * useful macros
 */
#define bad(x)		((x).dptr == NULL || (x).dsize < 0)
#define exhash(item)	sdbm_hash((item).dptr, (item).dsize)
#define ioerr(db)	((db)->flags |= DBM_IOERR)

#define OFF_PAG(off)	(long) (off) * PBLKSIZ
#define OFF_DIR(off)	(long) (off) * DBLKSIZ

static long masks[] = {
	000000000000L, 000000000001L, 000000000003L,
	000000000007L, 000000000017L, 000000000037L,
	000000000077L, 000000000177L, 000000000377L,
	000000000777L, 000000001777L, 000000003777L,
	000000007777L, 000000017777L, 000000037777L,
	000000077777L, 000000177777L, 000000377777L,
	000000777777L, 000001777777L, 000003777777L,
	000007777777L, 000017777777L, 000037777777L,
	000077777777L, 000177777777L, 000377777777L,
	000777777777L, 001777777777L, 003777777777L,
	007777777777L, 017777777777L
};

datum nullitem = {NULL, 0};

DBM *
sdbm_open(file, flags, mode)
register char *file;
register int flags;
register int mode;
{
	register DBM *db;
	register char *dirname;
	register char *pagname;
	register int n;

	if (file == NULL || !*file)
		return errno = EINVAL, (DBM *) NULL;
/*
 * need space for two seperate filenames
 */
	n = strlen(file) * 2 + strlen(DIRFEXT) + strlen(PAGFEXT) + 2;

	if ((dirname = malloc((unsigned) n)) == NULL)
		return errno = ENOMEM, (DBM *) NULL;
/*
 * build the file names
 */
	dirname = strcat(strcpy(dirname, file), DIRFEXT);
	pagname = strcpy(dirname + strlen(dirname) + 1, file);
	pagname = strcat(pagname, PAGFEXT);

	db = sdbm_prep(dirname, pagname, flags, mode);
	free((char *) dirname);
	return db;
}

DBM *
sdbm_prep(dirname, pagname, flags, mode)
char *dirname;
char *pagname;
int flags;
int mode;
{
	register DBM *db;
	struct stat dstat;

	if ((db = (DBM *) malloc(sizeof(DBM))) == NULL)
		return errno = ENOMEM, (DBM *) NULL;

        db->flags = 0;
        db->hmask = 0;
        db->blkptr = 0;
        db->keyptr = 0;
/*
 * adjust user flags so that WRONLY becomes RDWR, 
 * as required by this package. Also set our internal
 * flag for RDONLY.
 */
	if (flags & O_WRONLY)
		flags = (flags & ~O_WRONLY) | O_RDWR;
	if (flags & O_RDONLY)
		db->flags = DBM_RDONLY;
/*
 * open the files in sequence, and stat the dirfile.
 * If we fail anywhere, undo everything, return NULL.
 */
	flags |= O_BINARY;
	if ((db->pagf = open(pagname, flags, mode)) > -1) {
		if ((db->dirf = open(dirname, flags, mode)) > -1) {
/*
 * need the dirfile size to establish max bit number.
 */
			if (fstat(db->dirf, &dstat) == 0) {
/*
 * zero size: either a fresh database, or one with a single,
 * unsplit data page: dirpage is all zeros.
 */
				db->dirbno = (!dstat.st_size) ? 0 : -1;
				db->pagbno = -1;
				db->maxbno = dstat.st_size * (long) BYTESIZ;

				(void) memset(db->pagbuf, 0, PBLKSIZ);
				(void) memset(db->dirbuf, 0, DBLKSIZ);
			/*
			 * success
			 */
				return db;
			}
			(void) close(db->dirf);
		}
		(void) close(db->pagf);
	}
	free((char *) db);
	return (DBM *) NULL;
}

void
sdbm_close(db)
register DBM *db;
{
	if (db == NULL)
		errno = EINVAL;
	else {
		(void) close(db->dirf);
		(void) close(db->pagf);
		free((char *) db);
	}
}

datum
sdbm_fetch(db, key)
register DBM *db;
datum key;
{
	if (db == NULL || bad(key))
		return errno = EINVAL, nullitem;

	if (getpage(db, exhash(key)))
		return getpair(db->pagbuf, key);

	return ioerr(db), nullitem;
}

int
sdbm_delete(db, key)
register DBM *db;
datum key;
{
	if (db == NULL || bad(key))
		return errno = EINVAL, -1;
	if (sdbm_rdonly(db))
		return errno = EPERM, -1;

	if (getpage(db, exhash(key))) {
		if (!delpair(db->pagbuf, key))
			return -1;
/*
 * update the page file
 */
		if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
		    || write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
			return ioerr(db), -1;

		return 0;
	}

	return ioerr(db), -1;
}

int
sdbm_store(db, key, val, flags)
register DBM *db;
datum key;
datum val;
int flags;
{
	int need;
	register long hash;

	if (db == NULL || bad(key))
		return errno = EINVAL, -1;
	if (sdbm_rdonly(db))
		return errno = EPERM, -1;

	need = key.dsize + val.dsize;
/*
 * is the pair too big (or too small) for this database ??
 */
	if (need < 0 || need > PAIRMAX)
		return errno = EINVAL, -1;

	if (getpage(db, (hash = exhash(key)))) {
/*
 * if we need to replace, delete the key/data pair
 * first. If it is not there, ignore.
 */
		if (flags == DBM_REPLACE)
			(void) delpair(db->pagbuf, key);
#ifdef SEEDUPS
		else if (duppair(db->pagbuf, key))
			return 1;
#endif
/*
 * if we do not have enough room, we have to split.
 */
		if (!fitpair(db->pagbuf, need))
			if (!makroom(db, hash, need))
				return ioerr(db), -1;
/*
 * we have enough room or split is successful. insert the key,
 * and update the page file.
 */
		(void) putpair(db->pagbuf, key, val);

		if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
		    || write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
			return ioerr(db), -1;
	/*
	 * success
	 */
		return 0;
	}

	return ioerr(db), -1;
}

/*
 * makroom - make room by splitting the overfull page
 * this routine will attempt to make room for SPLTMAX times before
 * giving up.
 */
static int
makroom(db, hash, need)
register DBM *db;
long hash;
int need;
{
	long newp;
	char twin[PBLKSIZ];
#if defined MSDOS || (defined _WIN32 && !defined __CYGWIN__)
	char zer[PBLKSIZ];
	long oldtail;
#endif
	char *pag = db->pagbuf;
	char *new = twin;
	register int smax = SPLTMAX;

	do {
/*
 * split the current page
 */
		(void) splpage(pag, new, db->hmask + 1);
/*
 * address of the new page
 */
		newp = (hash & db->hmask) | (db->hmask + 1);
		debug(("newp: %ld\n", newp));
/*
 * write delay, read avoidence/cache shuffle:
 * select the page for incoming pair: if key is to go to the new page,
 * write out the previous one, and copy the new one over, thus making
 * it the current page. If not, simply write the new page, and we are
 * still looking at the page of interest. current page is not updated
 * here, as sdbm_store will do so, after it inserts the incoming pair.
 */

#if defined MSDOS || (defined _WIN32 && !defined __CYGWIN__)
	/*
	 * Fill hole with 0 if made it.
	 * (hole is NOT read as 0)
	 */
	oldtail = lseek(db->pagf, 0L, SEEK_END);
	memset(zer, 0, PBLKSIZ);
	while (OFF_PAG(newp) > oldtail) {
		if (lseek(db->pagf, 0L, SEEK_END) < 0 ||
		    write(db->pagf, zer, PBLKSIZ) < 0) {

			return 0;
		}
		oldtail += PBLKSIZ;
	}
#endif

		if (hash & (db->hmask + 1)) {
			if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
			    || write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
				return 0;
			db->pagbno = newp;
			(void) memcpy(pag, new, PBLKSIZ);
		}
		else if (lseek(db->pagf, OFF_PAG(newp), SEEK_SET) < 0
			 || write(db->pagf, new, PBLKSIZ) < 0)
			return 0;

		if (!setdbit(db, db->curbit))
			return 0;
/*
 * see if we have enough room now
 */
		if (fitpair(pag, need))
			return 1;
/*
 * try again... update curbit and hmask as getpage would have
 * done. because of our update of the current page, we do not
 * need to read in anything. BUT we have to write the current
 * [deferred] page out, as the window of failure is too great.
 */
		db->curbit = 2 * db->curbit + 
			((hash & (db->hmask + 1)) ? 2 : 1);
		db->hmask |= (db->hmask + 1);

		if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
		    || write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
			return 0;

	} while (--smax);
/*
 * if we are here, this is real bad news. After SPLTMAX splits,
 * we still cannot fit the key. say goodnight.
 */
#ifdef BADMESS
	(void) write(2, "sdbm: cannot insert after SPLTMAX attempts.\n", 44);
#endif
	return 0;

}

/*
 * the following two routines will break if
 * deletions aren't taken into account. (ndbm bug)
 */
datum
sdbm_firstkey(db)
register DBM *db;
{
	if (db == NULL)
		return errno = EINVAL, nullitem;
/*
 * start at page 0
 */
	(void) memset(db->pagbuf, 0, PBLKSIZ);
	if (lseek(db->pagf, OFF_PAG(0), SEEK_SET) < 0
	    || read(db->pagf, db->pagbuf, PBLKSIZ) < 0)
		return ioerr(db), nullitem;
	db->pagbno = 0;
	db->blkptr = 0;
	db->keyptr = 0;

	return getnext(db);
}

datum
sdbm_nextkey(db)
register DBM *db;
{
	if (db == NULL)
		return errno = EINVAL, nullitem;
	return getnext(db);
}

/*
 * all important binary trie traversal
 */
static int
getpage(db, hash)
register DBM *db;
register long hash;
{
	register int hbit;
	register long dbit;
	register long pagb;

	dbit = 0;
	hbit = 0;
	while (dbit < db->maxbno && getdbit(db, dbit))
		dbit = 2 * dbit + ((hash & ((long) 1 << hbit++)) ? 2 : 1);

	debug(("dbit: %d...", dbit));

	db->curbit = dbit;
	db->hmask = masks[hbit];

	pagb = hash & db->hmask;
/*
 * see if the block we need is already in memory.
 * note: this lookaside cache has about 10% hit rate.
 */
	if (pagb != db->pagbno) { 
/*
 * note: here, we assume a "hole" is read as 0s.
 * if not, must zero pagbuf first.
 */
		(void) memset(db->pagbuf, 0, PBLKSIZ);

		if (lseek(db->pagf, OFF_PAG(pagb), SEEK_SET) < 0
		    || read(db->pagf, db->pagbuf, PBLKSIZ) < 0)
			return 0;
		if (!chkpage(db->pagbuf)) {
			return 0;
		}
		db->pagbno = pagb;

		debug(("pag read: %d\n", pagb));
	}
	return 1;
}

static int
getdbit(db, dbit)
register DBM *db;
register long dbit;
{
	register long c;
	register long dirb;

	c = dbit / BYTESIZ;
	dirb = c / DBLKSIZ;

	if (dirb != db->dirbno) {
		if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
		    || read(db->dirf, db->dirbuf, DBLKSIZ) < 0)
			return 0;
		db->dirbno = dirb;

		debug(("dir read: %d\n", dirb));
	}

	return db->dirbuf[c % DBLKSIZ] & (1 << (dbit % BYTESIZ));
}

static int
setdbit(db, dbit)
register DBM *db;
register long dbit;
{
	register long c;
	register long dirb;

	c = dbit / BYTESIZ;
	dirb = c / DBLKSIZ;

	if (dirb != db->dirbno) {
		if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
		    || read(db->dirf, db->dirbuf, DBLKSIZ) < 0)
			return 0;
		db->dirbno = dirb;

		debug(("dir read: %d\n", dirb));
	}

	db->dirbuf[c % DBLKSIZ] |= (1 << (dbit % BYTESIZ));

	if (dbit >= db->maxbno)
		db->maxbno += (long) DBLKSIZ * BYTESIZ;

	if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
	    || write(db->dirf, db->dirbuf, DBLKSIZ) < 0)
		return 0;

	return 1;
}

/*
 * getnext - get the next key in the page, and if done with
 * the page, try the next page in sequence
 */
static datum
getnext(db)
register DBM *db;
{
	datum key;

	for (;;) {
		db->keyptr++;
		key = getnkey(db->pagbuf, db->keyptr);
		if (key.dptr != NULL)
			return key;
/*
 * we either run out, or there is nothing on this page..
 * try the next one... If we lost our position on the
 * file, we will have to seek.
 */
		db->keyptr = 0;
		if (db->pagbno != db->blkptr++)
			if (lseek(db->pagf, OFF_PAG(db->blkptr), SEEK_SET) < 0)
				break;
		db->pagbno = db->blkptr;
		if (read(db->pagf, db->pagbuf, PBLKSIZ) <= 0)
			break;
		if (!chkpage(db->pagbuf)) {
			break;
		}
	}

	return ioerr(db), nullitem;
}

/* pair.c */
/*
 * sdbm - ndbm work-alike hashed database library
 * based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
 * author: oz@nexus.yorku.ca
 * status: public domain.
 *
 * page-level routines
 */

#ifndef lint
/*char pair_rcsid[] = "$Id$";*/
#endif

#ifndef BSD42
/*#include <memory.h>*/
#endif

#define exhash(item)	sdbm_hash((item).dptr, (item).dsize)

/* 
 * forward 
 */
static int seepair proto((char *, int, char *, int));

/*
 * page format:
 *	+------------------------------+
 * ino	| n | keyoff | datoff | keyoff |
 * 	+------------+--------+--------+
 *	| datoff | - - - ---->	       |
 *	+--------+---------------------+
 *	|	 F R E E A R E A       |
 *	+--------------+---------------+
 *	|  <---- - - - | data          |
 *	+--------+-----+----+----------+
 *	|  key   | data     | key      |
 *	+--------+----------+----------+
 *
 * calculating the offsets for free area:  if the number
 * of entries (ino[0]) is zero, the offset to the END of
 * the free area is the block size. Otherwise, it is the
 * nth (ino[ino[0]]) entry's offset.
 */

static int
fitpair(pag, need)
char *pag;
int need;
{
	register int n;
	register int off;
	register int free;
	register short *ino = (short *) pag;

	off = ((n = GET_SHORT(ino,0)) > 0) ? GET_SHORT(ino,n) : PBLKSIZ;
	free = off - (n + 1) * sizeof(short);
	need += 2 * sizeof(short);

	debug(("free %d need %d\n", free, need));

	return need <= free;
}

static void
putpair(pag, key, val)
char *pag;
datum key;
datum val;
{
	register int n;
	register int off;
	register short *ino = (short *) pag;

	off = ((n = GET_SHORT(ino,0)) > 0) ? GET_SHORT(ino,n) : PBLKSIZ;
/*
 * enter the key first
 */
	off -= key.dsize;
	if (key.dsize)
		(void) memcpy(pag + off, key.dptr, key.dsize);
	PUT_SHORT(ino,n + 1,off);
/*
 * now the data
 */
	off -= val.dsize;
	if (val.dsize)
		(void) memcpy(pag + off, val.dptr, val.dsize);
	PUT_SHORT(ino,n + 2,off);
/*
 * adjust item count
 */
	PUT_SHORT(ino,0,GET_SHORT(ino,0) + 2);
}

static datum
getpair(pag, key)
char *pag;
datum key;
{
	register int i;
	register int n;
	datum val;
	register short *ino = (short *) pag;

	if ((n = GET_SHORT(ino,0)) == 0)
		return nullitem;

	if ((i = seepair(pag, n, key.dptr, key.dsize)) == 0)
		return nullitem;

	val.dptr = pag + GET_SHORT(ino,i + 1);
	val.dsize = GET_SHORT(ino,i) - GET_SHORT(ino,i + 1);
	return val;
}

#ifdef SEEDUPS
static int
duppair(pag, key)
char *pag;
datum key;
{
	register short *ino = (short *) pag;
	return GET_SHORT(ino,0) > 0 &&
		   seepair(pag, GET_SHORT(ino,0), key.dptr, key.dsize) > 0;
}
#endif

static datum
getnkey(pag, num)
char *pag;
int num;
{
	datum key;
	register int off;
	register short *ino = (short *) pag;

	num = num * 2 - 1;
	if (GET_SHORT(ino,0) == 0 || num > GET_SHORT(ino,0))
		return nullitem;

	off = (num > 1) ? GET_SHORT(ino,num - 1) : PBLKSIZ;

	key.dptr = pag + GET_SHORT(ino,num);
	key.dsize = off - GET_SHORT(ino,num);

	return key;
}

static int
delpair(pag, key)
char *pag;
datum key;
{
	register int n;
	register int i;
	register short *ino = (short *) pag;

	if ((n = GET_SHORT(ino,0)) == 0)
		return 0;

	if ((i = seepair(pag, n, key.dptr, key.dsize)) == 0)
		return 0;
/*
 * found the key. if it is the last entry
 * [i.e. i == n - 1] we just adjust the entry count.
 * hard case: move all data down onto the deleted pair,
 * shift offsets onto deleted offsets, and adjust them.
 * [note: 0 < i < n]
 */
	if (i < n - 1) {
		register int m;
		register char *dst = pag + (i == 1 ? PBLKSIZ : GET_SHORT(ino,i - 1));
		register char *src = pag + GET_SHORT(ino,i + 1);
		register int   zoo = dst - src;

		debug(("free-up %d ", zoo));
/*
 * shift data/keys down
 */
		m = GET_SHORT(ino,i + 1) - GET_SHORT(ino,n);
#ifdef DUFF
#define MOVB 	*--dst = *--src

		if (m > 0) {
			register int loop = (m + 8 - 1) >> 3;

			switch (m & (8 - 1)) {
			case 0:	do {
				MOVB;	case 7:	MOVB;
			case 6:	MOVB;	case 5:	MOVB;
			case 4:	MOVB;	case 3:	MOVB;
			case 2:	MOVB;	case 1:	MOVB;
				} while (--loop);
			}
		}
#else
#ifdef MEMMOVE
		memmove(dst, src, m);
#else
		while (m--)
			*--dst = *--src;
#endif
#endif
/*
 * adjust offset index up
 */
		while (i < n - 1) {
			PUT_SHORT(ino,i, GET_SHORT(ino,i + 2) + zoo);
			i++;
		}
	}
	PUT_SHORT(ino, 0, GET_SHORT(ino, 0) - 2);
	return 1;
}

/*
 * search for the key in the page.
 * return offset index in the range 0 < i < n.
 * return 0 if not found.
 */
static int
seepair(pag, n, key, siz)
char *pag;
register int n;
register char *key;
register int siz;
{
	register int i;
	register int off = PBLKSIZ;
	register short *ino = (short *) pag;

	for (i = 1; i < n; i += 2) {
		if (siz == off - GET_SHORT(ino,i) &&
		    memcmp(key, pag + GET_SHORT(ino,i), siz) == 0)
			return i;
		off = GET_SHORT(ino,i + 1);
	}
	return 0;
}

static void
splpage(pag, new, sbit)
char *pag;
char *new;
long sbit;
{
	datum key;
	datum val;

	register int n;
	register int off = PBLKSIZ;
	char cur[PBLKSIZ];
	register short *ino = (short *) cur;

	(void) memcpy(cur, pag, PBLKSIZ);
	(void) memset(pag, 0, PBLKSIZ);
	(void) memset(new, 0, PBLKSIZ);

	n = GET_SHORT(ino,0);
	for (ino++; n > 0; ino += 2) {
		key.dptr = cur + GET_SHORT(ino,0); 
		key.dsize = off - GET_SHORT(ino,0);
		val.dptr = cur + GET_SHORT(ino,1);
		val.dsize = GET_SHORT(ino,0) - GET_SHORT(ino,1);
/*
 * select the page pointer (by looking at sbit) and insert
 */
		(void) putpair((exhash(key) & sbit) ? new : pag, key, val);

		off = GET_SHORT(ino,1);
		n -= 2;
	}

	debug(("%d split %d/%d\n", ((short *) cur)[0] / 2, 
	       ((short *) new)[0] / 2,
	       ((short *) pag)[0] / 2));
}

/*
 * check page sanity: 
 * number of entries should be something
 * reasonable, and all offsets in the index should be in order.
 * this could be made more rigorous.
 */
static int
chkpage(pag)
char *pag;
{
	register int n;
	register int off;
	register short *ino = (short *) pag;

	if ((n = GET_SHORT(ino,0)) < 0 || n > PBLKSIZ / sizeof(short))
		return 0;

	if (n > 0) {
		off = PBLKSIZ;
		for (ino++; n > 0; ino += 2) {
			if (GET_SHORT(ino,0) > off || GET_SHORT(ino,1) > off ||
			    GET_SHORT(ino,1) > GET_SHORT(ino,0))
				return 0;
			off = GET_SHORT(ino,1);
			n -= 2;
		}
	}
	return 1;
}

/* hash.c */
/*
 * sdbm - ndbm work-alike hashed database library
 * based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
 * author: oz@nexus.yorku.ca
 * status: public domain. keep it that way.
 *
 * hashing routine
 */

/*
 * polynomial conversion ignoring overflows
 * [this seems to work remarkably well, in fact better
 * then the ndbm hash function. Replace at your own risk]
 * use: 65599	nice.
 *      65587   even better. 
 */
long
sdbm_hash(str, len)
register char *str;
register int len;
{
	register unsigned long n = 0;

#ifdef DUFF

#define HASHC	n = *str++ + 65599 * n

	if (len > 0) {
		register int loop = (len + 8 - 1) >> 3;

		switch(len & (8 - 1)) {
		case 0:	do {
			HASHC;	case 7:	HASHC;
		case 6:	HASHC;	case 5:	HASHC;
		case 4:	HASHC;	case 3:	HASHC;
		case 2:	HASHC;	case 1:	HASHC;
			} while (--loop);
		}

	}
#else
	while (len--)
		n = ((*str++) & 255) + 65587L * n;
#endif
	return n;
}