summaryrefslogtreecommitdiff
path: root/src/memfile.c
blob: 4fe329439e7c9381502ba426ffa5496e89ceb287 (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
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
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
/* vi:set ts=8 sts=4 sw=4 noet:
 *
 * VIM - Vi IMproved	by Bram Moolenaar
 *
 * Do ":help uganda"  in Vim to read copying and usage conditions.
 * Do ":help credits" in Vim to see a list of people who contributed.
 * See README.txt for an overview of the Vim source code.
 */

/*
 * memfile.c: Contains the functions for handling blocks of memory which can
 * be stored in a file. This is the implementation of a sort of virtual memory.
 *
 * A memfile consists of a sequence of blocks. The blocks numbered from 0
 * upwards have been assigned a place in the actual file. The block number
 * is equal to the page number in the file. The
 * blocks with negative numbers are currently in memory only. They can be
 * assigned a place in the file when too much memory is being used. At that
 * moment they get a new, positive, number. A list is used for translation of
 * negative to positive numbers.
 *
 * The size of a block is a multiple of a page size, normally the page size of
 * the device the file is on. Most blocks are 1 page long. A Block of multiple
 * pages is used for a line that does not fit in a single page.
 *
 * Each block can be in memory and/or in a file. The block stays in memory
 * as long as it is locked. If it is no longer locked it can be swapped out to
 * the file. It is only written to the file if it has been changed.
 *
 * Under normal operation the file is created when opening the memory file and
 * deleted when closing the memory file. Only with recovery an existing memory
 * file is opened.
 */

#include "vim.h"

/*
 * Some systems have the page size in statfs.f_bsize, some in stat.st_blksize
 */
#ifdef HAVE_ST_BLKSIZE
# define STATFS stat
# define F_BSIZE st_blksize
# define fstatfs(fd, buf, len, nul) mch_fstat((fd), (buf))
#else
# ifdef HAVE_SYS_STATFS_H
#  include <sys/statfs.h>
#  define STATFS statfs
#  define F_BSIZE f_bsize
#  ifdef __MINT__		// do we still need this?
#   define fstatfs(fd, buf, len, nul) mch_fstat((fd), (buf))
#  endif
# endif
#endif

/*
 * for Amiga Dos 2.0x we use Flush
 */
#ifdef AMIGA
# ifdef FEAT_ARP
extern int dos2;			// this is in os_amiga.c
# endif
# ifdef SASC
#  include <proto/dos.h>
#  include <ios1.h>			// for chkufb()
# endif
#endif

#define MEMFILE_PAGE_SIZE 4096		// default page size

static long_u	total_mem_used = 0;	// total memory used for memfiles

static void mf_ins_hash(memfile_T *, bhdr_T *);
static void mf_rem_hash(memfile_T *, bhdr_T *);
static bhdr_T *mf_find_hash(memfile_T *, blocknr_T);
static void mf_ins_used(memfile_T *, bhdr_T *);
static void mf_rem_used(memfile_T *, bhdr_T *);
static bhdr_T *mf_release(memfile_T *, int);
static bhdr_T *mf_alloc_bhdr(memfile_T *, int);
static void mf_free_bhdr(bhdr_T *);
static void mf_ins_free(memfile_T *, bhdr_T *);
static bhdr_T *mf_rem_free(memfile_T *);
static int  mf_read(memfile_T *, bhdr_T *);
static int  mf_write(memfile_T *, bhdr_T *);
static int  mf_write_block(memfile_T *mfp, bhdr_T *hp, off_T offset, unsigned size);
static int  mf_trans_add(memfile_T *, bhdr_T *);
static void mf_do_open(memfile_T *, char_u *, int);
static void mf_hash_init(mf_hashtab_T *);
static void mf_hash_free(mf_hashtab_T *);
static void mf_hash_free_all(mf_hashtab_T *);
static mf_hashitem_T *mf_hash_find(mf_hashtab_T *, blocknr_T);
static void mf_hash_add_item(mf_hashtab_T *, mf_hashitem_T *);
static void mf_hash_rem_item(mf_hashtab_T *, mf_hashitem_T *);
static int mf_hash_grow(mf_hashtab_T *);

/*
 * The functions for using a memfile:
 *
 * mf_open()	    open a new or existing memfile
 * mf_open_file()   open a swap file for an existing memfile
 * mf_close()	    close (and delete) a memfile
 * mf_new()	    create a new block in a memfile and lock it
 * mf_get()	    get an existing block and lock it
 * mf_put()	    unlock a block, may be marked for writing
 * mf_free()	    remove a block
 * mf_sync()	    sync changed parts of memfile to disk
 * mf_release_all() release as much memory as possible
 * mf_trans_del()   may translate negative to positive block number
 * mf_fullname()    make file name full path (use before first :cd)
 */

/*
 * Open an existing or new memory block file.
 *
 *  fname:	name of file to use (NULL means no file at all)
 *		Note: fname must have been allocated, it is not copied!
 *			If opening the file fails, fname is freed.
 *  flags:	flags for open() call
 *
 *  If fname != NULL and file cannot be opened, fail.
 *
 * return value: identifier for this memory block file.
 */
    memfile_T *
mf_open(char_u *fname, int flags)
{
    memfile_T		*mfp;
    off_T		size;
#if defined(STATFS) && defined(UNIX) && !defined(__QNX__) && !defined(__minix)
# define USE_FSTATFS
    struct STATFS	stf;
#endif

    if ((mfp = ALLOC_ONE(memfile_T)) == NULL)
	return NULL;

    if (fname == NULL)	    // no file for this memfile, use memory only
    {
	mfp->mf_fname = NULL;
	mfp->mf_ffname = NULL;
	mfp->mf_fd = -1;
    }
    else
    {
	mf_do_open(mfp, fname, flags);	// try to open the file

	// if the file cannot be opened, return here
	if (mfp->mf_fd < 0)
	{
	    vim_free(mfp);
	    return NULL;
	}
    }

    mfp->mf_free_first = NULL;		// free list is empty
    mfp->mf_used_first = NULL;		// used list is empty
    mfp->mf_used_last = NULL;
    mfp->mf_dirty = FALSE;
    mfp->mf_used_count = 0;
    mf_hash_init(&mfp->mf_hash);
    mf_hash_init(&mfp->mf_trans);
    mfp->mf_page_size = MEMFILE_PAGE_SIZE;
#ifdef FEAT_CRYPT
    mfp->mf_old_key = NULL;
#endif

#ifdef USE_FSTATFS
    /*
     * Try to set the page size equal to the block size of the device.
     * Speeds up I/O a lot.
     * When recovering, the actual block size will be retrieved from block 0
     * in ml_recover().  The size used here may be wrong, therefore
     * mf_blocknr_max must be rounded up.
     */
    if (mfp->mf_fd >= 0
	    && fstatfs(mfp->mf_fd, &stf, sizeof(struct statfs), 0) == 0
	    && stf.F_BSIZE >= MIN_SWAP_PAGE_SIZE
	    && stf.F_BSIZE <= MAX_SWAP_PAGE_SIZE)
	mfp->mf_page_size = stf.F_BSIZE;
#endif

    if (mfp->mf_fd < 0 || (flags & (O_TRUNC|O_EXCL))
		  || (size = vim_lseek(mfp->mf_fd, (off_T)0L, SEEK_END)) <= 0)
	mfp->mf_blocknr_max = 0;	// no file or empty file
    else
	mfp->mf_blocknr_max = (blocknr_T)((size + mfp->mf_page_size - 1)
							 / mfp->mf_page_size);
    mfp->mf_blocknr_min = -1;
    mfp->mf_neg_count = 0;
    mfp->mf_infile_count = mfp->mf_blocknr_max;

    /*
     * Compute maximum number of pages ('maxmem' is in Kbyte):
     *	'mammem' * 1Kbyte / page-size-in-bytes.
     * Avoid overflow by first reducing page size as much as possible.
     */
    {
	int	    shift = 10;
	unsigned    page_size = mfp->mf_page_size;

	while (shift > 0 && (page_size & 1) == 0)
	{
	    page_size = page_size >> 1;
	    --shift;
	}
	mfp->mf_used_count_max = (p_mm << shift) / page_size;
	if (mfp->mf_used_count_max < 10)
	    mfp->mf_used_count_max = 10;
    }

    return mfp;
}

/*
 * Open a file for an existing memfile.  Used when updatecount set from 0 to
 * some value.
 * If the file already exists, this fails.
 * "fname" is the name of file to use (NULL means no file at all)
 * Note: "fname" must have been allocated, it is not copied!  If opening the
 * file fails, "fname" is freed.
 *
 * return value: FAIL if file could not be opened, OK otherwise
 */
    int
mf_open_file(memfile_T *mfp, char_u *fname)
{
    mf_do_open(mfp, fname, O_RDWR|O_CREAT|O_EXCL); // try to open the file

    if (mfp->mf_fd < 0)
	return FAIL;

    mfp->mf_dirty = TRUE;
    return OK;
}

/*
 * Close a memory file and delete the associated file if 'del_file' is TRUE.
 */
    void
mf_close(memfile_T *mfp, int del_file)
{
    bhdr_T	*hp, *nextp;

    if (mfp == NULL)		    // safety check
	return;
    if (mfp->mf_fd >= 0)
    {
	if (close(mfp->mf_fd) < 0)
	    emsg(_(e_swapclose));
    }
    if (del_file && mfp->mf_fname != NULL)
	mch_remove(mfp->mf_fname);
					    // free entries in used list
    for (hp = mfp->mf_used_first; hp != NULL; hp = nextp)
    {
	total_mem_used -= hp->bh_page_count * mfp->mf_page_size;
	nextp = hp->bh_next;
	mf_free_bhdr(hp);
    }
    while (mfp->mf_free_first != NULL)	    // free entries in free list
	vim_free(mf_rem_free(mfp));
    mf_hash_free(&mfp->mf_hash);
    mf_hash_free_all(&mfp->mf_trans);	    // free hashtable and its items
    vim_free(mfp->mf_fname);
    vim_free(mfp->mf_ffname);
    vim_free(mfp);
}

/*
 * Close the swap file for a memfile.  Used when 'swapfile' is reset.
 */
    void
mf_close_file(
    buf_T	*buf,
    int		getlines)	// get all lines into memory?
{
    memfile_T	*mfp;
    linenr_T	lnum;

    mfp = buf->b_ml.ml_mfp;
    if (mfp == NULL || mfp->mf_fd < 0)		// nothing to close
	return;

    if (getlines)
    {
	// get all blocks in memory by accessing all lines (clumsy!)
	mf_dont_release = TRUE;
	for (lnum = 1; lnum <= buf->b_ml.ml_line_count; ++lnum)
	    (void)ml_get_buf(buf, lnum, FALSE);
	mf_dont_release = FALSE;
	// TODO: should check if all blocks are really in core
    }

    if (close(mfp->mf_fd) < 0)			// close the file
	emsg(_(e_swapclose));
    mfp->mf_fd = -1;

    if (mfp->mf_fname != NULL)
    {
	mch_remove(mfp->mf_fname);		// delete the swap file
	VIM_CLEAR(mfp->mf_fname);
	VIM_CLEAR(mfp->mf_ffname);
    }
}

/*
 * Set new size for a memfile.  Used when block 0 of a swapfile has been read
 * and the size it indicates differs from what was guessed.
 */
    void
mf_new_page_size(memfile_T *mfp, unsigned new_size)
{
    // Correct the memory used for block 0 to the new size, because it will be
    // freed with that size later on.
    total_mem_used += new_size - mfp->mf_page_size;
    mfp->mf_page_size = new_size;
}

/*
 * get a new block
 *
 *   negative: TRUE if negative block number desired (data block)
 */
    bhdr_T *
mf_new(memfile_T *mfp, int negative, int page_count)
{
    bhdr_T	*hp;	// new bhdr_T
    bhdr_T	*freep;	// first block in free list
    char_u	*p;

    /*
     * If we reached the maximum size for the used memory blocks, release one
     * If a bhdr_T is returned, use it and adjust the page_count if necessary.
     */
    hp = mf_release(mfp, page_count);

/*
 * Decide on the number to use:
 * If there is a free block, use its number.
 * Otherwise use mf_block_min for a negative number, mf_block_max for
 * a positive number.
 */
    freep = mfp->mf_free_first;
    if (!negative && freep != NULL && freep->bh_page_count >= page_count)
    {
	/*
	 * If the block in the free list has more pages, take only the number
	 * of pages needed and allocate a new bhdr_T with data
	 *
	 * If the number of pages matches and mf_release() did not return a
	 * bhdr_T, use the bhdr_T from the free list and allocate the data
	 *
	 * If the number of pages matches and mf_release() returned a bhdr_T,
	 * just use the number and free the bhdr_T from the free list
	 */
	if (freep->bh_page_count > page_count)
	{
	    if (hp == NULL && (hp = mf_alloc_bhdr(mfp, page_count)) == NULL)
		return NULL;
	    hp->bh_bnum = freep->bh_bnum;
	    freep->bh_bnum += page_count;
	    freep->bh_page_count -= page_count;
	}
	else if (hp == NULL)	    // need to allocate memory for this block
	{
	    if ((p = alloc(mfp->mf_page_size * page_count)) == NULL)
		return NULL;
	    hp = mf_rem_free(mfp);
	    hp->bh_data = p;
	}
	else		    // use the number, remove entry from free list
	{
	    freep = mf_rem_free(mfp);
	    hp->bh_bnum = freep->bh_bnum;
	    vim_free(freep);
	}
    }
    else	// get a new number
    {
	if (hp == NULL && (hp = mf_alloc_bhdr(mfp, page_count)) == NULL)
	    return NULL;
	if (negative)
	{
	    hp->bh_bnum = mfp->mf_blocknr_min--;
	    mfp->mf_neg_count++;
	}
	else
	{
	    hp->bh_bnum = mfp->mf_blocknr_max;
	    mfp->mf_blocknr_max += page_count;
	}
    }
    hp->bh_flags = BH_LOCKED | BH_DIRTY;	// new block is always dirty
    mfp->mf_dirty = TRUE;
    hp->bh_page_count = page_count;
    mf_ins_used(mfp, hp);
    mf_ins_hash(mfp, hp);

    /*
     * Init the data to all zero, to avoid reading uninitialized data.
     * This also avoids that the passwd file ends up in the swap file!
     */
    (void)vim_memset((char *)(hp->bh_data), 0,
				      (size_t)mfp->mf_page_size * page_count);

    return hp;
}

/*
 * Get existing block "nr" with "page_count" pages.
 *
 * Note: The caller should first check a negative nr with mf_trans_del()
 */
    bhdr_T *
mf_get(memfile_T *mfp, blocknr_T nr, int page_count)
{
    bhdr_T    *hp;
						// doesn't exist
    if (nr >= mfp->mf_blocknr_max || nr <= mfp->mf_blocknr_min)
	return NULL;

    /*
     * see if it is in the cache
     */
    hp = mf_find_hash(mfp, nr);
    if (hp == NULL)	// not in the hash list
    {
	if (nr < 0 || nr >= mfp->mf_infile_count)   // can't be in the file
	    return NULL;

	// could check here if the block is in the free list

	/*
	 * Check if we need to flush an existing block.
	 * If so, use that block.
	 * If not, allocate a new block.
	 */
	hp = mf_release(mfp, page_count);
	if (hp == NULL && (hp = mf_alloc_bhdr(mfp, page_count)) == NULL)
	    return NULL;

	hp->bh_bnum = nr;
	hp->bh_flags = 0;
	hp->bh_page_count = page_count;
	if (mf_read(mfp, hp) == FAIL)	    // cannot read the block!
	{
	    mf_free_bhdr(hp);
	    return NULL;
	}
    }
    else
    {
	mf_rem_used(mfp, hp);	// remove from list, insert in front below
	mf_rem_hash(mfp, hp);
    }

    hp->bh_flags |= BH_LOCKED;
    mf_ins_used(mfp, hp);	// put in front of used list
    mf_ins_hash(mfp, hp);	// put in front of hash list

    return hp;
}

/*
 * release the block *hp
 *
 *   dirty: Block must be written to file later
 *   infile: Block should be in file (needed for recovery)
 *
 *  no return value, function cannot fail
 */
    void
mf_put(
    memfile_T	*mfp,
    bhdr_T	*hp,
    int		dirty,
    int		infile)
{
    int		flags;

    flags = hp->bh_flags;

    if ((flags & BH_LOCKED) == 0)
	iemsg(_("E293: block was not locked"));
    flags &= ~BH_LOCKED;
    if (dirty)
    {
	flags |= BH_DIRTY;
	mfp->mf_dirty = TRUE;
    }
    hp->bh_flags = flags;
    if (infile)
	mf_trans_add(mfp, hp);	    // may translate negative in positive nr
}

/*
 * block *hp is no longer in used, may put it in the free list of memfile *mfp
 */
    void
mf_free(memfile_T *mfp, bhdr_T *hp)
{
    vim_free(hp->bh_data);	// free the memory
    mf_rem_hash(mfp, hp);	// get *hp out of the hash list
    mf_rem_used(mfp, hp);	// get *hp out of the used list
    if (hp->bh_bnum < 0)
    {
	vim_free(hp);		// don't want negative numbers in free list
	mfp->mf_neg_count--;
    }
    else
	mf_ins_free(mfp, hp);	// put *hp in the free list
}

#if defined(__MORPHOS__) && defined(__libnix__)
// function is missing in MorphOS libnix version
extern unsigned long *__stdfiledes;

    static unsigned long
fdtofh(int filedescriptor)
{
    return __stdfiledes[filedescriptor];
}
#endif

/*
 * Sync the memory file *mfp to disk.
 * Flags:
 *  MFS_ALL	If not given, blocks with negative numbers are not synced,
 *		even when they are dirty!
 *  MFS_STOP	Stop syncing when a character becomes available, but sync at
 *		least one block.
 *  MFS_FLUSH	Make sure buffers are flushed to disk, so they will survive a
 *		system crash.
 *  MFS_ZERO	Only write block 0.
 *
 * Return FAIL for failure, OK otherwise
 */
    int
mf_sync(memfile_T *mfp, int flags)
{
    int		status;
    bhdr_T	*hp;
    int		got_int_save = got_int;

    if (mfp->mf_fd < 0)	    // there is no file, nothing to do
    {
	mfp->mf_dirty = FALSE;
	return FAIL;
    }

    // Only a CTRL-C while writing will break us here, not one typed
    // previously.
    got_int = FALSE;

    /*
     * sync from last to first (may reduce the probability of an inconsistent
     * file) If a write fails, it is very likely caused by a full filesystem.
     * Then we only try to write blocks within the existing file. If that also
     * fails then we give up.
     */
    status = OK;
    for (hp = mfp->mf_used_last; hp != NULL; hp = hp->bh_prev)
	if (((flags & MFS_ALL) || hp->bh_bnum >= 0)
		&& (hp->bh_flags & BH_DIRTY)
		&& (status == OK || (hp->bh_bnum >= 0
		    && hp->bh_bnum < mfp->mf_infile_count)))
	{
	    if ((flags & MFS_ZERO) && hp->bh_bnum != 0)
		continue;
	    if (mf_write(mfp, hp) == FAIL)
	    {
		if (status == FAIL)	// double error: quit syncing
		    break;
		status = FAIL;
	    }
	    if (flags & MFS_STOP)
	    {
		// Stop when char available now.
		if (ui_char_avail())
		    break;
	    }
	    else
		ui_breakcheck();
	    if (got_int)
		break;
	}

    /*
     * If the whole list is flushed, the memfile is not dirty anymore.
     * In case of an error this flag is also set, to avoid trying all the time.
     */
    if (hp == NULL || status == FAIL)
	mfp->mf_dirty = FALSE;

    if ((flags & MFS_FLUSH) && *p_sws != NUL)
    {
#if defined(UNIX)
# ifdef HAVE_FSYNC
	/*
	 * most Unixes have the very useful fsync() function, just what we need.
	 */
	if (STRCMP(p_sws, "fsync") == 0)
	{
	    if (vim_fsync(mfp->mf_fd))
		status = FAIL;
	}
	else
# endif
	    // OpenNT is strictly POSIX (Benzinger)
	    // Tandem/Himalaya NSK-OSS doesn't have sync()
	    // No sync() on Stratus VOS
# if defined(__OPENNT) || defined(__TANDEM) || defined(__VOS__)
	    fflush(NULL);
# else
	    sync();
# endif
#endif
#ifdef VMS
	if (STRCMP(p_sws, "fsync") == 0)
	{
	    if (vim_fsync(mfp->mf_fd))
		status = FAIL;
	}
#endif
#ifdef MSWIN
	if (_commit(mfp->mf_fd))
	    status = FAIL;
#endif
#ifdef AMIGA
# if defined(__AROS__) || defined(__amigaos4__)
	if (vim_fsync(mfp->mf_fd) != 0)
	    status = FAIL;
# else
	/*
	 * Flush() only exists for AmigaDos 2.0.
	 * For 1.3 it should be done with close() + open(), but then the risk
	 * is that the open() may fail and lose the file....
	 */
#  ifdef FEAT_ARP
	if (dos2)
#  endif
#  ifdef SASC
	{
	    struct UFB *fp = chkufb(mfp->mf_fd);

	    if (fp != NULL)
		Flush(fp->ufbfh);
	}
#  else
#   if defined(_DCC) || defined(__GNUC__) || defined(__MORPHOS__)
	{
#    if defined(__GNUC__) && !defined(__MORPHOS__) && defined(__libnix__)
	    // Have function (in libnix at least),
	    // but ain't got no prototype anywhere.
	    extern unsigned long fdtofh(int filedescriptor);
#    endif
#    if !defined(__libnix__)
	    fflush(NULL);
#    else
	    BPTR fh = (BPTR)fdtofh(mfp->mf_fd);

	    if (fh != 0)
		Flush(fh);
#    endif
	}
#   else // assume Manx
	    Flush(_devtab[mfp->mf_fd].fd);
#   endif
#  endif
# endif
#endif // AMIGA
    }

    got_int |= got_int_save;

    return status;
}

/*
 * For all blocks in memory file *mfp that have a positive block number set
 * the dirty flag.  These are blocks that need to be written to a newly
 * created swapfile.
 */
    void
mf_set_dirty(memfile_T *mfp)
{
    bhdr_T	*hp;

    for (hp = mfp->mf_used_last; hp != NULL; hp = hp->bh_prev)
	if (hp->bh_bnum > 0)
	    hp->bh_flags |= BH_DIRTY;
    mfp->mf_dirty = TRUE;
}

/*
 * insert block *hp in front of hashlist of memfile *mfp
 */
    static void
mf_ins_hash(memfile_T *mfp, bhdr_T *hp)
{
    mf_hash_add_item(&mfp->mf_hash, (mf_hashitem_T *)hp);
}

/*
 * remove block *hp from hashlist of memfile list *mfp
 */
    static void
mf_rem_hash(memfile_T *mfp, bhdr_T *hp)
{
    mf_hash_rem_item(&mfp->mf_hash, (mf_hashitem_T *)hp);
}

/*
 * look in hash lists of memfile *mfp for block header with number 'nr'
 */
    static bhdr_T *
mf_find_hash(memfile_T *mfp, blocknr_T nr)
{
    return (bhdr_T *)mf_hash_find(&mfp->mf_hash, nr);
}

/*
 * insert block *hp in front of used list of memfile *mfp
 */
    static void
mf_ins_used(memfile_T *mfp, bhdr_T *hp)
{
    hp->bh_next = mfp->mf_used_first;
    mfp->mf_used_first = hp;
    hp->bh_prev = NULL;
    if (hp->bh_next == NULL)	    // list was empty, adjust last pointer
	mfp->mf_used_last = hp;
    else
	hp->bh_next->bh_prev = hp;
    mfp->mf_used_count += hp->bh_page_count;
    total_mem_used += hp->bh_page_count * mfp->mf_page_size;
}

/*
 * remove block *hp from used list of memfile *mfp
 */
    static void
mf_rem_used(memfile_T *mfp, bhdr_T *hp)
{
    if (hp->bh_next == NULL)	    // last block in used list
	mfp->mf_used_last = hp->bh_prev;
    else
	hp->bh_next->bh_prev = hp->bh_prev;
    if (hp->bh_prev == NULL)	    // first block in used list
	mfp->mf_used_first = hp->bh_next;
    else
	hp->bh_prev->bh_next = hp->bh_next;
    mfp->mf_used_count -= hp->bh_page_count;
    total_mem_used -= hp->bh_page_count * mfp->mf_page_size;
}

/*
 * Release the least recently used block from the used list if the number
 * of used memory blocks gets to big.
 *
 * Return the block header to the caller, including the memory block, so
 * it can be re-used. Make sure the page_count is right.
 *
 * Returns NULL if no block is released.
 */
    static bhdr_T *
mf_release(memfile_T *mfp, int page_count)
{
    bhdr_T	*hp;
    int		need_release;
    buf_T	*buf;

    // don't release while in mf_close_file()
    if (mf_dont_release)
	return NULL;

    /*
     * Need to release a block if the number of blocks for this memfile is
     * higher than the maximum or total memory used is over 'maxmemtot'
     */
    need_release = ((mfp->mf_used_count >= mfp->mf_used_count_max)
				  || (total_mem_used >> 10) >= (long_u)p_mmt);

    /*
     * Try to create a swap file if the amount of memory used is getting too
     * high.
     */
    if (mfp->mf_fd < 0 && need_release && p_uc)
    {
	// find for which buffer this memfile is
	FOR_ALL_BUFFERS(buf)
	    if (buf->b_ml.ml_mfp == mfp)
		break;
	if (buf != NULL && buf->b_may_swap)
	    ml_open_file(buf);
    }

    /*
     * don't release a block if
     *	there is no file for this memfile
     * or
     *	the number of blocks for this memfile is lower than the maximum
     *	  and
     *	total memory used is not up to 'maxmemtot'
     */
    if (mfp->mf_fd < 0 || !need_release)
	return NULL;

    for (hp = mfp->mf_used_last; hp != NULL; hp = hp->bh_prev)
	if (!(hp->bh_flags & BH_LOCKED))
	    break;
    if (hp == NULL)	// not a single one that can be released
	return NULL;

    /*
     * If the block is dirty, write it.
     * If the write fails we don't free it.
     */
    if ((hp->bh_flags & BH_DIRTY) && mf_write(mfp, hp) == FAIL)
	return NULL;

    mf_rem_used(mfp, hp);
    mf_rem_hash(mfp, hp);

    /*
     * If a bhdr_T is returned, make sure that the page_count of bh_data is
     * right
     */
    if (hp->bh_page_count != page_count)
    {
	vim_free(hp->bh_data);
	if ((hp->bh_data = alloc(mfp->mf_page_size * page_count)) == NULL)
	{
	    vim_free(hp);
	    return NULL;
	}
	hp->bh_page_count = page_count;
    }
    return hp;
}

/*
 * release as many blocks as possible
 * Used in case of out of memory
 *
 * return TRUE if any memory was released
 */
    int
mf_release_all(void)
{
    buf_T	*buf;
    memfile_T	*mfp;
    bhdr_T	*hp;
    int		retval = FALSE;

    FOR_ALL_BUFFERS(buf)
    {
	mfp = buf->b_ml.ml_mfp;
	if (mfp != NULL)
	{
	    // If no swap file yet, may open one
	    if (mfp->mf_fd < 0 && buf->b_may_swap)
		ml_open_file(buf);

	    // only if there is a swapfile
	    if (mfp->mf_fd >= 0)
	    {
		for (hp = mfp->mf_used_last; hp != NULL; )
		{
		    if (!(hp->bh_flags & BH_LOCKED)
			    && (!(hp->bh_flags & BH_DIRTY)
				|| mf_write(mfp, hp) != FAIL))
		    {
			mf_rem_used(mfp, hp);
			mf_rem_hash(mfp, hp);
			mf_free_bhdr(hp);
			hp = mfp->mf_used_last;	// re-start, list was changed
			retval = TRUE;
		    }
		    else
			hp = hp->bh_prev;
		}
	    }
	}
    }
    return retval;
}

/*
 * Allocate a block header and a block of memory for it
 */
    static bhdr_T *
mf_alloc_bhdr(memfile_T *mfp, int page_count)
{
    bhdr_T	*hp;

    if ((hp = ALLOC_ONE(bhdr_T)) != NULL)
    {
	if ((hp->bh_data = alloc(mfp->mf_page_size * page_count)) == NULL)
	{
	    vim_free(hp);	    // not enough memory
	    return NULL;
	}
	hp->bh_page_count = page_count;
    }
    return hp;
}

/*
 * Free a block header and the block of memory for it
 */
    static void
mf_free_bhdr(bhdr_T *hp)
{
    vim_free(hp->bh_data);
    vim_free(hp);
}

/*
 * insert entry *hp in the free list
 */
    static void
mf_ins_free(memfile_T *mfp, bhdr_T *hp)
{
    hp->bh_next = mfp->mf_free_first;
    mfp->mf_free_first = hp;
}

/*
 * remove the first entry from the free list and return a pointer to it
 * Note: caller must check that mfp->mf_free_first is not NULL!
 */
    static bhdr_T *
mf_rem_free(memfile_T *mfp)
{
    bhdr_T	*hp;

    hp = mfp->mf_free_first;
    mfp->mf_free_first = hp->bh_next;
    return hp;
}

/*
 * read a block from disk
 *
 * Return FAIL for failure, OK otherwise
 */
    static int
mf_read(memfile_T *mfp, bhdr_T *hp)
{
    off_T	offset;
    unsigned	page_size;
    unsigned	size;

    if (mfp->mf_fd < 0)	    // there is no file, can't read
	return FAIL;

    page_size = mfp->mf_page_size;
    offset = (off_T)page_size * hp->bh_bnum;
    size = page_size * hp->bh_page_count;
    if (vim_lseek(mfp->mf_fd, offset, SEEK_SET) != offset)
    {
	PERROR(_("E294: Seek error in swap file read"));
	return FAIL;
    }
    if ((unsigned)read_eintr(mfp->mf_fd, hp->bh_data, size) != size)
    {
	PERROR(_("E295: Read error in swap file"));
	return FAIL;
    }

#ifdef FEAT_CRYPT
    // Decrypt if 'key' is set and this is a data block. And when changing the
    // key.
    if (*mfp->mf_buffer->b_p_key != NUL || mfp->mf_old_key != NULL)
	ml_decrypt_data(mfp, hp->bh_data, offset, size);
#endif

    return OK;
}

/*
 * write a block to disk
 *
 * Return FAIL for failure, OK otherwise
 */
    static int
mf_write(memfile_T *mfp, bhdr_T *hp)
{
    off_T	offset;	    // offset in the file
    blocknr_T	nr;	    // block nr which is being written
    bhdr_T	*hp2;
    unsigned	page_size;  // number of bytes in a page
    unsigned	page_count; // number of pages written
    unsigned	size;	    // number of bytes written

    if (mfp->mf_fd < 0 && !mfp->mf_reopen)
	// there is no file and there was no file, can't write
	return FAIL;

    if (hp->bh_bnum < 0)	// must assign file block number
	if (mf_trans_add(mfp, hp) == FAIL)
	    return FAIL;

    page_size = mfp->mf_page_size;

    /*
     * We don't want gaps in the file. Write the blocks in front of *hp
     * to extend the file.
     * If block 'mf_infile_count' is not in the hash list, it has been
     * freed. Fill the space in the file with data from the current block.
     */
    for (;;)
    {
	int attempt;

	nr = hp->bh_bnum;
	if (nr > mfp->mf_infile_count)		// beyond end of file
	{
	    nr = mfp->mf_infile_count;
	    hp2 = mf_find_hash(mfp, nr);	// NULL caught below
	}
	else
	    hp2 = hp;

	offset = (off_T)page_size * nr;
	if (hp2 == NULL)	    // freed block, fill with dummy data
	    page_count = 1;
	else
	    page_count = hp2->bh_page_count;
	size = page_size * page_count;

	for (attempt = 1; attempt <= 2; ++attempt)
	{
	    if (mfp->mf_fd >= 0)
	    {
		if (vim_lseek(mfp->mf_fd, offset, SEEK_SET) != offset)
		{
		    PERROR(_("E296: Seek error in swap file write"));
		    return FAIL;
		}
		if (mf_write_block(mfp,
				   hp2 == NULL ? hp : hp2, offset, size) == OK)
		    break;
	    }

	    if (attempt == 1)
	    {
		// If the swap file is on a network drive, and the network
		// gets disconnected and then re-connected, we can maybe fix it
		// by closing and then re-opening the file.
		if (mfp->mf_fd >= 0)
		    close(mfp->mf_fd);
		mfp->mf_fd = mch_open_rw((char *)mfp->mf_fname, mfp->mf_flags);
		mfp->mf_reopen = (mfp->mf_fd < 0);
	    }
	    if (attempt == 2 || mfp->mf_fd < 0)
	    {
		// Avoid repeating the error message, this mostly happens when
		// the disk is full. We give the message again only after a
		// successful write or when hitting a key. We keep on trying,
		// in case some space becomes available.
		if (!did_swapwrite_msg)
		    emsg(_("E297: Write error in swap file"));
		did_swapwrite_msg = TRUE;
		return FAIL;
	    }
	}

	did_swapwrite_msg = FALSE;
	if (hp2 != NULL)		    // written a non-dummy block
	    hp2->bh_flags &= ~BH_DIRTY;
					    // appended to the file
	if (nr + (blocknr_T)page_count > mfp->mf_infile_count)
	    mfp->mf_infile_count = nr + page_count;
	if (nr == hp->bh_bnum)		    // written the desired block
	    break;
    }
    return OK;
}

/*
 * Write block "hp" with data size "size" to file "mfp->mf_fd".
 * Takes care of encryption.
 * Return FAIL or OK.
 */
    static int
mf_write_block(
    memfile_T	*mfp,
    bhdr_T	*hp,
    off_T	offset UNUSED,
    unsigned	size)
{
    char_u	*data = hp->bh_data;
    int		result = OK;

#ifdef FEAT_CRYPT
    // Encrypt if 'key' is set and this is a data block.
    if (*mfp->mf_buffer->b_p_key != NUL)
    {
	data = ml_encrypt_data(mfp, data, offset, size);
	if (data == NULL)
	    return FAIL;
    }
#endif

    if ((unsigned)write_eintr(mfp->mf_fd, data, size) != size)
	result = FAIL;

#ifdef FEAT_CRYPT
    if (data != hp->bh_data)
	vim_free(data);
#endif

    return result;
}

/*
 * Make block number for *hp positive and add it to the translation list
 *
 * Return FAIL for failure, OK otherwise
 */
    static int
mf_trans_add(memfile_T *mfp, bhdr_T *hp)
{
    bhdr_T	*freep;
    blocknr_T	new_bnum;
    NR_TRANS	*np;
    int		page_count;

    if (hp->bh_bnum >= 0)		    // it's already positive
	return OK;

    if ((np = ALLOC_ONE(NR_TRANS)) == NULL)
	return FAIL;

/*
 * Get a new number for the block.
 * If the first item in the free list has sufficient pages, use its number
 * Otherwise use mf_blocknr_max.
 */
    freep = mfp->mf_free_first;
    page_count = hp->bh_page_count;
    if (freep != NULL && freep->bh_page_count >= page_count)
    {
	new_bnum = freep->bh_bnum;
	/*
	 * If the page count of the free block was larger, reduce it.
	 * If the page count matches, remove the block from the free list
	 */
	if (freep->bh_page_count > page_count)
	{
	    freep->bh_bnum += page_count;
	    freep->bh_page_count -= page_count;
	}
	else
	{
	    freep = mf_rem_free(mfp);
	    vim_free(freep);
	}
    }
    else
    {
	new_bnum = mfp->mf_blocknr_max;
	mfp->mf_blocknr_max += page_count;
    }

    np->nt_old_bnum = hp->bh_bnum;	    // adjust number
    np->nt_new_bnum = new_bnum;

    mf_rem_hash(mfp, hp);		    // remove from old hash list
    hp->bh_bnum = new_bnum;
    mf_ins_hash(mfp, hp);		    // insert in new hash list

    // Insert "np" into "mf_trans" hashtable with key "np->nt_old_bnum"
    mf_hash_add_item(&mfp->mf_trans, (mf_hashitem_T *)np);

    return OK;
}

/*
 * Lookup a translation from the trans lists and delete the entry.
 *
 * Return the positive new number when found, the old number when not found
 */
    blocknr_T
mf_trans_del(memfile_T *mfp, blocknr_T old_nr)
{
    NR_TRANS	*np;
    blocknr_T	new_bnum;

    np = (NR_TRANS *)mf_hash_find(&mfp->mf_trans, old_nr);

    if (np == NULL)		// not found
	return old_nr;

    mfp->mf_neg_count--;
    new_bnum = np->nt_new_bnum;

    // remove entry from the trans list
    mf_hash_rem_item(&mfp->mf_trans, (mf_hashitem_T *)np);

    vim_free(np);

    return new_bnum;
}

/*
 * Set mfp->mf_ffname according to mfp->mf_fname and some other things.
 * Only called when creating or renaming the swapfile.	Either way it's a new
 * name so we must work out the full path name.
 */
    void
mf_set_ffname(memfile_T *mfp)
{
    mfp->mf_ffname = FullName_save(mfp->mf_fname, FALSE);
}

/*
 * Make the name of the file used for the memfile a full path.
 * Used before doing a :cd
 */
    void
mf_fullname(memfile_T *mfp)
{
    if (mfp != NULL && mfp->mf_fname != NULL && mfp->mf_ffname != NULL)
    {
	vim_free(mfp->mf_fname);
	mfp->mf_fname = mfp->mf_ffname;
	mfp->mf_ffname = NULL;
    }
}

/*
 * return TRUE if there are any translations pending for 'mfp'
 */
    int
mf_need_trans(memfile_T *mfp)
{
    return (mfp->mf_fname != NULL && mfp->mf_neg_count > 0);
}

/*
 * Open a swap file for a memfile.
 * The "fname" must be in allocated memory, and is consumed (also when an
 * error occurs).
 */
    static void
mf_do_open(
    memfile_T	*mfp,
    char_u	*fname,
    int		flags)		// flags for open()
{
#ifdef HAVE_LSTAT
    stat_T	sb;
#endif

    mfp->mf_fname = fname;

    /*
     * Get the full path name before the open, because this is
     * not possible after the open on the Amiga.
     * fname cannot be NameBuff, because it must have been allocated.
     */
    mf_set_ffname(mfp);
#if defined(MSWIN)
    /*
     * A ":!cd e:xxx" may change the directory without us knowing, use the
     * full pathname always.  Careful: This frees fname!
     */
    mf_fullname(mfp);
#endif

#ifdef HAVE_LSTAT
    /*
     * Extra security check: When creating a swap file it really shouldn't
     * exist yet.  If there is a symbolic link, this is most likely an attack.
     */
    if ((flags & O_CREAT) && mch_lstat((char *)mfp->mf_fname, &sb) >= 0)
    {
	mfp->mf_fd = -1;
	emsg(_("E300: Swap file already exists (symlink attack?)"));
    }
    else
#endif
    {
	/*
	 * try to open the file
	 */
	flags |= O_EXTRA | O_NOFOLLOW;
#ifdef MSWIN
	// Prevent handle inheritance that cause problems with Cscope
	// (swap file may not be deleted if cscope connection was open after
	// the file)
	flags |= O_NOINHERIT;
#endif
	mfp->mf_flags = flags;
	mfp->mf_fd = mch_open_rw((char *)mfp->mf_fname, flags);
    }

    /*
     * If the file cannot be opened, use memory only
     */
    if (mfp->mf_fd < 0)
    {
	VIM_CLEAR(mfp->mf_fname);
	VIM_CLEAR(mfp->mf_ffname);
    }
    else
    {
#ifdef HAVE_FD_CLOEXEC
	int fdflags = fcntl(mfp->mf_fd, F_GETFD);
	if (fdflags >= 0 && (fdflags & FD_CLOEXEC) == 0)
	    (void)fcntl(mfp->mf_fd, F_SETFD, fdflags | FD_CLOEXEC);
#endif
#if defined(HAVE_SELINUX) || defined(HAVE_SMACK)
	mch_copy_sec(fname, mfp->mf_fname);
#endif
	mch_hide(mfp->mf_fname);    // try setting the 'hidden' flag
    }
}

/*
 * Implementation of mf_hashtab_T follows.
 */

/*
 * The number of buckets in the hashtable is increased by a factor of
 * MHT_GROWTH_FACTOR when the average number of items per bucket
 * exceeds 2 ^ MHT_LOG_LOAD_FACTOR.
 */
#define MHT_LOG_LOAD_FACTOR 6
#define MHT_GROWTH_FACTOR   2   // must be a power of two

/*
 * Initialize an empty hash table.
 */
    static void
mf_hash_init(mf_hashtab_T *mht)
{
    CLEAR_POINTER(mht);
    mht->mht_buckets = mht->mht_small_buckets;
    mht->mht_mask = MHT_INIT_SIZE - 1;
}

/*
 * Free the array of a hash table.  Does not free the items it contains!
 * The hash table must not be used again without another mf_hash_init() call.
 */
    static void
mf_hash_free(mf_hashtab_T *mht)
{
    if (mht->mht_buckets != mht->mht_small_buckets)
	vim_free(mht->mht_buckets);
}

/*
 * Free the array of a hash table and all the items it contains.
 */
    static void
mf_hash_free_all(mf_hashtab_T *mht)
{
    long_u	    idx;
    mf_hashitem_T   *mhi;
    mf_hashitem_T   *next;

    for (idx = 0; idx <= mht->mht_mask; idx++)
	for (mhi = mht->mht_buckets[idx]; mhi != NULL; mhi = next)
	{
	    next = mhi->mhi_next;
	    vim_free(mhi);
	}

    mf_hash_free(mht);
}

/*
 * Find "key" in hashtable "mht".
 * Returns a pointer to a mf_hashitem_T or NULL if the item was not found.
 */
    static mf_hashitem_T *
mf_hash_find(mf_hashtab_T *mht, blocknr_T key)
{
    mf_hashitem_T   *mhi;

    mhi = mht->mht_buckets[key & mht->mht_mask];
    while (mhi != NULL && mhi->mhi_key != key)
	mhi = mhi->mhi_next;

    return mhi;
}

/*
 * Add item "mhi" to hashtable "mht".
 * "mhi" must not be NULL.
 */
    static void
mf_hash_add_item(mf_hashtab_T *mht, mf_hashitem_T *mhi)
{
    long_u	    idx;

    idx = mhi->mhi_key & mht->mht_mask;
    mhi->mhi_next = mht->mht_buckets[idx];
    mhi->mhi_prev = NULL;
    if (mhi->mhi_next != NULL)
	mhi->mhi_next->mhi_prev = mhi;
    mht->mht_buckets[idx] = mhi;

    mht->mht_count++;

    /*
     * Grow hashtable when we have more thank 2^MHT_LOG_LOAD_FACTOR
     * items per bucket on average
     */
    if (mht->mht_fixed == 0
	&& (mht->mht_count >> MHT_LOG_LOAD_FACTOR) > mht->mht_mask)
    {
	if (mf_hash_grow(mht) == FAIL)
	{
	    // stop trying to grow after first failure to allocate memory
	    mht->mht_fixed = 1;
	}
    }
}

/*
 * Remove item "mhi" from hashtable "mht".
 * "mhi" must not be NULL and must have been inserted into "mht".
 */
    static void
mf_hash_rem_item(mf_hashtab_T *mht, mf_hashitem_T *mhi)
{
    if (mhi->mhi_prev == NULL)
	mht->mht_buckets[mhi->mhi_key & mht->mht_mask] = mhi->mhi_next;
    else
	mhi->mhi_prev->mhi_next = mhi->mhi_next;

    if (mhi->mhi_next != NULL)
	mhi->mhi_next->mhi_prev = mhi->mhi_prev;

    mht->mht_count--;

    // We could shrink the table here, but it typically takes little memory,
    // so why bother?
}

/*
 * Increase number of buckets in the hashtable by MHT_GROWTH_FACTOR and
 * rehash items.
 * Returns FAIL when out of memory.
 */
    static int
mf_hash_grow(mf_hashtab_T *mht)
{
    long_u	    i, j;
    int		    shift;
    mf_hashitem_T   *mhi;
    mf_hashitem_T   *tails[MHT_GROWTH_FACTOR];
    mf_hashitem_T   **buckets;
    size_t	    size;

    size = (mht->mht_mask + 1) * MHT_GROWTH_FACTOR * sizeof(void *);
    buckets = lalloc_clear(size, FALSE);
    if (buckets == NULL)
	return FAIL;

    shift = 0;
    while ((mht->mht_mask >> shift) != 0)
	shift++;

    for (i = 0; i <= mht->mht_mask; i++)
    {
	/*
	 * Traverse the items in the i-th original bucket and move them into
	 * MHT_GROWTH_FACTOR new buckets, preserving their relative order
	 * within each new bucket.  Preserving the order is important because
	 * mf_get() tries to keep most recently used items at the front of
	 * each bucket.
	 *
	 * Here we strongly rely on the fact the hashes are computed modulo
	 * a power of two.
	 */

	CLEAR_FIELD(tails);

	for (mhi = mht->mht_buckets[i]; mhi != NULL; mhi = mhi->mhi_next)
	{
	    j = (mhi->mhi_key >> shift) & (MHT_GROWTH_FACTOR - 1);
	    if (tails[j] == NULL)
	    {
		buckets[i + (j << shift)] = mhi;
		tails[j] = mhi;
		mhi->mhi_prev = NULL;
	    }
	    else
	    {
		tails[j]->mhi_next = mhi;
		mhi->mhi_prev = tails[j];
		tails[j] = mhi;
	    }
	}

	for (j = 0; j < MHT_GROWTH_FACTOR; j++)
	    if (tails[j] != NULL)
		tails[j]->mhi_next = NULL;
    }

    if (mht->mht_buckets != mht->mht_small_buckets)
	vim_free(mht->mht_buckets);

    mht->mht_buckets = buckets;
    mht->mht_mask = (mht->mht_mask + 1) * MHT_GROWTH_FACTOR - 1;

    return OK;
}