summaryrefslogtreecommitdiffstats
path: root/src/H5FDdirect.c
blob: bae1a711b6bf667939f371979f7ac02bacdb1646 (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
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * Copyright by The HDF Group.                                               *
 * All rights reserved.                                                      *
 *                                                                           *
 * This file is part of HDF5.  The full HDF5 copyright notice, including     *
 * terms governing use, modification, and redistribution, is contained in    *
 * the COPYING file, which can be found at the root of the source code       *
 * distribution tree, or in https://www.hdfgroup.org/licenses.               *
 * If you do not have access to either file, you may request a copy from     *
 * help@hdfgroup.org.                                                        *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/*
 * Programmer:  Raymond Lu
 *              Wednesday, 20 September 2006
 *
 * Purpose:  The Direct I/O file driver forces the data to be written to
 *    the file directly without being copied into system kernel
 *    buffer.  The main system support this feature is Linux.
 */

#include "H5FDdrvr_module.h" /* This source code file is part of the H5FD driver module */

#include "H5private.h"   /* Generic Functions        */
#include "H5Eprivate.h"  /* Error handling           */
#include "H5Fprivate.h"  /* File access              */
#include "H5FDprivate.h" /* File drivers             */
#include "H5FDdirect.h"  /* Direct file driver       */
#include "H5FLprivate.h" /* Free Lists               */
#include "H5Iprivate.h"  /* IDs                      */
#include "H5MMprivate.h" /* Memory management        */
#include "H5Pprivate.h"  /* Property lists           */

#ifdef H5_HAVE_DIRECT

/* The driver identification number, initialized at runtime */
static hid_t H5FD_DIRECT_g = 0;

/* Whether to ignore file locks when disabled (env var value) */
static htri_t ignore_disabled_file_locks_s = FAIL;

/* File operations */
#define OP_UNKNOWN 0
#define OP_READ    1
#define OP_WRITE   2

/* Driver-specific file access properties */
typedef struct H5FD_direct_fapl_t {
    size_t  mboundary;  /* Memory boundary for alignment    */
    size_t  fbsize;     /* File system block size      */
    size_t  cbsize;     /* Maximal buffer size for copying user data  */
    hbool_t must_align; /* Decides if data alignment is required        */
} H5FD_direct_fapl_t;

/*
 * The description of a file belonging to this driver. The `eoa' and `eof'
 * determine the amount of hdf5 address space in use and the high-water mark
 * of the file (the current size of the underlying Unix file). The `pos'
 * value is used to eliminate file position updates when they would be a
 * no-op. Unfortunately we've found systems that use separate file position
 * indicators for reading and writing so the lseek can only be eliminated if
 * the current operation is the same as the previous operation.  When opening
 * a file the `eof' will be set to the current file size, `eoa' will be set
 * to zero, `pos' will be set to H5F_ADDR_UNDEF (as it is when an error
 * occurs), and `op' will be set to H5F_OP_UNKNOWN.
 */
typedef struct H5FD_direct_t {
    H5FD_t             pub; /*public stuff, must be first  */
    int                fd;  /*the unix file      */
    haddr_t            eoa; /*end of allocated region  */
    haddr_t            eof; /*end of file; current file size*/
    haddr_t            pos; /*current file I/O position  */
    int                op;  /*last operation    */
    H5FD_direct_fapl_t fa;  /*file access properties  */
    hbool_t            ignore_disabled_file_locks;
#ifndef H5_HAVE_WIN32_API
    /*
     * On most systems the combination of device and i-node number uniquely
     * identify a file.
     */
    dev_t device; /*file device number    */
    ino_t inode;  /*file i-node number    */
#else
    /*
     * On H5_HAVE_WIN32_API the low-order word of a unique identifier associated with the
     * file and the volume serial number uniquely identify a file. This number
     * (which, both? -rpm) may change when the system is restarted or when the
     * file is opened. After a process opens a file, the identifier is
     * constant until the file is closed. An application can use this
     * identifier and the volume serial number to determine whether two
     * handles refer to the same file.
     */
    DWORD fileindexlo;
    DWORD fileindexhi;
#endif

} H5FD_direct_t;

/*
 * These macros check for overflow of various quantities.  These macros
 * assume that HDoff_t is signed and haddr_t and size_t are unsigned.
 *
 * ADDR_OVERFLOW:  Checks whether a file address of type `haddr_t'
 *      is too large to be represented by the second argument
 *      of the file seek function.
 *
 * SIZE_OVERFLOW:  Checks whether a buffer size of type `hsize_t' is too
 *      large to be represented by the `size_t' type.
 *
 * REGION_OVERFLOW:  Checks whether an address and size pair describe data
 *      which can be addressed entirely by the second
 *      argument of the file seek function.
 */
#define MAXADDR          (((haddr_t)1 << (8 * sizeof(HDoff_t) - 1)) - 1)
#define ADDR_OVERFLOW(A) (HADDR_UNDEF == (A) || ((A) & ~(haddr_t)MAXADDR))
#define SIZE_OVERFLOW(Z) ((Z) & ~(hsize_t)MAXADDR)
#define REGION_OVERFLOW(A, Z)                                                                                \
    (ADDR_OVERFLOW(A) || SIZE_OVERFLOW(Z) || HADDR_UNDEF == (A) + (Z) || (HDoff_t)((A) + (Z)) < (HDoff_t)(A))

/* Prototypes */
static herr_t  H5FD__direct_term(void);
static void   *H5FD__direct_fapl_get(H5FD_t *file);
static void   *H5FD__direct_fapl_copy(const void *_old_fa);
static H5FD_t *H5FD__direct_open(const char *name, unsigned flags, hid_t fapl_id, haddr_t maxaddr);
static herr_t  H5FD__direct_close(H5FD_t *_file);
static int     H5FD__direct_cmp(const H5FD_t *_f1, const H5FD_t *_f2);
static herr_t  H5FD__direct_query(const H5FD_t *_f1, unsigned long *flags);
static haddr_t H5FD__direct_get_eoa(const H5FD_t *_file, H5FD_mem_t type);
static herr_t  H5FD__direct_set_eoa(H5FD_t *_file, H5FD_mem_t type, haddr_t addr);
static haddr_t H5FD__direct_get_eof(const H5FD_t *_file, H5FD_mem_t type);
static herr_t  H5FD__direct_get_handle(H5FD_t *_file, hid_t fapl, void **file_handle);
static herr_t  H5FD__direct_read(H5FD_t *_file, H5FD_mem_t type, hid_t fapl_id, haddr_t addr, size_t size,
                                 void *buf);
static herr_t  H5FD__direct_write(H5FD_t *_file, H5FD_mem_t type, hid_t fapl_id, haddr_t addr, size_t size,
                                  const void *buf);
static herr_t  H5FD__direct_truncate(H5FD_t *_file, hid_t dxpl_id, hbool_t closing);
static herr_t  H5FD__direct_lock(H5FD_t *_file, hbool_t rw);
static herr_t  H5FD__direct_unlock(H5FD_t *_file);

static const H5FD_class_t H5FD_direct_g = {
    "direct",                   /* name                 */
    MAXADDR,                    /* maxaddr              */
    H5F_CLOSE_WEAK,             /* fc_degree            */
    H5FD__direct_term,          /* terminate            */
    NULL,                       /* sb_size              */
    NULL,                       /* sb_encode            */
    NULL,                       /* sb_decode            */
    sizeof(H5FD_direct_fapl_t), /* fapl_size            */
    H5FD__direct_fapl_get,      /* fapl_get             */
    H5FD__direct_fapl_copy,     /* fapl_copy            */
    NULL,                       /* fapl_free            */
    0,                          /* dxpl_size            */
    NULL,                       /* dxpl_copy            */
    NULL,                       /* dxpl_free            */
    H5FD__direct_open,          /* open                 */
    H5FD__direct_close,         /* close                */
    H5FD__direct_cmp,           /* cmp                  */
    H5FD__direct_query,         /* query                */
    NULL,                       /* get_type_map         */
    NULL,                       /* alloc                */
    NULL,                       /* free                 */
    H5FD__direct_get_eoa,       /* get_eoa              */
    H5FD__direct_set_eoa,       /* set_eoa              */
    H5FD__direct_get_eof,       /* get_eof              */
    H5FD__direct_get_handle,    /* get_handle           */
    H5FD__direct_read,          /* read                 */
    H5FD__direct_write,         /* write                */
    NULL,                       /* flush                */
    H5FD__direct_truncate,      /* truncate             */
    H5FD__direct_lock,          /* lock                 */
    H5FD__direct_unlock,        /* unlock               */
    H5FD_FLMAP_DICHOTOMY        /* fl_map               */
};

/* Declare a free list to manage the H5FD_direct_t struct */
H5FL_DEFINE_STATIC(H5FD_direct_t);

/*--------------------------------------------------------------------------
NAME
   H5FD__init_package -- Initialize interface-specific information
USAGE
    herr_t H5FD__init_package()
RETURNS
    Non-negative on success/Negative on failure
DESCRIPTION
    Initializes any interface-specific data or routines.  (Just calls
    H5FD_direct_init currently).

--------------------------------------------------------------------------*/
static herr_t
H5FD__init_package(void)
{
    char  *lock_env_var = NULL; /* Environment variable pointer */
    herr_t ret_value    = SUCCEED;

    FUNC_ENTER_STATIC

    /* Check the use disabled file locks environment variable */
    lock_env_var = HDgetenv("HDF5_USE_FILE_LOCKING");
    if (lock_env_var && !HDstrcmp(lock_env_var, "BEST_EFFORT"))
        ignore_disabled_file_locks_s = TRUE; /* Override: Ignore disabled locks */
    else if (lock_env_var && (!HDstrcmp(lock_env_var, "TRUE") || !HDstrcmp(lock_env_var, "1")))
        ignore_disabled_file_locks_s = FALSE; /* Override: Don't ignore disabled locks */
    else
        ignore_disabled_file_locks_s = FAIL; /* Environment variable not set, or not set correctly */

    if (H5FD_direct_init() < 0)
        HGOTO_ERROR(H5E_VFL, H5E_CANTINIT, FAIL, "unable to initialize direct VFD")

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* H5FD__init_package() */

/*-------------------------------------------------------------------------
 * Function:    H5FD_direct_init
 *
 * Purpose:     Initialize this driver by registering the driver with the
 *              library.
 *
 * Return:      Success:    The driver ID for the direct driver
 *              Failure:    H5I_INVALID_HID
 *
 * Programmer:  Raymond Lu
 *              Wednesday, 20 September 2006
 *
 *-------------------------------------------------------------------------
 */
hid_t
H5FD_direct_init(void)
{
    hid_t ret_value = H5I_INVALID_HID; /* Return value */

    FUNC_ENTER_NOAPI(H5I_INVALID_HID)

    if (H5I_VFL != H5I_get_type(H5FD_DIRECT_g)) {
        H5FD_DIRECT_g = H5FD_register(&H5FD_direct_g, sizeof(H5FD_class_t), FALSE);
        if (H5I_INVALID_HID == H5FD_DIRECT_g)
            HGOTO_ERROR(H5E_ATOM, H5E_CANTREGISTER, H5I_INVALID_HID, "unable to register direct");
    }

    /* Set return value */
    ret_value = H5FD_DIRECT_g;

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5FD_direct_init() */

/*---------------------------------------------------------------------------
 * Function:  H5FD__direct_term
 *
 * Purpose:  Shut down the VFD
 *
 * Returns:     Non-negative on success or negative on failure
 *
 * Programmer:  Raymond Lu
 *              Wednesday, 20 September 2006
 *
 *---------------------------------------------------------------------------
 */
static herr_t
H5FD__direct_term(void)
{
    FUNC_ENTER_STATIC_NOERR

    /* Reset VFL ID */
    H5FD_DIRECT_g = 0;

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* end H5FD__direct_term() */

/*-------------------------------------------------------------------------
 * Function:  H5Pset_fapl_direct
 *
 * Purpose:  Modify the file access property list to use the H5FD_DIRECT
 *    driver defined in this source file.  There are no driver
 *    specific properties.
 *
 * Return:  Non-negative on success/Negative on failure
 *
 * Programmer:  Raymond Lu
 *    Wednesday, 20 September 2006
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Pset_fapl_direct(hid_t fapl_id, size_t boundary, size_t block_size, size_t cbuf_size)
{
    H5P_genplist_t    *plist; /* Property list pointer */
    H5FD_direct_fapl_t fa;
    herr_t             ret_value;

    FUNC_ENTER_API(FAIL)
    H5TRACE4("e", "izzz", fapl_id, boundary, block_size, cbuf_size);

    if (NULL == (plist = H5P_object_verify(fapl_id, H5P_FILE_ACCESS)))
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a file access property list")

    HDmemset(&fa, 0, sizeof(H5FD_direct_fapl_t));
    if (boundary != 0)
        fa.mboundary = boundary;
    else
        fa.mboundary = MBOUNDARY_DEF;
    if (block_size != 0)
        fa.fbsize = block_size;
    else
        fa.fbsize = FBSIZE_DEF;
    if (cbuf_size != 0)
        fa.cbsize = cbuf_size;
    else
        fa.cbsize = CBSIZE_DEF;

    /* Set the default to be true for data alignment */
    fa.must_align = TRUE;

    /* Copy buffer size must be a multiple of file block size */
    if (fa.cbsize % fa.fbsize != 0)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "copy buffer size must be a multiple of block size")

    ret_value = H5P_set_driver(plist, H5FD_DIRECT, &fa);

done:
    FUNC_LEAVE_API(ret_value)
}

/*-------------------------------------------------------------------------
 * Function:  H5Pget_fapl_direct
 *
 * Purpose:  Returns information about the direct file access property
 *    list though the function arguments.
 *
 * Return:  Success:  Non-negative
 *
 *    Failure:  Negative
 *
 * Programmer:  Raymond Lu
 *              Wednesday, October 18, 2006
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Pget_fapl_direct(hid_t fapl_id, size_t *boundary /*out*/, size_t *block_size /*out*/,
                   size_t *cbuf_size /*out*/)
{
    H5P_genplist_t           *plist; /* Property list pointer */
    const H5FD_direct_fapl_t *fa;
    herr_t                    ret_value = SUCCEED; /* Return value */

    FUNC_ENTER_API(FAIL)
    H5TRACE4("e", "ixxx", fapl_id, boundary, block_size, cbuf_size);

    if (NULL == (plist = H5P_object_verify(fapl_id, H5P_FILE_ACCESS)))
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a file access list")
    if (H5FD_DIRECT != H5P_peek_driver(plist))
        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "incorrect VFL driver")
    if (NULL == (fa = H5P_peek_driver_info(plist)))
        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "bad VFL driver info")
    if (boundary)
        *boundary = fa->mboundary;
    if (block_size)
        *block_size = fa->fbsize;
    if (cbuf_size)
        *cbuf_size = fa->cbsize;

done:
    FUNC_LEAVE_API(ret_value)
} /* end H5Pget_fapl_direct() */

/*-------------------------------------------------------------------------
 * Function:  H5FD__direct_fapl_get
 *
 * Purpose:  Returns a file access property list which indicates how the
 *    specified file is being accessed. The return list could be
 *    used to access another file the same way.
 *
 * Return:  Success:  Ptr to new file access property list with all
 *        members copied from the file struct.
 *
 *    Failure:  NULL
 *
 * Programmer:  Raymond Lu
 *              Wednesday, 18 October 2006
 *
 *-------------------------------------------------------------------------
 */
static void *
H5FD__direct_fapl_get(H5FD_t *_file)
{
    H5FD_direct_t *file      = (H5FD_direct_t *)_file;
    void          *ret_value = NULL; /* Return value */

    FUNC_ENTER_STATIC_NOERR

    /* Set return value */
    ret_value = H5FD__direct_fapl_copy(&(file->fa));

    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5FD__direct_fapl_get() */

/*-------------------------------------------------------------------------
 * Function:  H5FD__direct_fapl_copy
 *
 * Purpose:  Copies the direct-specific file access properties.
 *
 * Return:  Success:  Ptr to a new property list
 *
 *    Failure:  NULL
 *
 * Programmer:  Raymond Lu
 *              Wednesday, 18 October 2006
 *
 *-------------------------------------------------------------------------
 */
static void *
H5FD__direct_fapl_copy(const void *_old_fa)
{
    const H5FD_direct_fapl_t *old_fa = (const H5FD_direct_fapl_t *)_old_fa;
    H5FD_direct_fapl_t       *new_fa = H5MM_calloc(sizeof(H5FD_direct_fapl_t));

    FUNC_ENTER_STATIC_NOERR

    HDassert(new_fa);

    /* Copy the general information */
    H5MM_memcpy(new_fa, old_fa, sizeof(H5FD_direct_fapl_t));

    FUNC_LEAVE_NOAPI(new_fa)
} /* end H5FD__direct_fapl_copy() */

/*-------------------------------------------------------------------------
 * Function:  H5FD__direct_open
 *
 * Purpose:  Create and/or opens a Unix file for direct I/O as an HDF5 file.
 *
 * Return:  Success:  A pointer to a new file data structure. The
 *        public fields will be initialized by the
 *        caller, which is always H5FD_open().
 *
 *    Failure:  NULL
 *
 * Programmer:  Raymond Lu
 *              Wednesday, 20 September 2006
 *
 *-------------------------------------------------------------------------
 */
static H5FD_t *
H5FD__direct_open(const char *name, unsigned flags, hid_t fapl_id, haddr_t maxaddr)
{
    int                       o_flags;
    int                       fd   = (-1);
    H5FD_direct_t            *file = NULL;
    const H5FD_direct_fapl_t *fa;
#ifdef H5_HAVE_WIN32_API
    HFILE                              filehandle;
    struct _BY_HANDLE_FILE_INFORMATION fileinfo;
#endif
    h5_stat_t       sb;
    H5P_genplist_t *plist; /* Property list */
    void           *buf1, *buf2;
    H5FD_t         *ret_value = NULL;

    FUNC_ENTER_STATIC

    /* Sanity check on file offsets */
    HDassert(sizeof(HDoff_t) >= sizeof(size_t));

    /* Check arguments */
    if (!name || !*name)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL, "invalid file name")
    if (0 == maxaddr || HADDR_UNDEF == maxaddr)
        HGOTO_ERROR(H5E_ARGS, H5E_BADRANGE, NULL, "bogus maxaddr")
    if (ADDR_OVERFLOW(maxaddr))
        HGOTO_ERROR(H5E_ARGS, H5E_OVERFLOW, NULL, "bogus maxaddr")

    /* Build the open flags */
    o_flags = (H5F_ACC_RDWR & flags) ? O_RDWR : O_RDONLY;
    if (H5F_ACC_TRUNC & flags)
        o_flags |= O_TRUNC;
    if (H5F_ACC_CREAT & flags)
        o_flags |= O_CREAT;
    if (H5F_ACC_EXCL & flags)
        o_flags |= O_EXCL;

    /* Flag for Direct I/O */
    o_flags |= O_DIRECT;

    /* Open the file */
    if ((fd = HDopen(name, o_flags, H5_POSIX_CREATE_MODE_RW)) < 0)
        HSYS_GOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, NULL, "unable to open file")

    if (HDfstat(fd, &sb) < 0)
        HSYS_GOTO_ERROR(H5E_FILE, H5E_BADFILE, NULL, "unable to fstat file")

    /* Create the new file struct */
    if (NULL == (file = H5FL_CALLOC(H5FD_direct_t)))
        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "unable to allocate file struct")

    /* Get the driver specific information */
    if (NULL == (plist = H5P_object_verify(fapl_id, H5P_FILE_ACCESS)))
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, NULL, "not a file access property list")
    if (NULL == (fa = (const H5FD_direct_fapl_t *)H5P_peek_driver_info(plist)))
        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, NULL, "bad VFL driver info")

    file->fd = fd;
    H5_CHECKED_ASSIGN(file->eof, haddr_t, sb.st_size, h5_stat_size_t);
    file->pos = HADDR_UNDEF;
    file->op  = OP_UNKNOWN;
#ifdef H5_HAVE_WIN32_API
    filehandle = _get_osfhandle(fd);
    (void)GetFileInformationByHandle((HANDLE)filehandle, &fileinfo);
    file->fileindexhi = fileinfo.nFileIndexHigh;
    file->fileindexlo = fileinfo.nFileIndexLow;
#else
    file->device = sb.st_dev;
    file->inode  = sb.st_ino;
#endif /*H5_HAVE_WIN32_API*/
    file->fa.mboundary = fa->mboundary;
    file->fa.fbsize    = fa->fbsize;
    file->fa.cbsize    = fa->cbsize;

    /* Check the file locking flags in the fapl */
    if (ignore_disabled_file_locks_s != FAIL)
        /* The environment variable was set, so use that preferentially */
        file->ignore_disabled_file_locks = ignore_disabled_file_locks_s;
    else {
        /* Use the value in the property list */
        if (H5P_get(plist, H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_NAME, &file->ignore_disabled_file_locks) < 0)
            HGOTO_ERROR(H5E_VFL, H5E_CANTGET, NULL, "can't get ignore disabled file locks property")
    }

    /* Try to decide if data alignment is required.  The reason to check it here
     * is to handle correctly the case that the file is in a different file system
     * than the one where the program is running.
     */
    /* NOTE: Use HDmalloc and HDfree here to ensure compatibility with
     *       HDposix_memalign.
     */
    buf1 = HDmalloc(sizeof(int));
    if (HDposix_memalign(&buf2, file->fa.mboundary, file->fa.fbsize) != 0)
        HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, NULL, "HDposix_memalign failed")

    if (o_flags & O_CREAT) {
        if (HDwrite(file->fd, buf1, sizeof(int)) < 0) {
            if (HDwrite(file->fd, buf2, file->fa.fbsize) < 0)
                HGOTO_ERROR(H5E_FILE, H5E_WRITEERROR, NULL, "file system may not support Direct I/O")
            else
                file->fa.must_align = TRUE;
        }
        else {
            file->fa.must_align = FALSE;
            if (-1 == HDftruncate(file->fd, (HDoff_t)0))
                HSYS_GOTO_ERROR(H5E_IO, H5E_SEEKERROR, NULL, "unable to truncate file")
        }
    }
    else {
        if (HDread(file->fd, buf1, sizeof(int)) < 0) {
            if (HDread(file->fd, buf2, file->fa.fbsize) < 0)
                HGOTO_ERROR(H5E_FILE, H5E_READERROR, NULL, "file system may not support Direct I/O")
            else
                file->fa.must_align = TRUE;
        }
        else {
            if (o_flags & O_RDWR) {
                if (HDlseek(file->fd, (HDoff_t)0, SEEK_SET) < 0)
                    HSYS_GOTO_ERROR(H5E_IO, H5E_SEEKERROR, NULL, "unable to seek to proper position")
                if (HDwrite(file->fd, buf1, sizeof(int)) < 0)
                    file->fa.must_align = TRUE;
                else
                    file->fa.must_align = FALSE;
            }
            else
                file->fa.must_align = FALSE;
        }
    }

    if (buf1)
        HDfree(buf1);
    if (buf2)
        HDfree(buf2);

    /* Set return value */
    ret_value = (H5FD_t *)file;

done:
    if (ret_value == NULL) {
        if (fd >= 0)
            HDclose(fd);
    } /* end if */

    FUNC_LEAVE_NOAPI(ret_value)
}

/*-------------------------------------------------------------------------
 * Function:  H5FD__direct_close
 *
 * Purpose:  Closes the file.
 *
 * Return:  Success:  0
 *
 *    Failure:  -1, file not closed.
 *
 * Programmer:  Raymond Lu
 *              Wednesday, 20 September 2006
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD__direct_close(H5FD_t *_file)
{
    H5FD_direct_t *file      = (H5FD_direct_t *)_file;
    herr_t         ret_value = SUCCEED; /* Return value */

    FUNC_ENTER_STATIC

    if (HDclose(file->fd) < 0)
        HSYS_GOTO_ERROR(H5E_IO, H5E_CANTCLOSEFILE, FAIL, "unable to close file")

    H5FL_FREE(H5FD_direct_t, file);

done:
    FUNC_LEAVE_NOAPI(ret_value)
}

/*-------------------------------------------------------------------------
 * Function:  H5FD__direct_cmp
 *
 * Purpose:  Compares two files belonging to this driver using an
 *    arbitrary (but consistent) ordering.
 *
 * Return:  Success:  A value like strcmp()
 *
 *    Failure:  never fails (arguments were checked by the
 *        caller).
 *
 * Programmer:  Raymond Lu
 *              Thursday, 21 September 2006
 *
 *-------------------------------------------------------------------------
 */
static int
H5FD__direct_cmp(const H5FD_t *_f1, const H5FD_t *_f2)
{
    const H5FD_direct_t *f1        = (const H5FD_direct_t *)_f1;
    const H5FD_direct_t *f2        = (const H5FD_direct_t *)_f2;
    int                  ret_value = 0;

    FUNC_ENTER_STATIC_NOERR

#ifdef H5_HAVE_WIN32_API
    if (f1->fileindexhi < f2->fileindexhi)
        HGOTO_DONE(-1)
    if (f1->fileindexhi > f2->fileindexhi)
        HGOTO_DONE(1)

    if (f1->fileindexlo < f2->fileindexlo)
        HGOTO_DONE(-1)
    if (f1->fileindexlo > f2->fileindexlo)
        HGOTO_DONE(1)

#else
#ifdef H5_DEV_T_IS_SCALAR
    if (f1->device < f2->device)
        HGOTO_DONE(-1)
    if (f1->device > f2->device)
        HGOTO_DONE(1)
#else  /* H5_DEV_T_IS_SCALAR */
    /* If dev_t isn't a scalar value on this system, just use memcmp to
     * determine if the values are the same or not.  The actual return value
     * shouldn't really matter...
     */
    if (HDmemcmp(&(f1->device), &(f2->device), sizeof(dev_t)) < 0)
        HGOTO_DONE(-1)
    if (HDmemcmp(&(f1->device), &(f2->device), sizeof(dev_t)) > 0)
        HGOTO_DONE(1)
#endif /* H5_DEV_T_IS_SCALAR */

    if (f1->inode < f2->inode)
        HGOTO_DONE(-1)
    if (f1->inode > f2->inode)
        HGOTO_DONE(1)

#endif

done:
    FUNC_LEAVE_NOAPI(ret_value)
}

/*-------------------------------------------------------------------------
 * Function:  H5FD__direct_query
 *
 * Purpose:  Set the flags that this VFL driver is capable of supporting.
 *              (listed in H5FDpublic.h)
 *
 * Return:  Success:  non-negative
 *
 *    Failure:  negative
 *
 * Programmer:  Raymond Lu
 *              Thursday, 21 September 2006
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD__direct_query(const H5FD_t H5_ATTR_UNUSED *_f, unsigned long *flags /* out */)
{
    FUNC_ENTER_STATIC_NOERR

    /* Set the VFL feature flags that this driver supports */
    if (flags) {
        *flags = 0;
        *flags |= H5FD_FEAT_AGGREGATE_METADATA;  /* OK to aggregate metadata allocations  */
        *flags |= H5FD_FEAT_ACCUMULATE_METADATA; /* OK to accumulate metadata for faster writes */
        *flags |= H5FD_FEAT_DATA_SIEVE; /* OK to perform data sieving for faster raw data reads & writes    */
        *flags |= H5FD_FEAT_AGGREGATE_SMALLDATA;    /* OK to aggregate "small" raw data allocations    */
        *flags |= H5FD_FEAT_DEFAULT_VFD_COMPATIBLE; /* VFD creates a file which can be opened with the default
                                                       VFD      */
    }

    FUNC_LEAVE_NOAPI(SUCCEED)
}

/*-------------------------------------------------------------------------
 * Function:  H5FD__direct_get_eoa
 *
 * Purpose:  Gets the end-of-address marker for the file. The EOA marker
 *    is the first address past the last byte allocated in the
 *    format address space.
 *
 * Return:  Success:  The end-of-address marker.
 *
 *    Failure:  HADDR_UNDEF
 *
 * Programmer:  Raymond Lu
 *              Wednesday, 20 September 2006
 *
 *-------------------------------------------------------------------------
 */
static haddr_t
H5FD__direct_get_eoa(const H5FD_t *_file, H5FD_mem_t H5_ATTR_UNUSED type)
{
    const H5FD_direct_t *file = (const H5FD_direct_t *)_file;

    FUNC_ENTER_STATIC_NOERR

    FUNC_LEAVE_NOAPI(file->eoa)
}

/*-------------------------------------------------------------------------
 * Function:  H5FD__direct_set_eoa
 *
 * Purpose:  Set the end-of-address marker for the file. This function is
 *    called shortly after an existing HDF5 file is opened in order
 *    to tell the driver where the end of the HDF5 data is located.
 *
 * Return:  Success:  0
 *
 *    Failure:  -1
 *
 * Programmer:  Raymond Lu
 *              Wednesday, 20 September 2006
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD__direct_set_eoa(H5FD_t *_file, H5FD_mem_t H5_ATTR_UNUSED type, haddr_t addr)
{
    H5FD_direct_t *file = (H5FD_direct_t *)_file;

    FUNC_ENTER_STATIC_NOERR

    file->eoa = addr;

    FUNC_LEAVE_NOAPI(SUCCEED)
}

/*-------------------------------------------------------------------------
 * Function:  H5FD__direct_get_eof
 *
 * Purpose:  Returns the end-of-file marker, which is the greater of
 *    either the Unix end-of-file or the HDF5 end-of-address
 *    markers.
 *
 * Return:  Success:  End of file address, the first address past
 *        the end of the "file", either the Unix file
 *        or the HDF5 file.
 *
 *    Failure:  HADDR_UNDEF
 *
 * Programmer:  Raymond Lu
 *              Wednesday, 20 September 2006
 *
 *-------------------------------------------------------------------------
 */
static haddr_t
H5FD__direct_get_eof(const H5FD_t *_file, H5FD_mem_t H5_ATTR_UNUSED type)
{
    const H5FD_direct_t *file = (const H5FD_direct_t *)_file;

    FUNC_ENTER_STATIC_NOERR

    FUNC_LEAVE_NOAPI(file->eof)
}

/*-------------------------------------------------------------------------
 * Function:       H5FD_diect_get_handle
 *
 * Purpose:        Returns the file handle of direct file driver.
 *
 * Returns:        Non-negative if succeed or negative if fails.
 *
 * Programmer:     Raymond Lu
 *                 21 September 2006
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD__direct_get_handle(H5FD_t *_file, hid_t H5_ATTR_UNUSED fapl, void **file_handle)
{
    H5FD_direct_t *file      = (H5FD_direct_t *)_file;
    herr_t         ret_value = SUCCEED;

    FUNC_ENTER_STATIC

    if (!file_handle)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "file handle not valid")
    *file_handle = &(file->fd);

done:
    FUNC_LEAVE_NOAPI(ret_value)
}

/*-------------------------------------------------------------------------
 * Function:  H5FD__direct_read
 *
 * Purpose:  Reads SIZE bytes of data from FILE beginning at address ADDR
 *    into buffer BUF according to data transfer properties in
 *    DXPL_ID.
 *
 * Return:  Success:  Zero. Result is stored in caller-supplied
 *        buffer BUF.
 *
 *    Failure:  -1, Contents of buffer BUF are undefined.
 *
 * Programmer:  Raymond Lu
 *              Thursday, 21 September 2006
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD__direct_read(H5FD_t *_file, H5FD_mem_t H5_ATTR_UNUSED type, hid_t H5_ATTR_UNUSED dxpl_id, haddr_t addr,
                  size_t size, void *buf /*out*/)
{
    H5FD_direct_t *file = (H5FD_direct_t *)_file;
    ssize_t        nbytes;
    hbool_t        _must_align = TRUE;
    herr_t         ret_value   = SUCCEED; /* Return value */
    size_t         alloc_size;
    void          *copy_buf = NULL, *p2;
    size_t         _boundary;
    size_t         _fbsize;
    size_t         _cbsize;
    haddr_t        read_size;        /* Size to read into copy buffer */
    size_t         copy_size = size; /* Size remaining to read when using copy buffer */
    size_t         copy_offset;      /* Offset into copy buffer of the requested data */

    FUNC_ENTER_STATIC

    HDassert(file && file->pub.cls);
    HDassert(buf);

    /* Check for overflow conditions */
    if (HADDR_UNDEF == addr)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "addr undefined")
    if (REGION_OVERFLOW(addr, size))
        HGOTO_ERROR(H5E_ARGS, H5E_OVERFLOW, FAIL, "addr overflow")

    /* If the system doesn't require data to be aligned, read the data in
     * the same way as sec2 driver.
     */
    _must_align = file->fa.must_align;

    /* Get the memory boundary for alignment, file system block size, and maximal
     * copy buffer size.
     */
    _boundary = file->fa.mboundary;
    _fbsize   = file->fa.fbsize;
    _cbsize   = file->fa.cbsize;

    /* if the data is aligned or the system doesn't require data to be aligned,
     * read it directly from the file.  If not, read a bigger
     * and aligned data first, then copy the data into memory buffer.
     */
    if (!_must_align || ((addr % _fbsize == 0) && (size % _fbsize == 0) && ((size_t)buf % _boundary == 0))) {
        /* Seek to the correct location */
        if ((addr != file->pos || OP_READ != file->op) && HDlseek(file->fd, (HDoff_t)addr, SEEK_SET) < 0)
            HSYS_GOTO_ERROR(H5E_IO, H5E_SEEKERROR, FAIL, "unable to seek to proper position")
        /* Read the aligned data in file first, being careful of interrupted
         * system calls and partial results. */
        while (size > 0) {
            do {
                nbytes = HDread(file->fd, buf, size);
            } while (-1 == nbytes && EINTR == errno);
            if (-1 == nbytes) /* error */
                HSYS_GOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "file read failed")
            if (0 == nbytes) {
                /* end of file but not end of format address space */
                HDmemset(buf, 0, size);
                break;
            }
            HDassert(nbytes >= 0);
            HDassert((size_t)nbytes <= size);
            H5_CHECK_OVERFLOW(nbytes, ssize_t, size_t);
            size -= (size_t)nbytes;
            H5_CHECK_OVERFLOW(nbytes, ssize_t, haddr_t);
            addr += (haddr_t)nbytes;
            buf = (char *)buf + nbytes;
        }
    }
    else {
        /* Calculate where we will begin copying from the copy buffer */
        copy_offset = (size_t)(addr % _fbsize);

        /* allocate memory needed for the Direct IO option up to the maximal
         * copy buffer size. Make a bigger buffer for aligned I/O if size is
         * smaller than maximal copy buffer. */
        alloc_size = ((copy_offset + size - 1) / _fbsize + 1) * _fbsize;
        if (alloc_size > _cbsize)
            alloc_size = _cbsize;
        HDassert(!(alloc_size % _fbsize));
        if (HDposix_memalign(&copy_buf, _boundary, alloc_size) != 0)
            HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL, "HDposix_memalign failed")

        /* look for the aligned position for reading the data */
        HDassert(!(((addr / _fbsize) * _fbsize) % _fbsize));
        if (HDlseek(file->fd, (HDoff_t)((addr / _fbsize) * _fbsize), SEEK_SET) < 0)
            HSYS_GOTO_ERROR(H5E_IO, H5E_SEEKERROR, FAIL, "unable to seek to proper position")

        /*
         * Read the aligned data in file into aligned buffer first, then copy the data
         * into the final buffer.  If the data size is bigger than maximal copy buffer
         * size, do the reading by segment (the outer while loop).  If not, do one step
         * reading.
         */
        do {
            /* Read the aligned data in file first.  Not able to handle interrupted
             * system calls and partial results like sec2 driver does because the
             * data may no longer be aligned. It's especially true when the data in
             * file is smaller than ALLOC_SIZE. */
            HDmemset(copy_buf, 0, alloc_size);

            /* Calculate how much data we have to read in this iteration
             * (including unused parts of blocks) */
            if ((copy_size + copy_offset) < alloc_size)
                read_size = ((copy_size + copy_offset - 1) / _fbsize + 1) * _fbsize;
            else
                read_size = alloc_size;

            HDassert(!(read_size % _fbsize));
            do {
                nbytes = HDread(file->fd, copy_buf, read_size);
            } while (-1 == nbytes && EINTR == errno);

            if (-1 == nbytes) /* error */
                HSYS_GOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "file read failed")

            /* Copy the needed data from the copy buffer to the output
             * buffer, and update copy_size.  If the copy buffer does not
             * contain the rest of the data, just copy what's in the copy
             * buffer and also update read_addr and copy_offset to read the
             * next section of data. */
            p2 = (unsigned char *)copy_buf + copy_offset;
            if ((copy_size + copy_offset) <= alloc_size) {
                H5MM_memcpy(buf, p2, copy_size);
                buf       = (unsigned char *)buf + copy_size;
                copy_size = 0;
            } /* end if */
            else {
                H5MM_memcpy(buf, p2, alloc_size - copy_offset);
                buf = (unsigned char *)buf + alloc_size - copy_offset;
                copy_size -= alloc_size - copy_offset;
                copy_offset = 0;
            } /* end else */
        } while (copy_size > 0);

        /*Final step: update address*/
        addr = (haddr_t)(((addr + size - 1) / _fbsize + 1) * _fbsize);

        if (copy_buf) {
            /* Free with HDfree since it came from posix_memalign */
            HDfree(copy_buf);
            copy_buf = NULL;
        } /* end if */
    }

    /* Update current position */
    file->pos = addr;
    file->op  = OP_READ;

done:
    if (ret_value < 0) {
        /* Free with HDfree since it came from posix_memalign */
        if (copy_buf)
            HDfree(copy_buf);

        /* Reset last file I/O information */
        file->pos = HADDR_UNDEF;
        file->op  = OP_UNKNOWN;
    } /* end if */

    FUNC_LEAVE_NOAPI(ret_value)
}

/*-------------------------------------------------------------------------
 * Function:  H5FD__direct_write
 *
 * Purpose:  Writes SIZE bytes of data to FILE beginning at address ADDR
 *    from buffer BUF according to data transfer properties in
 *    DXPL_ID.
 *
 * Return:  Success:  Zero
 *
 *    Failure:  -1
 *
 * Programmer:  Raymond Lu
 *              Thursday, 21 September 2006
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD__direct_write(H5FD_t *_file, H5FD_mem_t H5_ATTR_UNUSED type, hid_t H5_ATTR_UNUSED dxpl_id, haddr_t addr,
                   size_t size, const void *buf)
{
    H5FD_direct_t *file = (H5FD_direct_t *)_file;
    ssize_t        nbytes;
    hbool_t        _must_align = TRUE;
    herr_t         ret_value   = SUCCEED; /* Return value */
    size_t         alloc_size;
    void          *copy_buf = NULL, *p1;
    const void    *p3;
    size_t         _boundary;
    size_t         _fbsize;
    size_t         _cbsize;
    haddr_t        write_addr;       /* Address to write copy buffer */
    haddr_t        write_size;       /* Size to write from copy buffer */
    haddr_t        read_size;        /* Size to read into copy buffer */
    size_t         copy_size = size; /* Size remaining to write when using copy buffer */
    size_t         copy_offset;      /* Offset into copy buffer of the data to write */

    FUNC_ENTER_STATIC

    HDassert(file && file->pub.cls);
    HDassert(buf);

    /* Check for overflow conditions */
    if (HADDR_UNDEF == addr)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "addr undefined")
    if (REGION_OVERFLOW(addr, size))
        HGOTO_ERROR(H5E_ARGS, H5E_OVERFLOW, FAIL, "addr overflow")

    /* If the system doesn't require data to be aligned, read the data in
     * the same way as sec2 driver.
     */
    _must_align = file->fa.must_align;

    /* Get the memory boundary for alignment, file system block size, and maximal
     * copy buffer size.
     */
    _boundary = file->fa.mboundary;
    _fbsize   = file->fa.fbsize;
    _cbsize   = file->fa.cbsize;

    /* if the data is aligned or the system doesn't require data to be aligned,
     * write it directly to the file.  If not, read a bigger and aligned data
     * first, update buffer with user data, then write the data out.
     */
    if (!_must_align || ((addr % _fbsize == 0) && (size % _fbsize == 0) && ((size_t)buf % _boundary == 0))) {
        /* Seek to the correct location */
        if ((addr != file->pos || OP_WRITE != file->op) && HDlseek(file->fd, (HDoff_t)addr, SEEK_SET) < 0)
            HSYS_GOTO_ERROR(H5E_IO, H5E_SEEKERROR, FAIL, "unable to seek to proper position")

        while (size > 0) {
            do {
                nbytes = HDwrite(file->fd, buf, size);
            } while (-1 == nbytes && EINTR == errno);
            if (-1 == nbytes) /* error */
                HSYS_GOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "file write failed")
            HDassert(nbytes > 0);
            HDassert((size_t)nbytes <= size);
            H5_CHECK_OVERFLOW(nbytes, ssize_t, size_t);
            size -= (size_t)nbytes;
            H5_CHECK_OVERFLOW(nbytes, ssize_t, haddr_t);
            addr += (haddr_t)nbytes;
            buf = (const char *)buf + nbytes;
        }
    }
    else {
        /* Calculate where we will begin reading from (on disk) and where we
         * will begin copying from the copy buffer */
        write_addr  = (addr / _fbsize) * _fbsize;
        copy_offset = (size_t)(addr % _fbsize);

        /* allocate memory needed for the Direct IO option up to the maximal
         * copy buffer size. Make a bigger buffer for aligned I/O if size is
         * smaller than maximal copy buffer.
         */
        alloc_size = ((copy_offset + size - 1) / _fbsize + 1) * _fbsize;
        if (alloc_size > _cbsize)
            alloc_size = _cbsize;
        HDassert(!(alloc_size % _fbsize));

        if (HDposix_memalign(&copy_buf, _boundary, alloc_size) != 0)
            HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL, "HDposix_memalign failed")

        /* look for the right position for reading or writing the data */
        if (HDlseek(file->fd, (HDoff_t)write_addr, SEEK_SET) < 0)
            HSYS_GOTO_ERROR(H5E_IO, H5E_SEEKERROR, FAIL, "unable to seek to proper position")

        p3 = buf;
        do {
            /* Calculate how much data we have to write in this iteration
             * (including unused parts of blocks) */
            if ((copy_size + copy_offset) < alloc_size)
                write_size = ((copy_size + copy_offset - 1) / _fbsize + 1) * _fbsize;
            else
                write_size = alloc_size;

            /*
             * Read the aligned data first if the aligned region doesn't fall
             * entirely in the range to be written.  Not able to handle interrupted
             * system calls and partial results like sec2 driver does because the
             * data may no longer be aligned. It's especially true when the data in
             * file is smaller than ALLOC_SIZE.  Only read the entire section if
             * both ends are misaligned, otherwise only read the block on the
             * misaligned end.
             */
            HDmemset(copy_buf, 0, _fbsize);

            if (copy_offset > 0) {
                if ((write_addr + write_size) > (addr + size)) {
                    HDassert((write_addr + write_size) - (addr + size) < _fbsize);
                    read_size = write_size;
                    p1        = copy_buf;
                } /* end if */
                else {
                    read_size = _fbsize;
                    p1        = copy_buf;
                } /* end else */
            }     /* end if */
            else if ((write_addr + write_size) > (addr + size)) {
                HDassert((write_addr + write_size) - (addr + size) < _fbsize);
                read_size = _fbsize;
                p1        = (unsigned char *)copy_buf + write_size - _fbsize;

                /* Seek to the last block, for reading */
                HDassert(!((write_addr + write_size - _fbsize) % _fbsize));
                if (HDlseek(file->fd, (HDoff_t)(write_addr + write_size - _fbsize), SEEK_SET) < 0)
                    HSYS_GOTO_ERROR(H5E_IO, H5E_SEEKERROR, FAIL, "unable to seek to proper position")
            } /* end if */
            else
                p1 = NULL;

            if (p1) {
                HDassert(!(read_size % _fbsize));
                do {
                    nbytes = HDread(file->fd, p1, read_size);
                } while (-1 == nbytes && EINTR == errno);

                if (-1 == nbytes) /* error */
                    HSYS_GOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "file read failed")
            } /* end if */

            /* look for the right position and append or copy the data to be written to
             * the aligned buffer.
             * Consider all possible situations here: file address is not aligned on
             * file block size; the end of data address is not aligned; the end of data
             * address is aligned; data size is smaller or bigger than maximal copy size.
             */
            p1 = (unsigned char *)copy_buf + copy_offset;
            if ((copy_size + copy_offset) <= alloc_size) {
                H5MM_memcpy(p1, p3, copy_size);
                copy_size = 0;
            } /* end if */
            else {
                H5MM_memcpy(p1, p3, alloc_size - copy_offset);
                p3 = (const unsigned char *)p3 + (alloc_size - copy_offset);
                copy_size -= alloc_size - copy_offset;
                copy_offset = 0;
            } /* end else */

            /*look for the aligned position for writing the data*/
            HDassert(!(write_addr % _fbsize));
            if (HDlseek(file->fd, (HDoff_t)write_addr, SEEK_SET) < 0)
                HSYS_GOTO_ERROR(H5E_IO, H5E_SEEKERROR, FAIL, "unable to seek to proper position")

            /*
             * Write the data. It doesn't truncate the extra data introduced by
             * alignment because that step is done in H5FD_direct_flush.
             */
            HDassert(!(write_size % _fbsize));
            do {
                nbytes = HDwrite(file->fd, copy_buf, write_size);
            } while (-1 == nbytes && EINTR == errno);

            if (-1 == nbytes) /* error */
                HSYS_GOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "file write failed")

            /* update the write address */
            write_addr += write_size;
        } while (copy_size > 0);

        /*Update the address and size*/
        addr = write_addr;
        buf  = (const char *)buf + size;

        if (copy_buf) {
            /* Free with HDfree since it came from posix_memalign */
            HDfree(copy_buf);
            copy_buf = NULL;
        } /* end if */
    }

    /* Update current position and eof */
    file->pos = addr;
    file->op  = OP_WRITE;
    if (file->pos > file->eof)
        file->eof = file->pos;

done:
    if (ret_value < 0) {
        /* Free with HDfree since it came from posix_memalign */
        if (copy_buf)
            HDfree(copy_buf);

        /* Reset last file I/O information */
        file->pos = HADDR_UNDEF;
        file->op  = OP_UNKNOWN;
    } /* end if */

    FUNC_LEAVE_NOAPI(ret_value)
}

/*-------------------------------------------------------------------------
 * Function:  H5FD__direct_truncate
 *
 * Purpose:  Makes sure that the true file size is the same (or larger)
 *    than the end-of-address.
 *
 * Return:  Success:  Non-negative
 *
 *    Failure:  Negative
 *
 * Programmer:  Raymond Lu
 *              Thursday, 21 September 2006
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD__direct_truncate(H5FD_t *_file, hid_t H5_ATTR_UNUSED dxpl_id, hbool_t H5_ATTR_UNUSED closing)
{
    H5FD_direct_t *file      = (H5FD_direct_t *)_file;
    herr_t         ret_value = SUCCEED; /* Return value */

    FUNC_ENTER_STATIC

    HDassert(file);

    /* Extend the file to make sure it's large enough */
    if (file->eoa != file->eof) {
#ifdef H5_HAVE_WIN32_API
        HFILE         filehandle; /* Windows file handle */
        LARGE_INTEGER li;         /* 64-bit integer for SetFilePointer() call */

        /* Map the posix file handle to a Windows file handle */
        filehandle = _get_osfhandle(file->fd);

        /* Translate 64-bit integers into form Windows wants */
        /* [This algorithm is from the Windows documentation for SetFilePointer()] */
        li.QuadPart = (LONGLONG)file->eoa;
        (void)SetFilePointer((HANDLE)filehandle, li.LowPart, &li.HighPart, FILE_BEGIN);
        if (SetEndOfFile((HANDLE)filehandle) == 0)
            HGOTO_ERROR(H5E_IO, H5E_SEEKERROR, FAIL, "unable to extend file properly")
#else  /* H5_HAVE_WIN32_API */
        if (-1 == HDftruncate(file->fd, (HDoff_t)file->eoa))
            HSYS_GOTO_ERROR(H5E_IO, H5E_SEEKERROR, FAIL, "unable to extend file properly")
#endif /* H5_HAVE_WIN32_API */

        /* Update the eof value */
        file->eof = file->eoa;

        /* Reset last file I/O information */
        file->pos = HADDR_UNDEF;
        file->op  = OP_UNKNOWN;
    }
    else if (file->fa.must_align) {
        /*Even though eof is equal to eoa, file is still truncated because Direct I/O
         *write introduces some extra data for alignment.
         */
        if (-1 == HDftruncate(file->fd, (HDoff_t)file->eof))
            HSYS_GOTO_ERROR(H5E_IO, H5E_SEEKERROR, FAIL, "unable to extend file properly")
    }

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5FD__direct_truncate() */

/*-------------------------------------------------------------------------
 * Function:    H5FD__direct_lock
 *
 * Purpose:     To place an advisory lock on a file.
 *		The lock type to apply depends on the parameter "rw":
 *			TRUE--opens for write: an exclusive lock
 *			FALSE--opens for read: a shared lock
 *
 * Return:      SUCCEED/FAIL
 *
 * Programmer:  Vailin Choi; May 2013
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD__direct_lock(H5FD_t *_file, hbool_t rw)
{
    H5FD_direct_t *file = (H5FD_direct_t *)_file; /* VFD file struct      */
    int            lock_flags;                    /* file locking flags   */
    herr_t         ret_value = SUCCEED;           /* Return value         */

    FUNC_ENTER_STATIC

    HDassert(file);

    /* Set exclusive or shared lock based on rw status */
    lock_flags = rw ? LOCK_EX : LOCK_SH;

    /* Place a non-blocking lock on the file */
    if (HDflock(file->fd, lock_flags | LOCK_NB) < 0) {
        if (file->ignore_disabled_file_locks && ENOSYS == errno) {
            /* When errno is set to ENOSYS, the file system does not support
             * locking, so ignore it.
             */
            errno = 0;
        }
        else
            HSYS_GOTO_ERROR(H5E_VFL, H5E_CANTLOCKFILE, FAIL, "unable to lock file")
    }

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5FD__direct_lock() */

/*-------------------------------------------------------------------------
 * Function:    H5FD__direct_unlock
 *
 * Purpose:     To remove the existing lock on the file
 *
 * Return:      SUCCEED/FAIL
 *
 * Programmer:  Vailin Choi; May 2013
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD__direct_unlock(H5FD_t *_file)
{
    H5FD_direct_t *file      = (H5FD_direct_t *)_file; /* VFD file struct */
    herr_t         ret_value = SUCCEED;                /* Return value */

    FUNC_ENTER_STATIC

    HDassert(file);

    if (HDflock(file->fd, LOCK_UN) < 0) {
        if (file->ignore_disabled_file_locks && ENOSYS == errno) {
            /* When errno is set to ENOSYS, the file system does not support
             * locking, so ignore it.
             */
            errno = 0;
        }
        else
            HSYS_GOTO_ERROR(H5E_VFL, H5E_CANTUNLOCKFILE, FAIL, "unable to unlock file")
    }

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5FD__direct_unlock() */

#endif /* H5_HAVE_DIRECT */