summaryrefslogtreecommitdiffstats
path: root/src/H5FDgass.c
blob: 91514400eec9b7c41d56db8901761a415077d7fa (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
/*
 * Copyright © 1999-2001 NCSA
 *                       All rights reserved.
 *
 * Programmer:  Saurabh Bagchi (bagchi@uiuc.edu)
 *              Thursday, August 12 -Tuesday, August 17, 1999
 *
 * Purpose:	This is the GASS I/O driver.
 *
 */
#include "H5private.h"		/*library functions			*/
#include "H5Eprivate.h"		/*error handling			*/
#include "H5Fprivate.h"		/*files					*/
#include "H5FDprivate.h"	/*file driver				  */
#include "H5FDgass.h"       /* Core file driver */
#include "H5MMprivate.h"    /* Memory allocation */
#include "H5Pprivate.h"		/*property lists			*/


#undef MAX
#define MAX(X,Y)	((X)>(Y)?(X):(Y))

/* The driver identification number, initialized at runtime */
static hid_t H5FD_GASS_g = 0;

#ifdef H5_HAVE_GASS

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

/*
 * 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_gass_t {
    H5FD_t	pub;			/*public stuff, must be first	*/
    int		fd;			/*the unix file			*/
    GASS_Info   info;                   /*file information */
    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_gass_t;

/*
 * This driver supports systems that have the lseek64() function by defining
 * some macros here so we don't have to have conditional compilations later
 * throughout the code.
 *
 * file_offset_t:	The datatype for file offsets, the second argument of
 *			the lseek() or lseek64() call.
 *
 * file_seek:		The function which adjusts the current file position,
 *			either lseek() or lseek64().
 */
#ifdef H5_HAVE_LSEEK64
#   define file_offset_t	off64_t
#   define file_seek		lseek64
#else
#   define file_offset_t	off_t
#   define file_seek		lseek
#endif

/*
 * These macros check for overflow of various quantities.  These macros
 * assume that file_offset_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(file_offset_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) ||      \
				 sizeof(file_offset_t)<sizeof(size_t) ||      \
                                 HADDR_UNDEF==(A)+(Z) ||		      \
				 (file_offset_t)((A)+(Z))<(file_offset_t)(A))

/* Prototypes */
static H5FD_t *H5FD_gass_open(const char *name, unsigned flags, hid_t fapl_id,
			      haddr_t maxaddr);
static herr_t H5FD_gass_close(H5FD_t *_file);
static herr_t H5FD_gass_query(const H5FD_t *_f1, unsigned long *flags);
static haddr_t H5FD_gass_get_eoa(H5FD_t *_file);
static herr_t H5FD_gass_set_eoa(H5FD_t *_file, haddr_t addr);
static haddr_t H5FD_gass_get_eof(H5FD_t *_file);
static herr_t H5FD_gass_read(H5FD_t *_file, H5FD_mem_t type, hid_t fapl_id, haddr_t addr,
			     hsize_t size, void *buf);
static herr_t H5FD_gass_write(H5FD_t *_file, H5FD_mem_t type, hid_t fapl_id, haddr_t addr,
			      hsize_t size, const void *buf);

/* GASS I/O-specific file access properties */
typedef struct H5FD_gass_fapl_t {
  GASS_Info            info;      /* access property parameters */
} H5FD_gass_fapl_t;

/* The GASS IO driver information */
static const H5FD_class_t H5FD_gass_g = {
    "gass",					/*name			*/
    MAXADDR,					/*maxaddr		*/
    NULL,					/*sb_size		*/
    NULL,					/*sb_encode		*/
    NULL,					/*sb_decode		*/
    sizeof(H5FD_gass_fapl_t), 			/*fapl_size		*/
    NULL,					/*fapl_get		*/
    NULL,					/*fapl_copy		*/
    NULL, 					/*fapl_free		*/
    0,						/*dxpl_size		*/
    NULL,					/*dxpl_copy		*/
    NULL,					/*dxpl_free		*/
    H5FD_gass_open,				/*open			*/
    H5FD_gass_close,				/*close			*/
    NULL,				        /*cmp			*/
    H5FD_gass_query,				/*query			*/
    NULL,					/*alloc			*/
    NULL,					/*free			*/
    H5FD_gass_get_eoa,				/*get_eoa		*/
    H5FD_gass_set_eoa, 				/*set_eoa		*/
    H5FD_gass_get_eof,				/*get_eof		*/
    H5FD_gass_read,				/*read			*/
    H5FD_gass_write,				/*write			*/
    NULL,				        /*flush			*/
    H5FD_FLMAP_SINGLE,				/*fl_map		*/
};

/* Interface initialization */
#define PABLO_MASK	H5FD_gass_mask
#define INTERFACE_INIT	H5FD_gass_init
static intn interface_initialize_g = 0;


/*-------------------------------------------------------------------------
 * Function:	H5FD_gass_init
 *
 * Purpose:	Initialize this driver by registering the driver with the
 *		library.
 *
 * Return:	Success:	The driver ID for the gass driver.
 *
 *		Failure:	Negative.
 *
 * Programmer:	Saurabh Bagchi
 *              Friday, August 13, 1999
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
hid_t
H5FD_gass_init(void)
{
    FUNC_ENTER(H5FD_gass_init, FAIL);

    if (!H5FD_GASS_g)
        H5FD_GASS_g = H5FDregister(&H5FD_gass_g);

    globus_module_activate (GLOBUS_COMMON_MODULE);
    globus_module_activate (GLOBUS_GASS_FILE_MODULE);

    FUNC_LEAVE(H5FD_GASS_g);
}


/*-------------------------------------------------------------------------
 * Function:	H5Pset_fapl_gass
 *
 * Purpose:	Store the user supplied GASS INFO in
 *		the file access property list FAPL_ID which can then be used
 *		to create and/or open the file. 
 *
 *		GASS info object to be used for file open using GASS.
 *              Any modification to info after
 *		this function call returns may have undetermined effect
 *		to the access property list.  Users should call this
 *		function again to setup the property list.
 *
 *
 * Return:	Success:	Non-negative
 *
 * 		Failure:	Negative
 *
 * Programmer:	Saurabh Bagchi
 *		Friday, August 13, 1999
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Pset_fapl_gass(hid_t fapl_id, GASS_Info info)
{
    herr_t ret_value=FAIL;
    H5FD_gass_fapl_t	fa;
    
    FUNC_ENTER(H5Pset_fapl_gass, FAIL);
    
    /* Check arguments */
    if (H5P_FILE_ACCESS!=H5Pget_class(fapl_id))
        HRETURN_ERROR(H5E_PLIST, H5E_BADTYPE, FAIL, "not a fapl");
#ifdef LATER
#warning "We need to verify that INFO contain sensible information."
#endif

    /* Initialize driver specific properties */
    fa.info = info;

    ret_value= H5Pset_driver(fapl_id, H5FD_GASS, &fa);

    FUNC_LEAVE(ret_value);
}


/*-------------------------------------------------------------------------
 * Function:	H5Pget_fapl_gass
 *
 * Purpose:	If the file access property list is set to the H5FD_GASS
 *		driver then this function returns the GASS info object
 *		through the INFO pointer.
 *
 * Return:	Success:	Non-negative with the info object returned 
 *                              through the INFO arguments if non-null. 
 *				The information is copied and it is therefore
 *				valid only until the file access property
 *				list is modified or closed.
 *
 * 		Failure:	Negative
 *
 * Programmer:	Saurabh Bagchi
 *		Friday, August 13, 1999
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Pget_fapl_gass(hid_t fapl_id, GASS_Info *info/*out*/)
{
    H5FD_gass_fapl_t	*fa;
    
    FUNC_ENTER(H5Pget_fapl_gass, FAIL);
    H5TRACE2("e","ix",fapl_id,info);

    if (H5P_FILE_ACCESS!=H5Pget_class(fapl_id))
        HRETURN_ERROR(H5E_PLIST, H5E_BADTYPE, FAIL, "not a fapl");
    if (H5FD_GASS!=H5P_get_driver(fapl_id))
        HRETURN_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "incorrect VFL driver");
    if (NULL==(fa=H5Pget_driver_info(fapl_id)))
        HRETURN_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "bad VFL driver info");

    if (info)
        *info = fa->info;

    FUNC_LEAVE(SUCCEED);
}


/*-------------------------------------------------------------------------
 * Function:	H5FD_gass_open
 *
 * Purpose:	Opens a file with name NAME.  The FLAGS are a bit field with
 *		purpose similar to the second argument of open(2) and which
 *		are defined in H5Fpublic.h. The file access property list
 *		FAPL_ID contains the driver properties and MAXADDR
 *		is the largest address which this file will be expected to
 *		access.
 *
 * 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:	Saurabh Bagchi
 *              Friday, August 13, 1999
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static H5FD_t *
H5FD_gass_open(const char *name, unsigned flags, hid_t fapl_id,
	       haddr_t maxaddr)
{
    int		fd;
    struct stat	sb;
    H5FD_gass_t	*file=NULL;
    const H5FD_gass_fapl_t	*fa=NULL;
    H5FD_gass_fapl_t		_fa;
    char *filename = (char *) H5MM_malloc(80 * sizeof(char));
    
    FUNC_ENTER(H5FD_gass_open, NULL);

    /* fprintf(stdout, "Entering H5FD_gass_open name=%s flags=0x%x\n", name, flags); */

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

    strcpy (filename, name);
    
    /* Obtain a pointer to gass-specific file access properties */
    if (H5P_DEFAULT==fapl_id || H5FD_GASS!=H5P_get_driver(fapl_id)) {
        GASS_INFO_NULL (_fa.info);
        /* _fa.info = GASS_INFO_NULL; */
        /* _fa.info = {0,0}; */ /*default*/
        fa = &_fa;
    } else {
        fa = H5Pget_driver_info(fapl_id);
        assert(fa);
    }
    
    /* When I come down here, the possible flag values and the correct
       responses are given here :-

       1. H5F_ACC_CREAT | H5F_ACC_RDWR | H5F_ACC_EXCL : The file is 
          a new one. Go ahead and open it in O_RDWR. 

       2. H5F_ACC_CREAT | H5F_ACC_RDWR | H5F_ACC_TRUNC : Use
          O_RDWR | O_TRUNC with gass_open.

       3. H5F_ACC_RDWR | H5F_ACC_TRUNC : File already exists. Truncate it.
	  
       4. H5F_ACC_RDWR : Use O_RDWR with gass_open

       5. H5F_ACC_RDWR is not set : Use O_RDONLY with gass_open

       One reason why we cannot simply pass on the flags to gass_open
       is that gass_open does not support many of them (e.g., O_CREAT)
    */

    
    if ((flags & H5F_ACC_CREAT) && (flags & H5F_ACC_RDWR) && (flags & H5F_ACC_EXCL)) {
      if ((fd = globus_gass_open (filename, O_RDWR|O_TRUNC)) < 0)
        HRETURN_ERROR(H5E_IO, H5E_CANTOPENFILE, NULL, "open failed");
    }
    else if ((flags & H5F_ACC_CREAT) && (flags & H5F_ACC_RDWR) && (flags & H5F_ACC_TRUNC)) {
      if ((fd = globus_gass_open (filename, O_RDWR|O_TRUNC)) < 0)
        HRETURN_ERROR(H5E_IO, H5E_CANTOPENFILE, NULL, "open failed");
      
    }
    else if ((flags & H5F_ACC_RDWR) && (flags & H5F_ACC_TRUNC)) {
      if ((fd = globus_gass_open (filename, O_RDWR|O_TRUNC)) < 0)
        HRETURN_ERROR(H5E_IO, H5E_CANTOPENFILE, NULL, "open failed");
    
    }
    else if (flags & H5F_ACC_RDWR) {
      printf ("I'm here in H5FDgass_open going to call globus_gass_open with O_RDWR. \n");
      printf ("Name of URL =%s \n", filename);
      if ((fd = globus_gass_open (filename, O_RDWR)) < 0)
        HRETURN_ERROR(H5E_IO, H5E_CANTOPENFILE, NULL, "open failed");
      
    }
    else { /* This is case where H5F_ACC_RDWR is not set */
      if ((fd = globus_gass_open (filename, O_RDONLY)) < 0)
        HRETURN_ERROR(H5E_IO, H5E_CANTOPENFILE, NULL, "open failed");
      
    }
   
     if (fstat(fd, &sb)<0) {
        close(fd);
        HRETURN_ERROR(H5E_IO, H5E_BADFILE, NULL, "fstat failed");
    }

    /* Create the new file struct */
    if (NULL==(file=H5MM_calloc(sizeof(H5FD_gass_t))))
        HRETURN_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "can't allocate file struct");
    file->fd = fd;
    file->eof = sb.st_size;
    file->pos = HADDR_UNDEF;
    file->op = OP_UNKNOWN;
    file->info = fa->info;
    
    FUNC_LEAVE((H5FD_t*)file);
}

/*-------------------------------------------------------------------------
 * Function:	H5FD_gass_close
 *
 * Purpose:	Closes a GASS file.
 *
 * Return:	Success:	0
 *
 *		Failure:	-1, file not closed.
 *
 * Programmer:	Saurabh Bagchi
 *              Monday, August 16, 1999
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD_gass_close (H5FD_t *_file)
{
    H5FD_gass_t *file = (H5FD_gass_t *)_file;

    FUNC_ENTER(H5FD_gass_close, FAIL);

	if (file == NULL)
	  HRETURN_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid file handle");
	
	if (globus_gass_close (file->fd) < 0)
	  HRETURN_ERROR(H5E_IO, H5E_CANTCLOSEFILE, FAIL, "can't close GASS file");

    H5MM_xfree(file);

    FUNC_LEAVE(SUCCEED);
}

	

/*-------------------------------------------------------------------------
 * Function:	H5FD_gass_query
 *
 * Purpose:	Set the flags that this VFL driver is capable of supporting.
 *              (listed in H5FDpublic.h)
 *
 * Return:	Success:	non-negative
 *
 *		Failure:	negative
 *
 * Programmer:	Quincey Koziol
 *              Tuesday, September 26, 2000
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD_gass_query(const UNUSED H5FD_t *_f, unsigned long *flags /* out */)
{
    herr_t ret_value=SUCCEED;

    FUNC_ENTER(H5FD_gass_query, FAIL);

    /* Set the VFL feature flags that this driver supports */
    if(flags) {
        *flags = 0;
        *flags|=H5FD_FEAT_DATA_SIEVE;       /* OK to perform data sieving for faster raw data reads & writes */
    }

    FUNC_LEAVE(ret_value);
}


/*-------------------------------------------------------------------------
 * Function:	H5FD_gass_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:  Saurabh Bagchi
 *              Monday, August 16, 1999
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static haddr_t
H5FD_gass_get_eoa(H5FD_t *_file)
{
	H5FD_gass_t *file = (H5FD_gass_t *)_file;

    FUNC_ENTER(H5FD_gass_get_eoa, HADDR_UNDEF);

    FUNC_LEAVE(file->eoa);
}


/*-------------------------------------------------------------------------
 * Function:    H5FD_gass_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
 *
 * Programmer:  Saurabh Bagchi
 *              Monday, August 16, 1999
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD_gass_set_eoa(H5FD_t *_file, haddr_t addr)
{
    H5FD_gass_t *file = (H5FD_gass_t *)_file;

    FUNC_ENTER(H5FD_gass_set_eoa, FAIL);

    file->eoa = addr;

    FUNC_LEAVE(SUCCEED);
}


/*-------------------------------------------------------------------------
 * Function:    H5FD_gass_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:  Saurabh Bagchi
 *              Monday, August 16, 1999
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static haddr_t
H5FD_gass_get_eof(H5FD_t *_file)
{
    H5FD_gass_t *file = (H5FD_gass_t*)_file;

    FUNC_ENTER(H5FD_gass_get_eof, HADDR_UNDEF);

    FUNC_LEAVE(MAX(file->eof, file->eoa));
}

/*-------------------------------------------------------------------------
 * Function:    H5FD_gass_read
 *
 * Purpose:     Reads SIZE bytes of data from FILE beginning at address ADDR
 *              into buffer BUF.
 *
 * Return:      Success:        Zero. Result is stored in caller-supplied
 *                              buffer BUF.
 *
 *              Failure:        -1, Contents of buffer BUF are undefined.
 *
 * Programmer:  Saurabh Bagchi
 *              Monday, August 16, 1999
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD_gass_read(H5FD_t *_file, H5FD_mem_t UNUSED type, hid_t dxpl_id/*unused*/, haddr_t addr,
               hsize_t size, void *buf/*out*/)
{
    H5FD_gass_t         *file = (H5FD_gass_t*)_file;
    ssize_t             nbytes;

    FUNC_ENTER(H5FD_gass_read, FAIL);

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

    /* Check for overflow conditions */
    if (HADDR_UNDEF==addr)
        HRETURN_ERROR(H5E_ARGS, H5E_BADRANGE, FAIL, "addr undefined");
    if (REGION_OVERFLOW(addr, size))
        HRETURN_ERROR(H5E_ARGS, H5E_OVERFLOW, FAIL, "addr too large");
    if (addr+size>file->eoa)
        HRETURN_ERROR(H5E_ARGS, H5E_OVERFLOW, FAIL, "addr too large");

    /* Seek to the correct location */
    if ((addr!=file->pos || OP_READ!=file->op) &&
            file_seek(file->fd, (file_offset_t)addr, SEEK_SET)<0) {
        file->pos = HADDR_UNDEF;
        file->op = OP_UNKNOWN;
        HRETURN_ERROR(H5E_IO, H5E_SEEKERROR, FAIL, "gass file seek failed");
    }

    /*
     * Read data, being careful of interrupted system calls, partial results,
     * and the end of the file.
     */
    while (size>0) {
        do 
            nbytes = read(file->fd, buf, size);
        while (-1==nbytes && EINTR==errno);

        if (-1==nbytes) {
            /* error */
            file->pos = HADDR_UNDEF;
            file->op = OP_UNKNOWN;
            HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL, "gass file read failed");
        }
        if (0==nbytes) {
            /* end of file but not end of format address space */
            memset(buf, 0, size);
            size = 0;
        }
        assert(nbytes>=0);
        assert((hsize_t)nbytes<=size);
        size -= (hsize_t)nbytes;
        addr += (haddr_t)nbytes;
        buf = (char*)buf + nbytes;
    }

    /* Update current position */
    file->pos = addr;
    file->op = OP_READ;
    FUNC_LEAVE(SUCCEED);
}

/*-------------------------------------------------------------------------
 * Function:    H5FD_gass_write
 *
 * Purpose:     Writes SIZE bytes of data to FILE beginning at address ADDR
 *              from buffer BUF.
 *
 * Return:      Success:        Zero
 *
 *              Failure:        -1
 *
 * Programmer:  Saurabh Bagchi
 *              Tuesday, August 17, 1999
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD_gass_write(H5FD_t *_file, H5FD_mem_t type, hid_t dxpl_id/*unused*/, haddr_t addr,
                hsize_t size, const void *buf)
{
    H5FD_gass_t         *file = (H5FD_gass_t*)_file;
    ssize_t             nbytes;

    FUNC_ENTER(H5FD_gass_write, FAIL);

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

    /* Check for overflow conditions */
    if (HADDR_UNDEF==addr)
        HRETURN_ERROR(H5E_ARGS, H5E_BADRANGE, FAIL, "addr undefined");
    if (REGION_OVERFLOW(addr, size))
        HRETURN_ERROR(H5E_ARGS, H5E_OVERFLOW, FAIL, "addr too large");
    if (addr+size>file->eoa)
        HRETURN_ERROR(H5E_ARGS, H5E_OVERFLOW, FAIL, "addr too large");

    /* Seek to the correct location */
    if ((addr!=file->pos || OP_WRITE!=file->op) &&
        file_seek(file->fd, (file_offset_t)addr, SEEK_SET)<0) {
        file->pos = HADDR_UNDEF;
        file->op = OP_UNKNOWN;
        HRETURN_ERROR(H5E_IO, H5E_SEEKERROR, FAIL, "gass file seek failed");
    }

    /*
     * Write the data, being careful of interrupted system calls and partial
     * results
     */
    while (size>0) {
        do
            nbytes = write(file->fd, buf, size);
        while (-1==nbytes && EINTR==errno);

        if (-1==nbytes) {
            /* error */
            file->pos = HADDR_UNDEF;
            file->op = OP_UNKNOWN;
            HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "gass file write failed");
        }
        assert(nbytes>0);
        assert((hsize_t)nbytes<=size);
        size -= (hsize_t)nbytes;
        addr += (haddr_t)nbytes;
        buf = (const char*)buf + nbytes;
    }

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

    FUNC_LEAVE(SUCCEED);
}

#endif  /* H5_HAVE_GASS */