summaryrefslogtreecommitdiffstats
path: root/kexi/3rdparty/kexisql3/src/os_mac.c
blob: f393b423b42f2e8728458de487766309d18f8789 (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
/*
** 2004 May 22
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
******************************************************************************
**
** This file contains code that is specific classic mac.  Mac OS X
** uses the os_unix.c file, not this one.
*/
#include "os.h"          /* Must be first to enable large file support */
#if OS_MAC               /* This file used on classic mac only */
#include "sqliteInt.h"

#include <extras.h>
#include <path2fss.h>
#include <TextUtils.h>
#include <FinderRegistry.h>
#include <Folders.h>
#include <Timer.h>
#include <OSUtils.h>

/*
** Macros used to determine whether or not to use threads.
*/
#if defined(THREADSAFE) && THREADSAFE
# include <Multiprocessing.h>
# define SQLITE_MACOS_MULTITASKING 1
#endif

/*
** Include code that is common to all os_*.c files
*/
#include "os_common.h"

/*
** Delete the named file
*/
int sqlite3OsDelete(const char *zFilename){
  unlink(zFilename);
  return SQLITE_OK;
}

/*
** Return TRUE if the named file exists.
*/
int sqlite3OsFileExists(const char *zFilename){
  return access(zFilename, 0)==0;
}

/*
** Attempt to open a file for both reading and writing.  If that
** fails, try opening it read-only.  If the file does not exist,
** try to create it.
**
** On success, a handle for the open file is written to *id
** and *pReadonly is set to 0 if the file was opened for reading and
** writing or 1 if the file was opened read-only.  The function returns
** SQLITE_OK.
**
** On failure, the function returns SQLITE_CANTOPEN and leaves
** *id and *pReadonly unchanged.
*/
int sqlite3OsOpenReadWrite(
  const char *zFilename,
  OsFile *id,
  int *pReadonly,
  int exclusiveFlag,
  int allowReadonly
){
  FSSpec fsSpec;
# ifdef _LARGE_FILE
  HFSUniStr255 dfName;
  FSRef fsRef;
  if( __path2fss(zFilename, &fsSpec) != noErr ){
    if( HCreate(fsSpec.vRefNum, fsSpec.parID, fsSpec.name, 'SQLI', cDocumentFile) != noErr )
      return SQLITE_CANTOPEN;
  }
  if( FSpMakeFSRef(&fsSpec, &fsRef) != noErr )
    return SQLITE_CANTOPEN;
  FSGetDataForkName(&dfName);
  if( FSOpenFork(&fsRef, dfName.length, dfName.tqunicode,
                 fsRdWrShPerm, &(id->refNum)) != noErr ){
    if( FSOpenFork(&fsRef, dfName.length, dfName.tqunicode,
                   fsRdWrPerm, &(id->refNum)) != noErr ){
      if (FSOpenFork(&fsRef, dfName.length, dfName.tqunicode,
                   fsRdPerm, &(id->refNum)) != noErr )
        return SQLITE_CANTOPEN;
      else
        *pReadonly = 1;
    } else
      *pReadonly = 0;
  } else
    *pReadonly = 0;
# else
  __path2fss(zFilename, &fsSpec);
  if( !sqlite3OsFileExists(zFilename) ){
    if( HCreate(fsSpec.vRefNum, fsSpec.parID, fsSpec.name, 'SQLI', cDocumentFile) != noErr )
      return SQLITE_CANTOPEN;
  }
  if( HOpenDF(fsSpec.vRefNum, fsSpec.parID, fsSpec.name, fsRdWrShPerm, &(id->refNum)) != noErr ){
    if( HOpenDF(fsSpec.vRefNum, fsSpec.parID, fsSpec.name, fsRdWrPerm, &(id->refNum)) != noErr ){
      if( HOpenDF(fsSpec.vRefNum, fsSpec.parID, fsSpec.name, fsRdPerm, &(id->refNum)) != noErr )
        return SQLITE_CANTOPEN;
      else
        *pReadonly = 1;
    } else
      *pReadonly = 0;
  } else
    *pReadonly = 0;
# endif
  if( HOpenRF(fsSpec.vRefNum, fsSpec.parID, fsSpec.name, fsRdWrShPerm, &(id->refNumRF)) != noErr){
    id->refNumRF = -1;
  }
  id->locked = 0;
  id->delOnClose = 0;
  OpenCounter(+1);
  return SQLITE_OK;
}


/*
** Attempt to open a new file for exclusive access by this process.
** The file will be opened for both reading and writing.  To avoid
** a potential security problem, we do not allow the file to have
** previously existed.  Nor do we allow the file to be a symbolic
** link.
**
** If delFlag is true, then make arrangements to automatically delete
** the file when it is closed.
**
** On success, write the file handle into *id and return SQLITE_OK.
**
** On failure, return SQLITE_CANTOPEN.
*/
int sqlite3OsOpenExclusive(const char *zFilename, OsFile *id, int delFlag){
  FSSpec fsSpec;
# ifdef _LARGE_FILE
  HFSUniStr255 dfName;
  FSRef fsRef;
  __path2fss(zFilename, &fsSpec);
  if( HCreate(fsSpec.vRefNum, fsSpec.parID, fsSpec.name, 'SQLI', cDocumentFile) != noErr )
    return SQLITE_CANTOPEN;
  if( FSpMakeFSRef(&fsSpec, &fsRef) != noErr )
    return SQLITE_CANTOPEN;
  FSGetDataForkName(&dfName);
  if( FSOpenFork(&fsRef, dfName.length, dfName.tqunicode,
                 fsRdWrPerm, &(id->refNum)) != noErr )
    return SQLITE_CANTOPEN;
# else
  __path2fss(zFilename, &fsSpec);
  if( HCreate(fsSpec.vRefNum, fsSpec.parID, fsSpec.name, 'SQLI', cDocumentFile) != noErr )
    return SQLITE_CANTOPEN;
  if( HOpenDF(fsSpec.vRefNum, fsSpec.parID, fsSpec.name, fsRdWrPerm, &(id->refNum)) != noErr )
    return SQLITE_CANTOPEN;
# endif
  id->refNumRF = -1;
  id->locked = 0;
  id->delOnClose = delFlag;
  if (delFlag)
    id->pathToDel = sqlite3OsFullPathname(zFilename);
  OpenCounter(+1);
  return SQLITE_OK;
}

/*
** Attempt to open a new file for read-only access.
**
** On success, write the file handle into *id and return SQLITE_OK.
**
** On failure, return SQLITE_CANTOPEN.
*/
int sqlite3OsOpenReadOnly(const char *zFilename, OsFile *id){
  FSSpec fsSpec;
# ifdef _LARGE_FILE
  HFSUniStr255 dfName;
  FSRef fsRef;
  if( __path2fss(zFilename, &fsSpec) != noErr )
    return SQLITE_CANTOPEN;
  if( FSpMakeFSRef(&fsSpec, &fsRef) != noErr )
    return SQLITE_CANTOPEN;
  FSGetDataForkName(&dfName);
  if( FSOpenFork(&fsRef, dfName.length, dfName.tqunicode,
                 fsRdPerm, &(id->refNum)) != noErr )
    return SQLITE_CANTOPEN;
# else
  __path2fss(zFilename, &fsSpec);
  if( HOpenDF(fsSpec.vRefNum, fsSpec.parID, fsSpec.name, fsRdPerm, &(id->refNum)) != noErr )
    return SQLITE_CANTOPEN;
# endif
  if( HOpenRF(fsSpec.vRefNum, fsSpec.parID, fsSpec.name, fsRdWrShPerm, &(id->refNumRF)) != noErr){
    id->refNumRF = -1;
  }
  id->locked = 0;
  id->delOnClose = 0;
  OpenCounter(+1);
  return SQLITE_OK;
}

/*
** Attempt to open a file descriptor for the directory that contains a
** file.  This file descriptor can be used to fsync() the directory
** in order to make sure the creation of a new file is actually written
** to disk.
**
** This routine is only meaningful for Unix.  It is a no-op under
** windows since windows does not support hard links.
**
** On success, a handle for a previously open file is at *id is
** updated with the new directory file descriptor and SQLITE_OK is
** returned.
**
** On failure, the function returns SQLITE_CANTOPEN and leaves
** *id unchanged.
*/
int sqlite3OsOpenDirectory(
  const char *zDirname,
  OsFile *id
){
  return SQLITE_OK;
}

/*
** Create a temporary file name in zBuf.  zBuf must be big enough to
** hold at least SQLITE_TEMPNAME_SIZE characters.
*/
int sqlite3OsTempFileName(char *zBuf){
  static char zChars[] =
    "abcdefghijklmnopqrstuvwxyz"
    "ABCDEFGHIJKLMNOPTQRSTUVWXYZ"
    "0123456789";
  int i, j;
  char zTempPath[SQLITE_TEMPNAME_SIZE];
  char zdirName[32];
  CInfoPBRec infoRec;
  Str31 dirName;
  memset(&infoRec, 0, sizeof(infoRec));
  memset(zTempPath, 0, SQLITE_TEMPNAME_SIZE);
  if( FindFolder(kOnSystemDisk, kTemporaryFolderType,  kCreateFolder,
       &(infoRec.dirInfo.ioVRefNum), &(infoRec.dirInfo.ioDrParID)) == noErr ){
    infoRec.dirInfo.ioNamePtr = dirName;
    do{
      infoRec.dirInfo.ioFDirIndex = -1;
      infoRec.dirInfo.ioDrDirID = infoRec.dirInfo.ioDrParID;
      if( PBGetCatInfoSync(&infoRec) == noErr ){
        CopyPascalStringToC(dirName, zdirName);
        i = strlen(zdirName);
        memmove(&(zTempPath[i+1]), zTempPath, strlen(zTempPath));
        strcpy(zTempPath, zdirName);
        zTempPath[i] = ':';
      }else{
        *zTempPath = 0;
        break;
      }
    } while( infoRec.dirInfo.ioDrDirID != fsRtDirID );
  }
  if( *zTempPath == 0 )
    getcwd(zTempPath, SQLITE_TEMPNAME_SIZE-24);
  for(;;){
    sprintf(zBuf, "%s"TEMP_FILE_PREFIX, zTempPath);
    j = strlen(zBuf);
    sqlite3Randomness(15, &zBuf[j]);
    for(i=0; i<15; i++, j++){
      zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ];
    }
    zBuf[j] = 0;
    if( !sqlite3OsFileExists(zBuf) ) break;
  }
  return SQLITE_OK; 
}

/*
** Close a file.
*/
int sqlite3OsClose(OsFile *id){
  if( id->refNumRF!=-1 )
    FSClose(id->refNumRF);
# ifdef _LARGE_FILE
  FSCloseFork(id->refNum);
# else
  FSClose(id->refNum);
# endif
  if( id->delOnClose ){
    unlink(id->pathToDel);
    sqliteFree(id->pathToDel);
  }
  OpenCounter(-1);
  return SQLITE_OK;
}

/*
** Read data from a file into a buffer.  Return SQLITE_OK if all
** bytes were read successfully and SQLITE_IOERR if anything goes
** wrong.
*/
int sqlite3OsRead(OsFile *id, void *pBuf, int amt){
  int got;
  SimulateIOError(SQLITE_IOERR);
  TRACE2("READ %d\n", last_page);
# ifdef _LARGE_FILE
  FSReadFork(id->refNum, fsAtMark, 0, (ByteCount)amt, pBuf, (ByteCount*)&got);
# else
  got = amt;
  FSRead(id->refNum, &got, pBuf);
# endif
  if( got==amt ){
    return SQLITE_OK;
  }else{
    return SQLITE_IOERR;
  }
}

/*
** Write data from a buffer into a file.  Return SQLITE_OK on success
** or some other error code on failure.
*/
int sqlite3OsWrite(OsFile *id, const void *pBuf, int amt){
  OSErr oserr;
  int wrote = 0;
  SimulateIOError(SQLITE_IOERR);
  TRACE2("WRITE %d\n", last_page);
  while( amt>0 ){
# ifdef _LARGE_FILE
    oserr = FSWriteFork(id->refNum, fsAtMark, 0,
                        (ByteCount)amt, pBuf, (ByteCount*)&wrote);
# else
    wrote = amt;
    oserr = FSWrite(id->refNum, &wrote, pBuf);
# endif
    if( wrote == 0 || oserr != noErr)
      break;
    amt -= wrote;
    pBuf = &((char*)pBuf)[wrote];
  }
  if( oserr != noErr || amt>wrote ){
    return SQLITE_FULL;
  }
  return SQLITE_OK;
}

/*
** Move the read/write pointer in a file.
*/
int sqlite3OsSeek(OsFile *id, off_t offset){
  off_t curSize;
  SEEK(offset/1024 + 1);
  if( sqlite3OsFileSize(id, &curSize) != SQLITE_OK ){
    return SQLITE_IOERR;
  }
  if( offset >= curSize ){
    if( sqlite3OsTruncate(id, offset+1) != SQLITE_OK ){
      return SQLITE_IOERR;
    }
  }
# ifdef _LARGE_FILE
  if( FSSetForkPosition(id->refNum, fsFromStart, offset) != noErr ){
# else
  if( SetFPos(id->refNum, fsFromStart, offset) != noErr ){
# endif
    return SQLITE_IOERR;
  }else{
    return SQLITE_OK;
  }
}

/*
** Make sure all writes to a particular file are committed to disk.
**
** Under Unix, also make sure that the directory entry for the file
** has been created by fsync-ing the directory that contains the file.
** If we do not do this and we encounter a power failure, the directory
** entry for the journal might not exist after we reboot.  The next
** SQLite to access the file will not know that the journal exists (because
** the directory entry for the journal was never created) and the transaction
** will not roll back - possibly leading to database corruption.
*/
int sqlite3OsSync(OsFile *id){
# ifdef _LARGE_FILE
  if( FSFlushFork(id->refNum) != noErr ){
# else
  ParamBlockRec params;
  memset(&params, 0, sizeof(ParamBlockRec));
  params.ioParam.ioRefNum = id->refNum;
  if( PBFlushFileSync(&params) != noErr ){
# endif
    return SQLITE_IOERR;
  }else{
    return SQLITE_OK;
  }
}

/*
** Sync the directory zDirname. This is a no-op on operating systems other
** than UNIX.
*/
int sqlite3OsSyncDirectory(const char *zDirname){
  SimulateIOError(SQLITE_IOERR);
  return SQLITE_OK;
}

/*
** Truncate an open file to a specified size
*/
int sqlite3OsTruncate(OsFile *id, off_t nByte){
  SimulateIOError(SQLITE_IOERR);
# ifdef _LARGE_FILE
  if( FSSetForkSize(id->refNum, fsFromStart, nByte) != noErr){
# else
  if( SetEOF(id->refNum, nByte) != noErr ){
# endif
    return SQLITE_IOERR;
  }else{
    return SQLITE_OK;
  }
}

/*
** Determine the current size of a file in bytes
*/
int sqlite3OsFileSize(OsFile *id, off_t *pSize){
# ifdef _LARGE_FILE
  if( FSGetForkSize(id->refNum, pSize) != noErr){
# else
  if( GetEOF(id->refNum, pSize) != noErr ){
# endif
    return SQLITE_IOERR;
  }else{
    return SQLITE_OK;
  }
}

/*
** Windows file locking notes:  [similar issues apply to MacOS]
**
** We cannot use LockFileEx() or UnlockFileEx() on Win95/98/ME because
** those functions are not available.  So we use only LockFile() and
** UnlockFile().
**
** LockFile() prevents not just writing but also reading by other processes.
** (This is a design error on the part of Windows, but there is nothing
** we can do about that.)  So the region used for locking is at the
** end of the file where it is unlikely to ever interfere with an
** actual read attempt.
**
** A database read lock is obtained by locking a single randomly-chosen 
** byte out of a specific range of bytes. The lock byte is obtained at 
** random so two separate readers can probably access the file at the 
** same time, unless they are unlucky and choose the same lock byte.
** A database write lock is obtained by locking all bytes in the range.
** There can only be one writer.
**
** A lock is obtained on the first byte of the lock range before acquiring
** either a read lock or a write lock.  This prevents two processes from
** attempting to get a lock at a same time.  The semantics of 
** sqlite3OsReadLock() require that if there is already a write lock, that
** lock is converted into a read lock atomically.  The lock on the first
** byte allows us to drop the old write lock and get the read lock without
** another process jumping into the middle and messing us up.  The same
** argument applies to sqlite3OsWriteLock().
**
** On WinNT/2K/XP systems, LockFileEx() and UnlockFileEx() are available,
** which means we can use reader/writer locks.  When reader writer locks
** are used, the lock is placed on the same range of bytes that is used
** for probabilistic locking in Win95/98/ME.  Hence, the locking scheme
** will support two or more Win95 readers or two or more WinNT readers.
** But a single Win95 reader will lock out all WinNT readers and a single
** WinNT reader will lock out all other Win95 readers.
**
** Note: On MacOS we use the resource fork for locking.
**
** The following #defines specify the range of bytes used for locking.
** N_LOCKBYTE is the number of bytes available for doing the locking.
** The first byte used to hold the lock while the lock is changing does
** not count toward this number.  FIRST_LOCKBYTE is the address of
** the first byte in the range of bytes used for locking.
*/
#define N_LOCKBYTE       10239
#define FIRST_LOCKBYTE   (0x000fffff - N_LOCKBYTE)

/*
** Change the status of the lock on the file "id" to be a readlock.
** If the file was write locked, then this reduces the lock to a read.
** If the file was read locked, then this acquires a new read lock.
**
** Return SQLITE_OK on success and SQLITE_BUSY on failure.  If this
** library was compiled with large file support (LFS) but LFS is not
** available on the host, then an SQLITE_NOLFS is returned.
*/
int sqlite3OsReadLock(OsFile *id){
  int rc;
  if( id->locked>0 || id->refNumRF == -1 ){
    rc = SQLITE_OK;
  }else{
    int lk;
    OSErr res;
    int cnt = 5;
    ParamBlockRec params;
    sqlite3Randomness(sizeof(lk), &lk);
    lk = (lk & 0x7fffffff)%N_LOCKBYTE + 1;
    memset(&params, 0, sizeof(params));
    params.ioParam.ioRefNum = id->refNumRF;
    params.ioParam.ioPosMode = fsFromStart;
    params.ioParam.ioPosOffset = FIRST_LOCKBYTE;
    params.ioParam.ioRetqCount = 1;
    while( cnt-->0 && (res = PBLockRangeSync(&params))!=noErr ){
      UInt32 finalTicks;
      Delay(1, &finalTicks); /* 1/60 sec */
    }
    if( res == noErr ){
      params.ioParam.ioPosOffset = FIRST_LOCKBYTE+1;
      params.ioParam.ioRetqCount = N_LOCKBYTE;
      PBUnlockRangeSync(&params);
      params.ioParam.ioPosOffset = FIRST_LOCKBYTE+lk;
      params.ioParam.ioRetqCount = 1;
      res = PBLockRangeSync(&params);
      params.ioParam.ioPosOffset = FIRST_LOCKBYTE;
      params.ioParam.ioRetqCount = 1;
      PBUnlockRangeSync(&params);
    }
    if( res == noErr ){
      id->locked = lk;
      rc = SQLITE_OK;
    }else{
      rc = SQLITE_BUSY;
    }
  }
  return rc;
}

/*
** Change the lock status to be an exclusive or write lock.  Return
** SQLITE_OK on success and SQLITE_BUSY on a failure.  If this
** library was compiled with large file support (LFS) but LFS is not
** available on the host, then an SQLITE_NOLFS is returned.
*/
int sqlite3OsWriteLock(OsFile *id){
  int rc;
  if( id->locked<0 || id->refNumRF == -1 ){
    rc = SQLITE_OK;
  }else{
    OSErr res;
    int cnt = 5;
    ParamBlockRec params;
    memset(&params, 0, sizeof(params));
    params.ioParam.ioRefNum = id->refNumRF;
    params.ioParam.ioPosMode = fsFromStart;
    params.ioParam.ioPosOffset = FIRST_LOCKBYTE;
    params.ioParam.ioRetqCount = 1;
    while( cnt-->0 && (res = PBLockRangeSync(&params))!=noErr ){
      UInt32 finalTicks;
      Delay(1, &finalTicks); /* 1/60 sec */
    }
    if( res == noErr ){
      params.ioParam.ioPosOffset = FIRST_LOCKBYTE + id->locked;
      params.ioParam.ioRetqCount = 1;
      if( id->locked==0 
            || PBUnlockRangeSync(&params)==noErr ){
        params.ioParam.ioPosOffset = FIRST_LOCKBYTE+1;
        params.ioParam.ioRetqCount = N_LOCKBYTE;
        res = PBLockRangeSync(&params);
      }else{
        res = afpRangeNotLocked;
      }
      params.ioParam.ioPosOffset = FIRST_LOCKBYTE;
      params.ioParam.ioRetqCount = 1;
      PBUnlockRangeSync(&params);
    }
    if( res == noErr ){
      id->locked = -1;
      rc = SQLITE_OK;
    }else{
      rc = SQLITE_BUSY;
    }
  }
  return rc;
}

/*
** Unlock the given file descriptor.  If the file descriptor was
** not previously locked, then this routine is a no-op.  If this
** library was compiled with large file support (LFS) but LFS is not
** available on the host, then an SQLITE_NOLFS is returned.
*/
int sqlite3OsUnlock(OsFile *id){
  int rc;
  ParamBlockRec params;
  memset(&params, 0, sizeof(params));
  params.ioParam.ioRefNum = id->refNumRF;
  params.ioParam.ioPosMode = fsFromStart;
  if( id->locked==0 || id->refNumRF == -1 ){
    rc = SQLITE_OK;
  }else if( id->locked<0 ){
    params.ioParam.ioPosOffset = FIRST_LOCKBYTE+1;
    params.ioParam.ioRetqCount = N_LOCKBYTE;
    PBUnlockRangeSync(&params);
    rc = SQLITE_OK;
    id->locked = 0;
  }else{
    params.ioParam.ioPosOffset = FIRST_LOCKBYTE+id->locked;
    params.ioParam.ioRetqCount = 1;
    PBUnlockRangeSync(&params);
    rc = SQLITE_OK;
    id->locked = 0;
  }
  return rc;
}

/*
** Get information to seed the random number generator.  The seed
** is written into the buffer zBuf[256].  The calling function must
** supply a sufficiently large buffer.
*/
int sqlite3OsRandomSeed(char *zBuf){
  /* We have to initialize zBuf to prevent valgrind from reporting
  ** errors.  The reports issued by valgrind are incorrect - we would
  ** prefer that the randomness be increased by making use of the
  ** uninitialized space in zBuf - but valgrind errors tend to worry
  ** some users.  Rather than argue, it seems easier just to initialize
  ** the whole array and silence valgrind, even if that means less randomness
  ** in the random seed.
  **
  ** When testing, initializing zBuf[] to zero is all we do.  That means
  ** that we always use the same random number sequence.* This makes the
  ** tests repeatable.
  */
  memset(zBuf, 0, 256);
#if !defined(SQLITE_TEST)
  {
    int pid;
    Microseconds((UnsignedWide*)zBuf);
    pid = getpid();
    memcpy(&zBuf[sizeof(UnsignedWide)], &pid, sizeof(pid));
  }
#endif
  return SQLITE_OK;
}

/*
** Sleep for a little while.  Return the amount of time slept.
*/
int sqlite3OsSleep(int ms){
  UInt32 finalTicks;
  UInt32 ticks = (((UInt32)ms+16)*3)/50;  /* 1/60 sec per tick */
  Delay(ticks, &finalTicks);
  return (int)((ticks*50)/3);
}

/*
** Static variables used for thread synchronization
*/
static int inMutex = 0;
#ifdef SQLITE_MACOS_MULTITASKING
  static MPCriticalRegionID criticalRegion;
#endif

/*
** The following pair of routine implement mutual exclusion for
** multi-threaded processes.  Only a single thread is allowed to
** executed code that is surrounded by EnterMutex() and LeaveMutex().
**
** SQLite uses only a single Mutex.  There is not much critical
** code and what little there is executes quickly and without blocking.
*/
void sqlite3OsEnterMutex(){
#ifdef SQLITE_MACOS_MULTITASKING
  static volatile int notInit = 1;
  if( notInit ){
    if( notInit == 2 ) /* as close as you can get to thread safe init */
      MPYield();
    else{
      notInit = 2;
      MPCreateCriticalRegion(&criticalRegion);
      notInit = 0;
    }
  }
  MPEnterCriticalRegion(criticalRegion, kDurationForever);
#endif
  assert( !inMutex );
  inMutex = 1;
}
void sqlite3OsLeaveMutex(){
  assert( inMutex );
  inMutex = 0;
#ifdef SQLITE_MACOS_MULTITASKING
  MPExitCriticalRegion(criticalRegion);
#endif
}

/*
** Turn a relative pathname into a full pathname.  Return a pointer
** to the full pathname stored in space obtained from sqliteMalloc().
** The calling function is responsible for freeing this space once it
** is no longer needed.
*/
char *sqlite3OsFullPathname(const char *zRelative){
  char *zFull = 0;
  if( zRelative[0]==':' ){
    char zBuf[_MAX_PATH+1];
    sqlite3SetString(&zFull, getcwd(zBuf, sizeof(zBuf)), &(zRelative[1]),
                    (char*)0);
  }else{
    if( strchr(zRelative, ':') ){
      sqlite3SetString(&zFull, zRelative, (char*)0);
    }else{
    char zBuf[_MAX_PATH+1];
      sqlite3SetString(&zFull, getcwd(zBuf, sizeof(zBuf)), zRelative, (char*)0);
    }
  }
  return zFull;
}

/*
** The following variable, if set to a non-zero value, becomes the result
** returned from sqlite3OsCurrentTime().  This is used for testing.
*/
#ifdef SQLITE_TEST
int sqlite3_current_time = 0;
#endif

/*
** Find the current time (in Universal Coordinated Time).  Write the
** current time and date as a Julian Day number into *prNow and
** return 0.  Return 1 if the time and date cannot be found.
*/
int sqlite3OsCurrentTime(double *prNow){
  *prNow = 0.0;   /**** FIX ME *****/
#ifdef SQLITE_TEST
  if( sqlite3_current_time ){
    *prNow = sqlite3_current_time/86400.0 + 2440587.5;
  }
#endif
  return 0;
}

#endif /* OS_MAC */