/ Check-in [40f55c09]
Login
SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Cleanup the locking-style code in os_unix.c. (CVS 4837)
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 40f55c09dbd31f861b9f9c7641cce92553d94e35
User & Date: drh 2008-03-07 15:34:11
Context
2008-03-07
19:51
Correctly handle I/O errors that occur during OsUnlock(). Before this fix, an I/O error during OsUnlock() could lead to database corruption. That is not a serious problem, though, since errors during OsUnlock() are not possible on most systems. (CVS 4838) check-in: b4c1258e user: drh tags: trunk
15:34
Cleanup the locking-style code in os_unix.c. (CVS 4837) check-in: 40f55c09 user: drh tags: trunk
03:20
Trivial documentation fixes (CVS 4836) check-in: 9819cefb user: mlcreech tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/os_unix.c.

348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
...
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
....
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
....
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554

1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589

1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
....
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
....
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
....
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880

1881
1882
1883
1884
1885
1886
1887
1888
1889
1890

1891
1892
1893
1894
1895
1896


1897
1898
1899
1900
1901
1902
1903
1904
....
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930

1931
1932
1933
1934
1935
1936
1937
1938
....
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
....
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
....
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
....
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
....
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218






2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238




2239
2240
2241
2242
2243
2244
2245
**   can be used on file systems that do not offer any reliable file locking
** NO locking means that no locking will be attempted, this is only used for
**   read-only file systems currently
** UNSUPPORTED means that no locking will be attempted, this is only used for
**   file systems that are known to be unsupported
*/
typedef enum {
        posixLockingStyle = 0,       /* standard posix-advisory locks */
        afpLockingStyle,             /* use afp locks */
        flockLockingStyle,           /* use flock() */
        dotlockLockingStyle,         /* use <file>.lock files */
        noLockingStyle,              /* useful for read-only file system */
        unsupportedLockingStyle      /* indicates unsupported file system */
} sqlite3LockingStyle;
#endif /* SQLITE_ENABLE_LOCKING_STYLE */

/*
** Helper functions to obtain and relinquish the global mutex.
*/
static void enterMutex(){
................................................................................
){

#ifdef SQLITE_FIXED_LOCKING_STYLE
  return (sqlite3LockingStyle)SQLITE_FIXED_LOCKING_STYLE;
#else
  struct statfs fsInfo;

  if (statfs(filePath, &fsInfo) == -1)
    return sqlite3TestLockingStyle(filePath, fd);
  
  if (fsInfo.f_flags & MNT_RDONLY)
    return noLockingStyle;
  
  if( (!strcmp(fsInfo.f_fstypename, "hfs")) ||
    (!strcmp(fsInfo.f_fstypename, "ufs")) )
                return posixLockingStyle;
  
  if(!strcmp(fsInfo.f_fstypename, "afpfs"))
    return afpLockingStyle;
  
  if(!strcmp(fsInfo.f_fstypename, "nfs")) 
    return sqlite3TestLockingStyle(filePath, fd);
  
  if(!strcmp(fsInfo.f_fstypename, "smbfs"))
    return flockLockingStyle;
  
  if(!strcmp(fsInfo.f_fstypename, "msdos"))
    return dotlockLockingStyle;
  
  if(!strcmp(fsInfo.f_fstypename, "webdav"))
    return unsupportedLockingStyle;
  
  return sqlite3TestLockingStyle(filePath, fd);  
#endif /* SQLITE_FIXED_LOCKING_STYLE */
}

#endif /* SQLITE_ENABLE_LOCKING_STYLE */

/*
................................................................................
#pragma mark AFP Support

/*
 ** The afpLockingContext structure contains all afp lock specific state
 */
typedef struct afpLockingContext afpLockingContext;
struct afpLockingContext {
  unsigned long long sharedLockByte;
  char *filePath;
};

struct ByteRangeLockPB2
{
  unsigned long long offset;        /* offset to first byte to lock */
  unsigned long long length;        /* nbr of bytes to lock */
  unsigned long long retRangeStart; /* nbr of 1st byte locked if successful */
................................................................................
  OSTRACE3("TEST WR-LOCK %d %d\n", pFile->h, r);
  
  return r;
}

/* AFP-style locking following the behavior of unixLock, see the unixLock 
** function comments for details of lock management. */
static int afpUnixLock(sqlite3_file *id, int locktype)
{
  int rc = SQLITE_OK;
  unixFile *pFile = (unixFile*)id;
  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
  int gotPendingLock = 0;
  
  assert( pFile );
  OSTRACE5("LOCK    %d %s was %s pid=%d\n", pFile->h,
         locktypeName(locktype), locktypeName(pFile->locktype), getpid());  

  /* If there is already a lock of this type or more restrictive on the
    ** unixFile, do nothing. Don't use the afp_end_lock: exit path, as
    ** enterMutex() hasn't been called yet.
    */
  if( pFile->locktype>=locktype ){
    OSTRACE3("LOCK    %d %s ok (already held)\n", pFile->h,
           locktypeName(locktype));
    return SQLITE_OK;
  }

  /* Make sure the locking sequence is correct
    */
  assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
  assert( locktype!=PENDING_LOCK );
  assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
  
  /* This mutex is needed because pFile->pLock is shared across threads
    */
  enterMutex();

  /* Make sure the current thread owns the pFile.
    */
  rc = transferOwnership(pFile);
  if( rc!=SQLITE_OK ){
    leaveMutex();
    return rc;
  }
    
  /* A PENDING lock is needed before acquiring a SHARED lock and before
    ** acquiring an EXCLUSIVE lock.  For the SHARED lock, the PENDING will
    ** be released.
    */
  if( locktype==SHARED_LOCK 
      || (locktype==EXCLUSIVE_LOCK && pFile->locktype<PENDING_LOCK)
      ){

    int failed = _AFPFSSetLock(context->filePath, pFile->h, 
      PENDING_BYTE, 1, 1);
    if (failed) {
      rc = SQLITE_BUSY;
      goto afp_end_lock;
    }
  }
  
  /* If control gets to this point, then actually go ahead and make
    ** operating system calls for the specified lock.
    */
  if( locktype==SHARED_LOCK ){
    int lk, failed;
    int tries = 0;
    
    /* Now get the read-lock */
    /* note that the quality of the randomness doesn't matter that much */
    lk = random(); 
................................................................................
  if( rc==SQLITE_OK ){
    pFile->locktype = locktype;
  }else if( locktype==EXCLUSIVE_LOCK ){
    pFile->locktype = PENDING_LOCK;
  }
  
afp_end_lock:
    leaveMutex();
  OSTRACE4("LOCK    %d %s %s\n", pFile->h, locktypeName(locktype), 
         rc==SQLITE_OK ? "ok" : "failed");
  return rc;
}

/*
 ** Lower the locking level on file descriptor pFile to locktype.  locktype
 ** must be either NO_LOCK or SHARED_LOCK.
 **
 ** If the locking level of the file descriptor is already at or below
 ** the requested locking level, this routine is a no-op.
 */
static int afpUnixUnlock(sqlite3_file *id, int locktype) {
  struct flock lock;
  int rc = SQLITE_OK;
  unixFile *pFile = (unixFile*)id;
  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;

  assert( pFile );
................................................................................
  if (rc == SQLITE_OK)
    pFile->locktype = locktype;
  leaveMutex();
  return rc;
}

/*
 ** Close a file & cleanup AFP specific locking context 
 */
static int afpUnixClose(sqlite3_file *id) {
  unixFile *pFile = (unixFile*)id;

  if( !pFile ) return SQLITE_OK;
  afpUnixUnlock(id, NO_LOCK);
  /* free the AFP locking structure */
  if (pFile->lockingContext != NULL) {
    if (((afpLockingContext *)pFile->lockingContext)->filePath != NULL)
      sqlite3_free(((afpLockingContext*)pFile->lockingContext)->filePath);
    sqlite3_free(pFile->lockingContext);
  }

  if( pFile->dirfd>=0 ) close(pFile->dirfd);
  pFile->dirfd = -1;
  enterMutex();
  close(pFile->h);
  leaveMutex();
  OSTRACE2("CLOSE   %-3d\n", pFile->h);
  OpenCounter(-1);
  memset(pFile, 0, sizeof(unixFile));
  return SQLITE_OK;
}


#pragma mark flock() style locking

/*
 ** The flockLockingContext is not used
 */
typedef void flockLockingContext;

static int flockUnixCheckReservedLock(sqlite3_file *id) {
  unixFile *pFile = (unixFile*)id;
  
  if (pFile->locktype == RESERVED_LOCK) {
    return 1; /* already have a reserved lock */
  } else {
    /* attempt to get the lock */
    int rc = flock(pFile->h, LOCK_EX | LOCK_NB);
................................................................................
  else {
    pFile->locktype = NO_LOCK;
    return SQLITE_OK;
  }
}

/*
 ** Close a file.
 */
static int flockUnixClose(sqlite3_file *id) {
  unixFile *pFile = (unixFile*)id;
  
  if( !pFile ) return SQLITE_OK;
  flockUnixUnlock(id, NO_LOCK);
  
  if( pFile->dirfd>=0 ) close(pFile->dirfd);
  pFile->dirfd = -1;

  enterMutex();
  close(pFile->h);  
  leaveMutex();
  OSTRACE2("CLOSE   %-3d\n", pFile->h);
  OpenCounter(-1);
  memset(pFile, 0, sizeof(unixFile));
  return SQLITE_OK;
}

#pragma mark Old-School .lock file based locking

/*
 ** The dotlockLockingContext structure contains all dotlock (.lock) lock
 ** specific state
 */
typedef struct dotlockLockingContext dotlockLockingContext;
struct dotlockLockingContext {
  char *lockPath;
};


static int dotlockUnixCheckReservedLock(sqlite3_file *id) {
  unixFile *pFile = (unixFile*)id;
  dotlockLockingContext *context = 
    (dotlockLockingContext *) pFile->lockingContext;
  

  if (pFile->locktype == RESERVED_LOCK) {
    return 1; /* already have a reserved lock */
  } else {
    struct stat statBuf;
    if (lstat(context->lockPath,&statBuf) == 0)
      /* file exists, someone else has the lock */
      return 1;
    else
      /* file does not exist, we could have it if we want it */
      return 0;

  }
}

static int dotlockUnixLock(sqlite3_file *id, int locktype) {
  unixFile *pFile = (unixFile*)id;
  dotlockLockingContext *context = 


    (dotlockLockingContext *) pFile->lockingContext;
  
  /* if we already have a lock, it is exclusive.  
  ** Just adjust level and punt on outta here. */
  if (pFile->locktype > NO_LOCK) {
    pFile->locktype = locktype;
    
    /* Always update the timestamp on the old file */
................................................................................
  /* check to see if lock file already exists */
  struct stat statBuf;
  if (lstat(context->lockPath,&statBuf) == 0){
    return SQLITE_BUSY; /* it does, busy */
  }
  
  /* grab an exclusive lock */
  int fd = open(context->lockPath,O_RDONLY|O_CREAT|O_EXCL,0600);
  if (fd < 0) {
    /* failed to open/create the file, someone else may have stolen the lock */
    return SQLITE_BUSY; 
  }
  close(fd);
  
  /* got it, set the type and return ok */
  pFile->locktype = locktype;
  return SQLITE_OK;
}

static int dotlockUnixUnlock(sqlite3_file *id, int locktype) {
  unixFile *pFile = (unixFile*)id;
  dotlockLockingContext *context = 

    (dotlockLockingContext *) pFile->lockingContext;
  
  assert( locktype<=SHARED_LOCK );
  
  /* no-op if possible */
  if( pFile->locktype==locktype ){
    return SQLITE_OK;
  }
................................................................................
 ** Close a file.
 */
static int dotlockUnixClose(sqlite3_file *id) {
  unixFile *pFile = (unixFile*)id;
  
  if( !pFile ) return SQLITE_OK;
  dotlockUnixUnlock(id, NO_LOCK);
  /* free the dotlock locking structure */
  if (pFile->lockingContext != NULL) {
    if (((dotlockLockingContext *)pFile->lockingContext)->lockPath != NULL)
      sqlite3_free( ( (dotlockLockingContext *)
        pFile->lockingContext)->lockPath);
    sqlite3_free(pFile->lockingContext);
  }
  
  if( pFile->dirfd>=0 ) close(pFile->dirfd);
  pFile->dirfd = -1;
  enterMutex();  
  close(pFile->h);
  leaveMutex();
  OSTRACE2("CLOSE   %-3d\n", pFile->h);
  OpenCounter(-1);
  memset(pFile, 0, sizeof(unixFile));
  return SQLITE_OK;
}


#pragma mark No locking

/*
 ** The nolockLockingContext is void
 */
typedef void nolockLockingContext;

static int nolockUnixCheckReservedLock(sqlite3_file *id) {
  return 0;
}

static int nolockUnixLock(sqlite3_file *id, int locktype) {
................................................................................
}

static int nolockUnixUnlock(sqlite3_file *id, int locktype) {
  return SQLITE_OK;
}

/*
 ** Close a file.
 */
static int nolockUnixClose(sqlite3_file *id) {
  unixFile *pFile = (unixFile*)id;
  
  if( !pFile ) return SQLITE_OK;
  if( pFile->dirfd>=0 ) close(pFile->dirfd);
  pFile->dirfd = -1;
  enterMutex();
  close(pFile->h);
  leaveMutex();
  OSTRACE2("CLOSE   %-3d\n", pFile->h);
  OpenCounter(-1);
  memset(pFile, 0, sizeof(unixFile));
  return SQLITE_OK;
}

#endif /* SQLITE_ENABLE_LOCKING_STYLE */
................................................................................
  unixFileControl,
  unixSectorSize,
  unixDeviceCharacteristics
};

/*
** This vector defines all the methods that can operate on an sqlite3_file
** for unix with dotlock style file locking.
*/
static const sqlite3_io_methods sqlite3NolockLockingUnixIoMethod = {
  1,                        /* iVersion */
  nolockUnixClose,
  unixRead,
  unixWrite,
  unixTruncate,
................................................................................
  int rc;

#ifdef FD_CLOEXEC
  fcntl(h, F_SETFD, fcntl(h, F_GETFD, 0) | FD_CLOEXEC);
#endif

  lockingStyle = sqlite3DetectLockingStyle(zFilename, h);
  if ( lockingStyle == posixLockingStyle ) {
      
    enterMutex();
    rc = findLockInfo(h, &pNew->pLock, &pNew->pOpen);
    leaveMutex();
    if( rc ){
      if( dirfd>=0 ) close(dirfd);
      close(h);
      return SQLITE_NOMEM;
................................................................................
  pNew->dirfd = dirfd;
  SET_THREADID(pNew);
    
  switch(lockingStyle) {
    case afpLockingStyle: {
      /* afp locking uses the file path so it needs to be included in
      ** the afpLockingContext */
      int nFilename;
      pNew->pMethod = &sqlite3AFPLockingUnixIoMethod;
      pNew->lockingContext = 
        sqlite3_malloc(sizeof(afpLockingContext));
      nFilename = strlen(zFilename)+1;
      ((afpLockingContext *)pNew->lockingContext)->filePath = 
        sqlite3_malloc(nFilename);
      memcpy(((afpLockingContext *)pNew->lockingContext)->filePath, 
             zFilename, nFilename);






      srandomdev();
      break;
    }
    case flockLockingStyle:
      /* flock locking doesn't need additional lockingContext information */
      pNew->pMethod = &sqlite3FlockLockingUnixIoMethod;
      break;
    case dotlockLockingStyle: {
      /* dotlock locking uses the file path so it needs to be included in
       ** the dotlockLockingContext */
      int nFilename;
      pNew->pMethod = &sqlite3DotlockLockingUnixIoMethod;
      pNew->lockingContext = sqlite3_malloc(
        sizeof(dotlockLockingContext));
      nFilename = strlen(zFilename) + 6;
      ((dotlockLockingContext *)pNew->lockingContext)->lockPath = 
          sqlite3_malloc( nFilename );
      sqlite3_snprintf(nFilename, 
              ((dotlockLockingContext *)pNew->lockingContext)->lockPath, 
              "%s.lock", zFilename);




      break;
    }
    case posixLockingStyle:
      /* posix locking doesn't need additional lockingContext information */
      pNew->pMethod = &sqlite3UnixIoMethod;
      break;
    case noLockingStyle:







|
|
|
|
|
|







 







|

|
|

|
|
|
|
|
|

|
|

|
|

|
|

|
|

|







 







|
|







 







|
<







|
>

|
|
|







|





|



|







|
|
|


|
>
|
<







|
|







 







|






|
|
|
|
|
|







 







|
|





<
<
<
<
|
<
<


<

<










|
|


|







 







|
|








<
<

<









|
|
|








|
<
|
>




|


|


>





|
>
>
|







 







|
|












|
>
|







 







<
<
<
<
<
|
<
<


<

<










|
|







 







|
|






<

<







 







|







 







|
<







 







|

|
|
|
|
|
<
<
>
>
>
>
>
>









|
|
|
|
|
|
|
|
|
|
|
>
>
>
>







348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
...
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
....
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
....
1538
1539
1540
1541
1542
1543
1544
1545

1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591

1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
....
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
....
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751




1752


1753
1754

1755

1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
....
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845


1846

1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867

1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
....
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
....
1946
1947
1948
1949
1950
1951
1952





1953


1954
1955

1956

1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
....
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991

1992

1993
1994
1995
1996
1997
1998
1999
....
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
....
2159
2160
2161
2162
2163
2164
2165
2166

2167
2168
2169
2170
2171
2172
2173
....
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197


2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
**   can be used on file systems that do not offer any reliable file locking
** NO locking means that no locking will be attempted, this is only used for
**   read-only file systems currently
** UNSUPPORTED means that no locking will be attempted, this is only used for
**   file systems that are known to be unsupported
*/
typedef enum {
  posixLockingStyle = 0,       /* standard posix-advisory locks */
  afpLockingStyle,             /* use afp locks */
  flockLockingStyle,           /* use flock() */
  dotlockLockingStyle,         /* use <file>.lock files */
  noLockingStyle,              /* useful for read-only file system */
  unsupportedLockingStyle      /* indicates unsupported file system */
} sqlite3LockingStyle;
#endif /* SQLITE_ENABLE_LOCKING_STYLE */

/*
** Helper functions to obtain and relinquish the global mutex.
*/
static void enterMutex(){
................................................................................
){

#ifdef SQLITE_FIXED_LOCKING_STYLE
  return (sqlite3LockingStyle)SQLITE_FIXED_LOCKING_STYLE;
#else
  struct statfs fsInfo;

  if( statfs(filePath, &fsInfo) == -1 ){
    return sqlite3TestLockingStyle(filePath, fd);
  }
  if( fsInfo.f_flags & MNT_RDONLY ){
    return noLockingStyle;
  }
  if( strcmp(fsInfo.f_fstypename, "hfs")==0 ||
      strcmp(fsInfo.f_fstypename, "ufs")==0 ){
    return posixLockingStyle;
  }
  if( strcmp(fsInfo.f_fstypename, "afpfs")==0 ){
    return afpLockingStyle;
  }
  if( strcmp(fsInfo.f_fstypename, "nfs")==0 ){
    return sqlite3TestLockingStyle(filePath, fd);
  }
  if( strcmp(fsInfo.f_fstypename, "smbfs")==0 ){
    return flockLockingStyle;
  }
  if( strcmp(fsInfo.f_fstypename, "msdos")==0 ){
    return dotlockLockingStyle;
  }
  if( strcmp(fsInfo.f_fstypename, "webdav")==0 ){
    return unsupportedLockingStyle;
  }
  return sqlite3TestLockingStyle(filePath, fd);  
#endif /* SQLITE_FIXED_LOCKING_STYLE */
}

#endif /* SQLITE_ENABLE_LOCKING_STYLE */

/*
................................................................................
#pragma mark AFP Support

/*
 ** The afpLockingContext structure contains all afp lock specific state
 */
typedef struct afpLockingContext afpLockingContext;
struct afpLockingContext {
  unsigned long long sharedLockByte;  /* Byte offset of shared lock byte */
  const char *filePath;               /* Name of the file */
};

struct ByteRangeLockPB2
{
  unsigned long long offset;        /* offset to first byte to lock */
  unsigned long long length;        /* nbr of bytes to lock */
  unsigned long long retRangeStart; /* nbr of 1st byte locked if successful */
................................................................................
  OSTRACE3("TEST WR-LOCK %d %d\n", pFile->h, r);
  
  return r;
}

/* AFP-style locking following the behavior of unixLock, see the unixLock 
** function comments for details of lock management. */
static int afpUnixLock(sqlite3_file *id, int locktype){

  int rc = SQLITE_OK;
  unixFile *pFile = (unixFile*)id;
  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
  int gotPendingLock = 0;
  
  assert( pFile );
  OSTRACE5("LOCK    %d %s was %s pid=%d\n", pFile->h,
         locktypeName(locktype), locktypeName(pFile->locktype), getpid());

  /* If there is already a lock of this type or more restrictive on the
  ** unixFile, do nothing. Don't use the afp_end_lock: exit path, as
  ** enterMutex() hasn't been called yet.
  */
  if( pFile->locktype>=locktype ){
    OSTRACE3("LOCK    %d %s ok (already held)\n", pFile->h,
           locktypeName(locktype));
    return SQLITE_OK;
  }

  /* Make sure the locking sequence is correct
  */
  assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
  assert( locktype!=PENDING_LOCK );
  assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
  
  /* This mutex is needed because pFile->pLock is shared across threads
  */
  enterMutex();

  /* Make sure the current thread owns the pFile.
  */
  rc = transferOwnership(pFile);
  if( rc!=SQLITE_OK ){
    leaveMutex();
    return rc;
  }
    
  /* A PENDING lock is needed before acquiring a SHARED lock and before
  ** acquiring an EXCLUSIVE lock.  For the SHARED lock, the PENDING will
  ** be released.
  */
  if( locktype==SHARED_LOCK 
      || (locktype==EXCLUSIVE_LOCK && pFile->locktype<PENDING_LOCK)
  ){
    int failed;
    failed = _AFPFSSetLock(context->filePath, pFile->h, PENDING_BYTE, 1, 1);

    if (failed) {
      rc = SQLITE_BUSY;
      goto afp_end_lock;
    }
  }
  
  /* If control gets to this point, then actually go ahead and make
  ** operating system calls for the specified lock.
  */
  if( locktype==SHARED_LOCK ){
    int lk, failed;
    int tries = 0;
    
    /* Now get the read-lock */
    /* note that the quality of the randomness doesn't matter that much */
    lk = random(); 
................................................................................
  if( rc==SQLITE_OK ){
    pFile->locktype = locktype;
  }else if( locktype==EXCLUSIVE_LOCK ){
    pFile->locktype = PENDING_LOCK;
  }
  
afp_end_lock:
  leaveMutex();
  OSTRACE4("LOCK    %d %s %s\n", pFile->h, locktypeName(locktype), 
         rc==SQLITE_OK ? "ok" : "failed");
  return rc;
}

/*
** Lower the locking level on file descriptor pFile to locktype.  locktype
** must be either NO_LOCK or SHARED_LOCK.
**
** If the locking level of the file descriptor is already at or below
** the requested locking level, this routine is a no-op.
*/
static int afpUnixUnlock(sqlite3_file *id, int locktype) {
  struct flock lock;
  int rc = SQLITE_OK;
  unixFile *pFile = (unixFile*)id;
  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;

  assert( pFile );
................................................................................
  if (rc == SQLITE_OK)
    pFile->locktype = locktype;
  leaveMutex();
  return rc;
}

/*
** Close a file & cleanup AFP specific locking context 
*/
static int afpUnixClose(sqlite3_file *id) {
  unixFile *pFile = (unixFile*)id;

  if( !pFile ) return SQLITE_OK;
  afpUnixUnlock(id, NO_LOCK);




  sqlite3_free(pFile->lockingContext);


  if( pFile->dirfd>=0 ) close(pFile->dirfd);
  pFile->dirfd = -1;

  close(pFile->h);

  OSTRACE2("CLOSE   %-3d\n", pFile->h);
  OpenCounter(-1);
  memset(pFile, 0, sizeof(unixFile));
  return SQLITE_OK;
}


#pragma mark flock() style locking

/*
** The flockLockingContext is not used
*/
typedef void flockLockingContext;

static int flockUnixCheckReservedLock(sqlite3_file *id){
  unixFile *pFile = (unixFile*)id;
  
  if (pFile->locktype == RESERVED_LOCK) {
    return 1; /* already have a reserved lock */
  } else {
    /* attempt to get the lock */
    int rc = flock(pFile->h, LOCK_EX | LOCK_NB);
................................................................................
  else {
    pFile->locktype = NO_LOCK;
    return SQLITE_OK;
  }
}

/*
** Close a file.
*/
static int flockUnixClose(sqlite3_file *id) {
  unixFile *pFile = (unixFile*)id;
  
  if( !pFile ) return SQLITE_OK;
  flockUnixUnlock(id, NO_LOCK);
  
  if( pFile->dirfd>=0 ) close(pFile->dirfd);
  pFile->dirfd = -1;


  close(pFile->h);  

  OSTRACE2("CLOSE   %-3d\n", pFile->h);
  OpenCounter(-1);
  memset(pFile, 0, sizeof(unixFile));
  return SQLITE_OK;
}

#pragma mark Old-School .lock file based locking

/*
** The dotlockLockingContext structure contains all dotlock (.lock) lock
** specific state
*/
typedef struct dotlockLockingContext dotlockLockingContext;
struct dotlockLockingContext {
  char *lockPath;
};


static int dotlockUnixCheckReservedLock(sqlite3_file *id) {
  unixFile *pFile = (unixFile*)id;
  dotlockLockingContext *context;


  context = (dotlockLockingContext*)pFile->lockingContext;
  if (pFile->locktype == RESERVED_LOCK) {
    return 1; /* already have a reserved lock */
  } else {
    struct stat statBuf;
    if (lstat(context->lockPath,&statBuf) == 0){
      /* file exists, someone else has the lock */
      return 1;
    }else{
      /* file does not exist, we could have it if we want it */
      return 0;
    }
  }
}

static int dotlockUnixLock(sqlite3_file *id, int locktype) {
  unixFile *pFile = (unixFile*)id;
  dotlockLockingContext *context;
  int fd;

  context = (dotlockLockingContext*)pFile->lockingContext;
  
  /* if we already have a lock, it is exclusive.  
  ** Just adjust level and punt on outta here. */
  if (pFile->locktype > NO_LOCK) {
    pFile->locktype = locktype;
    
    /* Always update the timestamp on the old file */
................................................................................
  /* check to see if lock file already exists */
  struct stat statBuf;
  if (lstat(context->lockPath,&statBuf) == 0){
    return SQLITE_BUSY; /* it does, busy */
  }
  
  /* grab an exclusive lock */
  fd = open(context->lockPath,O_RDONLY|O_CREAT|O_EXCL,0600);
  if( fd<0 ){
    /* failed to open/create the file, someone else may have stolen the lock */
    return SQLITE_BUSY; 
  }
  close(fd);
  
  /* got it, set the type and return ok */
  pFile->locktype = locktype;
  return SQLITE_OK;
}

static int dotlockUnixUnlock(sqlite3_file *id, int locktype) {
  unixFile *pFile = (unixFile*)id;
  dotlockLockingContext *context;

  context = (dotlockLockingContext*)pFile->lockingContext;
  
  assert( locktype<=SHARED_LOCK );
  
  /* no-op if possible */
  if( pFile->locktype==locktype ){
    return SQLITE_OK;
  }
................................................................................
 ** Close a file.
 */
static int dotlockUnixClose(sqlite3_file *id) {
  unixFile *pFile = (unixFile*)id;
  
  if( !pFile ) return SQLITE_OK;
  dotlockUnixUnlock(id, NO_LOCK);





  sqlite3_free(pFile->lockingContext);


  if( pFile->dirfd>=0 ) close(pFile->dirfd);
  pFile->dirfd = -1;

  close(pFile->h);

  OSTRACE2("CLOSE   %-3d\n", pFile->h);
  OpenCounter(-1);
  memset(pFile, 0, sizeof(unixFile));
  return SQLITE_OK;
}


#pragma mark No locking

/*
** The nolockLockingContext is void
*/
typedef void nolockLockingContext;

static int nolockUnixCheckReservedLock(sqlite3_file *id) {
  return 0;
}

static int nolockUnixLock(sqlite3_file *id, int locktype) {
................................................................................
}

static int nolockUnixUnlock(sqlite3_file *id, int locktype) {
  return SQLITE_OK;
}

/*
** Close a file.
*/
static int nolockUnixClose(sqlite3_file *id) {
  unixFile *pFile = (unixFile*)id;
  
  if( !pFile ) return SQLITE_OK;
  if( pFile->dirfd>=0 ) close(pFile->dirfd);
  pFile->dirfd = -1;

  close(pFile->h);

  OSTRACE2("CLOSE   %-3d\n", pFile->h);
  OpenCounter(-1);
  memset(pFile, 0, sizeof(unixFile));
  return SQLITE_OK;
}

#endif /* SQLITE_ENABLE_LOCKING_STYLE */
................................................................................
  unixFileControl,
  unixSectorSize,
  unixDeviceCharacteristics
};

/*
** This vector defines all the methods that can operate on an sqlite3_file
** for unix with nolock style file locking.
*/
static const sqlite3_io_methods sqlite3NolockLockingUnixIoMethod = {
  1,                        /* iVersion */
  nolockUnixClose,
  unixRead,
  unixWrite,
  unixTruncate,
................................................................................
  int rc;

#ifdef FD_CLOEXEC
  fcntl(h, F_SETFD, fcntl(h, F_GETFD, 0) | FD_CLOEXEC);
#endif

  lockingStyle = sqlite3DetectLockingStyle(zFilename, h);
  if ( lockingStyle==posixLockingStyle ){

    enterMutex();
    rc = findLockInfo(h, &pNew->pLock, &pNew->pOpen);
    leaveMutex();
    if( rc ){
      if( dirfd>=0 ) close(dirfd);
      close(h);
      return SQLITE_NOMEM;
................................................................................
  pNew->dirfd = dirfd;
  SET_THREADID(pNew);
    
  switch(lockingStyle) {
    case afpLockingStyle: {
      /* afp locking uses the file path so it needs to be included in
      ** the afpLockingContext */
      afpLockingContext *context;
      pNew->pMethod = &sqlite3AFPLockingUnixIoMethod;
      pNew->lockingContext = context = sqlite3_malloc( sizeof(*context) );
      if( context==0 ){
        close(h);
        if( dirfd>=0 ) close(dirfd);
        return SQLITE_NOMEM;


      }

      /* NB: zFilename exists and remains valid until the file is closed
      ** according to requirement F11141.  So we do not need to make a
      ** copy of the filename. */
      context->filePath = zFilename;
      srandomdev();
      break;
    }
    case flockLockingStyle:
      /* flock locking doesn't need additional lockingContext information */
      pNew->pMethod = &sqlite3FlockLockingUnixIoMethod;
      break;
    case dotlockLockingStyle: {
      /* dotlock locking uses the file path so it needs to be included in
      ** the dotlockLockingContext */
      dotlockLockingContext *context;
      int nFilename;
      nFilename = strlen(zFilename);
      pNew->pMethod = &sqlite3DotlockLockingUnixIoMethod;
      pNew->lockingContext = context = 
         sqlite3_malloc( sizeof(*context) + nFilename + 6 );
      if( context==0 ){
        close(h);
        if( dirfd>=0 ) close(dirfd);
        return SQLITE_NOMEM;
      }
      context->lockPath = (char*)&context[1];
      sqlite3_snprintf(nFilename, context->lockPath,
                       "%s.lock", zFilename);
      break;
    }
    case posixLockingStyle:
      /* posix locking doesn't need additional lockingContext information */
      pNew->pMethod = &sqlite3UnixIoMethod;
      break;
    case noLockingStyle: