SQLite

#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
  /*
  ** If this Btree is a candidate for shared cache, try to find an
  ** existing BtShared object that we can share with
  */
  if( isMemdb==0 && zFilename && zFilename[0] ){
    if( vfsFlags & SQLITE_OPEN_SHAREDCACHE ){
      int nFullPathname = pVfs->mxPathname+1;
      char *zFullPathname = sqlite3Malloc(nFullPathname);
      sqlite3_mutex *mutexShared;
      p->sharable = 1;
      if( !zFullPathname ){
        sqlite3_free(p);
        return SQLITE_NOMEM;

    isThreadsafe = 0;
  }else if( flags & SQLITE_OPEN_NOMUTEX ){
    isThreadsafe = 0;
  }else if( flags & SQLITE_OPEN_FULLMUTEX ){
    isThreadsafe = 1;
  }else{
    isThreadsafe = sqlite3GlobalConfig.bFullMutex;
  }
  if( flags & SQLITE_OPEN_PRIVATECACHE ){
    flags &= SQLITE_OPEN_SHAREDCACHE;
  }else if( sqlite3GlobalConfig.sharedCacheEnabled ){
    flags |= SQLITE_OPEN_SHAREDCACHE;
  }

  /* Remove harmful bits from the flags parameter
  **
  ** The SQLITE_OPEN_NOMUTEX and SQLITE_OPEN_FULLMUTEX flags were
  ** dealt with in the previous code block.  Besides these, the only
  ** valid input flags for sqlite3_open_v2() are SQLITE_OPEN_READONLY,

  const char *zPath, 
  sqlite3_file *pFile, 
  int flags, 
  int *pFlagsOut
){
  int rc;
  DO_OS_MALLOC_TEST(0);
  /* 0x7f1f is a mask of SQLITE_OPEN_ flags that are valid to be passed
  ** down into the VFS layer.  Some SQLITE_OPEN_ flags (for example,
  ** SQLITE_OPEN_FULLMUTEX or SQLITE_OPEN_SHAREDCACHE) are blocked before
  ** reaching the VFS. */
  rc = pVfs->xOpen(pVfs, zPath, pFile, flags & 0x7f1f, pFlagsOut);
  assert( rc==SQLITE_OK || pFile->pMethods==0 );
  return rc;
}
int sqlite3OsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
  return pVfs->xDelete(pVfs, zPath, dirSync);
}
int sqlite3OsAccess(

#define SQLITE_OPEN_TRANSIENT_DB     0x00000400  /* VFS only */
#define SQLITE_OPEN_MAIN_JOURNAL     0x00000800  /* VFS only */
#define SQLITE_OPEN_TEMP_JOURNAL     0x00001000  /* VFS only */
#define SQLITE_OPEN_SUBJOURNAL       0x00002000  /* VFS only */
#define SQLITE_OPEN_MASTER_JOURNAL   0x00004000  /* VFS only */
#define SQLITE_OPEN_NOMUTEX          0x00008000  /* Ok for sqlite3_open_v2() */
#define SQLITE_OPEN_FULLMUTEX        0x00010000  /* Ok for sqlite3_open_v2() */
#define SQLITE_OPEN_SHAREDCACHE      0x00020000  /* Ok for sqlite3_open_v2() */
#define SQLITE_OPEN_PRIVATECACHE     0x00040000  /* Ok for sqlite3_open_v2() */

/*
** CAPI3REF: Device Characteristics {H10240} <H11120>
**
** The xDeviceCapabilities method of the [sqlite3_io_methods]
** object returns an integer which is a vector of the these
** bit values expressing I/O characteristics of the mass storage

** associated with the [database connection] handle should be released by
** passing it to [sqlite3_close()] when it is no longer required.
**
** The sqlite3_open_v2() interface works like sqlite3_open()
** except that it accepts two additional parameters for additional control
** over the new database connection.  The flags parameter can take one of
** the following three values, optionally combined with the 
** [SQLITE_OPEN_NOMUTEX], [SQLITE_OPEN_FULLMUTEX], [SQLITE_OPEN_SHAREDCACHE],
** and/or [SQLITE_OPEN_PRIVATECACHE] flags:
**
** <dl>
** <dt>[SQLITE_OPEN_READONLY]</dt>
** <dd>The database is opened in read-only mode.  If the database does not
** already exist, an error is returned.</dd>
**
** <dt>[SQLITE_OPEN_READWRITE]</dt>
** <dd>The database is opened for reading and writing if possible, or reading
** only if the file is write protected by the operating system.  In either
** case the database must already exist, otherwise an error is returned.</dd>
**
** <dt>[SQLITE_OPEN_READWRITE] | [SQLITE_OPEN_CREATE]</dt>
** <dd>The database is opened for reading and writing, and is creates it if
** it does not already exist. This is the behavior that is always used for
** sqlite3_open() and sqlite3_open16().</dd>
** </dl>
**
** If the 3rd parameter to sqlite3_open_v2() is not one of the
** combinations shown above or one of the combinations shown above combined
** with the [SQLITE_OPEN_NOMUTEX], [SQLITE_OPEN_FULLMUTEX],
** [SQLITE_OPEN_SHAREDCACHE] and/or [SQLITE_OPEN_SHAREDCACHE] flags,
** then the behavior is undefined.
**
** If the [SQLITE_OPEN_NOMUTEX] flag is set, then the database connection
** opens in the multi-thread [threading mode] as long as the single-thread
** mode has not been set at compile-time or start-time.  If the
** [SQLITE_OPEN_FULLMUTEX] flag is set then the database connection opens
** in the serialized [threading mode] unless single-thread was
** previously selected at compile-time or start-time.
** The [SQLITE_OPEN_SHAREDCACHE] flag causes the database connection to be
** eligible to use [shared cache mode], regardless of whether or not shared
** cache is enabled using [sqlite3_enable_shared_cache()].  The
** [SQLITE_OPEN_PRIVATECACHE] flag causes the database connection to not
** participate in [shared cache mode] even if it is enabled.
**
** If the filename is ":memory:", then a private, temporary in-memory database
** is created for the connection.  This in-memory database will vanish when
** the database connection is closed.  Future versions of SQLite might
** make use of additional special filenames that begin with the ":" character.
** It is recommended that when a database filename actually does begin with
** a ":" character you should prefix the filename with a pathname such as