SQLite

** or pages with the Pager.noSync flag set.
**
** If successful, or if called on a pager for which it is a no-op, this
** function returns SQLITE_OK. Otherwise, an IO error code is returned.
*/
int sqlite3PagerSync(Pager *pPager){
  int rc;                              /* Return code */
  if( pPager->noSync ){
  if( !pPager->noSync ){
    rc = SQLITE_OK;
  }else{
    assert( !MEMDB );
    rc = sqlite3OsSync(pPager->fd, pPager->syncFlags);
  }
  if( isOpen(pPager->fd) ){
  }else if( isOpen(pPager->fd) ){
    assert( !MEMDB );
    sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SYNC, (void *)&rc);
    sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SYNC_OMITTED, (void *)&rc);
  }else{
    rc = SQLITE_OK;
  }
  return rc;
}

/*
** This function may only be called while a write-transaction is active in
** rollback. If the connection is in WAL mode, this call is a no-op. 

** improve performance on some systems.
**
** The [SQLITE_FCNTL_FILE_POINTER] opcode is used to obtain a pointer
** to the [sqlite3_file] object associated with a particular database
** connection.  See the [sqlite3_file_control()] documentation for
** additional information.
**
** The [SQLITE_FCNTL_SYNC] opcode is used internally. SQLite calls
** the file-control method with this opcode immediately after the database
** file is synced, or if the database is running in synchronous=off mode
** immediately after it would have been synced otherwise. This makes it
** easier to write special VFS modules that depend on the xSync call.
** ^(The [SQLITE_FCNTL_SYNC_OMITTED] opcode is generated internally by
** SQLite and sent to all VFSes in place of a call to the xSync method
** when the database connection has [PRAGMA synchronous] set to OFF.)^
** Some specialized VFSes need this signal in order to operate correctly
** when [PRAGMA synchronous | PRAGMA synchronous=OFF] is set, but most 
** VFSes do not need this signal and should silently ignore this opcode.
** Applications should not call [sqlite3_file_control()] with this
** opcode as doing so may disrupt the operation of the specilized VFSes
** that do require it.  
*/
#define SQLITE_FCNTL_LOCKSTATE        1
#define SQLITE_GET_LOCKPROXYFILE      2
#define SQLITE_SET_LOCKPROXYFILE      3
#define SQLITE_LAST_ERRNO             4
#define SQLITE_FCNTL_SIZE_HINT        5
#define SQLITE_FCNTL_CHUNK_SIZE       6
#define SQLITE_FCNTL_FILE_POINTER     7
#define SQLITE_FCNTL_SYNC             8
#define SQLITE_FCNTL_SYNC_OMITTED     8


/*
** CAPI3REF: Mutex Handle
**
** The mutex module within SQLite defines [sqlite3_mutex] to be an
** abstract type for a mutex object.  The SQLite core never looks