Main Page   Namespace List   Class Hierarchy   Alphabetical List   Compound List   File List   Namespace Members   Compound Members   File Members   Related Pages   Examples  

ost::SharedFile Class Reference

This class defines a database I/O file service that can be shared by multiple processes. This class defines a database I/O file service that can be shared by multiple processes. More...

#include <file.h>

Inheritance diagram for ost::SharedFile::

ost::RandomFile ost::Mutex ost::File List of all members.

Public Methods

 SharedFile (const char *path)
 Open or create a new database file. More...

 SharedFile (const SharedFile &file)
 Create a shared file as a duplicate of an existing shared file. More...

virtual ~SharedFile ()
 Close and finish a database file. More...

Error restart (void)
 Restart an existing database; close and re-open. More...

Error fetch (char *address=NULL, ccxx_size_t length=0, off_t position=-1)
 Lock and Fetch a portion of the file into physical memory. More...

Error update (char *address=NULL, ccxx_size_t length=0, off_t position=-1)
 Update a portion of a file from physical memory. More...

Error clear (ccxx_size_t length=0, off_t pos=-1)
 Clear a lock held from a previous fetch operation without updating. More...

Error append (char *address=NULL, ccxx_size_t length=0)
 Add new data to the end of the file. More...

off_t getPosition (void)
 Fetch the current file position marker for this thread. More...

bool operator++ (void)
bool operator-- (void)

Detailed Description

This class defines a database I/O file service that can be shared by multiple processes. This class defines a database I/O file service that can be shared by multiple processes.

Each thread should access a dup of the database object, and mutex locks can be used to preserve transaction integrety if multiple threads are used.

SharedFile is used when a database may be shared between multiple processes. SharedFile automatically applies low level byte-range "file locks", and provides an interface to fetch and release byte-range locked portions of a file.

Author:
David Sugar <dyfet@ostel.com>


Constructor & Destructor Documentation

ost::SharedFile::SharedFile ( const char * path )
 

Open or create a new database file.

You should also use Initial.

Parameters:
path   pathname of database to open.

ost::SharedFile::SharedFile ( const SharedFile & file )
 

Create a shared file as a duplicate of an existing shared file.

Parameters:
file   original file.

ost::SharedFile::~SharedFile ( ) [virtual]
 

Close and finish a database file.


Member Function Documentation

Error ost::SharedFile::append ( char * address = NULL,
ccxx_size_t length = 0 )
 

Add new data to the end of the file.

Locks file during append.

Parameters:
address   address to use, or NULL if same as last I/O.
length   length to use, or 0 if same as last I/O.

Error ost::SharedFile::clear ( ccxx_size_t length = 0,
off_t pos = -1 )
 

Clear a lock held from a previous fetch operation without updating.

Returns:
errSuccess on success.
Parameters:
length   length to use, or 0 if same as last I/O.
pos   file position to use or -1 if same as last I/O.

Error ost::SharedFile::fetch ( char * address = NULL,
ccxx_size_t length = 0,
off_t position = -1 )
 

Lock and Fetch a portion of the file into physical memory.

This can use state information to fetch the current record multiple times.

Returns:
errSuccess on success.
Parameters:
address   address to use, or NULL if same as last I/O.
length   length to use, or 0 if same as last I/O.
position   file position to use -1 if same as last I/O.

off_t ost::SharedFile::getPosition ( void )
 

Fetch the current file position marker for this thread.

Returns:
file position offset.

bool ost::SharedFile::operator++ ( void )
 

bool ost::SharedFile::operator-- ( void )
 

Error ost::SharedFile::restart ( void ) [inline, virtual]
 

Restart an existing database; close and re-open.

Returns:
errSuccess if successful.

Reimplemented from ost::RandomFile.

Error ost::SharedFile::update ( char * address = NULL,
ccxx_size_t length = 0,
off_t position = -1 )
 

Update a portion of a file from physical memory.

This can use state information to commit the last read record. The current lock is also cleared.

Returns:
errSuccess on success.
Parameters:
address   address to use, or NULL if same as last I/O.
length   length to use, or 0 if same as last I/O.
position   file position to use or -1 if same as last I/O.


The documentation for this class was generated from the following file:
Generated at Sat May 12 18:59:44 2007 for GNU CommonC++ by doxygen1.2.8.1 written by Dimitri van Heesch, © 1997-2001