GNU CommonC++
Public Member Functions

ost::SharedFile Class Reference

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 Member Functions

 SharedFile (const char *path)
 Open or create a new database file.
 SharedFile (const SharedFile &file)
 Create a shared file as a duplicate of an existing shared file.
virtual ~SharedFile ()
 Close and finish a database file.
Error restart (void)
 Restart an existing database; close and re-open.
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.
Error update (char *address=NULL, ccxx_size_t length=0, off_t position=-1)
 Update a portion of a file from physical memory.
Error clear (ccxx_size_t length=0, off_t pos=-1)
 Clear a lock held from a previous fetch operation without updating.
Error append (char *address=NULL, ccxx_size_t length=0)
 Add new data to the end of the file.
off_t getPosition (void)
 Fetch the current file position marker for this thread.
bool operator++ (void)
bool operator-- (void)

Detailed Description

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

Constructor & Destructor Documentation

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

Open or create a new database file.

You should also use Initial.

Parameters:
pathpathname of database to open.
ost::SharedFile::SharedFile ( const SharedFile file)

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

Parameters:
fileoriginal file.
virtual 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:
addressaddress to use, or NULL if same as last I/O.
lengthlength 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:
lengthlength to use, or 0 if same as last I/O.
posfile 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:
addressaddress to use, or NULL if same as last I/O.
lengthlength to use, or 0 if same as last I/O.
positionfile 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:
addressaddress to use, or NULL if same as last I/O.
lengthlength to use, or 0 if same as last I/O.
positionfile position to use or -1 if same as last I/O.

The documentation for this class was generated from the following file: