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:

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)

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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>

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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.

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

Close and finish a database file.

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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.

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

• file.h

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