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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 SharedFile::

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...
fileerror_t	Restart (void)
	Restart an existing database; close and re-open. More...
fileerror_t	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...
fileerror_t	Update (char *address=NULL, ccxx_size_t length=0, off_t position=-1)
	Update a portion of a file from physical memory. More...
fileerror_t	Clear (ccxx_size_t length=0, off_t pos=-1)
	Clear a lock held from a previous fetch operation without updating. More...
fileerror_t	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)

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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

SharedFile::SharedFile (  const char *   path )

Open or create a new database file. You should also use Initial. Parameters: pathname   of database to open. file   access mode.

SharedFile::SharedFile (  const SharedFile &   file )

Create a shared file as a duplicate of an existing shared file. Parameters: original   file.

virtual SharedFile::~SharedFile (    )  [virtual]

Close and finish a database file.

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Member Function Documentation

fileerror_t 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   to use, or NULL if same as last I/O. length   to use, or 0 if same as last I/O.

fileerror_t SharedFile::Clear (  ccxx_size_t   length = 0, off_t   pos = -1 )

Clear a lock held from a previous fetch operation without updating. Returns: FILE_SUCCESS on success. Parameters: length   to use, or 0 if same as last I/O. file   position to use or -1 if same as last I/O.

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

fileerror_t SharedFile::Restart (  void   )  [inline, virtual]

Restart an existing database; close and re-open. Returns: FILE_SUCCESS if successful. Reimplemented from RandomFile.

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

off_t SharedFile::getPosition (  void   )

Fetch the current file position marker for this thread. Returns: file position offset.

bool SharedFile::operator++ (  void   )

bool SharedFile::operator-- (  void   )

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

• file.h

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