ost_SharedFile (3)

#include <file.h>

Inherits ost::RandomFile.

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 (caddr_t address=NULL, ccxx_size_t length=0, off_t position=-1)

Lock and Fetch a portion of the file into physical memory. Error update (caddr_t 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 (caddr_t 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)

Additional Inherited Members

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

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 \fBSharedFile\fP &file)

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

Parameters:

file original file.

virtual ost::SharedFile::~SharedFile ()\fC [virtual]\fP

Close and finish a database file.

\fBError\fP ost::SharedFile::append (caddr_taddress = \fCNULL\fP, \fBccxx_size_t\fPlength = \fC0\fP)

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.

\fBError\fP ost::SharedFile::clear (\fBccxx_size_t\fPlength = \fC0\fP, off_tpos = \fC-1\fP)

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.

\fBError\fP ost::SharedFile::fetch (caddr_taddress = \fCNULL\fP, \fBccxx_size_t\fPlength = \fC0\fP, off_tposition = \fC-1\fP)

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)

\fBError\fP ost::SharedFile::restart (void)\fC [inline]\fP, \fC [virtual]\fP

Restart an existing database; close and re-open.

Returns:

errSuccess if successful.

Reimplemented from ost::RandomFile.

\fBError\fP ost::SharedFile::update (caddr_taddress = \fCNULL\fP, \fBccxx_size_t\fPlength = \fC0\fP, off_tposition = \fC-1\fP)

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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