ost::sharedfile(3)
NAME
ost::SharedFile - This class defines a database I/O file service that
can be shared by multiple processes.
SYNOPSIS
#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 (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:
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.
Member Function Documentation
- 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::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. - 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. - 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::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.
- 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)
Author
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code.