| ost::SharedFile(3) | Library Functions Manual | 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 (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¶
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::append (caddr_t 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.
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.
pos file position to use or -1 if same as last I/O.
Error ost::SharedFile::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. 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.
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 (caddr_t 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.
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.
Author¶
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