GNU CommonC++
Public Member Functions

ost::ThreadFile Class Reference

This class defines a database I/O file service that can be shared by multiple threads. More...

#include <file.h>

Inheritance diagram for ost::ThreadFile:
ost::RandomFile ost::Mutex ost::File

List of all members.

Public Member Functions

 ThreadFile (const char *path)
 Open or create a new database file.
virtual ~ThreadFile ()
 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)
 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 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 threads.

All threads access a global copy of the database object, and mutex locks can be used to preserve transaction integrety. pread/pwrite calls can be used for optimized I/O when supported.

ThreadFile is meant for use by a threaded database server where multiple threads may each perform semi-independent operations on a given database table stored on disk. A special "fcb" structure is used to hold file "state", and pread/pwrite is used whenever possible for optimized I/O. On systems that do not offer pwread/pwrite, a Mutex lock is used to protect concurrent lseek and read/write operations. ThreadFile managed databases are assumed to be used only by the local server and through a single file descriptor.

Author:
David Sugar <dyfet@ostel.com> This class defines a database I/O file service that can be shared by multiple threads.

Constructor & Destructor Documentation

ost::ThreadFile::ThreadFile ( const char *  path)

Open or create a new database file.

You should also use Initial.

Parameters:
pathpathname of database to open.
virtual ost::ThreadFile::~ThreadFile ( ) [virtual]

Close and finish a database file.


Member Function Documentation

Error ost::ThreadFile::append ( char *  address = NULL,
ccxx_size_t  length = 0 
)

Add new data to the end of the file.

Parameters:
addressaddress to use, or NULL if same as last I/O.
lengthlength to use, or 0 if same as last I/O.
Error ost::ThreadFile::fetch ( char *  address = NULL,
ccxx_size_t  length = 0,
off_t  position = -1 
)

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:
addressaddress to use, or NULL if same as last I/O.
lengthlength to use, or 0 if same as last I/O.
positionfile position to use -1 if same as last I/O.
off_t ost::ThreadFile::getPosition ( void  )

Fetch the current file position marker for this thread.

Returns:
file position offset.
bool ost::ThreadFile::operator++ ( void  )
bool ost::ThreadFile::operator-- ( void  )
Error ost::ThreadFile::restart ( void  ) [virtual]

Restart an existing database; close and re-open.

Returns:
errSuccess if successful.

Reimplemented from ost::RandomFile.

Error ost::ThreadFile::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.

Returns:
errSuccess on success.
Parameters:
addressaddress to use, or NULL if same as last I/O.
lengthlength to use, or 0 if same as last I/O.
positionfile position to use or -1 if same as last I/O.

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