ost::threadfile(3)
NAME
ost::ThreadFile - This class defines a database I/O file service that
can be shared by multiple threads.
SYNOPSIS
#include <file.h> Inherits ost::RandomFile. 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:
path pathname of database to open.
- virtual ost::ThreadFile::~ThreadFile () [virtual]
- Close and finish a database file.
Member Function Documentation
- 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::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:
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::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:
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::ThreadFile::append (char * address = NULL, ccxx_size_t length =
- 0)
Add new data to the end of the file. - 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::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)
Author
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code.