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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.
ThreadFile (const char *path)
| ThreadFile |
Open or create a new database file. You should also use Initial.
Parameters:
pathname | of database to open. |
~ThreadFile ()
| ~ThreadFile |
[virtual]
Close and finish a database file.
fileerror_t Restart (void)
| Restart |
Restart an existing database; close and re-open.
Returns: FILE_SUCCESS if successful.
Reimplemented from RandomFile.
fileerror_t Fetch (char * address = NULL, ccxx_size_t length = 0, off_t position = -1)
| Fetch |
Fetch a portion of the file into physical memory. This can use state information to fetch the current record multiple times.
Parameters:
address | to use, or NULL if same as last I/O. |
length | to use, or 0 if same as last I/O. |
file | position to use -1 if same as last I/O. |
Returns: FILE_SUCCESS on success.
fileerror_t Update (char * address = NULL, ccxx_size_t length = 0, off_t position = -1)
| Update |
Update a portion of a file from physical memory. This can use state information to commit the last read record.
Parameters:
address | to use, or NULL if same as last I/O. |
length | to use, or 0 if same as last I/O. |
file | position to use or -1 if same as last I/O. |
Returns: FILE_SUCCESS on success.
fileerror_t Append (char * address = NULL, ccxx_size_t length = 0)
| Append |
Add new data to the end of the file.
Parameters:
address | to use, or NULL if same as last I/O. |
length | to use, or 0 if same as last I/O. |
off_t getPosition (void)
| getPosition |
Fetch the current file position marker for this thread.
Returns: file position offset.
bool operator++ (void)
| operator++ |
bool operator-- (void)
| operator-- |
ThreadFile (const char *path)
| ThreadFile |
Open or create a new database file. You should also use Initial.
Parameters:
pathname | of database to open. |
~ThreadFile ()
| ~ThreadFile |
[virtual]
Close and finish a database file.
fileerror_t Restart (void)
| Restart |
Restart an existing database; close and re-open.
Returns: FILE_SUCCESS if successful.
Reimplemented from RandomFile.
fileerror_t Fetch (char * address = NULL, ccxx_size_t length = 0, off_t position = -1)
| Fetch |
Fetch a portion of the file into physical memory. This can use state information to fetch the current record multiple times.
Parameters:
address | to use, or NULL if same as last I/O. |
length | to use, or 0 if same as last I/O. |
file | position to use -1 if same as last I/O. |
Returns: FILE_SUCCESS on success.
fileerror_t Update (char * address = NULL, ccxx_size_t length = 0, off_t position = -1)
| Update |
Update a portion of a file from physical memory. This can use state information to commit the last read record.
Parameters:
address | to use, or NULL if same as last I/O. |
length | to use, or 0 if same as last I/O. |
file | position to use or -1 if same as last I/O. |
Returns: FILE_SUCCESS on success.
fileerror_t Append (char * address = NULL, ccxx_size_t length = 0)
| Append |
Add new data to the end of the file.
Parameters:
address | to use, or NULL if same as last I/O. |
length | to use, or 0 if same as last I/O. |
off_t getPosition (void)
| getPosition |
Fetch the current file position marker for this thread.
Returns: file position offset.
bool operator++ (void)
| operator++ |
bool operator-- (void)
| operator-- |