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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.
SharedFile (const char *path)
| SharedFile |
Open or create a new database file. You should also use Initial.
Parameters:
pathname | of database to open. |
file | access mode. |
SharedFile (const SharedFile &file)
| SharedFile |
Create a shared file as a duplicate of an existing shared file.
Parameters:
original | file. |
~SharedFile ()
| ~SharedFile |
[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 |
Lock and 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. The current lock is also cleared.
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 Clear (ccxx_size_t length = 0, off_t pos = -1)
| Clear |
Clear a lock held from a previous fetch operation without updating.
Parameters:
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. Locks file during append.
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-- |
SharedFile (const char *path)
| SharedFile |
Open or create a new database file. You should also use Initial.
Parameters:
pathname | of database to open. |
file | access mode. |
SharedFile (const SharedFile &file)
| SharedFile |
Create a shared file as a duplicate of an existing shared file.
Parameters:
original | file. |
~SharedFile ()
| ~SharedFile |
[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 |
Lock and 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. The current lock is also cleared.
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 Clear (ccxx_size_t length = 0, off_t pos = -1)
| Clear |
Clear a lock held from a previous fetch operation without updating.
Parameters:
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. Locks file during append.
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-- |