NAME
SharedFile - This class defines a database I/O file service that can be shared by multiple processes. This class defines a database I/O file service that can be shared by multiple processes.
SYNOPSIS
#include <file.h>
Inherits RandomFile.
Public Methods
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 (char *address=NULL, ccxx_size_t length=0, off_t position=-1)
Lock and 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 clear (ccxx_size_t length=0, off_t pos=-1)
Clear a lock held from a previous fetch operation without updating. 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 processes. 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 <[email protected]>
CONSTRUCTOR & DESTRUCTOR DOCUMENTATION
SharedFile::SharedFile (const char * path)
Open or create a new database file.
You should also use Initial.
Parameters:
- path
-
pathname of database to open.
SharedFile::SharedFile (const SharedFile & file)
Create a shared file as a duplicate of an existing shared file.
Parameters:
- file
-
original file.
virtual SharedFile::~SharedFile () [virtual]
Close and finish a database file.
MEMBER FUNCTION DOCUMENTATION
Error SharedFile::append (char * 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.
Error 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.
Error SharedFile::fetch (char * 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.
off_t SharedFile::getPosition (void)
Fetch the current file position marker for this thread.
Returns: file position offset.
bool SharedFile::operator++ (void)
bool SharedFile::operator-- (void)
Error SharedFile::restart (void) [inline, virtual]
Restart an existing database; close and re-open.
Returns: errSuccess if successful.
Reimplemented from RandomFile.
Error SharedFile::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. 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.
AUTHOR
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