NAME
ThreadFile - This class defines a database I/O file service that can be shared by multiple threads. This class defines a database I/O file service that can be shared by multiple threads.
SYNOPSIS
#include <file.h>
Inherits RandomFile.
Public Methods
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. 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 <[email protected]>
CONSTRUCTOR & DESTRUCTOR DOCUMENTATION
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 ThreadFile::~ThreadFile () [virtual]
Close and finish a database file.
MEMBER FUNCTION DOCUMENTATION
Error 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.
Error 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.
off_t ThreadFile::getPosition (void)
Fetch the current file position marker for this thread.
Returns: file position offset.
bool ThreadFile::operator++ (void)
bool ThreadFile::operator-- (void)
Error ThreadFile::restart (void) [inline, virtual]
Restart an existing database; close and re-open.
Returns: errSuccess if successful.
Reimplemented from RandomFile.
Error 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.
AUTHOR
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