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ThreadFile Class Reference

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. More...

#include <file.h>

Inheritance diagram for ThreadFile::

List of all members.

Public Methods
	ThreadFile (const char *path)
	Open or create a new database file. More...
virtual	~ThreadFile ()
	Close and finish a database file. More...
fileerror_t	Restart (void)
	Restart an existing database; close and re-open. More...
fileerror_t	Fetch (char *address=NULL, ccxx_size_t length=0, off_t position=-1)
	Fetch a portion of the file into physical memory. More...
fileerror_t	Update (char *address=NULL, ccxx_size_t length=0, off_t position=-1)
	Update a portion of a file from physical memory. More...
fileerror_t	Append (char *address=NULL, ccxx_size_t length=0)
	Add new data to the end of the file. More...
off_t	getPosition (void)
	Fetch the current file position marker for this thread. More...
bool	operator++ (void)
bool	operator-- (void)

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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 <dyfet@ostel.com>

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Constructor & Destructor Documentation

ThreadFile::ThreadFile (  const char *   path )

Open or create a new database file. You should also use Initial. Parameters: pathname   of database to open.

virtual ThreadFile::~ThreadFile (    )  [virtual]

Close and finish a database file.

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Member Function Documentation

fileerror_t ThreadFile::Append (  char *   address = NULL, ccxx_size_t   length = 0 )

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.

fileerror_t 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: FILE_SUCCESS on success. 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.

fileerror_t ThreadFile::Restart (  void   )  [inline, virtual]

Restart an existing database; close and re-open. Returns: FILE_SUCCESS if successful. Reimplemented from RandomFile.

fileerror_t 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: FILE_SUCCESS on success. 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.

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   )

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The documentation for this class was generated from the following file:

• file.h

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