NAME

       ost::ThreadFile - This class defines a database I/O file service that can be shared by
       multiple threads.

SYNOPSIS

       #include <file.h>

       Inherits ost::RandomFile.

   Public Member Functions
       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 (caddr_t address=NULL, ccxx_size_t length=0, off_t position=-1)
           Fetch a portion of the file into physical memory.
       Error update (caddr_t address=NULL, ccxx_size_t length=0, off_t position=-1)
           Update a portion of a file from physical memory.
       Error append (caddr_t 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)

   Additional Inherited Members

Detailed Description

       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

       This class defines a database I/O file service that can be shared by multiple threads.

Constructor & Destructor Documentation

   ost::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 ost::ThreadFile::~ThreadFile () [virtual]
       Close and finish a database file.

Member Function Documentation

   Error ost::ThreadFile::append (caddr_t 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 ost::ThreadFile::fetch (caddr_t 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 ost::ThreadFile::getPosition (void)
       Fetch the current file position marker for this thread.

       Returns
           file position offset.

   bool ost::ThreadFile::operator++ (void)
   bool ost::ThreadFile::operator-- (void)
   Error ost::ThreadFile::restart (void) [virtual]
       Restart an existing database; close and re-open.

       Returns
           errSuccess if successful.

       Reimplemented from ost::RandomFile.

   Error ost::ThreadFile::update (caddr_t 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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