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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