O file service that can be shared by multiple threads.

NAME

ost::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 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 (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 <dyfet@ostel.com>

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 (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 ost::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 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 (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.