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ost::ThreadFile

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
(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.

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 AT ostel DOT 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 (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.

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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