ost::MappedFile Class Reference

Create and map a disk file into memory. More...

#include <file.h>

Inheritance diagram for ost::MappedFile:

Collaboration diagram for ost::MappedFile:

Public Member Functions
char *	fetch (size_t offset=0)
	Fetch a pointer to an offset within the memory mapped portion of the disk file. More...
char *	fetch (off_t pos, size_t len)
	Fetch and map a portion of a disk file to a logical memory block. More...
bool	lock (void)
	Lock the currently mapped portion of a file. More...
	MappedFile (const char *fname, Access mode)
	Open a file for mapping. More...
	MappedFile (const char *fname, Access mode, size_t size)
	Create if not exists, and map a file of specified size into memory. More...
	MappedFile (const char *fname, pos_t offset, size_t size, Access mode)
	Map a portion or all of a specified file in the specified shared memory access mode. More...
size_t	pageAligned (size_t size)
	Compute map size to aligned page boundry. More...
void	release (char *address, size_t len)
	Release (unmap) a memory segment. More...
void	sync (void)
	Synchronize the contents of the mapped portion of memory with the disk file and wait for completion. More...
void	sync (char *address, size_t len)
	Synchronize a segment of memory mapped from a segment fetch. More...
void	unlock (void)
	Unlock a locked mapped portion of a file.
void	update (size_t offset=0, size_t len=0)
	Map a portion of the memory mapped from the file back to the file and do not wait for completion. More...
void	update (char *address, size_t len)
	Update a mapped region back to disk as specified by address and length. More...
virtual	~MappedFile ()
	Release a mapped section of memory associated with a file. More...
Public Member Functions inherited from ost::RandomFile
off_t	getCapacity (void)
	Get current file capacity. More...
Error	getErrorNumber (void) const
	Return current error id. More...
char *	getErrorString (void) const
	Return current error string. More...
bool	initial (void)
	This method should be called right after a RandomFile derived object has been created. More...
	operator bool () const
bool	operator! (void) const
virtual Error	restart (void)
	This method is commonly used to close and re-open an existing database. More...
virtual	~RandomFile ()
	Destroy a random access file or it's derived class.

Additional Inherited Members
Protected Member Functions inherited from ost::RandomFile
Error	error (Error errid, char *errstr=NULL)
	Post an error event. More...
Error	error (char *err)
	Post an extended string error message. More...
void	final (void)
	Close the file.
virtual Attr	initialize (void)
	This method is used to initialize a newly created file as indicated by the "initial" flag. More...
	RandomFile (const char *name=NULL)
	Create an unopened random access file.
	RandomFile (const RandomFile &rf)
	Default copy constructor.
Error	setCompletion (Complete mode)
	Used to set file completion modes. More...
void	setError (bool enable)
	Used to enable or disable throwing of exceptions on errors. More...
void	setTemporary (bool enable)
	Used to set the temporary attribute for the file. More...
Protected Attributes inherited from ost::RandomFile
Access	access
int	fd
struct {
unsigned   count: 16
bool   immediate: 1
bool   initial: 1
bool   temp: 1
bool   thrown: 1
}	flags
char *	pathname
Related Functions inherited from ost::RandomFile
bool	canAccess (const char *path)
bool	canModify (const char *path)
bool	isDevice (const char *path)
bool	isDir (const char *path)
bool	isFile (const char *path)
time_t	lastAccessed (const char *path)
time_t	lastModified (const char *path)

Detailed Description

Create and map a disk file into memory.

This portable class works under both Posix via mmap and under the win32 API. A mapped file can be referenced directly by it's memory segment. One can map and unmap portions of a file on demand, and update changed memory pages mapped from files immediately through sync().

Author

David Sugar dyfet.nosp@m.@ost.nosp@m.el.co.nosp@m.m Map a named disk file into memory.

Definition at line 663 of file file.h.

Constructor & Destructor Documentation

MappedFile() [1/3]

ost::MappedFile::MappedFile	(	const char *	fname,
		Access	mode
	)

Open a file for mapping.

More than one segment of a file may be mapped into seperate regions of memory.

Parameters

fname	file name to access for mapping.
mode	access mode to map file.

MappedFile() [2/3]

ost::MappedFile::MappedFile	(	const char *	fname,
		Access	mode,
		size_t	size
	)

Create if not exists, and map a file of specified size into memory.

Parameters

fname	file name to access for mapping.
mode	access mode to map file.
size	of file to map.

MappedFile() [3/3]

ost::MappedFile::MappedFile	(	const char *	fname,
		pos_t	offset,
		size_t	size,
		Access	mode
	)

Map a portion or all of a specified file in the specified shared memory access mode.

Valid mapping modes include mappedRead, mappedWrite, and mappedReadWrite.

Parameters

fname	pathname of file to map into memory.
offset	from start of file to begin mapping in bytes.
size	of mapped area in bytes.
mode	to map file.

~MappedFile()

virtual ost::MappedFile::~MappedFile ( )

virtual

Release a mapped section of memory associated with a file.

The mapped area is updated back to disk.

Member Function Documentation

fetch() [1/2]

char* ost::MappedFile::fetch ( size_t  offset = 0 )

inline

Fetch a pointer to an offset within the memory mapped portion of the disk file.

This really is used for convience of matching operations between Update and Fetch, as one could simply have accessed the base pointer where the file was mapped directly.

Parameters

offset

from start of mapped memory.

Definition at line 764 of file file.h.

fetch() [2/2]

char* ost::MappedFile::fetch	(	off_t	pos,
		size_t	len
	)

Fetch and map a portion of a disk file to a logical memory block.

Returns

pointer to memory segment.

Parameters

pos	offset of file segment to map.
len	size of memory segment to map.

lock()

bool ost::MappedFile::lock

(

void

)

Lock the currently mapped portion of a file.

Returns

true if pages are locked.

pageAligned()

size_t ost::MappedFile::pageAligned

(

size_t

size

)

Compute map size to aligned page boundry.

Parameters

size

request.

Returns

page aligned size.

release()

void ost::MappedFile::release	(	char *	address,
		size_t	len
	)

Release (unmap) a memory segment.

Parameters

address	address of memory segment to release.
len	length of memory segment to release.

sync() [1/2]

void ost::MappedFile::sync

(

void

)

Synchronize the contents of the mapped portion of memory with the disk file and wait for completion.

This assures the memory mapped from the file is written back.

sync() [2/2]

void ost::MappedFile::sync	(	char *	address,
		size_t	len
	)

Synchronize a segment of memory mapped from a segment fetch.

Parameters

address	memory address to update.
len	size of segment.

update() [1/2]

void ost::MappedFile::update	(	size_t	offset = 0,
		size_t	len = 0
	)

Map a portion of the memory mapped from the file back to the file and do not wait for completion.

This is useful when mapping a database file and updating a single record.

Parameters

offset	offset into the mapped region of memory.
len	length of partial region (example, record length).

update() [2/2]

void ost::MappedFile::update	(	char *	address,
		size_t	len
	)

Update a mapped region back to disk as specified by address and length.

Parameters

address	address of segment.
len	length of segment.

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

• commoncpp/file.h