GNU CommonC++
Public Member Functions

ost::MappedFile Class Reference

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

#include <file.h>

Inheritance diagram for ost::MappedFile:
ost::RandomFile ost::Mutex ost::File

List of all members.

Public Member Functions

 MappedFile (const char *fname, Access mode)
 Open a file for mapping.
 MappedFile (const char *fname, Access mode, size_t size)
 Create if not exists, and map a file of specified size into memory.
 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.
virtual ~MappedFile ()
 Release a mapped section of memory associated with a file.
void sync (void)
 Synchronize the contents of the mapped portion of memory with the disk file and wait for completion.
void sync (char *address, size_t len)
 Synchronize a segment of memory mapped from a segment fetch.
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.
void update (char *address, size_t len)
 Update a mapped region back to disk as specified by address and length.
void release (char *address, size_t len)
 Release (unmap) a memory segment.
char * fetch (size_t offset=0)
 Fetch a pointer to an offset within the memory mapped portion of the disk file.
char * fetch (off_t pos, size_t len)
 Fetch and map a portion of a disk file to a logical memory block.
bool lock (void)
 Lock the currently mapped portion of a file.
void unlock (void)
 Unlock a locked mapped portion of a file.
size_t pageAligned (size_t size)
 Compute map size to aligned page boundry.

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@ostel.com> Map a named disk file into memory.

Constructor & Destructor Documentation

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:
fnamefile name to access for mapping.
modeaccess mode to map file.
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:
fnamefile name to access for mapping.
modeaccess mode to map file.
sizeof file to map.
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:
fnamepathname of file to map into memory.
offsetfrom start of file to begin mapping in bytes.
sizeof mapped area in bytes.
modeto map file.
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

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:
offsetfrom start of mapped memory.
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:
posoffset of file segment to map.
lensize of memory segment to map.
bool ost::MappedFile::lock ( void  )

Lock the currently mapped portion of a file.

Returns:
true if pages are locked.
size_t ost::MappedFile::pageAligned ( size_t  size)

Compute map size to aligned page boundry.

Parameters:
sizerequest.
Returns:
page aligned size.
void ost::MappedFile::release ( char *  address,
size_t  len 
)

Release (unmap) a memory segment.

Parameters:
addressaddress of memory segment to release.
lenlength of memory segment to release.
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.

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

Synchronize a segment of memory mapped from a segment fetch.

Parameters:
addressmemory address to update.
lensize of segment.
void ost::MappedFile::unlock ( void  )

Unlock a locked mapped portion of a file.

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:
offsetoffset into the mapped region of memory.
lenlength of partial region (example, record length).
void ost::MappedFile::update ( char *  address,
size_t  len 
)

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

Parameters:
addressaddress of segment.
lenlength of segment.

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