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ost::MappedFile Class Reference

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

#include <file.h>

Inheritance diagram for ost::MappedFile:

List of all members.

Public Methods
	MappedFile (const char *fname, Access mode)
	Open a file for mapping.
	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.

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Detailed Description

Create and map a disk file into memory. Map a named 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>

Todo:

implement in win32

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

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.

virtual ost::MappedFile::~MappedFile (    )  [virtual]

Release a mapped section of memory associated with a file. The mapped area is updated back to disk.

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Member Function Documentation

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.

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.

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.

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.

void ost::MappedFile::sync (  void    )  [inline]

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::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.

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).

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

• file.h

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