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ost::MappedFile(3) Library Functions Manual ost::MappedFile(3)

NAME

ost::MappedFile - Create and map a disk file into memory.

SYNOPSIS

#include <file.h>

Inherits ost::RandomFile.

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 (caddr_t 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 (caddr_t address, size_t len)
Update a mapped region back to disk as specified by address and length. void release (caddr_t address, size_t len)
Release (unmap) a memory segment. caddr_t fetch (size_t offset=0)
Fetch a pointer to an offset within the memory mapped portion of the disk file. caddr_t 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.

Additional Inherited Members

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 separate regions of memory.

Parameters

fname file name to access for mapping.
mode access 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

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

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.

Member Function Documentation

caddr_t 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.

caddr_t 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.

References ost::File::_fcb::address.

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

size request.

Returns

page aligned size.

void ost::MappedFile::release (caddr_t 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 (caddr_t 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)

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::unlock (void)

Unlock a locked mapped portion of a file.

void ost::MappedFile::update (caddr_t 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).

Author

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Sat Dec 28 2019 GNU CommonC++