class MappedFile

map a named disk file into memory. More...

Definition#include <file.h>
InheritsFile [protected]
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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.

MappedFile (const char *fname, pos_t offset, size_t size, int mode)

Map a portion or all of a specified file in the specified shared memory access mode. Valid mapping modes include FILE_MAPPED_READ, FILE_MAPPED_WRITE, and FILE_MAPPED_RDWR.

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.

~MappedFile ()
[virtual]

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

inline void 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.

inline void Update (unsigned offset, size_t len)

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:
offsetinto the mapped region of memory.
lenof partial region (example, record length).

inline void * Fetch (unsigned offset)

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.