sc::shmmemorygrp(3)

NAME

sc::ShmMemoryGrp - The ShmMemoryGrp concrete class provides an implementation of MsgMemoryGrp.

SYNOPSIS

#include <memshm.h>
Inherits sc::MsgMemoryGrp.
Public Member Functions
ShmMemoryGrp (const Ref< MessageGrp > &msg)
ShmMemoryGrp (const Ref< KeyVal > &)
void set_localsize (size_t)
    Set the size of locally held memory.
void * localdata ()
    Returns a pointer to the local data.
void * obtain_readwrite (distsize_t offset, int size)
    Only one thread can have an unreleased obtain_readwrite at a time.
void * obtain_readonly (distsize_t offset, int size)
    This gives read access to the memory location. No locking is done.
void * obtain_writeonly (distsize_t offset, int size)
    This gives write access to the memory location. No locking is done.
void release_readonly (void *data, distsize_t offset, int size)
    This is called when read access is no longer needed.
void release_writeonly (void *data, distsize_t offset, int size)
    This is called when write access is no longer needed.
void release_readwrite (void *data, distsize_t offset, int size)
    This is called when read/write access is no longer needed.
void print (std::ostream &o=ExEnv::out0()) const
    Prints out information about the object.

Detailed Description

The ShmMemoryGrp concrete class provides an implementation of MsgMemoryGrp.

It uses SYSV IPC to provided shared memory in a system that provide
shared memory in hardware. It is very fast and reliable.

Member Function Documentation

void sc::ShmMemoryGrp::set_localsize (size_t) [virtual]

Set the size of locally held memory.

When memory is accessed using a global offset counting starts at node 0 and proceeds up to node n() - 1.

Reimplemented from sc::MsgMemoryGrp.

void* sc::ShmMemoryGrp::obtain_readwrite (distsize_t offset, int size)

[virtual]
Only one thread can have an unreleased obtain_readwrite at a time.

The actual memory region locked can be larger than that requested. If
the memory region is already locked this will block. For this reason,
data should be held as read/write for as short a time as possible.

Implements sc::MemoryGrp.

void sc::ShmMemoryGrp::release_readwrite (void * data, distsize_t offset,

int size) [virtual]
This is called when read/write access is no longer needed.

The memory will be unlocked.

Implements sc::MemoryGrp.

Author

Generated automatically by Doxygen for MPQC from the source code.

Version 2.3.1 15 Mar 2008 sc::ShmMemoryGrp(3)