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sc::ShmMemoryGrp Class Reference

The ShmMemoryGrp concrete class provides an implementation of MsgMemoryGrp. More...

#include <memshm.h>

Inheritance diagram for sc::ShmMemoryGrp:

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Collaboration diagram for sc::ShmMemoryGrp:

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List of all members.

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::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.

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.


The documentation for this class was generated from the following file:
Generated at Sat Dec 18 15:15:24 2004 for MPQC 2.2.3 using the documentation package Doxygen 1.3.7-20040617.