.TH "sc::ShmMemoryGrp" 3 "Sun Oct 4 2020" "Version 2.3.1" "MPQC" \" -*- nroff -*-
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.SH NAME
sc::ShmMemoryGrp \- The \fBShmMemoryGrp\fP concrete class provides an implementation of \fBMsgMemoryGrp\fP\&.  

.SH SYNOPSIS
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.PP
.PP
\fC#include <memshm\&.h>\fP
.PP
Inherits \fBsc::MsgMemoryGrp\fP\&.
.SS "Public Member Functions"

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.ti -1c
.RI "\fBShmMemoryGrp\fP (const \fBRef\fP< \fBMessageGrp\fP > &msg)"
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.ti -1c
.RI "\fBShmMemoryGrp\fP (const \fBRef\fP< \fBKeyVal\fP > &)"
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.RI "void \fBset_localsize\fP (size_t)"
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.RI "Set the size of locally held memory\&. "
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.RI "void * \fBlocaldata\fP ()"
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.RI "Returns a pointer to the local data\&. "
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.RI "void * \fBobtain_readwrite\fP (\fBdistsize_t\fP \fBoffset\fP, int \fBsize\fP)"
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.RI "Only one thread can have an unreleased obtain_readwrite at a time\&. "
.ti -1c
.RI "void * \fBobtain_readonly\fP (\fBdistsize_t\fP \fBoffset\fP, int \fBsize\fP)"
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.RI "This gives read access to the memory location\&. No locking is done\&. "
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.RI "void * \fBobtain_writeonly\fP (\fBdistsize_t\fP \fBoffset\fP, int \fBsize\fP)"
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.RI "This gives write access to the memory location\&. No locking is done\&. "
.ti -1c
.RI "void \fBrelease_readonly\fP (void *data, \fBdistsize_t\fP \fBoffset\fP, int \fBsize\fP)"
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.RI "This is called when read access is no longer needed\&. "
.ti -1c
.RI "void \fBrelease_writeonly\fP (void *data, \fBdistsize_t\fP \fBoffset\fP, int \fBsize\fP)"
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.RI "This is called when write access is no longer needed\&. "
.ti -1c
.RI "void \fBrelease_readwrite\fP (void *data, \fBdistsize_t\fP \fBoffset\fP, int \fBsize\fP)"
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.RI "This is called when read/write access is no longer needed\&. "
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.RI "void \fBprint\fP (std::ostream &o=\fBExEnv::out0\fP()) const"
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.RI "Prints out information about the object\&. "
.in -1c
.SS "Additional Inherited Members"
.SH "Detailed Description"
.PP 
The \fBShmMemoryGrp\fP concrete class provides an implementation of \fBMsgMemoryGrp\fP\&. 

It uses SYSV IPC to provided shared memory in a system that provide shared memory in hardware\&. It is very fast and reliable\&. 
.SH "Member Function Documentation"
.PP 
.SS "void* sc::ShmMemoryGrp::obtain_readwrite (\fBdistsize_t\fP offset, int size)\fC [virtual]\fP"

.PP
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\&. 
.PP
Implements \fBsc::MemoryGrp\fP\&.
.SS "void sc::ShmMemoryGrp::release_readwrite (void * data, \fBdistsize_t\fP offset, int size)\fC [virtual]\fP"

.PP
This is called when read/write access is no longer needed\&. The memory will be unlocked\&. 
.PP
Implements \fBsc::MemoryGrp\fP\&.
.SS "void sc::ShmMemoryGrp::set_localsize (size_t)\fC [virtual]\fP"

.PP
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 \fBn()\fP - 1\&. 
.PP
Reimplemented from \fBsc::MsgMemoryGrp\fP\&.

.SH "Author"
.PP 
Generated automatically by Doxygen for MPQC from the source code\&.