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Documentation                       Search   shared_memory.cpp Go to the documentation of this file. /* Copyright, 2000-2002 Nevrax Ltd. * * This file is part of NEVRAX NEL. * NEVRAX NEL is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2, or (at your option) * any later version. * NEVRAX NEL is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * You should have received a copy of the GNU General Public License * along with NEVRAX NEL; see the file COPYING. If not, write to the * Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, * MA 02111-1307, USA. */ #include "stdmisc.h" #include "nel/misc/shared_memory.h" #ifdef NL_OS_WINDOWS #include <windows.h> #else # include <sys/types.h> # include <sys/ipc.h> # include <sys/shm.h> #endif using namespace std; namespace NLMISC { #ifdef NL_OS_WINDOWS // Storage for file handles, necessary to close the handles map<void*,HANDLE> AccessAddressesToHandles; #else // Storage for shmid, necessary to destroy the segments map<TSharedMemId, int> SharedMemIdsToShmids; #endif /* * Create a shared memory segment */ void *CSharedMemory::createSharedMemory( TSharedMemId sharedMemId, uint32 size ) { #ifdef NL_OS_WINDOWS // Create a file mapping backed by the virtual memory swap file (not a data file) HANDLE hMapFile = CreateFileMapping( INVALID_HANDLE_VALUE, NULL, PAGE_READWRITE, 0, size, sharedMemId ); if ( (hMapFile == NULL) || (GetLastError() == ERROR_ALREADY_EXISTS) ) return NULL; // Map the file into memory address space void *accessAddress = MapViewOfFile( hMapFile, FILE_MAP_ALL_ACCESS, 0, 0, 0 ); AccessAddressesToHandles.insert( make_pair( accessAddress, hMapFile ) ); return accessAddress; #else // Create a shared memory segment int shmid = shmget( sharedMemId, size, IPC_CREAT | IPC_EXCL | 0666 ); if ( shmid == -1 ) return NULL; SharedMemIdsToShmids.insert( make_pair( sharedMemId, shmid ) ); // Map the segment into memory address space void *accessAddress = (void*)shmat( shmid, 0, 0 ); if ( accessAddress == (void*)-1 ) return NULL; else return accessAddress; #endif } /* * Get access to an existing shared memory segment */ void *CSharedMemory::accessSharedMemory( TSharedMemId sharedMemId ) { #ifdef NL_OS_WINDOWS // Open the existing file mapping by name HANDLE hMapFile = OpenFileMapping( FILE_MAP_ALL_ACCESS, false, sharedMemId ); if ( hMapFile == NULL ) return NULL; // Map the file into memory address space void *accessAddress = MapViewOfFile( hMapFile, FILE_MAP_ALL_ACCESS, 0, 0, 0 ); AccessAddressesToHandles.insert( make_pair( accessAddress, hMapFile ) ); return accessAddress; #else // Open an existing shared memory segment int shmid = shmget( sharedMemId, 0, 0666 ); if ( shmid == -1 ) return NULL; // Map the segment into memory address space void *accessAddress = (void*)shmat( shmid, 0, 0 ); if ( accessAddress == (void*)-1 ) return NULL; else return accessAddress; #endif } /* * Close a shared memory segment */ bool CSharedMemory::closeSharedMemory( void *accessAddress ) { #ifdef NL_OS_WINDOWS // Unmap the file from memory address space if ( UnmapViewOfFile( accessAddress ) == 0 ) return false; // Close the corresponding handle map<void*,HANDLE>::iterator im = AccessAddressesToHandles.find( accessAddress ); if ( im != AccessAddressesToHandles.end() ) { CloseHandle( (*im).second ); AccessAddressesToHandles.erase( im ); return true; } else { return false; } #else // Detach the shared memory segment return ( shmdt( accessAddress ) != -1 ); #endif } /* * Destroy a shared memory segment (to call only by the process that created the segment) * Note: does nothing under Windows, it is automatic. */ void CSharedMemory::destroySharedMemory( TSharedMemId sharedMemId, bool force ) { #ifndef NL_OS_WINDOWS // Set the segment to auto-destroying (when the last process detaches) map<TSharedMemId,int>::iterator im = SharedMemIdsToShmids.find( sharedMemId ); if ( im != SharedMemIdsToShmids.end() ) { // Destroy the segment created before shmctl( (*im).second, IPC_RMID, 0 ); SharedMemIdsToShmids.erase( im ); } else if ( force ) { // Open and destroy the segment int shmid = shmget( sharedMemId, 0, 0666 ); if ( shmid != -1 ) { // Destroy the segment shmctl( shmid, IPC_RMID, 0 ); } } #endif } } // NLMISC