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/****************************************************************************
* Copyright (C) from 2009 to Present EPAM Systems.
*
* This file is part of Indigo toolkit.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
***************************************************************************/
#if !defined(_WIN32)
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <unistd.h>
#include "base_cpp/shmem.h"
using namespace indigo;
IMPL_ERROR(SharedMemory, "shared memory");
SharedMemory::SharedMemory(const char* name, int size, bool no_map_if_first)
{
snprintf(_filename, sizeof(_filename), "/tmp/indigo_shm_%s", name);
_pointer = NULL;
_was_first = false;
int key = ftok(_filename, 'D'); // 'D' has no actual meaning
if (key == -1 && errno == ENOENT)
{
// create file
int fd = creat(_filename, 0666);
if (fd == -1)
throw Error("can't create %s: %s", _filename, strerror(errno));
key = ftok(_filename, 'D');
}
if (key == -1)
throw Error("can't get key: %s", strerror(errno));
_shm_id = -1;
if (!no_map_if_first)
{
// try to create
_shm_id = shmget(key, size, IPC_CREAT | IPC_EXCL | 0666);
if (_shm_id == -1)
{
if (errno != EEXIST)
throw Error("can't shmget: %s", strerror(errno));
}
else
_was_first = true;
}
if (_shm_id == -1)
{
_shm_id = shmget(key, size, 0666);
if (_shm_id == -1)
{
if (errno == ENOENT)
return;
throw Error("can't second shmget (%d): %s", key, strerror(errno));
}
}
_pointer = shmat(_shm_id, NULL, 0);
if (_pointer == (void*)-1)
throw Error("can't shmat: %s", strerror(errno));
strncpy(_id, name, sizeof(_id));
if (_was_first)
memset(_pointer, 0, size);
}
SharedMemory::~SharedMemory()
{
struct shmid_ds ds;
// detach from the memory segment
if (shmdt((char*)_pointer) != 0)
return; // throwing exceptions on destructor is bad
// get information about the segment
if (shmctl(_shm_id, IPC_STAT, &ds) != 0)
return;
if (ds.shm_nattch < 1)
{
// nobody is using the segment; remove it
shmctl(_shm_id, IPC_RMID, NULL);
// and remove the temporary file
unlink(_filename);
}
}
#endif
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