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/****************************************************************************
**
** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the QtGui module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** GNU Lesser General Public License Usage
** This file may be used under the terms of the GNU Lesser General Public
** License version 2.1 as published by the Free Software Foundation and
** appearing in the file LICENSE.LGPL included in the packaging of this
** file. Please review the following information to ensure the GNU Lesser
** General Public License version 2.1 requirements will be met:
** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights. These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU General
** Public License version 3.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of this
** file. Please review the following information to ensure the GNU General
** Public License version 3.0 requirements will be met:
** http://www.gnu.org/copyleft/gpl.html.
**
** Other Usage
** Alternatively, this file may be used in accordance with the terms and
** conditions contained in a signed written agreement between you and Nokia.
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "qwssharedmemory_p.h"
#if !defined(QT_NO_QWS_MULTIPROCESS)
#include <sys/types.h>
#include <sys/ipc.h>
#ifndef QT_POSIX_IPC
#include <sys/shm.h>
#else
#include <sys/mman.h>
#include <sys/stat.h>
#endif
#include <fcntl.h>
#include <unistd.h>
#include <private/qcore_unix_p.h>
//#define QT_SHM_DEBUG
QT_BEGIN_NAMESPACE
#ifdef QT_POSIX_IPC
#include <QtCore/QAtomicInt>
static QBasicAtomicInt localUniqueId = Q_BASIC_ATOMIC_INITIALIZER(1);
static inline QByteArray makeKey(int id)
{
return "/qwsshm_" + QByteArray::number(id, 16);
}
#endif
QWSSharedMemory::QWSSharedMemory()
: shmId(-1), shmBase(0), shmSize(0)
#ifdef QT_POSIX_IPC
, hand(-1)
#endif
{
}
QWSSharedMemory::~QWSSharedMemory()
{
detach();
}
bool QWSSharedMemory::create(int size)
{
if (shmId != -1)
detach();
#ifndef QT_POSIX_IPC
shmId = shmget(IPC_PRIVATE, size, IPC_CREAT | 0600);
#else
// ### generate really unique IDs
shmId = (getpid() << 16) + (localUniqueId.fetchAndAddRelaxed(1) % ushort(-1));
QByteArray shmName = makeKey(shmId);
EINTR_LOOP(hand, shm_open(shmName.constData(), O_RDWR | O_CREAT, 0660));
if (hand != -1) {
// the size may only be set once; ignore errors
int ret;
EINTR_LOOP(ret, ftruncate(hand, size));
if (ret == -1)
shmId = -1;
} else {
shmId = -1;
}
#endif
if (shmId == -1) {
#ifdef QT_SHM_DEBUG
perror("QWSSharedMemory::create():");
qWarning("Error allocating shared memory of size %d", size);
#endif
detach();
return false;
}
#ifndef QT_POSIX_IPC
shmBase = shmat(shmId, 0, 0);
// On Linux, it is possible to attach a shared memory segment even if it
// is already marked to be deleted. However, POSIX.1-2001 does not specify
// this behaviour and many other implementations do not support it.
shmctl(shmId, IPC_RMID, 0);
#else
// grab the size
QT_STATBUF st;
if (QT_FSTAT(hand, &st) != -1) {
shmSize = st.st_size;
// grab the memory
shmBase = mmap(0, shmSize, PROT_READ | PROT_WRITE, MAP_SHARED, hand, 0);
}
#endif
if (shmBase == (void*)-1 || !shmBase) {
#ifdef QT_SHM_DEBUG
perror("QWSSharedMemory::create():");
qWarning("Error attaching to shared memory id %d", shmId);
#endif
detach();
return false;
}
return true;
}
bool QWSSharedMemory::attach(int id)
{
if (shmId == id)
return id != -1;
detach();
if (id == -1)
return false;
shmId = id;
#ifndef QT_POSIX_IPC
shmBase = shmat(shmId, 0, 0);
#else
QByteArray shmName = makeKey(shmId);
EINTR_LOOP(hand, shm_open(shmName.constData(), O_RDWR, 0660));
if (hand != -1) {
// grab the size
QT_STATBUF st;
if (QT_FSTAT(hand, &st) != -1) {
shmSize = st.st_size;
// grab the memory
shmBase = mmap(0, shmSize, PROT_READ | PROT_WRITE, MAP_SHARED, hand, 0);
}
}
#endif
if (shmBase == (void*)-1 || !shmBase) {
#ifdef QT_SHM_DEBUG
perror("QWSSharedMemory::attach():");
qWarning("Error attaching to shared memory id %d", shmId);
#endif
detach();
return false;
}
return true;
}
void QWSSharedMemory::detach()
{
#ifndef QT_POSIX_IPC
if (shmBase && shmBase != (void*)-1)
shmdt(shmBase);
#else
if (shmBase && shmBase != (void*)-1)
munmap(shmBase, shmSize);
if (hand > 0) {
// get the number of current attachments
int shm_nattch = 0;
QT_STATBUF st;
if (QT_FSTAT(hand, &st) == 0) {
// subtract 2 from linkcount: one for our own open and one for the dir entry
shm_nattch = st.st_nlink - 2;
}
qt_safe_close(hand);
// if there are no attachments then unlink the shared memory
if (shm_nattch == 0) {
QByteArray shmName = makeKey(shmId);
shm_unlink(shmName.constData());
}
}
#endif
shmBase = 0;
shmSize = 0;
shmId = -1;
}
int QWSSharedMemory::size() const
{
if (shmId == -1)
return 0;
#ifndef QT_POSIX_IPC
if (!shmSize) {
struct shmid_ds shm;
shmctl(shmId, IPC_STAT, &shm);
shmSize = shm.shm_segsz;
}
#endif
return shmSize;
}
QT_END_NAMESPACE
#endif // QT_NO_QWS_MULTIPROCESS
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