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    41 

    42 #include "qsystemreadwritelock_p.h"

    43 

    44 #include <QSharedMemory>

    45 #include <QSystemSemaphore>

    46 

    47 ///#define QSYSTEMREADWRITELOCK_DEBUG 1

    48 #ifdef QSYSTEMREADWRITELOCK_DEBUG

    49 #include <QDebug>

    50 #endif

    51 

    52 QT_USE_NAMESPACE

    53 

    54 QTM_BEGIN_NAMESPACE

    55 

    56 class QSystemReadWriteLockPrivate

    57 {

    58 public:

    59     QSystemReadWriteLockPrivate(const QString &key, QSystemReadWriteLock::AccessMode mode);

    60     ~QSystemReadWriteLockPrivate();

    61 

    62     int &accessCount();

    63     unsigned int &waitingReaders();

    64     unsigned int &waitingWriters();

    65 

    66     QSystemReadWriteLock::SystemReadWriteLockError convertError(QSystemSemaphore::SystemSemaphoreError error);

    67     QSystemReadWriteLock::SystemReadWriteLockError convertError(QSharedMemory::SharedMemoryError error);

    68 

    69     QString m_key;

    70 

    71     QSharedMemory m_counts;

    72     QSystemSemaphore m_readerWait;

    73     QSystemSemaphore m_writerWait;

    74     bool m_isInitialized;

    75 

    76     QSystemReadWriteLock::SystemReadWriteLockError m_error;

    77     QString m_errorString;

    78 };

    79 

    80 QSystemReadWriteLockPrivate::QSystemReadWriteLockPrivate(const QString &key, QSystemReadWriteLock::AccessMode mode)

    81     :m_key(key), m_counts(key + QLatin1String("_counts")),

    82     m_readerWait(key + QLatin1String("_readerWait"), 0, (mode==QSystemReadWriteLock::Create)?QSystemSemaphore::Create:QSystemSemaphore::Open),

    83     m_writerWait(key + QLatin1String("_writerWait"), 0, (mode==QSystemReadWriteLock::Create)?QSystemSemaphore::Create:QSystemSemaphore::Open),

    84     m_isInitialized(false), m_error(QSystemReadWriteLock::NoError), m_errorString(QString())

    85 {

    86     bool isAttached = false;

    87     int retries=5;

    88     for (int i=0; i < retries; ++i){

    89         if (m_counts.attach()) {

    90             isAttached = true;

    91             break;

    92         }

    93         else {

    94             if (m_counts.error() == QSharedMemory::NotFound) {

    95                 if (m_counts.create(3 * sizeof(int))) {

    96                     isAttached = true;

    97                     break;

    98                 }

    99             }

   100         }

   101     }

   102 

   103     if (!isAttached) {

   104         m_error = convertError(m_counts.error());

   105         m_errorString = QObject::tr("QSystemReadWriteLockPrivate::QSystemReadWriteLockPrivate: "

   106                                         "Unable to create/attach to shared memory");

   107         return;

   108     } else {

   109         if (mode == QSystemReadWriteLock::Create) {

   110             if(!m_counts.lock()) {

   111                 m_error = convertError(m_counts.error());

   112                 m_errorString = QObject::tr("QSystemReadWriteLockPrivate::QSystemReadWriteLockPrivate: "

   113                                                 "Unable to initialize shared memory");

   114                 return;

   115             }

   116             int * data = (int *)m_counts.data();

   117             ::memset(data, 0, 3 * sizeof(int));

   118             m_counts.unlock();

   119         }

   120         m_isInitialized = true;

   121     }

   122 }

   123 

   124 QSystemReadWriteLockPrivate::~QSystemReadWriteLockPrivate()

   125 {

   126 }

   127 

   128 QSystemReadWriteLock::SystemReadWriteLockError QSystemReadWriteLockPrivate::convertError(QSystemSemaphore::SystemSemaphoreError error)

   129 {

   130     switch(error) {

   131         case QSystemSemaphore::NoError:

   132             return QSystemReadWriteLock::NoError;

   133         case QSystemSemaphore::PermissionDenied:

   134             return QSystemReadWriteLock::PermissionDenied;

   135         case QSystemSemaphore::KeyError:

   136             return QSystemReadWriteLock::KeyError;

   137         case QSystemSemaphore::NotFound:

   138             return QSystemReadWriteLock::NotFound;

   139         case QSystemSemaphore::OutOfResources:

   140             return QSystemReadWriteLock::OutOfResources;

   141         case QSystemSemaphore::AlreadyExists:

   142         case QSystemSemaphore::UnknownError:

   143         default:

   144             return QSystemReadWriteLock::UnknownError;

   145     }

   146 }

   147 

   148 QSystemReadWriteLock::SystemReadWriteLockError QSystemReadWriteLockPrivate::convertError(QSharedMemory::SharedMemoryError error)

   149 {

   150     switch(error){

   151         case QSharedMemory::NoError:

   152             return QSystemReadWriteLock::NoError;

   153         case QSharedMemory::PermissionDenied:

   154             return QSystemReadWriteLock::PermissionDenied;

   155         case QSharedMemory::KeyError:

   156             return QSystemReadWriteLock::KeyError;

   157         case QSharedMemory::NotFound:

   158             return QSystemReadWriteLock::NotFound;

   159         case QSharedMemory::LockError:

   160             return QSystemReadWriteLock::LockError;

   161         case QSharedMemory::UnknownError:

   162         default:

   163             return QSystemReadWriteLock::UnknownError;

   164     }

   165 }

   166 

   167 QSystemReadWriteLock::QSystemReadWriteLock(const QString &key, AccessMode mode)

   168     :d(new QSystemReadWriteLockPrivate(key,mode))

   169 {

   170 }

   171 

   172 QSystemReadWriteLock::~QSystemReadWriteLock()

   173 {

   174     Q_ASSERT(d);

   175     delete d;

   176     d = 0;

   177 }

   178 

   179 bool QSystemReadWriteLock::lockForRead()

   180 {

   181 #if defined QSYSTEMREADWRITELOCK_DEBUG

   182     qDebug() << "QSystemReadWriteLock::lockForRead() <start>\naccessCount ="

   183         << d->accessCount() << "\twaitingWriters=" << d->waitingWriters() << "\twaitingReaders=" << d->waitingReaders();

   184 #endif

   185     if (!d->m_isInitialized) {

   186         d->m_error = QSystemReadWriteLock::FailedToInitialize;

   187         d->m_errorString = QObject::tr("QSystemReadWriteLock::lockForRead(): cannot peform operation, lock initialization had not been successful");

   188         return false;

   189     }

   190 

   191     if(!d->m_counts.lock()) {

   192         d->m_error = d->convertError(d->m_counts.error());

   193         d->m_errorString = QObject::tr("QSystemReadWriteLock::lockForRead(): cannot perform operation, locking of shared memory was unsuccessful");

   194         return false;

   195     }

   196 

   197     while(d->accessCount() < 0 || d->waitingWriters() > 0 ) {

   198         ++d->waitingReaders();

   199         d->m_counts.unlock();

   200         d->m_readerWait.acquire();

   201         d->m_counts.lock();

   202         --d->waitingReaders();

   203     }

   204     ++d->accessCount();

   205     Q_ASSERT_X(d->accessCount() > 0, "QSystemReadWriteLock::lockForRead()", "Overflow in lock counter");

   206 #if defined QSYSTEMREADWRITELOCK_DEBUG

   207     qDebug() << "QSystemReadWriteLock::lockForRead() <end>\naccessCount ="

   208         << d->accessCount() << "\twaitingWriters=" << d->waitingWriters() << "\twaitingReaders=" << d->waitingReaders();

   209 #endif

   210 

   211     d->m_error = QSystemReadWriteLock::NoError;

   212     d->m_errorString.clear();

   213     d->m_counts.unlock();

   214     return true;

   215 }

   216 

   217 bool QSystemReadWriteLock::lockForWrite()

   218 {

   219 #if defined QSYSTEMREADWRITELOCK_DEBUG

   220     qDebug() << "QSystemReadWriteLock::lockForWrite() <start>\naccessCount ="

   221         << d->accessCount() << "\twaitingWriters=" << d->waitingWriters() << "\twaitingReaders=" << d->waitingReaders();

   222 #endif

   223     if (!d->m_isInitialized) {

   224         d->m_error = QSystemReadWriteLock::FailedToInitialize;

   225         d->m_errorString = QObject::tr("QSystemReadWriteLock::lockForWrite(): cannot peform operation, lock initialization had not been successful");

   226         return false;

   227     }

   228 

   229     if(!d->m_counts.lock()) {

   230         d->m_error = d->convertError(d->m_counts.error());

   231         d->m_errorString = QObject::tr("QSystemReadWriteLock::lockForwrite(): cannot perform operation, locking of shared memory was unsuccessful");

   232         return false;

   233     }

   234 

   235 #if defined QSYSTEMREADWRITELOCK_DEBUG

   236     qDebug() << "QSystemReadWriteLock::lockForWrite() <start>\naccessCount =" 

   237         << d->accessCount() << "\twaitingWriters=" << d->waitingWriters() << "\twaitingReaders=" << d->waitingReaders();

   238 #endif

   239     while(d->accessCount() != 0) {

   240         ++d->waitingWriters();

   241         d->m_counts.unlock();

   242         d->m_writerWait.acquire();

   243         d->m_counts.lock();

   244         --d->waitingWriters();

   245     }

   246     --d->accessCount();

   247 #if defined QSYSTEMREADWRITELOCK_DEBUG

   248     qDebug() << "QSystemReadWriteLock::lockForWrite() <end>\naccessCount =" 

   249         << d->accessCount() << "\twaitingWriters=" << d->waitingWriters() << "\twaitingReaders=" << d->waitingReaders();

   250 #endif

   251 

   252     Q_ASSERT_X(d->accessCount() < 0, "QSystemReadWriteLock::lockForWrite()", "Overflow in lock counter");

   253 

   254     d->m_error = QSystemReadWriteLock::NoError;

   255     d->m_errorString.clear();

   256     d->m_counts.unlock();

   257     return true;

   258 }

   259 

   260 void QSystemReadWriteLock::unlock()

   261 {

   262     if (!d->m_isInitialized) {

   263         d->m_error = QSystemReadWriteLock::FailedToInitialize;

   264         d->m_errorString = QObject::tr("QSystemReadWriteLock::unlock(): cannot peform operation, lock initialization had not been successful");

   265         return;

   266     }

   267 

   268     if(!d->m_counts.lock()) {

   269         d->m_error = d->convertError(d->m_counts.error());

   270         d->m_errorString = QObject::tr("QSystemReadWriteLock::lockForwrite(): cannot perform operation, locking of shared memory was unsuccessful");

   271         return;

   272     }

   273 

   274     Q_ASSERT_X(d->accessCount() != 0, "QSystemReadWriteLock::unlock()", "Cannot unlock an unlocked lock");

   275 

   276     bool unlocked = false;

   277     if (d->accessCount() > 0) {

   278         unlocked = --d->accessCount() == 0;

   279     } else if (d->accessCount() < 0 && ++d->accessCount() == 0) {

   280         unlocked = true;

   281     }

   282 

   283     if (unlocked) {

   284         if (d->waitingWriters() > 0 ) {

   285             d->m_writerWait.release();

   286         } else if (d->waitingReaders()) {

   287             d->m_readerWait.release(d->waitingReaders());

   288         }

   289     }

   290 #if defined QSYSTEMREADWRITELOCK_DEBUG

   291     qDebug() << "QSystemReadWriteLock::unlock() <end>\naccessCount =" 

   292         << d->accessCount() << "\twaitingWriters=" << d->waitingWriters() << "\twaitingReaders=" << d->waitingReaders();

   293 #endif

   294     d->m_error = QSystemReadWriteLock::NoError;

   295     d->m_errorString.clear();

   296     d->m_counts.unlock();

   297     return;

   298 }

   299 

   300 int& QSystemReadWriteLockPrivate::accessCount()

   301 {

   302     return *((int *)m_counts.data());

   303 }

   304 

   305 unsigned int &QSystemReadWriteLockPrivate::waitingReaders()

   306 {

   307     return *(((unsigned int*)m_counts.data())+1);

   308 }

   309 

   310 unsigned int &QSystemReadWriteLockPrivate::waitingWriters()

   311 {

   312     return *(((unsigned int*)m_counts.data())+2);

   313 }

   314 

   315 QSystemReadWriteLock::SystemReadWriteLockError QSystemReadWriteLock::error() const

   316 {

   317     return d->m_error;

   318 }

   319 

   320 QString QSystemReadWriteLock::errorString() const

   321 {

   322     return d->m_errorString;

   323 }

   324 

   325 QString QSystemReadWriteLock::key() const

   326 {

   327     return d->m_key;

   328 }

   329 

   330 QTM_END_NAMESPACE