diff options
| -rw-r--r-- | src/corelib/global/qglobal.cpp | 28 | ||||
| -rw-r--r-- | src/corelib/plugin/quuid.cpp | 13 | ||||
| -rw-r--r-- | tests/auto/quuid/tst_quuid.cpp | 26 |
3 files changed, 63 insertions, 4 deletions
diff --git a/src/corelib/global/qglobal.cpp b/src/corelib/global/qglobal.cpp index 742f4ec..9fc3c8d 100644 --- a/src/corelib/global/qglobal.cpp +++ b/src/corelib/global/qglobal.cpp @@ -46,6 +46,7 @@ #include "qthreadstorage.h" #include "qdir.h" #include "qstringlist.h" +#include "qdatetime.h" #ifndef QT_NO_QOBJECT #include <private/qthread_p.h> @@ -2523,6 +2524,33 @@ void qsrand(uint seed) #endif } +/*! \internal + \relates <QtGlobal> + \since 4.6 + + Seed the PRNG, but only if it has not already been seeded. + + The default seed is a combination of current time, a stack address and a + serial counter (since thread stack addresses are re-used). +*/ +void qsrand() +{ +#if defined(Q_OS_UNIX) && !defined(QT_NO_THREAD) && !defined(Q_OS_SYMBIAN) + SeedStorageType *pseed = randTLS()->localData(); + if (pseed) { + // already seeded + return; + } + randTLS()->setLocalData(pseed = new SeedStorageType); + static QBasicAtomicInt serial = Q_BASIC_ATOMIC_INITIALIZER(0); + *pseed = QDateTime::currentDateTime().toTime_t() + + quintptr(&pseed) + + serial.fetchAndAddRelaxed(1); +#else + // On Windows, we assume that rand() already does the right thing +#endif +} + /*! \relates <QtGlobal> \since 4.2 diff --git a/src/corelib/plugin/quuid.cpp b/src/corelib/plugin/quuid.cpp index 7224ad3..3c79653 100644 --- a/src/corelib/plugin/quuid.cpp +++ b/src/corelib/plugin/quuid.cpp @@ -548,9 +548,11 @@ bool QUuid::operator>(const QUuid &other) const On any platform other than Windows, this function returns a new UUID with variant QUuid::DCE and version QUuid::Random. The random numbers used to construct the UUID are obtained from the local - pseudo-random generator, which is usually not a cryptographic + pseudo-random generator, qrand(), which is usually not a cryptographic quality random number generator. Therefore, a UUID generated by - this function can't be guaranteed to be unique. + this function can't be guaranteed to be unique. If the pseudo-random + number generator for the calling thread has not yet been seeded, this + function will seed the pseudo-random number generator by calling qsrand(). On a Windows platform, a GUID is generated, which almost certainly \e{will} be unique, on this or any other system, networked or not. @@ -578,6 +580,8 @@ QT_BEGIN_INCLUDE_NAMESPACE #include "stdlib.h" // For srand/rand QT_END_INCLUDE_NAMESPACE +extern void qsrand(); // in qglobal.cpp + QUuid QUuid::createUuid() { static const int intbits = sizeof(int)*8; @@ -585,10 +589,11 @@ QUuid QUuid::createUuid() if (!randbits) { int max = RAND_MAX; do { ++randbits; } while ((max=max>>1)); - qsrand((uint)QDateTime::currentDateTime().toTime_t()); - qrand(); // Skip first } + // reseed, but only if not already seeded + qsrand(); + QUuid result; uint *data = &(result.data1); int chunks = 16 / sizeof(uint); diff --git a/tests/auto/quuid/tst_quuid.cpp b/tests/auto/quuid/tst_quuid.cpp index e262be7..d78fda5 100644 --- a/tests/auto/quuid/tst_quuid.cpp +++ b/tests/auto/quuid/tst_quuid.cpp @@ -72,6 +72,8 @@ private slots: void variants(); void versions(); + void threadUniqueness(); + public: // Variables QUuid uuidA; @@ -169,6 +171,30 @@ void tst_QUuid::versions() QVERIFY( NCS.version() == QUuid::VerUnknown ); } +class UuidThread : public QThread +{ +public: + QUuid uuid; + + void run() + { + uuid = QUuid::createUuid(); + } +}; + +void tst_QUuid::threadUniqueness() +{ + QVector<UuidThread *> threads(qMax(2, QThread::idealThreadCount())); + for (int i = 0; i < threads.count(); ++i) + threads[i] = new UuidThread; + for (int i = 0; i < threads.count(); ++i) + threads[i]->start(); + for (int i = 0; i < threads.count(); ++i) + QVERIFY(threads[i]->wait(1000)); + for (int i = 1; i < threads.count(); ++i) + QVERIFY(threads[0]->uuid != threads[i]->uuid); + qDeleteAll(threads); +} QTEST_MAIN(tst_QUuid) #include "tst_quuid.moc" |