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just generate some heat from QUuid::createUuid()

Browse source 
it is simply faster

Signed-off-by: Ivailo Monev <xakepa10@laimg.moc>
This commit is contained in:
Ivailo Monev 2016-07-24 09:03:48 +00:00
parent 37e0c5bb84
commit 487b736da1
1 changed files with 28 additions and 57 deletions
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85
src/core/plugin/quuid.cpp
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@ -827,74 +827,45 @@ QT_BEGIN_INCLUDE_NAMESPACE
#include <stdlib.h> // for RAND_MAX
QT_END_INCLUDE_NAMESPACE
#if !defined(QT_BOOTSTRAPPED) && defined(Q_OS_UNIX)
Q_GLOBAL_STATIC(QThreadStorage<QFile *>, devUrandomStorage)
#endif
QUuid QUuid::createUuid()
{
QUuid result;
uint *data = &(result.data1);
#if defined(Q_OS_UNIX)
QFile *devUrandom;
# if !defined(QT_BOOTSTRAPPED)
devUrandom = devUrandomStorage()->localData();
if (!devUrandom) {
devUrandom = new QFile(QLatin1String("/dev/urandom"));
devUrandom->open(QIODevice::ReadOnly | QIODevice::Unbuffered);
devUrandomStorage()->setLocalData(devUrandom);
static const int intbits = sizeof(int)*8;
static int randbits = 0;
if (!randbits) {
int r = 0;
int max = RAND_MAX;
do { ++r; } while ((max=max>>1));
randbits = r;
}
# else
QFile file(QLatin1String("/dev/urandom"));
devUrandom = &file;
devUrandom->open(QIODevice::ReadOnly | QIODevice::Unbuffered);
# endif
enum { AmountToRead = 4 * sizeof(uint) };
if (devUrandom->isOpen()
&& devUrandom->read((char *) data, AmountToRead) == AmountToRead) {
// we got what we wanted, nothing more to do
;
} else
#endif
{
static const int intbits = sizeof(int)*8;
static int randbits = 0;
if (!randbits) {
int r = 0;
int max = RAND_MAX;
do { ++r; } while ((max=max>>1));
randbits = r;
}
// Seed the PRNG once per thread with a combination of current time, a
// stack address and a serial counter (since thread stack addresses are
// re-used).
// Seed the PRNG once per thread with a combination of current time, a
// stack address and a serial counter (since thread stack addresses are
// re-used).
#ifndef QT_BOOTSTRAPPED
static QThreadStorage<int *> uuidseed;
if (!uuidseed.hasLocalData())
{
int *pseed = new int;
static QBasicAtomicInt serial = Q_BASIC_ATOMIC_INITIALIZER(2);
qsrand(*pseed = QDateTime::currentDateTime().toTime_t()
+ quintptr(&pseed)
+ serial.fetchAndAddRelaxed(1));
uuidseed.setLocalData(pseed);
}
static QThreadStorage<int *> uuidseed;
if (!uuidseed.hasLocalData()) {
int *pseed = new int;
static QBasicAtomicInt serial = Q_BASIC_ATOMIC_INITIALIZER(2);
qsrand(*pseed = QDateTime::currentDateTime().toTime_t()
+ quintptr(&pseed)
+ serial.fetchAndAddRelaxed(1));
uuidseed.setLocalData(pseed);
}
#else
static bool seeded = false;
if (!seeded)
qsrand(QDateTime::currentDateTime().toTime_t()
+ quintptr(&seeded));
static bool seeded = false;
if (!seeded)
qsrand(QDateTime::currentDateTime().toTime_t() + quintptr(&seeded));
#endif
int chunks = 16 / sizeof(uint);
while (chunks--) {
uint randNumber = 0;
for (int filled = 0; filled < intbits; filled += randbits)
randNumber |= qrand()<<filled;
*(data+chunks) = randNumber;
}
int chunks = 16 / sizeof(uint);
while (chunks--) {
uint randNumber = 0;
for (int filled = 0; filled < intbits; filled += randbits)
randNumber |= qrand()<<filled;
*(data+chunks) = randNumber;
}
result.data4[0] = (result.data4[0] & 0x3F) | 0x80; // UV_DCE