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Enhance QPromise::finally implementation

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Make sure that the chained value is not copied when `finally` is called for a fulfilled input promise. The value was copied 7 times in the previous version because it was captured in a lambda, which one copied multiple times.
This commit is contained in:
Simon Brunel 2017-08-23 10:56:39 +02:00
parent 49a1d6a57b
commit 25d2bad54f
4 changed files with 96 additions and 86 deletions
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9
src/qtpromise/qpromise.h
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@ -40,6 +40,9 @@ public:
inline typename QtPromisePrivate::PromiseHandler<T, std::nullptr_t>::Promise
fail(TRejected&& rejected) const;
template <typename THandler>
inline QPromise<T> finally(THandler handler) const;
inline QPromise<T> wait() const;
void swap(QPromiseBase<T>& other) { qSwap(m_d, other.m_d); }
@ -63,9 +66,6 @@ public:
template <typename F>
QPromise(F&& resolver): QPromiseBase<T>(std::forward<F>(resolver)) { }
template <typename THandler>
inline QPromise<T> finally(THandler handler) const;
public: // STATIC
inline static QPromise<QVector<T> > all(const QVector<QPromise<T> >& promises);
inline static QPromise<T> resolve(T&& value);
@ -81,9 +81,6 @@ public:
template <typename F>
QPromise(F&& resolver): QPromiseBase<void>(std::forward<F>(resolver)) { }
template <typename THandler>
inline QPromise<void> finally(THandler handler) const;
public: // STATIC
inline static QPromise<void> all(const QVector<QPromise<void> >& promises);
inline static QPromise<void> resolve();

40
src/qtpromise/qpromise.inl
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@ -129,6 +129,16 @@ QPromiseBase<T>::fail(TRejected&& rejected) const
return then(nullptr, std::forward<TRejected>(rejected));
}
template <typename T>
template <typename THandler>
inline QPromise<T> QPromiseBase<T>::finally(THandler handler) const
{
QPromise<T> p = *this;
return p.then(handler, handler).then([=]() {
return p;
});
}
template <typename T>
inline QPromise<T> QPromiseBase<T>::wait() const
{
@ -150,23 +160,6 @@ inline QPromise<T> QPromiseBase<T>::reject(E&& error)
});
}
template <typename T>
template <typename THandler>
inline QPromise<T> QPromise<T>::finally(THandler handler) const
{
return this->then([=](const T& res) {
return QPromise<void>::resolve().then(handler).then([=](){
return res;
});
}, [=]() {
const auto exception = std::current_exception();
return QPromise<void>::resolve().then(handler).then([=](){
std::rethrow_exception(exception);
return T();
});
});
}
template <typename T>
inline QPromise<QVector<T> > QPromise<T>::all(const QVector<QPromise<T> >& promises)
{
@ -206,19 +199,6 @@ inline QPromise<T> QPromise<T>::resolve(T&& value)
});
}
template <typename THandler>
inline QPromise<void> QPromise<void>::finally(THandler handler) const
{
return this->then([=]() {
return QPromise<void>::resolve().then(handler).then([](){});
}, [=]() {
const auto exception = std::current_exception();
return QPromise<void>::resolve().then(handler).then([=](){
std::rethrow_exception(exception);
});
});
}
inline QPromise<void> QPromise<void>::all(const QVector<QPromise<void> >& promises)
{
const int count = promises.size();

33
tests/auto/benchmark/tst_benchmark.cpp
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@ -14,6 +14,7 @@ private Q_SLOTS:
void valueResolve();
void valueReject();
void valueThen();
void valueFinally();
void valueDelayed();
void errorReject();
void errorThen();
@ -129,7 +130,7 @@ void tst_benchmark::valueThen()
QCOMPARE(Data::logs().ctor, 0);
QCOMPARE(Data::logs().copy, 0);
QCOMPARE(Data::logs().move, 0); // move value to the promise data
QCOMPARE(Data::logs().move, 0);
QCOMPARE(Data::logs().refs, 0);
QCOMPARE(error, QString("foo"));
QCOMPARE(value, -1);
@ -193,6 +194,36 @@ void tst_benchmark::valueDelayed()
}
}
void tst_benchmark::valueFinally()
{
{ // should not copy the value on continutation if fulfilled
int value = -1;
Data::logs().reset();
QPromise<Data>::resolve(Data(42)).finally([&]() {
value = 42;
}).wait();
QCOMPARE(Data::logs().ctor, 1);
QCOMPARE(Data::logs().copy, 0);
QCOMPARE(Data::logs().move, 1); // move value to the input and output promise data
QCOMPARE(Data::logs().refs, 0);
QCOMPARE(value, 42);
}
{ // should not create value on continutation if rejected
int value = -1;
Data::logs().reset();
QPromise<Data>::reject(QString("foo")).finally([&]() {
value = 42;
}).wait();
QCOMPARE(Data::logs().ctor, 0);
QCOMPARE(Data::logs().copy, 0);
QCOMPARE(Data::logs().move, 0);
QCOMPARE(Data::logs().refs, 0);
QCOMPARE(value, 42);
}
}
void tst_benchmark::errorReject()
{
{ // should create one copy of the error when rejected by rvalue

44
tests/auto/qpromise/tst_qpromise.cpp
View File

@ -30,8 +30,10 @@ private Q_SLOTS:
void failBaseClass();
void failCatchAll();
void finallyReturns();
void finallyReturns_void();
void finallyFulfilled();
void finallyFulfilled_void();
void finallyRejected();
void finallyRejected_void();
void finallyThrows();
void finallyThrows_void();
void finallyDelayedResolved();
@ -355,9 +357,8 @@ void tst_qpromise::failCatchAll()
QCOMPARE(error, QString("bar"));
}
void tst_qpromise::finallyReturns()
void tst_qpromise::finallyFulfilled()
{
{ // fulfilled
int value = -1;
auto p = QPromise<int>::resolve(42).finally([&]() {
value = 8;
@ -369,23 +370,9 @@ void tst_qpromise::finallyReturns()
QCOMPARE(p.isFulfilled(), true);
QCOMPARE(value, 8);
}
{ // rejected
int value = -1;
auto p = QPromise<int>::reject(QString("foo")).finally([&]() {
value = 8;
return 16; // ignored!
});
Q_STATIC_ASSERT((std::is_same<decltype(p), QPromise<int> >::value));
QCOMPARE(waitForError(p, QString()), QString("foo"));
QCOMPARE(p.isRejected(), true);
QCOMPARE(value, 8);
}
}
void tst_qpromise::finallyReturns_void()
void tst_qpromise::finallyFulfilled_void()
{
{ // fulfilled
int value = -1;
auto p = QPromise<void>::resolve().finally([&]() {
value = 8;
@ -397,7 +384,23 @@ void tst_qpromise::finallyReturns_void()
QCOMPARE(p.isFulfilled(), true);
QCOMPARE(value, 8);
}
{ // rejected
void tst_qpromise::finallyRejected()
{
int value = -1;
auto p = QPromise<int>::reject(QString("foo")).finally([&]() {
value = 8;
return 16; // ignored!
});
Q_STATIC_ASSERT((std::is_same<decltype(p), QPromise<int> >::value));
QCOMPARE(waitForError(p, QString()), QString("foo"));
QCOMPARE(p.isRejected(), true);
QCOMPARE(value, 8);
}
void tst_qpromise::finallyRejected_void()
{
int value = -1;
auto p = QPromise<void>::reject(QString("foo")).finally([&]() {
value = 8;
@ -409,7 +412,6 @@ void tst_qpromise::finallyReturns_void()
QCOMPARE(p.isRejected(), true);
QCOMPARE(value, 8);
}
}
void tst_qpromise::finallyThrows()
{