qtpromise/tests/auto/benchmark/tst_benchmark.cpp

// QtPromise
#include <QtPromise>

// Qt
#include <QtTest>

using namespace QtPromise;

class tst_benchmark : public QObject
{
    Q_OBJECT

private Q_SLOTS:
    void valueResolve();
    void valueReject();
    void valueThen();
    void errorReject();
    void errorThen();

}; // class tst_benchmark

QTEST_MAIN(tst_benchmark)
#include "tst_benchmark.moc"

struct Logs {
    int ctor = 0;
    int copy = 0;
    int move = 0;
    int refs = 0;

    void reset() {
        ctor = 0;
        copy = 0;
        move = 0;
        refs = 0;
    }
};

struct Logger
{
    Logger() { logs().ctor++; logs().refs++; }
    Logger(const Logger&) { logs().copy++; logs().refs++; }
    Logger(Logger&&) { logs().move++; logs().refs++; }
    ~Logger() { logs().refs--; }

    Logger& operator=(const Logger&) { logs().copy++; return *this; }
    Logger& operator=(Logger&&) { logs().move++; return *this; }

public: // STATICS
    static Logs& logs() { static Logs logs; return logs; }
};

struct Data : public Logger
{
    Data(int v): Logger(), m_value(v) {}
    int value() const { return m_value; }

private:
    int m_value;
};

void tst_benchmark::valueResolve()
{
    {   // should move the value when resolved by rvalue
        Data::logs().reset();
        QPromise<Data>([&](const QPromiseResolve<Data>& resolve) {
            resolve(Data(42));
        }).wait();

        QCOMPARE(Data::logs().ctor, 1);
        QCOMPARE(Data::logs().copy, 0);
        QCOMPARE(Data::logs().move, 1);     // move value to the promise data
        QCOMPARE(Data::logs().refs, 0);
    }
    {   // should create one copy of the value when resolved by lvalue
        Data::logs().reset();
        QPromise<Data>([&](const QPromiseResolve<Data>& resolve) {
            Data value(42);
            resolve(value);
        }).wait();

        QCOMPARE(Data::logs().ctor, 1);
        QCOMPARE(Data::logs().copy, 1);     // copy value to the promise data
        QCOMPARE(Data::logs().move, 0);
        QCOMPARE(Data::logs().refs, 0);
    }
}

void tst_benchmark::valueReject()
{
    {   // should not create any data if rejected
        Data::logs().reset();
        QPromise<Data>([&](const QPromiseResolve<Data>&, const QPromiseReject<Data>& reject) {
            reject(QString("foo"));
        }).wait();

        QCOMPARE(Data::logs().ctor, 0);
        QCOMPARE(Data::logs().copy, 0);
        QCOMPARE(Data::logs().move, 0);
        QCOMPARE(Data::logs().refs, 0);
    }
}

void tst_benchmark::valueThen()
{
    {   // should not copy value on continutation if fulfilled
        int value = -1;
        Data::logs().reset();
        QPromise<Data>::resolve(Data(42)).then([&](const Data& res) {
            value = res.value();
        }).wait();

        QCOMPARE(Data::logs().ctor, 1);
        QCOMPARE(Data::logs().copy, 0);
        QCOMPARE(Data::logs().move, 1);     // move value to the promise data
        QCOMPARE(Data::logs().refs, 0);
        QCOMPARE(value, 42);
    }
    {   // should not create value on continutation if rejected
        int value = -1;
        QString error;
        Data::logs().reset();
        QPromise<Data>::reject(QString("foo")).then([&](const Data& res) {
            value = res.value();
        }, [&](const QString& err) {
            error = err;
        }).wait();

        QCOMPARE(Data::logs().ctor, 0);
        QCOMPARE(Data::logs().copy, 0);
        QCOMPARE(Data::logs().move, 0);     // move value to the promise data
        QCOMPARE(Data::logs().refs, 0);
        QCOMPARE(error, QString("foo"));
        QCOMPARE(value, -1);
    }
    {   // should move the returned value when fulfilled
        int value = -1;
        Data::logs().reset();
        QPromise<int>::resolve(42).then([&](int res) {
            return Data(res+2);
        }).then([&](const Data& res) {
            value = res.value();
        }).wait();

        QCOMPARE(Data::logs().ctor, 1);
        QCOMPARE(Data::logs().copy, 0);
        QCOMPARE(Data::logs().move, 1);     // move values to the next promise data
        QCOMPARE(Data::logs().refs, 0);
        QCOMPARE(value, 44);
    }
    {   // should not create any data if handler throws
        Data::logs().reset();
        QPromise<int>::resolve(42).then([&](int res) {
            throw QString("foo");
            return Data(res+2);
        }).wait();

        QCOMPARE(Data::logs().ctor, 0);
        QCOMPARE(Data::logs().copy, 0);
        QCOMPARE(Data::logs().move, 0);
        QCOMPARE(Data::logs().refs, 0);
    }
}

void tst_benchmark::errorReject()
{
    {   // should create one copy of the error when rejected by rvalue
        Data::logs().reset();
        QPromise<int>([&](const QPromiseResolve<int>&, const QPromiseReject<int>& reject) {
            reject(Data(42));
        }).wait();

        QCOMPARE(Data::logs().ctor, 1);
        QCOMPARE(Data::logs().copy, 1);     // copy value in std::exception_ptr
        QCOMPARE(Data::logs().move, 0);
        QCOMPARE(Data::logs().refs, 0);
    }
    {   // should create one copy of the error when rejected by lvalue (no extra copy)
        Data::logs().reset();
        QPromise<int>([&](const QPromiseResolve<int>&, const QPromiseReject<int>& reject) {
            Data error(42);
            reject(error);
        }).wait();

        QCOMPARE(Data::logs().ctor, 1);
        QCOMPARE(Data::logs().copy, 1);    // copy value to the promise data
        QCOMPARE(Data::logs().move, 0);
        QCOMPARE(Data::logs().refs, 0);
    }
}

void tst_benchmark::errorThen()
{
    {   // should not copy error on continutation if rejected
        int value = -1;
        Data::logs().reset();
        QPromise<void>::reject(Data(42)).fail([&](const Data& res) {
            value = res.value();
        }).wait();

        QCOMPARE(Data::logs().ctor, 1);
        QCOMPARE(Data::logs().copy, 1);     // (initial) copy value in std::exception_ptr
        QCOMPARE(Data::logs().move, 0);
        QCOMPARE(Data::logs().refs, 0);
        QCOMPARE(value, 42);
    }
    {   // should not copy error on continutation if rethrown
        int value = -1;
        Data::logs().reset();
        QPromise<void>::reject(Data(42)).fail([](const Data&) {
            throw;
        }).fail([&](const Data& res) {
            value = res.value();
        }).wait();

        QCOMPARE(Data::logs().ctor, 1);
        QCOMPARE(Data::logs().copy, 1);     // (initial) copy value in std::exception_ptr
        QCOMPARE(Data::logs().move, 0);
        QCOMPARE(Data::logs().refs, 0);
        QCOMPARE(value, 42);
    }
}