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Allow methods returning IIterable<T> to be used as synchronous generators #361

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6dc6c18
Allow methods returning IIterable<T> to be used as synchronous genera…
Fulgen301 Sep 18, 2023
d4f4f48
Add test cases
Fulgen301 Sep 18, 2023
a2e9ae3
Constrain the generator implementation to `IIterator<T>` and add
Fulgen301 Sep 20, 2023
fc62916
Throw winrt::hresult_out_of_bounds when the iterator is at the end
Fulgen301 Sep 20, 2023
adbe1bd
Add missing @cond / @endcond for wil::details
Fulgen301 Sep 20, 2023
84affac
Merge branch 'master' into user/Fulgen301/iiterable-generator
jonwis Oct 27, 2023
f58cdcb
Rename make_iterable_from_iterator to make_iterable_from_generator
Fulgen301 Nov 2, 2023
7d038a6
Rename make_iterable_from_iterator to make_iterable_from_generator in…
Fulgen301 Nov 2, 2023
0a19f62
Merge branch 'master' into user/Fulgen301/iiterable-generator
dunhor Nov 7, 2023
3888b11
Merge branch 'master' into user/Fulgen301/iiterable-generator
dunhor Dec 1, 2023
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80 changes: 53 additions & 27 deletions include/wil/cppwinrt_helpers.h
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Original file line number Diff line number Diff line change
Expand Up @@ -321,16 +321,14 @@ namespace wil
namespace wil::details
{
template<typename TResult>
struct iterable_promise : winrt::implements<
iterable_promise<TResult>,
winrt::Windows::Foundation::Collections::IIterable<TResult>,
struct iterator_promise : winrt::implements<
iterator_promise<TResult>,
winrt::Windows::Foundation::Collections::IIterator<TResult>
>
{
private:
enum class IterationStatus
{
Initial,
Producing,
Value,
Done
Expand All @@ -344,18 +342,18 @@ namespace wil::details
if (remaining == 0)
{
std::atomic_thread_fence(std::memory_order_acquire);
coroutine_handle<iterable_promise>::from_promise(*this).destroy();
coroutine_handle<iterator_promise>::from_promise(*this).destroy();
}

return remaining;
}

winrt::Windows::Foundation::Collections::IIterable<TResult> get_return_object() noexcept
winrt::Windows::Foundation::Collections::IIterator<TResult> get_return_object() noexcept
{
return { winrt::get_abi(static_cast<winrt::Windows::Foundation::Collections::IIterable<TResult> const&>(*this)), winrt::take_ownership_from_abi };
return { winrt::get_abi(static_cast<winrt::Windows::Foundation::Collections::IIterator<TResult> const&>(*this)), winrt::take_ownership_from_abi };
}

suspend_always initial_suspend() const noexcept
suspend_never initial_suspend() const noexcept
{
return {};
}
Expand Down Expand Up @@ -421,7 +419,7 @@ namespace wil::details

uint32_t produce_values(winrt::array_view<TResult> const& view)
{
if (m_status != IterationStatus::Initial && m_status != IterationStatus::Value)
if (m_status != IterationStatus::Value)
{
return 0;
}
Expand All @@ -430,23 +428,11 @@ namespace wil::details
m_current = m_values.begin();
m_status = IterationStatus::Producing;

coroutine_handle<iterable_promise>::from_promise(*this).resume();
coroutine_handle<iterator_promise>::from_promise(*this).resume();

return static_cast<uint32_t>(m_current - m_values.begin());
}

winrt::Windows::Foundation::Collections::IIterator<TResult> First()
{
if (m_status != IterationStatus::Initial)
{
throw winrt::hresult_changed_state();
}

MoveNext();

return *this;
}

bool HasCurrent() const noexcept
{
return m_status == IterationStatus::Value;
Expand Down Expand Up @@ -487,11 +473,51 @@ namespace wil::details
}

private:
IterationStatus m_status{ IterationStatus::Initial };
winrt::array_view<TResult> m_values;
TResult* m_current{ nullptr };
IterationStatus m_status{ IterationStatus::Producing };
winrt::array_view<TResult> m_values{ &m_last_value, 1 };
TResult* m_current{ &m_last_value };
TResult m_last_value{ empty<TResult>() };
};

template<typename TResult, typename Func, typename... Args>
struct iterable_iterator_helper : winrt::implements<
iterable_iterator_helper<TResult, Func, Args...>,
winrt::Windows::Foundation::Collections::IIterable<TResult>
>
{
iterable_iterator_helper(Func&& func, Args&&... args) :
m_func{ std::forward<Func>(func) },
m_args{ std::forward<Args>(args)... }
{
}

auto First()
{
return std::apply(m_func, m_args);
}

private:
Func m_func;
std::tuple<Args...> m_args;
};

template<typename>
struct iterator_result;

template<typename TResult>
struct iterator_result<winrt::Windows::Foundation::Collections::IIterator<TResult>>
{
using type = TResult;
};
}

namespace wil
{
template<typename Func, typename... Args, typename TResult = typename details::iterator_result<std::invoke_result_t<Func, Args...>>::type>
winrt::Windows::Foundation::Collections::IIterable<TResult> make_iterable_from_iterator(Func&& func, Args&&... args)
{
return winrt::make<details::iterable_iterator_helper<TResult, Func, Args...>>(std::forward<Func>(func), std::forward<Args>(args)...);
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I suggest adding a way to keep a strong or weak reference to a class here, as well as a pointer. Maybe something similar to C++/WinRT's delegate implementation.

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If Func accepts those arguments, it's already possible (e.g. calling a member function with a strong reference that is stored in the IIterable<T> helper with wil::make_iterable_from_iterator(&Foo::Bar, get_strong()). That doesn't work with weak references, but what would the semantics be if the weak pointer's object has been destroyed? Should First return an empty iterator?

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A member function pointer won't take a strong reference as argument directly via std::invoke/std::apply.

Good point reguarding weak references, lets just ignore that for now.

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It will.

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Ah looks like std::invoke will try (*arg).(*f)(), I did not know that. Nothing to do here, then.

}
}

#ifdef __cpp_lib_coroutine
Expand All @@ -501,9 +527,9 @@ namespace std::experimental
#endif
{
template<typename T, typename... Args>
struct coroutine_traits<winrt::Windows::Foundation::Collections::IIterable<T>, Args...>
struct coroutine_traits<winrt::Windows::Foundation::Collections::IIterator<T>, Args...>
{
using promise_type = wil::details::iterable_promise<T>;
using promise_type = wil::details::iterator_promise<T>;
};
}
#endif
Expand Down
72 changes: 39 additions & 33 deletions tests/CppWinRTTests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -650,7 +650,7 @@ TEST_CASE("CppWinRTTests::ResumeForegroundTests", "[cppwinrt]")

namespace test
{
winrt::Windows::Foundation::Collections::IIterable<winrt::hstring> hello_world_generator()
winrt::Windows::Foundation::Collections::IIterator<winrt::hstring> hello_world_generator()
{
co_yield L"Hello";
co_yield L"World!";
Expand Down Expand Up @@ -694,8 +694,7 @@ TEST_CASE("CppWinRTTests::Generator", "[cppwinrt]")
{
SECTION("Hello World")
{
auto generator = test::hello_world_generator();
auto iterator = generator.First();
auto iterator = test::hello_world_generator();
REQUIRE(iterator.HasCurrent());
REQUIRE(iterator.Current() == L"Hello");

Expand All @@ -709,15 +708,14 @@ TEST_CASE("CppWinRTTests::Generator", "[cppwinrt]")

SECTION("Value types")
{
auto generator = []() -> winrt::Windows::Foundation::Collections::IIterable<int>
auto iterator = []() -> winrt::Windows::Foundation::Collections::IIterator<int>
{
for (int i = 0; i < 10; ++i)
{
co_yield i;
}
}();

auto iterator = generator.First();
REQUIRE(iterator.HasCurrent());
REQUIRE(iterator.MoveNext());
REQUIRE(iterator.Current() == 1);
Expand All @@ -732,17 +730,10 @@ TEST_CASE("CppWinRTTests::Generator", "[cppwinrt]")
REQUIRE(!iterator.HasCurrent());
}

SECTION("First can only be called once")
{
auto generator = test::hello_world_generator();
auto iterator = generator.First();
REQUIRE_THROWS_AS(generator.First(), winrt::hresult_changed_state);
}

SECTION("GetMany")
{
{
auto iterator = test::hello_world_generator().First();
auto iterator = test::hello_world_generator();

std::array<winrt::hstring, 2> values;
REQUIRE(iterator.GetMany(values) == 2);
Expand All @@ -752,7 +743,7 @@ TEST_CASE("CppWinRTTests::Generator", "[cppwinrt]")
}

{
auto iterator = test::hello_world_generator().First();
auto iterator = test::hello_world_generator();
std::array<winrt::hstring, 1> values;
REQUIRE(iterator.GetMany(values) == 1);
REQUIRE(values[0] == L"Hello");
Expand All @@ -767,7 +758,7 @@ TEST_CASE("CppWinRTTests::Generator", "[cppwinrt]")

SECTION("Coroutine destruction")
{
auto set_true_on_destruction_generator = [](test::set_true_on_destruction) -> winrt::Windows::Foundation::Collections::IIterable<winrt::hstring>
auto set_true_on_destruction_generator = [](test::set_true_on_destruction) -> winrt::Windows::Foundation::Collections::IIterator<winrt::hstring>
{
co_yield L"Hello";
co_yield L"World!";
Expand All @@ -779,26 +770,11 @@ TEST_CASE("CppWinRTTests::Generator", "[cppwinrt]")
}

REQUIRE(destroyed);

destroyed = false;
{
winrt::Windows::Foundation::Collections::IIterator<winrt::hstring> iterator;
{
auto generator = set_true_on_destruction_generator(destroyed);
iterator = generator.First();
}

REQUIRE(!destroyed);
REQUIRE(iterator.HasCurrent());
REQUIRE(iterator.Current() == L"Hello");
}

REQUIRE(destroyed);
}

SECTION("Coroutine destruction with exception")
{
auto set_true_on_destruction_generator = [](test::set_true_on_destruction) -> winrt::Windows::Foundation::Collections::IIterable<winrt::hstring>
auto set_true_on_destruction_generator = [](test::set_true_on_destruction) -> winrt::Windows::Foundation::Collections::IIterator<winrt::hstring>
{
co_yield L"Hello";

Expand All @@ -808,14 +784,44 @@ TEST_CASE("CppWinRTTests::Generator", "[cppwinrt]")
};

bool destroyed = false;
auto iterator = set_true_on_destruction_generator(destroyed).First();
auto iterator = set_true_on_destruction_generator(destroyed);
REQUIRE_THROWS_AS(iterator.MoveNext(), winrt::hresult_invalid_argument);
}

SECTION("make_iterable_from_iterator")
{
auto generator = wil::make_iterable_from_iterator(&test::hello_world_generator);
auto iterator = generator.First();

REQUIRE(iterator.Current() == L"Hello");
REQUIRE(iterator.MoveNext());
REQUIRE(iterator.Current() == L"World!");
REQUIRE(!iterator.MoveNext());

auto iterator2 = generator.First();
REQUIRE(iterator2.Current() == L"Hello");
REQUIRE(iterator2.MoveNext());
REQUIRE(iterator2.Current() == L"World!");
REQUIRE(!iterator2.MoveNext());
}

SECTION("make_iterable_from_iterator with arguments")
{
auto ptr = std::make_unique<int>(3);
auto const_ref_generator = wil::make_iterable_from_iterator([](const std::unique_ptr<int> &ptr) -> winrt::Windows::Foundation::Collections::IIterator<int>
{
co_yield *ptr;
}, ptr);

REQUIRE(const_ref_generator.First().Current() == 3);
*ptr = 4;
REQUIRE(const_ref_generator.First().Current() == 4);
}

SECTION("Range-based for loop")
{
std::wstring result;
for (const auto &i : test::hello_world_generator())
for (const auto &i : wil::make_iterable_from_iterator(&test::hello_world_generator))
{
result += i;
}
Expand Down