python: wrap python_async_result::iterator to free GIL in long operat…

…ions

Some operations on iterator cause waiting for new responses and without releasing GIL it sometimes leads to deadlock.

bindings/python/async_result.cpp

@@ -33,8 +33,53 @@ error get_async_result_error(const python_async_result<T> &async) {
 }
 
 template <typename T>
-struct def_async_result<T>
-{
+typename python_async_result<T>::iterator &python_async_result<T>::iterator::operator=(const iterator &other) {
+	py_allow_threads_scoped pythr;
+	m_inner = other.m_inner;
+	return *this;
+}
+
+template <typename T>
+bool python_async_result<T>::iterator::operator==(const iterator &other) const {
+	py_allow_threads_scoped pythr;
+	return m_inner == other.m_inner;
+}
+
+template <typename T>
+bool python_async_result<T>::iterator::operator!=(const iterator &other) const {
+	py_allow_threads_scoped pythr;
+	return m_inner != other.m_inner;
+}
+
+template <typename T>
+T python_async_result<T>::iterator::operator*() const {
+	py_allow_threads_scoped pythr;
+	return *m_inner;
+}
+
+template <typename T>
+T *python_async_result<T>::iterator::operator->() const {
+	py_allow_threads_scoped pythr;
+	return m_inner.operator->();
+}
+
+template <typename T>
+typename python_async_result<T>::iterator &python_async_result<T>::iterator::operator++() {
+	py_allow_threads_scoped pythr;
+	++m_inner;
+	return *this;
+}
+
+template <typename T>
+typename python_async_result<T>::iterator python_async_result<T>::iterator::operator++(int) {
+	py_allow_threads_scoped pythr;
+	iterator tmp(m_inner);
+	++m_inner;
+	return tmp;
+}
+
+template <typename T>
+struct def_async_result<T> {
 	static void init() {
 		bp::class_<python_async_result<T>>(
 		        "AsyncResult", "Future for waiting/getting results from asynchronous execution of operation")

bindings/python/async_result.h

@@ -89,20 +89,39 @@ struct callback_one_handlers {
 };
 
 template <typename T>
-struct python_async_result
-{
-	typedef typename async_result<T>::iterator iterator;
-
-	std::shared_ptr<async_result<T>> scope;
+struct python_async_result {
+	class iterator : public std::iterator<std::input_iterator_tag, T, std::ptrdiff_t, T *, T> {
+	public:
+		iterator()
+		: m_inner() {}
+		iterator(const typename async_result<T>::iterator &other)
+		: m_inner(other) {}
+		iterator(const iterator &other)
+		: m_inner(other.m_inner) {}
+		~iterator() {}
+
+		iterator &operator=(const iterator &other);
+
+		bool operator==(const iterator &other) const;
+		bool operator!=(const iterator &other) const;
+
+		T operator*() const;
+		T *operator->() const;
+
+		iterator &operator ++();
+		iterator operator ++(int);
+	private:
+		typename async_result<T>::iterator m_inner;
+	};
 
 	iterator begin() {
 		py_allow_threads_scoped pythr;
-		return scope->begin();
+		return iterator{scope->begin()};
 	}
 
 	iterator end() {
 		py_allow_threads_scoped pythr;
-		return scope->end();
+		return iterator{scope->end()};
 	}
 
 	bp::list get() {
@@ -152,6 +171,8 @@ struct python_async_result
 		auto callback = boost::make_shared<callback_all_handler<T>>(handler);
 		scope->connect(boost::bind(&callback_all_handler<T>::on_results, callback, _1, _2));
 	}
+
+	std::shared_ptr<async_result<T>> scope;
 };
 
 template <typename T>