CallbackTraits.hpp

// Copyright (c) 2021 Graphcore Ltd. All rights reserved.
#ifndef poplar_CallbackTraits_hpp
#define poplar_CallbackTraits_hpp
 
#include <poplar/ArrayRef.hpp>
 
#include <type_traits>
 
namespace poplar {
namespace traits {
 
// This fails to evaluate if any element in Args is not a valid type.
// Otherwise it evaluates to void.
template <typename... Args> using void_type = void;
 
// In general terms, not everything is invocable.
template <typename Result, typename Ret, typename = void>
struct is_invocable_impl : std::false_type {};
 
// Specialization for is_invocable_impl used when Result is a valid
// specialization of std::result_of<...>.
template <typename Result, typename Ret>
struct is_invocable_impl<Result, Ret, void_type<typename Result::type>>
    : std::is_void<Ret> {};
 
// Provides a boolean constant type that specifies whether or not the type F
// provides a function call operator that takes a void* argument and returns
// void.
template <typename F>
struct is_callback : is_invocable_impl<std::result_of<F &(void *)>, void> {};
 
// Provides a boolean constant type that specifies whether or not the type F
// provides a function call operator that takes a void* argument and returns
// void.
template <typename F>
struct is_host_callback
    : is_invocable_impl<
          std::result_of<F &(ArrayRef<const void *>, ArrayRef<void *>)>, void> {
};
 
template <typename T>
struct remove_cvref : std::remove_cv<typename std::remove_reference<T>::type> {
};
 
} // namespace traits
} // namespace poplar
 
#endif // poplar_CallbackTraits_hpp