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// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.
//===- llvm/ADT/STLExtras.h - Useful STL related functions ------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef WPIUTIL_WPI_FUNCTION_REF_H_
#define WPIUTIL_WPI_FUNCTION_REF_H_
#include <stdint.h>
#include <type_traits>
#include <utility>
namespace wpi {
/// An efficient, type-erasing, non-owning reference to a callable. This is
/// intended for use as the type of a function parameter that is not used
/// after the function in question returns.
///
/// This class does not own the callable, so it is not in general safe to store
/// a function_ref.
template <typename Fn>
class function_ref;
template <typename Ret, typename... Params>
class function_ref<Ret(Params...)> {
Ret (*callback)(intptr_t callable, Params... params) = nullptr;
intptr_t callable;
template <typename Callable>
static Ret callback_fn(intptr_t callable, Params... params) {
return (*reinterpret_cast<Callable*>(callable))(std::forward<Params>(
params)...);
}
public:
function_ref() = default;
/*implicit*/ function_ref(std::nullptr_t) {} // NOLINT
template <typename Callable>
/*implicit*/ function_ref( // NOLINT
Callable&& callable,
typename std::enable_if<
!std::is_same<typename std::remove_reference<Callable>::type,
function_ref>::value>::type* = nullptr)
: callback(callback_fn<typename std::remove_reference<Callable>::type>),
callable(reinterpret_cast<intptr_t>(&callable)) {}
Ret operator()(Params... params) const {
return callback(callable, std::forward<Params>(params)...);
}
explicit operator bool() const { return callback; }
};
} // namespace wpi
#endif // WPIUTIL_WPI_FUNCTION_REF_H_