1
0
mirror of https://github.com/danog/libtgvoip.git synced 2024-12-11 16:49:52 +01:00
libtgvoip/webrtc_dsp/rtc_base/function_view.h
Grishka 5caaaafa42 Updated WebRTC APM
I'm now using the entire audio processing module from WebRTC as opposed to individual DSP algorithms pulled from there before. Seems to work better this way.
2018-11-23 04:02:53 +03:00

131 lines
4.6 KiB
C++

/*
* Copyright 2016 The WebRTC Project Authors. All rights reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef RTC_BASE_FUNCTION_VIEW_H_
#define RTC_BASE_FUNCTION_VIEW_H_
#include <type_traits>
#include <utility>
#include "rtc_base/checks.h"
// Just like std::function, FunctionView will wrap any callable and hide its
// actual type, exposing only its signature. But unlike std::function,
// FunctionView doesn't own its callable---it just points to it. Thus, it's a
// good choice mainly as a function argument when the callable argument will
// not be called again once the function has returned.
//
// Its constructors are implicit, so that callers won't have to convert lambdas
// and other callables to FunctionView<Blah(Blah, Blah)> explicitly. This is
// safe because FunctionView is only a reference to the real callable.
//
// Example use:
//
// void SomeFunction(rtc::FunctionView<int(int)> index_transform);
// ...
// SomeFunction([](int i) { return 2 * i + 1; });
//
// Note: FunctionView is tiny (essentially just two pointers) and trivially
// copyable, so it's probably cheaper to pass it by value than by const
// reference.
namespace rtc {
template <typename T>
class FunctionView; // Undefined.
template <typename RetT, typename... ArgT>
class FunctionView<RetT(ArgT...)> final {
public:
// Constructor for lambdas and other callables; it accepts every type of
// argument except those noted in its enable_if call.
template <
typename F,
typename std::enable_if<
// Not for function pointers; we have another constructor for that
// below.
!std::is_function<typename std::remove_pointer<
typename std::remove_reference<F>::type>::type>::value &&
// Not for nullptr; we have another constructor for that below.
!std::is_same<std::nullptr_t,
typename std::remove_cv<F>::type>::value &&
// Not for FunctionView objects; we have another constructor for that
// (the implicitly declared copy constructor).
!std::is_same<FunctionView,
typename std::remove_cv<typename std::remove_reference<
F>::type>::type>::value>::type* = nullptr>
FunctionView(F&& f)
: call_(CallVoidPtr<typename std::remove_reference<F>::type>) {
f_.void_ptr = &f;
}
// Constructor that accepts function pointers. If the argument is null, the
// result is an empty FunctionView.
template <
typename F,
typename std::enable_if<std::is_function<typename std::remove_pointer<
typename std::remove_reference<F>::type>::type>::value>::type* =
nullptr>
FunctionView(F&& f)
: call_(f ? CallFunPtr<typename std::remove_pointer<F>::type> : nullptr) {
f_.fun_ptr = reinterpret_cast<void (*)()>(f);
}
// Constructor that accepts nullptr. It creates an empty FunctionView.
template <typename F,
typename std::enable_if<std::is_same<
std::nullptr_t,
typename std::remove_cv<F>::type>::value>::type* = nullptr>
FunctionView(F&& f) : call_(nullptr) {}
// Default constructor. Creates an empty FunctionView.
FunctionView() : call_(nullptr) {}
RetT operator()(ArgT... args) const {
RTC_DCHECK(call_);
return call_(f_, std::forward<ArgT>(args)...);
}
// Returns true if we have a function, false if we don't (i.e., we're null).
explicit operator bool() const { return !!call_; }
private:
union VoidUnion {
void* void_ptr;
void (*fun_ptr)();
};
template <typename F>
static RetT CallVoidPtr(VoidUnion vu, ArgT... args) {
return (*static_cast<F*>(vu.void_ptr))(std::forward<ArgT>(args)...);
}
template <typename F>
static RetT CallFunPtr(VoidUnion vu, ArgT... args) {
return (reinterpret_cast<typename std::add_pointer<F>::type>(vu.fun_ptr))(
std::forward<ArgT>(args)...);
}
// A pointer to the callable thing, with type information erased. It's a
// union because we have to use separate types depending on if the callable
// thing is a function pointer or something else.
VoidUnion f_;
// Pointer to a dispatch function that knows the type of the callable thing
// that's stored in f_, and how to call it. A FunctionView object is empty
// (null) iff call_ is null.
RetT (*call_)(VoidUnion, ArgT...);
};
} // namespace rtc
#endif // RTC_BASE_FUNCTION_VIEW_H_