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// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_BIND_HELPERS_H_
#define BASE_BIND_HELPERS_H_
#include <stddef.h>
#include <type_traits>
#include <utility>
#include "base/bind.h"
#include "base/callback.h"
#include "base/memory/weak_ptr.h"
#include "build/build_config.h"
// This defines a set of simple functions and utilities that people want when
// using {Once,Repeating}Callback<> and Bind{Once,Repeating}().
namespace base {
// Creates a null callback.
class BASE_EXPORT NullCallback {
public:
template <typename R, typename... Args>
operator RepeatingCallback<R(Args...)>() const {
return RepeatingCallback<R(Args...)>();
}
template <typename R, typename... Args>
operator OnceCallback<R(Args...)>() const {
return OnceCallback<R(Args...)>();
}
};
// Creates a callback that does nothing when called.
class BASE_EXPORT DoNothing {
public:
template <typename... Args>
operator RepeatingCallback<void(Args...)>() const {
return Repeatedly<Args...>();
}
template <typename... Args>
operator OnceCallback<void(Args...)>() const {
return Once<Args...>();
}
// Explicit way of specifying a specific callback type when the compiler can't
// deduce it.
template <typename... Args>
static RepeatingCallback<void(Args...)> Repeatedly() {
return BindRepeating([](Args... args) {});
}
template <typename... Args>
static OnceCallback<void(Args...)> Once() {
return BindOnce([](Args... args) {});
}
};
// Useful for creating a Closure that will delete a pointer when invoked. Only
// use this when necessary. In most cases MessageLoop::DeleteSoon() is a better
// fit.
template <typename T>
void DeletePointer(T* obj) {
delete obj;
}
} // namespace base
#endif // BASE_BIND_HELPERS_H_
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