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// Copyright (c) 2014 Marshall A. Greenblatt. Portions copyright (c) 2012
// Google Inc. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the name Chromium Embedded
// Framework nor the names of its contributors may be used to endorse
// or promote products derived from this software without specific prior
// written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// This defines helpful methods for dealing with Callbacks. Because Callbacks
// are implemented using templates, with a class per callback signature, adding
// methods to Callback<> itself is unattractive (lots of extra code gets
// generated). Instead, consider adding methods here.
#ifndef CEF_INCLUDE_BASE_CEF_CALLBACK_HELPERS_H_
#define CEF_INCLUDE_BASE_CEF_CALLBACK_HELPERS_H_
#pragma once
#if defined(USING_CHROMIUM_INCLUDES)
// When building CEF include the Chromium header directly.
#include "base/functional/callback_helpers.h"
#else // !USING_CHROMIUM_INCLUDES
// The following is substantially similar to the Chromium implementation.
// If the Chromium implementation diverges the below implementation should be
// updated to match.
#include <atomic>
#include <memory>
#include <type_traits>
#include <utility>
#include "include/base/cef_bind.h"
#include "include/base/cef_callback.h"
#include "include/base/cef_logging.h"
namespace base {
namespace internal {
template <typename T>
struct IsBaseCallbackImpl : std::false_type {};
template <typename R, typename... Args>
struct IsBaseCallbackImpl<OnceCallback<R(Args...)>> : std::true_type {};
template <typename R, typename... Args>
struct IsBaseCallbackImpl<RepeatingCallback<R(Args...)>> : std::true_type {};
template <typename T>
struct IsOnceCallbackImpl : std::false_type {};
template <typename R, typename... Args>
struct IsOnceCallbackImpl<OnceCallback<R(Args...)>> : std::true_type {};
} // namespace internal
///
/// IsBaseCallback<T>::value is true when T is any of the Closure or Callback
/// family of types.
///
template <typename T>
using IsBaseCallback = internal::IsBaseCallbackImpl<std::decay_t<T>>;
///
/// IsOnceCallback<T>::value is true when T is a OnceClosure or OnceCallback
/// type.
///
template <typename T>
using IsOnceCallback = internal::IsOnceCallbackImpl<std::decay_t<T>>;
///
/// SFINAE friendly enabler allowing to overload methods for both Repeating and
/// OnceCallbacks.
///
/// Usage:
/// <pre>
/// template <template <typename> class CallbackType,
/// ... other template args ...,
/// typename = EnableIfIsBaseCallback<CallbackType>>
/// void DoStuff(CallbackType<...> cb, ...);
/// </pre>
///
template <template <typename> class CallbackType>
using EnableIfIsBaseCallback =
std::enable_if_t<IsBaseCallback<CallbackType<void()>>::value>;
namespace internal {
template <typename... Args>
class OnceCallbackHolder final {
public:
OnceCallbackHolder(OnceCallback<void(Args...)> callback,
bool ignore_extra_runs)
: callback_(std::move(callback)), ignore_extra_runs_(ignore_extra_runs) {
DCHECK(callback_);
}
OnceCallbackHolder(const OnceCallbackHolder&) = delete;
OnceCallbackHolder& operator=(const OnceCallbackHolder&) = delete;
void Run(Args... args) {
if (has_run_.exchange(true)) {
CHECK(ignore_extra_runs_) << "Both OnceCallbacks returned by "
"base::SplitOnceCallback() were run. "
"At most one of the pair should be run.";
return;
}
DCHECK(callback_);
std::move(callback_).Run(std::forward<Args>(args)...);
}
private:
volatile std::atomic_bool has_run_{false};
base::OnceCallback<void(Args...)> callback_;
const bool ignore_extra_runs_;
};
} // namespace internal
///
/// Wraps the given OnceCallback into a RepeatingCallback that relays its
/// invocation to the original OnceCallback on the first invocation. The
/// following invocations are just ignored.
///
/// Note that this deliberately subverts the Once/Repeating paradigm of
/// Callbacks but helps ease the migration from old-style Callbacks. Avoid if
/// possible; use if necessary for migration.
///
// TODO(tzik): Remove it. https://crbug.com/730593
template <typename... Args>
RepeatingCallback<void(Args...)> AdaptCallbackForRepeating(
OnceCallback<void(Args...)> callback) {
using Helper = internal::OnceCallbackHolder<Args...>;
return base::BindRepeating(
&Helper::Run, std::make_unique<Helper>(std::move(callback),
/*ignore_extra_runs=*/true));
}
///
/// Wraps the given OnceCallback and returns two OnceCallbacks with an identical
/// signature. On first invokation of either returned callbacks, the original
/// callback is invoked. Invoking the remaining callback results in a crash.
///
template <typename... Args>
std::pair<OnceCallback<void(Args...)>, OnceCallback<void(Args...)>>
SplitOnceCallback(OnceCallback<void(Args...)> callback) {
using Helper = internal::OnceCallbackHolder<Args...>;
auto wrapped_once = base::BindRepeating(
&Helper::Run, std::make_unique<Helper>(std::move(callback),
/*ignore_extra_runs=*/false));
return std::make_pair(wrapped_once, wrapped_once);
}
///
/// ScopedClosureRunner is akin to std::unique_ptr<> for Closures. It ensures
/// that the Closure is executed no matter how the current scope exits.
/// If you are looking for "ScopedCallback", "CallbackRunner", or
/// "CallbackScoper" this is the class you want.
///
class ScopedClosureRunner {
public:
ScopedClosureRunner();
explicit ScopedClosureRunner(OnceClosure closure);
ScopedClosureRunner(ScopedClosureRunner&& other);
// Runs the current closure if it's set, then replaces it with the closure
// from |other|. This is akin to how unique_ptr frees the contained pointer in
// its move assignment operator. If you need to explicitly avoid running any
// current closure, use ReplaceClosure().
ScopedClosureRunner& operator=(ScopedClosureRunner&& other);
~ScopedClosureRunner();
explicit operator bool() const { return !!closure_; }
// Calls the current closure and resets it, so it wont be called again.
void RunAndReset();
// Replaces closure with the new one releasing the old one without calling it.
void ReplaceClosure(OnceClosure closure);
// Releases the Closure without calling.
[[nodiscard]] OnceClosure Release();
private:
OnceClosure closure_;
};
///
/// Creates a null callback.
///
class 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 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 // !USING_CHROMIUM_INCLUDES
#endif // CEF_INCLUDE_BASE_CEF_CALLBACK_HELPERS_H_