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