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Diffstat (limited to '')
-rw-r--r-- | security/sandbox/chromium/base/callback.h | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/security/sandbox/chromium/base/callback.h b/security/sandbox/chromium/base/callback.h new file mode 100644 index 0000000000..1427faaaea --- /dev/null +++ b/security/sandbox/chromium/base/callback.h @@ -0,0 +1,149 @@ +// Copyright (c) 2012 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. +// +// NOTE: Header files that do not require the full definition of +// base::{Once,Repeating}Callback or base::{Once,Repeating}Closure should +// #include "base/callback_forward.h" instead of this file. + +#ifndef BASE_CALLBACK_H_ +#define BASE_CALLBACK_H_ + +#include <stddef.h> + +#include "base/callback_forward.h" +#include "base/callback_internal.h" + +// ----------------------------------------------------------------------------- +// Usage documentation +// ----------------------------------------------------------------------------- +// +// Overview: +// A callback is similar in concept to a function pointer: it wraps a runnable +// object such as a function, method, lambda, or even another callback, allowing +// the runnable object to be invoked later via the callback object. +// +// Unlike function pointers, callbacks are created with base::BindOnce() or +// base::BindRepeating() and support partial function application. +// +// A base::OnceCallback may be Run() at most once; a base::RepeatingCallback may +// be Run() any number of times. |is_null()| is guaranteed to return true for a +// moved-from callback. +// +// // The lambda takes two arguments, but the first argument |x| is bound at +// // callback creation. +// base::OnceCallback<int(int)> cb = base::BindOnce([] (int x, int y) { +// return x + y; +// }, 1); +// // Run() only needs the remaining unbound argument |y|. +// printf("1 + 2 = %d\n", std::move(cb).Run(2)); // Prints 3 +// printf("cb is null? %s\n", +// cb.is_null() ? "true" : "false"); // Prints true +// std::move(cb).Run(2); // Crashes since |cb| has already run. +// +// Callbacks also support cancellation. A common use is binding the receiver +// object as a WeakPtr<T>. If that weak pointer is invalidated, calling Run() +// will be a no-op. Note that |IsCancelled()| and |is_null()| are distinct: +// simply cancelling a callback will not also make it null. +// +// base::Callback is currently a type alias for base::RepeatingCallback. In the +// future, we expect to flip this to default to base::OnceCallback. +// +// See //docs/callback.md for the full documentation. + +namespace base { + +template <typename R, typename... Args> +class OnceCallback<R(Args...)> : public internal::CallbackBase { + public: + using RunType = R(Args...); + using PolymorphicInvoke = R (*)(internal::BindStateBase*, + internal::PassingType<Args>...); + + constexpr OnceCallback() = default; + OnceCallback(std::nullptr_t) = delete; + + explicit OnceCallback(internal::BindStateBase* bind_state) + : internal::CallbackBase(bind_state) {} + + OnceCallback(const OnceCallback&) = delete; + OnceCallback& operator=(const OnceCallback&) = delete; + + OnceCallback(OnceCallback&&) noexcept = default; + OnceCallback& operator=(OnceCallback&&) noexcept = default; + + OnceCallback(RepeatingCallback<RunType> other) + : internal::CallbackBase(std::move(other)) {} + + OnceCallback& operator=(RepeatingCallback<RunType> other) { + static_cast<internal::CallbackBase&>(*this) = std::move(other); + return *this; + } + + R Run(Args... args) const & { + static_assert(!sizeof(*this), + "OnceCallback::Run() may only be invoked on a non-const " + "rvalue, i.e. std::move(callback).Run()."); + NOTREACHED(); + } + + R Run(Args... args) && { + // Move the callback instance into a local variable before the invocation, + // that ensures the internal state is cleared after the invocation. + // It's not safe to touch |this| after the invocation, since running the + // bound function may destroy |this|. + OnceCallback cb = std::move(*this); + PolymorphicInvoke f = + reinterpret_cast<PolymorphicInvoke>(cb.polymorphic_invoke()); + return f(cb.bind_state_.get(), std::forward<Args>(args)...); + } +}; + +template <typename R, typename... Args> +class RepeatingCallback<R(Args...)> : public internal::CallbackBaseCopyable { + public: + using RunType = R(Args...); + using PolymorphicInvoke = R (*)(internal::BindStateBase*, + internal::PassingType<Args>...); + + constexpr RepeatingCallback() = default; + RepeatingCallback(std::nullptr_t) = delete; + + explicit RepeatingCallback(internal::BindStateBase* bind_state) + : internal::CallbackBaseCopyable(bind_state) {} + + // Copyable and movable. + RepeatingCallback(const RepeatingCallback&) = default; + RepeatingCallback& operator=(const RepeatingCallback&) = default; + RepeatingCallback(RepeatingCallback&&) noexcept = default; + RepeatingCallback& operator=(RepeatingCallback&&) noexcept = default; + + bool operator==(const RepeatingCallback& other) const { + return EqualsInternal(other); + } + + bool operator!=(const RepeatingCallback& other) const { + return !operator==(other); + } + + R Run(Args... args) const & { + PolymorphicInvoke f = + reinterpret_cast<PolymorphicInvoke>(this->polymorphic_invoke()); + return f(this->bind_state_.get(), std::forward<Args>(args)...); + } + + R Run(Args... args) && { + // Move the callback instance into a local variable before the invocation, + // that ensures the internal state is cleared after the invocation. + // It's not safe to touch |this| after the invocation, since running the + // bound function may destroy |this|. + RepeatingCallback cb = std::move(*this); + PolymorphicInvoke f = + reinterpret_cast<PolymorphicInvoke>(cb.polymorphic_invoke()); + return f(std::move(cb).bind_state_.get(), std::forward<Args>(args)...); + } +}; + +} // namespace base + +#endif // BASE_CALLBACK_H_ |