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// 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.

///

/// \file

/// 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.

///

/// <pre>

/// // 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.

/// </pre>

///

/// 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.

///

/// See https://chromium.googlesource.com/chromium/src/+/lkgr/docs/callback.md

/// for the full documentation.

///

#ifndef CEF_INCLUDE_BASE_CEF_CALLBACK_H_

#define CEF_INCLUDE_BASE_CEF_CALLBACK_H_

#pragma once

#if defined(USING_CHROMIUM_INCLUDES)

// When building CEF include the Chromium header directly.

#include "base/functional/callback.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 <stddef.h>

#include <type_traits>

#include <utility>

#include "include/base/cef_bind.h"

#include "include/base/cef_callback_forward.h"

#include "include/base/cef_compiler_specific.h"

#include "include/base/cef_logging.h"

#include "include/base/internal/cef_callback_internal.h"

#include "include/base/internal/cef_callback_tags.h"

namespace base {

namespace cef_internal {

template <bool is_once,

typename R,

typename... UnboundArgs,

typename... BoundArgs>

auto ToDoNothingCallback(

DoNothingCallbackTag::WithBoundArguments<BoundArgs...> t);

} // namespace cef_internal

template <typename R, typename... Args>

class TRIVIAL_ABI OnceCallback<R(Args...)> {

public:

using ResultType = R;

using RunType = R(Args...);

using PolymorphicInvoke = R (*)(cef_internal::BindStateBase*,

cef_internal::PassingType<Args>...);

// Constructs a null `OnceCallback`. A null callback has no associated functor

// and cannot be run.

constexpr OnceCallback() = default;

// Disallowed to prevent ambiguity.

OnceCallback(std::nullptr_t) = delete;

// `OnceCallback` is not copyable since its bound functor may only run at most

// once.

OnceCallback(const OnceCallback&) = delete;

OnceCallback& operator=(const OnceCallback&) = delete;

// Subtle: since `this` is marked as TRIVIAL_ABI, the move operations

// must leave the moved-from callback in a trivially destructible state.

OnceCallback(OnceCallback&&) noexcept = default;

OnceCallback& operator=(OnceCallback&&) noexcept = default;

~OnceCallback() = default;

// A `OnceCallback` is a strict subset of `RepeatingCallback`'s functionality,

// so allow seamless conversion.

// NOLINTNEXTLINE(google-explicit-constructor)

OnceCallback(RepeatingCallback<RunType> other)

: holder_(std::move(other.holder_)) {}

OnceCallback& operator=(RepeatingCallback<RunType> other) {

holder_ = std::move(other.holder_);

return *this;

}

// Returns true if `this` is non-null and can be `Run()`.

explicit operator bool() const { return !!holder_; }

// Returns true if `this` is null and cannot be `Run()`.

bool is_null() const { return holder_.is_null(); }

// Returns true if calling `Run()` is a no-op because of cancellation.

// - Not thread-safe, i.e. must be called on the same sequence that will

// ultimately `Run()` the callback

// - May not be called on a null callback.

bool IsCancelled() const { return holder_.IsCancelled(); }

// Subtle version of `IsCancelled()` that allows cancellation state to be

// queried from any sequence. May return true even if the callback has

// actually been cancelled.

// Do not use. This is intended for internal //base usage.

// TODO(dcheng): Restrict this since it, in fact, being used outside of its

// originally intended use.

bool MaybeValid() const { return holder_.MaybeValid(); }

// Resets this to a null state.

REINITIALIZES_AFTER_MOVE void Reset() { holder_.Reset(); }

// Non-consuming `Run()` is disallowed for `OnceCallback`.

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();

}

// Calls the bound functor with any already-bound arguments + `args`. Consumes

// `this`, i.e. `this` becomes null.

// May not be called on a null callback.

R Run(Args... args) && {

CHECK(!is_null());

// 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|.

cef_internal::BindStateHolder holder = std::move(holder_);

PolymorphicInvoke f =

reinterpret_cast<PolymorphicInvoke>(holder.polymorphic_invoke());

return f(holder.bind_state().get(), std::forward<Args>(args)...);

}

// Then() returns a new OnceCallback that receives the same arguments as

// |this|, and with the return type of |then|. The returned callback will:

// 1) Run the functor currently bound to |this| callback.

// 2) Run the |then| callback with the result from step 1 as its single

// argument.

// 3) Return the value from running the |then| callback.

// Since this method generates a callback that is a replacement for `this`,

// `this` will be consumed and reset to a null callback to ensure the

// originally-bound functor can be run at most once.

template <typename ThenR, typename... ThenArgs>

OnceCallback<ThenR(Args...)> Then(OnceCallback<ThenR(ThenArgs...)> then) && {

CHECK(then);

return base::BindOnce(

cef_internal::ThenHelper<

OnceCallback, OnceCallback<ThenR(ThenArgs...)>>::CreateTrampoline(),

std::move(*this), std::move(then));

}

// This overload is required; even though RepeatingCallback is implicitly

// convertible to OnceCallback, that conversion will not used when matching

// for template argument deduction.

template <typename ThenR, typename... ThenArgs>

OnceCallback<ThenR(Args...)> Then(

RepeatingCallback<ThenR(ThenArgs...)> then) && {

CHECK(then);

return base::BindOnce(

cef_internal::ThenHelper<

OnceCallback,

RepeatingCallback<ThenR(ThenArgs...)>>::CreateTrampoline(),

std::move(*this), std::move(then));

}

// Internal constructors for various callback helper tag types, e.g.

// `base::DoNothing()`.

// NOLINTNEXTLINE(google-explicit-constructor)

constexpr OnceCallback(cef_internal::NullCallbackTag) : OnceCallback() {}

constexpr OnceCallback& operator=(cef_internal::NullCallbackTag) {

*this = OnceCallback();

return *this;

}

// NOLINTNEXTLINE(google-explicit-constructor)

constexpr OnceCallback(cef_internal::NullCallbackTag::WithSignature<RunType>)

: OnceCallback(cef_internal::NullCallbackTag()) {}

constexpr OnceCallback& operator=(

cef_internal::NullCallbackTag::WithSignature<RunType>) {

*this = cef_internal::NullCallbackTag();

return *this;

}

// NOLINTNEXTLINE(google-explicit-constructor)

constexpr OnceCallback(cef_internal::DoNothingCallbackTag)

requires(std::is_void_v<R>)

: OnceCallback(BindOnce([](Args... args) {})) {}

constexpr OnceCallback& operator=(cef_internal::DoNothingCallbackTag)

requires(std::is_void_v<R>)

{

*this = BindOnce([](Args... args) {});

return *this;

}

// NOLINTNEXTLINE(google-explicit-constructor)

constexpr OnceCallback(

cef_internal::DoNothingCallbackTag::WithSignature<RunType>)

requires(std::is_void_v<R>)

: OnceCallback(cef_internal::DoNothingCallbackTag()) {}

constexpr OnceCallback& operator=(

cef_internal::DoNothingCallbackTag::WithSignature<RunType>)

requires(std::is_void_v<R>)

{

*this = cef_internal::DoNothingCallbackTag();

return *this;

}

template <typename... BoundArgs>

// NOLINTNEXTLINE(google-explicit-constructor)

constexpr OnceCallback(

cef_internal::DoNothingCallbackTag::WithBoundArguments<BoundArgs...> tag)

requires(std::is_void_v<R>)

: OnceCallback(cef_internal::ToDoNothingCallback<true, R, Args...>(

std::move(tag))) {}

template <typename... BoundArgs>

constexpr OnceCallback& operator=(

cef_internal::DoNothingCallbackTag::WithBoundArguments<BoundArgs...> tag)

requires(std::is_void_v<R>)

{

*this = cef_internal::ToDoNothingCallback<true, R, Args...>(std::move(tag));

return *this;

}

// Internal constructor for `base::BindOnce()`.

explicit OnceCallback(cef_internal::BindStateBase* bind_state)

: holder_(bind_state) {}

private:

cef_internal::BindStateHolder holder_;

};

template <typename R, typename... Args>

class TRIVIAL_ABI RepeatingCallback<R(Args...)> {

public:

using ResultType = R;

using RunType = R(Args...);

using PolymorphicInvoke = R (*)(cef_internal::BindStateBase*,

cef_internal::PassingType<Args>...);

// Constructs a null `RepeatingCallback`. A null callback has no associated

// functor and cannot be run.

constexpr RepeatingCallback() = default;

// Disallowed to prevent ambiguity.

RepeatingCallback(std::nullptr_t) = delete;

// Unlike a `OnceCallback`, a `RepeatingCallback` may be copied since its

// bound functor may be run more than once.

RepeatingCallback(const RepeatingCallback&) = default;

RepeatingCallback& operator=(const RepeatingCallback&) = default;

// Subtle: since `this` is marked as TRIVIAL_ABI, the move operations

// must leave the moved-from callback in a trivially destructible state.

RepeatingCallback(RepeatingCallback&&) noexcept = default;

RepeatingCallback& operator=(RepeatingCallback&&) noexcept = default;

~RepeatingCallback() = default;

// Returns true if `this` is non-null and can be `Run()`.

explicit operator bool() const { return !!holder_; }

// Returns true if `this` is null and cannot be `Run()`.

bool is_null() const { return holder_.is_null(); }

// Returns true if calling `Run()` is a no-op because of cancellation.

// - Not thread-safe, i.e. must be called on the same sequence that will

// ultimately `Run()` the callback

// - May not be called on a null callback.

bool IsCancelled() const { return holder_.IsCancelled(); }

// Subtle version of `IsCancelled()` that allows cancellation state to be

// queried from any sequence. May return true even if the callback has

// actually been cancelled.

// Do not use. This is intended for internal //base usage.

// TODO(dcheng): Restrict this since it, in fact, being used outside of its

// originally intended use.

bool MaybeValid() const { return holder_.MaybeValid(); }

// Equality operators: two `RepeatingCallback`'s are equal

friend bool operator==(const RepeatingCallback&,

const RepeatingCallback&) = default;

// Resets this to null.

REINITIALIZES_AFTER_MOVE void Reset() { holder_.Reset(); }

// Calls the bound functor with any already-bound arguments + `args`. Does not

// consume `this`, i.e. this remains non-null.

// May not be called on a null callback.

R Run(Args... args) const& {

CHECK(!is_null());

// Keep `bind_state` alive at least until after the invocation to ensure all

// bound `Unretained` arguments remain valid.

scoped_refptr<cef_internal::BindStateBase> bind_state =

holder_.bind_state();

PolymorphicInvoke f =

reinterpret_cast<PolymorphicInvoke>(holder_.polymorphic_invoke());

return f(bind_state.get(), std::forward<Args>(args)...);

}

// Calls the bound functor with any already-bound arguments + `args`. Consumes

// `this`, i.e. `this` becomes null.

// May not be called on a null callback.

R Run(Args... args) && {

CHECK(!holder_.is_null());

// 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|.

cef_internal::BindStateHolder holder = std::move(holder_);

PolymorphicInvoke f =

reinterpret_cast<PolymorphicInvoke>(holder.polymorphic_invoke());

return f(holder.bind_state().get(), std::forward<Args>(args)...);

}

// Then() returns a new RepeatingCallback that receives the same arguments as

// |this|, and with the return type of |then|. The

// returned callback will:

// 1) Run the functor currently bound to |this| callback.

// 2) Run the |then| callback with the result from step 1 as its single

// argument.

// 3) Return the value from running the |then| callback.

// If called on an rvalue (e.g. std::move(cb).Then(...)), this method

// generates a callback that is a replacement for `this`. Therefore, `this`

// will be consumed and reset to a null callback to ensure the

// originally-bound functor will be run at most once.

template <typename ThenR, typename... ThenArgs>

RepeatingCallback<ThenR(Args...)> Then(

RepeatingCallback<ThenR(ThenArgs...)> then) const& {

CHECK(then);

return BindRepeating(

cef_internal::ThenHelper<

RepeatingCallback,

RepeatingCallback<ThenR(ThenArgs...)>>::CreateTrampoline(),

*this, std::move(then));

}

template <typename ThenR, typename... ThenArgs>

RepeatingCallback<ThenR(Args...)> Then(

RepeatingCallback<ThenR(ThenArgs...)> then) && {

CHECK(then);

return BindRepeating(

cef_internal::ThenHelper<

RepeatingCallback,

RepeatingCallback<ThenR(ThenArgs...)>>::CreateTrampoline(),

std::move(*this), std::move(then));

}

// Internal constructors for various callback helper tag types, e.g.

// `base::DoNothing()`.

// NOLINTNEXTLINE(google-explicit-constructor)

constexpr RepeatingCallback(cef_internal::NullCallbackTag)

: RepeatingCallback() {}

constexpr RepeatingCallback& operator=(cef_internal::NullCallbackTag) {

*this = RepeatingCallback();

return *this;

}

// NOLINTNEXTLINE(google-explicit-constructor)

constexpr RepeatingCallback(

cef_internal::NullCallbackTag::WithSignature<RunType>)

: RepeatingCallback(cef_internal::NullCallbackTag()) {}

constexpr RepeatingCallback& operator=(

cef_internal::NullCallbackTag::WithSignature<RunType>) {

*this = cef_internal::NullCallbackTag();

return *this;

}

// NOLINTNEXTLINE(google-explicit-constructor)

constexpr RepeatingCallback(cef_internal::DoNothingCallbackTag)

requires(std::is_void_v<R>)

: RepeatingCallback(BindRepeating([](Args... args) {})) {}

constexpr RepeatingCallback& operator=(cef_internal::DoNothingCallbackTag)

requires(std::is_void_v<R>)

{

*this = BindRepeating([](Args... args) {});

return *this;

}

// NOLINTNEXTLINE(google-explicit-constructor)

constexpr RepeatingCallback(

cef_internal::DoNothingCallbackTag::WithSignature<RunType>)

requires(std::is_void_v<R>)

: RepeatingCallback(cef_internal::DoNothingCallbackTag()) {}

constexpr RepeatingCallback& operator=(

cef_internal::DoNothingCallbackTag::WithSignature<RunType>)

requires(std::is_void_v<R>)

{

*this = cef_internal::DoNothingCallbackTag();

return *this;

}

template <typename... BoundArgs>

// NOLINTNEXTLINE(google-explicit-constructor)

constexpr RepeatingCallback(

cef_internal::DoNothingCallbackTag::WithBoundArguments<BoundArgs...> tag)

requires(std::is_void_v<R>)

: RepeatingCallback(cef_internal::ToDoNothingCallback<false, R, Args...>(

std::move(tag))) {}

template <typename... BoundArgs>

constexpr RepeatingCallback& operator=(

cef_internal::DoNothingCallbackTag::WithBoundArguments<BoundArgs...> tag)

requires(std::is_void_v<R>)

{

*this =

cef_internal::ToDoNothingCallback<false, R, Args...>(std::move(tag));

return this;

}

// Internal constructor for `base::BindRepeating()`.

explicit RepeatingCallback(cef_internal::BindStateBase* bind_state)

: holder_(bind_state) {}

private:

friend class OnceCallback<R(Args...)>;

cef_internal::BindStateHolder holder_;

};

namespace cef_internal {

// Helper for the `DoNothingWithBoundArgs()` implementation.

// Unlike the other helpers, this cannot be easily moved to callback_internal.h,

// since it depends on `BindOnce()` and `BindRepeating()`.

template <bool is_once,

typename R,

typename... UnboundArgs,

typename... BoundArgs>

auto ToDoNothingCallback(

DoNothingCallbackTag::WithBoundArguments<BoundArgs...> t) {

return std::apply(

[](auto&&... args) {

if constexpr (is_once) {

return base::BindOnce(

[](TransformToUnwrappedType<is_once, BoundArgs>...,

UnboundArgs...) {},

std::move(args)...);

} else {

return base::BindRepeating(

[](TransformToUnwrappedType<is_once, BoundArgs>...,

UnboundArgs...) {},

std::move(args)...);

}

std::move(t.bound_args));

}

} // namespace cef_internal

} // namespace base

#endif // !USING_CHROMIUM_INCLUDES

#endif // CEF_INCLUDE_BASE_CEF_CALLBACK_H_

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