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// Copyright 2022 gRPC authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef GRPC_SRC_CORE_LIB_PROMISE_CANCEL_CALLBACK_H
#define GRPC_SRC_CORE_LIB_PROMISE_CANCEL_CALLBACK_H
#include <grpc/support/port_platform.h>
#include <utility>
#include "src/core/lib/promise/detail/promise_like.h"
namespace grpc_core {
namespace cancel_callback_detail {
template <typename Fn>
class Handler {
public:
explicit Handler(Fn fn) : fn_(std::move(fn)) {}
Handler(const Handler&) = delete;
Handler& operator=(const Handler&) = delete;
~Handler() {
if (!done_) {
fn_();
}
}
Handler(Handler&& other) noexcept
: fn_(std::move(other.fn_)), done_(other.done_) {
other.done_ = true;
}
Handler& operator=(Handler&& other) noexcept {
fn_ = std::move(other.fn_);
done_ = other.done_;
other.done_ = true;
}
void Done() { done_ = true; }
private:
Fn fn_;
bool done_ = false;
};
} // namespace cancel_callback_detail
// Wrap main_fn so that it calls cancel_fn if the promise is destroyed prior to
// completion.
// Returns a promise with the same result type as main_fn.
template <typename MainFn, typename CancelFn>
auto OnCancel(MainFn main_fn, CancelFn cancel_fn) {
return [on_cancel =
cancel_callback_detail::Handler<CancelFn>(std::move(cancel_fn)),
main_fn = promise_detail::PromiseLike<MainFn>(
std::move(main_fn))]() mutable {
auto r = main_fn();
if (r.ready()) {
on_cancel.Done();
}
return r;
};
}
} // namespace grpc_core
#endif // GRPC_SRC_CORE_LIB_PROMISE_CANCEL_CALLBACK_H
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