70 lines
2.2 KiB
C++
70 lines
2.2 KiB
C++
// Copyright (c) Facebook, Inc. and its affiliates.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#pragma once
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#include <memory>
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#include <stdexcept>
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namespace yarpl {
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namespace observable {
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template <typename T>
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class Observable;
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} // namespace observable
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namespace flowable {
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template <typename T>
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class Subscriber;
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// Exception thrown in case the downstream can't keep up.
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class MissingBackpressureException : public std::runtime_error {
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public:
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MissingBackpressureException()
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: std::runtime_error("BACK_PRESSURE: DROP (missing credits onNext)") {}
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};
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} // namespace flowable
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/**
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*Strategy for backpressure when converting from Observable to Flowable.
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*/
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enum class BackpressureStrategy {
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BUFFER, // Buffers all onNext values until the downstream consumes them.
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DROP, // Drops the most recent onNext value if the downstream can't keep up.
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ERROR, // Signals a MissingBackpressureException in case the downstream can't
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// keep up.
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LATEST, // Keeps only the latest onNext value, overwriting any previous value
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// if the downstream can't keep up.
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MISSING // OnNext events are written without any buffering or dropping.
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};
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template <typename T>
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class IBackpressureStrategy {
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public:
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virtual ~IBackpressureStrategy() = default;
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virtual void init(
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std::shared_ptr<observable::Observable<T>> upstream,
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std::shared_ptr<flowable::Subscriber<T>> downstream) = 0;
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static std::shared_ptr<IBackpressureStrategy<T>> buffer();
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static std::shared_ptr<IBackpressureStrategy<T>> drop();
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static std::shared_ptr<IBackpressureStrategy<T>> error();
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static std::shared_ptr<IBackpressureStrategy<T>> latest();
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static std::shared_ptr<IBackpressureStrategy<T>> missing();
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};
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} // namespace yarpl
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