89 строки
2.2 KiB
C++
89 строки
2.2 KiB
C++
/**
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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#pragma once
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#include <mutex>
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#include <fabric/imagemanager/ImageResponse.h>
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#include <fabric/imagemanager/primitives.h>
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#include <folly/futures/Future.h>
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#include <folly/futures/FutureSplitter.h>
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namespace facebook {
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namespace react {
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/*
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* Represents ongoing request for an image resource.
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* The separate object must be constructed for every single separate
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* image request. The object cannot be copied because it would make managing of
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* event listeners hard and inefficient; the object can be moved though.
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* To subscribe for notifications use `getResponseFuture()` method.
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* Destroy to cancel the underlying request.
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*/
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class ImageRequest final {
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public:
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/*
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* The exception which is thrown when `ImageRequest` is being deallocated
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* if the future is not ready yet.
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*/
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class ImageNoLongerNeededException;
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/*
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* `ImageRequest` is constructed with `ImageSource` and
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* `ImageResponse` future which must be moved in inside the object.
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*/
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ImageRequest(
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const ImageSource &imageSource,
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folly::Future<ImageResponse> &&responseFuture);
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ImageRequest();
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/*
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* The move constructor.
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*/
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ImageRequest(ImageRequest &&other) noexcept;
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/*
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* `ImageRequest` does not support copying by design.
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*/
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ImageRequest(const ImageRequest &) = delete;
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~ImageRequest();
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/*
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* Creates and returns a *new* future object with promised `ImageResponse`
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* result. Multiple consumers can call this method many times to create
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* their own subscriptions to promised value.
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*/
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folly::Future<ImageResponse> getResponseFuture() const;
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private:
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/*
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* Mutext to protect an access to the future.
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*/
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mutable std::mutex mutex_;
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/*
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* Image source assosiated with the request.
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*/
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ImageSource imageSource_;
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/*
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* Future splitter powers factory-like `getResponseFuture()` method.
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*/
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mutable folly::FutureSplitter<ImageResponse> responseFutureSplitter_;
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/*
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* Indicates that the object was moved and hence cannot be used anymore.
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*/
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bool moved_{false};
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};
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} // namespace react
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} // namespace facebook
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