75 lines
2.6 KiB
C++
75 lines
2.6 KiB
C++
/*
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* Copyright (C) 2021 The Android Open Source Project
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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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*/
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#ifndef TNT_FILAMENT_BACKEND_CALLBACKHANDLER_H
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#define TNT_FILAMENT_BACKEND_CALLBACKHANDLER_H
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#include <utils/compiler.h>
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namespace filament::backend {
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/**
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* A generic interface to dispatch callbacks.
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*
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* All APIs that take a callback as argument also take a
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* CallbackHandler* which is used to dispatch the
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* callback: CallbackHandler::post() method is called from a service thread as soon
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* as possible (this will NEVER be the main thread), CallbackHandler::post()
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* is responsible for scheduling the callback onto the thread the
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* user desires.
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*
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* This is intended to make callbacks interoperate with
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* the platform/OS's own messaging system.
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*
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* CallbackHandler* can always be nullptr in which case the default handler is used. The
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* default handler always dispatches callbacks on filament's main thread opportunistically.
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*
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* Life time:
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* ---------
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*
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* Filament make no attempts to manage the life time of the CallbackHandler* and never takes
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* ownership.
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* In particular, this means that the CallbackHandler instance must stay valid until all
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* pending callbacks are been dispatched.
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*
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* Similarly, when shutting down filament, care must be taken to ensure that all pending callbacks
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* that might access filament's state have been dispatched. Filament can no longer ensure this
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* because callback execution is the responsibility of the CallbackHandler, which is external to
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* filament.
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* Typically, the concrete CallbackHandler would have a mechanism to drain and/or wait for all
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* callbacks to be processed.
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*
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*/
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class CallbackHandler {
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public:
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using Callback = void(*)(void* user);
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/**
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* Schedules the callback to be called onto the appropriate thread.
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* Typically this will be the application's main thead.
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*
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* Must be thread-safe.
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*/
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virtual void post(void* user, Callback callback) = 0;
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protected:
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virtual ~CallbackHandler() = default;
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};
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} // namespace filament::backend
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#endif // TNT_FILAMENT_BACKEND_CALLBACKHANDLER_H
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