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// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
namespace chromecast {
// A CastResource is a user of 1 or more Resources (primary screen, audio,
// etc). As a user, it is responsible for doing any cast-specific component
// initialization when the Resources it uses are granted. This initialization
// is referred to as "acquiring" the Resources. Conversely, when the Resources
// it uses are revoked, it must deinitialize these cast-specific components.
// This deinitialization is referred to as "releasing" the Resources.
class CastResource {
// Resources necessary to run cast apps. CastResource may contain union of the
// following types.
// TODO(yucliu): Split video resources and graphic resources.
enum Resource {
kResourceNone = 0,
// All resources necessary to render sounds, for example, audio pipeline,
// speaker, etc.
kResourceAudio = 1 << 0,
// All resources necessary to render videos or images, for example, video
// pipeline, primary graphics plane, display, etc.
kResourceScreenPrimary = 1 << 1,
// All resources necessary to render overlaid images, for example, secondary
// graphics plane, LCD, etc.
kResourceScreenSecondary = 1 << 2,
// Collection of resources used for display only combined with bitwise or.
kResourceDisplayOnly = (kResourceScreenPrimary | kResourceScreenSecondary),
// Collection of all resources combined with bitwise or.
kResourceAll =
(kResourceAudio | kResourceScreenPrimary | kResourceScreenSecondary),
// A Client is responsible for notifying all registered CastResource's when
// Resources are granted/revoked so that they can acquire/release those
// Resources. When a CastResource is done acquiring/releasing, it responds
// to the Client that it has completed. A Client can have multiple registered
// CastResource's, but each CastResouce has 1 Client that it responds to.
class Client {
// Called to register a CastResource with a Client. After registering, a
// CastResource will start getting notified when to acquire/release
// Resources. The Client does not take ownership of |cast_resource|. It can
// be called from any thread.
virtual void RegisterCastResource(CastResource* cast_resource) = 0;
// TODO(esum): Add OnResourceAcquired() here once AcquireResource is
// allowed to be asynchronous.
// Called when part or all resources are released. It can be called from any
// thread.
// |cast_resource| the CastResource that is released. The pointer may be
// invalid. Client can't call functions with that pointer.
// |remain| the unreleased resource of CastResource. If kResourceNone is
// returned, Client will remove the resource from its watching
// list.
virtual void OnResourceReleased(CastResource* cast_resource,
Resource remain) = 0;
virtual ~Client() {}
CastResource(const CastResource&) = delete;
CastResource& operator=(const CastResource&) = delete;
// Sets the Client for the CastResource to respond to when it is done with
// Acquire/ReleaseResource.
void SetCastResourceClient(Client* client);
// Called to acquire resources after OEM has granted them, and before
// they start getting used by consumers. Implementation must be synchronous
// since consumers will start using the resource immediately afterwards.
// TODO(esum): We should allow this method to be asynchronous in case an
// implementer needs to make expensive calls and doesn't want to block the
// UI thread (b/26239576). For now, don't do anything expensive in your
// implementation; if you really need to, then this bug has to be resolved.
virtual void AcquireResource(Resource resource) = 0;
// Called to release resources. Implementation should call
// Client::OnResourceReleased when resource is released on its side.
virtual void ReleaseResource(Resource resource) = 0;
CastResource() : client_(nullptr) {}
virtual ~CastResource() {}
// For derived classes to register themselves with their Client through
// Client::RegisterCastResource.
void RegisterWithClient();
void NotifyResourceReleased(Resource remain);
Client* client_;
} // namespace chromecast