130 lines
5.3 KiB
C++
130 lines
5.3 KiB
C++
/*
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* Copyright (C) 2022 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 FRAMEWORKS_AV_SERVICES_CAMERA_LIBCAMERASERVICE_AIDL_DEATHPIPE_H_
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#define FRAMEWORKS_AV_SERVICES_CAMERA_LIBCAMERASERVICE_AIDL_DEATHPIPE_H_
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#include <android/binder_auto_utils.h>
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#include <android/binder_ibinder.h>
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#include <binder/Parcel.h>
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#include <list>
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namespace android::frameworks::cameraservice::utils {
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/**
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* This is a helper class to pipe death notifications from VNDK {@code AIBinder} to
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* S/NDK {@code IBinder}.
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*
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* To use this class, create a DeathPipe member object as a field of NDK interface
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* implementation, and forward functions {@code BBinder::linkToDeath} and
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* {@code BBinder::unlinkToDeath} to corresponding DeathPipe functions.
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*/
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class DeathPipe {
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public:
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/**
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* @param parent the NDK Binder object. Assumed to live longer than the DeathPipe
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* object
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* @param binder the VNDK Binder object which DeathPipe with subscribe to.
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*/
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explicit DeathPipe(IBinder* parent, const ::ndk::SpAIBinder& binder);
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~DeathPipe();
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status_t linkToDeath(const sp<IBinder::DeathRecipient>& recipient, void* cookie,
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uint32_t flags);
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status_t unlinkToDeath(const wp<IBinder::DeathRecipient>& recipient,
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void* cookie, uint32_t flags, wp<IBinder::DeathRecipient>* outRecipient);
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// Static functions that will be called by VNDK binder upon death or unlinking
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static void onDeathCallback(void* cookie);
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static void onUnlinkedCallback(void* cookie);
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private:
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/**
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* {@code Obituary} is a tiny container that contains some metadata to pass VNDK binder's
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* death notification to the NDK binder. A pointer to the Obituary is used as the
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* {@code cookie} in VNDK binder's death notification.
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*
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* Theoretically, the VNDK binder might send out death notification after the DeathPipe
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* object is destroyed, so care must be taken to ensure that Obituaries aren't accidentally
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* destroyed before VNDK binder stops using its cookies.
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*
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*/
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struct Obituary: public std::enable_shared_from_this<Obituary> {
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wp<IBinder::DeathRecipient> recipient; // NDK death recipient
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void *cookie; // cookie sent by the NDK recipient
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uint32_t flags; // flags sent by the NDK recipient
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wp<IBinder> who; // NDK binder whose death 'recipient' subscribed to
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// Self ptr to ensure we don't destroy this obituary while it can still be notified by the
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// VNDK Binder. When populated with Obituary::immortalize, this Obituary won't be
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// garbage collected until Obituary::clear is called.
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std::shared_ptr<Obituary> mSelfPtr;
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Obituary(const wp<IBinder::DeathRecipient>& recipient, void* cookie,
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uint32_t flags, IBinder* who) :
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recipient(recipient), cookie(cookie), flags(flags),
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who(who), mSelfPtr(nullptr) {}
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// Function to be called when the VNDK Binder dies. Pipes the notification to the relevant
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// NDK recipient if it still exists
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void onDeath() const {
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sp<IBinder::DeathRecipient> r = recipient.promote();
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if (r == nullptr) { return; }
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r->binderDied(who);
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};
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// Should be called before calling AIBinder_linkToDeath. Once this function returns this
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// Obituary won't be garbage collected until Obituary::clear is called.
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void immortalize() {
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mSelfPtr = shared_from_this();
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}
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// Should be called when this Obituary can be garbage collected.
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// Typically, after the Obituary is no longer linked to a VNDK DeathRecipient
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void clear() {
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mSelfPtr = nullptr;
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}
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bool operator==(const Obituary& rhs) const {
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return recipient == rhs.recipient &&
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cookie == rhs.cookie &&
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flags == rhs.flags &&
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who == rhs.who;
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}
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};
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// Parent to which the cameraservice wants to subscribe to for death notification
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IBinder* mParent;
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// VNDK Binder object to which the death notification will be bound to. If it dies,
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// cameraservice will be notified as if mParent died.
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::ndk::SpAIBinder mAIBinder;
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// Owning VNDK's deathRecipient ensures that all linked death notifications are cleaned up
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// when this class destructs.
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::ndk::ScopedAIBinder_DeathRecipient mDeathRecipient;
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// Lock to protect access to fields below.
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std::mutex mLock;
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// List of all obituaries created by DeathPipe, used to unlink death subscription
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std::list<std::shared_ptr<Obituary>> mObituaries;
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};
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} // namespace android::frameworks::cameraservice::utils
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#endif // FRAMEWORKS_AV_SERVICES_CAMERA_LIBCAMERASERVICE_AIDL_DEATHPIPE_H_
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