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97 lines
3.1 KiB
97 lines
3.1 KiB
4 months ago
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/*
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* Copyright (C) 2019 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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#pragma once
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#include <mutex>
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#include <type_traits>
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#include <binder/IInterface.h>
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#include <binder/IServiceManager.h>
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#include <utils/Log.h>
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namespace android {
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// A simple utility that caches a proxy for a service and handles death notification.
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// Typically, intended to be used as a static-lifetime object.
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//
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// Example usage:
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// static BinderProxy<IMyInterface> myInterface("my_interface_svc");
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// ...
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// myInterface.waitServiceOrDie()->doSomething();
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//
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// If the service is unavailable, will wait until it becomes available.
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// Will die if the service doesn't implement the requested interface, or cannot be used for
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// permission reasons.
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template<typename ServiceType>
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class BinderProxy {
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public:
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static_assert(std::is_base_of_v<IInterface, ServiceType>,
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"Service type must be a sub-type of IInterface.");
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explicit BinderProxy(std::string_view serviceName)
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: mServiceName(serviceName), mDeathRecipient(new DeathRecipient(this)) {}
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~BinderProxy() {
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if (mDelegate != nullptr) {
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sp<IBinder> binder = IInterface::asBinder(mDelegate);
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if (binder != nullptr) {
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binder->unlinkToDeath(mDeathRecipient);
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}
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}
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}
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sp<ServiceType> waitServiceOrDie() {
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std::lock_guard<std::mutex> _l(mDelegateMutex);
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if (mDelegate == nullptr) {
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mDelegate = waitForService<ServiceType>(String16(mServiceName.c_str()));
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LOG_ALWAYS_FATAL_IF(mDelegate == nullptr,
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"Service %s doesn't implement the required interface.",
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mServiceName.c_str());
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sp<IBinder> binder = IInterface::asBinder(mDelegate);
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if (binder != nullptr) {
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binder->linkToDeath(mDeathRecipient);
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}
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}
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return mDelegate;
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}
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private:
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sp<ServiceType> mDelegate;
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std::mutex mDelegateMutex;
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const std::string mServiceName;
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sp<IBinder::DeathRecipient> mDeathRecipient;
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class DeathRecipient : public IBinder::DeathRecipient {
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public:
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DeathRecipient(BinderProxy* proxy) : mProxy(proxy) {}
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void binderDied(const wp<IBinder>&) override {
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mProxy->binderDied();
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}
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private:
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BinderProxy* const mProxy;
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};
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void binderDied() {
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std::lock_guard<std::mutex> _l(mDelegateMutex);
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mDelegate.clear();
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ALOGW("Binder died: %s", mServiceName.c_str());
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}
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};
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} // namespace android
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