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      1 /*
      2  * Copyright (C) 2017 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef HIDL_CALLBACK_UTIL_H_
     18 #define HIDL_CALLBACK_UTIL_H_
     19 
     20 #include <set>
     21 
     22 #include <hidl/HidlSupport.h>
     23 
     24 namespace {
     25 // Type of callback invoked by the death handler.
     26 using on_death_cb_function = std::function<void(uint64_t)>;
     27 
     28 // Private class used to keep track of death of individual
     29 // callbacks stored in HidlCallbackHandler.
     30 template <typename CallbackType>
     31 class HidlDeathHandler : public android::hardware::hidl_death_recipient {
     32  public:
     33   HidlDeathHandler(const on_death_cb_function& user_cb_function)
     34       : cb_function_(user_cb_function) {}
     35   ~HidlDeathHandler() = default;
     36 
     37   // Death notification for callbacks.
     38   void serviceDied(
     39       uint64_t cookie,
     40       const android::wp<android::hidl::base::V1_0::IBase>& /* who */) override {
     41     cb_function_(cookie);
     42   }
     43 
     44  private:
     45   on_death_cb_function cb_function_;
     46 
     47   DISALLOW_COPY_AND_ASSIGN(HidlDeathHandler);
     48 };
     49 }  // namespace
     50 
     51 namespace android {
     52 namespace hardware {
     53 namespace wifi {
     54 namespace V1_0 {
     55 namespace implementation {
     56 namespace hidl_callback_util {
     57 template <typename CallbackType>
     58 // Provides a class to manage callbacks for the various HIDL interfaces and
     59 // handle the death of the process hosting each callback.
     60 class HidlCallbackHandler {
     61  public:
     62   HidlCallbackHandler()
     63       : death_handler_(new HidlDeathHandler<CallbackType>(
     64             std::bind(&HidlCallbackHandler::onObjectDeath,
     65                       this,
     66                       std::placeholders::_1))) {}
     67   ~HidlCallbackHandler() = default;
     68 
     69   bool addCallback(const sp<CallbackType>& cb) {
     70     // TODO(b/33818800): Can't compare proxies yet. So, use the cookie
     71     // (callback proxy's raw pointer) to track the death of individual clients.
     72     uint64_t cookie = reinterpret_cast<uint64_t>(cb.get());
     73     if (cb_set_.find(cb) != cb_set_.end()) {
     74       LOG(WARNING) << "Duplicate death notification registration";
     75       return true;
     76     }
     77     if (!cb->linkToDeath(death_handler_, cookie)) {
     78       LOG(ERROR) << "Failed to register death notification";
     79       return false;
     80     }
     81     cb_set_.insert(cb);
     82     return true;
     83   }
     84 
     85   const std::set<android::sp<CallbackType>>& getCallbacks() { return cb_set_; }
     86 
     87   // Death notification for callbacks.
     88   void onObjectDeath(uint64_t cookie) {
     89     CallbackType* cb = reinterpret_cast<CallbackType*>(cookie);
     90     const auto& iter = cb_set_.find(cb);
     91     if (iter == cb_set_.end()) {
     92       LOG(ERROR) << "Unknown callback death notification received";
     93       return;
     94     }
     95     cb_set_.erase(iter);
     96     LOG(DEBUG) << "Dead callback removed from list";
     97   }
     98 
     99   void invalidate() {
    100     for (const sp<CallbackType>& cb : cb_set_) {
    101       if (!cb->unlinkToDeath(death_handler_)) {
    102         LOG(ERROR) << "Failed to deregister death notification";
    103       }
    104     }
    105     cb_set_.clear();
    106   }
    107 
    108  private:
    109   std::set<sp<CallbackType>> cb_set_;
    110   sp<HidlDeathHandler<CallbackType>> death_handler_;
    111 
    112   DISALLOW_COPY_AND_ASSIGN(HidlCallbackHandler);
    113 };
    114 
    115 }  // namespace hidl_callback_util
    116 }  // namespace implementation
    117 }  // namespace V1_0
    118 }  // namespace wifi
    119 }  // namespace hardware
    120 }  // namespace android
    121 #endif  // HIDL_CALLBACK_UTIL_H_
    122