1 /* 2 * Copyright (C) 2021 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 #pragma once 17 18 #include <memory> 19 20 #include <android-base/result.h> 21 #include <android-base/unique_fd.h> 22 #include <utils/Errors.h> 23 24 #include <binder/RpcTransport.h> 25 26 namespace android { 27 28 /** This is not a pipe. */ 29 class FdTrigger { 30 public: 31 /** Returns nullptr for error case */ 32 static std::unique_ptr<FdTrigger> make(); 33 34 /** 35 * Close the write end of the pipe so that the read end receives POLLHUP. 36 * Not threadsafe. 37 */ 38 void trigger(); 39 40 /** 41 * Check whether this has been triggered by checking the write end. Note: 42 * this has no internal locking, and it is inherently racey, but this is 43 * okay, because if we accidentally return false when a trigger has already 44 * happened, we can imagine that instead, the scheduler actually executed 45 * the code which is polling isTriggered earlier. 46 */ 47 [[nodiscard]] bool isTriggered(); 48 49 /** 50 * Poll for a read event. 51 * 52 * event - for pollfd 53 * 54 * Return: 55 * true - time to read! 56 * false - trigger happened 57 */ 58 [[nodiscard]] status_t triggerablePoll(const android::RpcTransportFd& transportFd, 59 int16_t event); 60 61 private: 62 #ifdef BINDER_RPC_SINGLE_THREADED 63 bool mTriggered = false; 64 #else 65 base::unique_fd mWrite; 66 base::unique_fd mRead; 67 #endif 68 }; 69 } // namespace android 70