001// Copyright (c) FIRST and other WPILib contributors. 002// Open Source Software; you can modify and/or share it under the terms of 003// the WPILib BSD license file in the root directory of this project. 004 005package edu.wpi.first.cscore; 006 007import java.util.HashMap; 008import java.util.Map; 009import java.util.concurrent.locks.Condition; 010import java.util.concurrent.locks.ReentrantLock; 011import java.util.function.Consumer; 012 013/** 014 * An event listener. This calls back to a desigated callback function when an event matching the 015 * specified mask is generated by the library. 016 */ 017public class VideoListener implements AutoCloseable { 018 /** 019 * Create an event listener. 020 * 021 * @param listener Listener function 022 * @param eventMask Bitmask of VideoEvent.Type values 023 * @param immediateNotify Whether callback should be immediately called with a representative set 024 * of events for the current library state. 025 */ 026 public VideoListener(Consumer<VideoEvent> listener, int eventMask, boolean immediateNotify) { 027 s_lock.lock(); 028 try { 029 if (s_poller == 0) { 030 s_poller = CameraServerJNI.createListenerPoller(); 031 startThread(); 032 } 033 m_handle = CameraServerJNI.addPolledListener(s_poller, eventMask, immediateNotify); 034 s_listeners.put(m_handle, listener); 035 } finally { 036 s_lock.unlock(); 037 } 038 } 039 040 @Override 041 public synchronized void close() { 042 if (m_handle != 0) { 043 s_lock.lock(); 044 try { 045 s_listeners.remove(m_handle); 046 } finally { 047 s_lock.unlock(); 048 } 049 CameraServerJNI.removeListener(m_handle); 050 m_handle = 0; 051 } 052 } 053 054 public boolean isValid() { 055 return m_handle != 0; 056 } 057 058 private int m_handle; 059 060 private static final ReentrantLock s_lock = new ReentrantLock(); 061 private static final Map<Integer, Consumer<VideoEvent>> s_listeners = new HashMap<>(); 062 private static Thread s_thread; 063 private static int s_poller; 064 private static boolean s_waitQueue; 065 private static final Condition s_waitQueueCond = s_lock.newCondition(); 066 067 private static void startThread() { 068 s_thread = 069 new Thread( 070 () -> { 071 boolean wasInterrupted = false; 072 while (!Thread.interrupted()) { 073 VideoEvent[] events; 074 try { 075 events = CameraServerJNI.pollListener(s_poller); 076 } catch (InterruptedException ex) { 077 s_lock.lock(); 078 try { 079 if (s_waitQueue) { 080 s_waitQueue = false; 081 s_waitQueueCond.signalAll(); 082 continue; 083 } 084 } finally { 085 s_lock.unlock(); 086 } 087 Thread.currentThread().interrupt(); 088 // don't try to destroy poller, as its handle is likely no longer valid 089 wasInterrupted = true; 090 break; 091 } 092 for (VideoEvent event : events) { 093 Consumer<VideoEvent> listener; 094 s_lock.lock(); 095 try { 096 listener = s_listeners.get(event.listener); 097 } finally { 098 s_lock.unlock(); 099 } 100 if (listener != null) { 101 try { 102 listener.accept(event); 103 } catch (Throwable throwable) { 104 System.err.println( 105 "Unhandled exception during listener callback: " + throwable); 106 throwable.printStackTrace(); 107 } 108 } 109 } 110 } 111 s_lock.lock(); 112 try { 113 if (!wasInterrupted) { 114 CameraServerJNI.destroyListenerPoller(s_poller); 115 } 116 s_poller = 0; 117 } finally { 118 s_lock.unlock(); 119 } 120 }, 121 "VideoListener"); 122 s_thread.setDaemon(true); 123 s_thread.start(); 124 } 125}