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 /** 055 * Returns true if the video listener handle is valid. 056 * 057 * @return True if the video listener handle is valid. 058 */ 059 public boolean isValid() { 060 return m_handle != 0; 061 } 062 063 private int m_handle; 064 065 private static final ReentrantLock s_lock = new ReentrantLock(); 066 private static final Map<Integer, Consumer<VideoEvent>> s_listeners = new HashMap<>(); 067 private static Thread s_thread; 068 private static int s_poller; 069 private static boolean s_waitQueue; 070 private static final Condition s_waitQueueCond = s_lock.newCondition(); 071 072 private static void startThread() { 073 s_thread = 074 new Thread( 075 () -> { 076 boolean wasInterrupted = false; 077 while (!Thread.interrupted()) { 078 VideoEvent[] events; 079 try { 080 events = CameraServerJNI.pollListener(s_poller); 081 } catch (InterruptedException ex) { 082 s_lock.lock(); 083 try { 084 if (s_waitQueue) { 085 s_waitQueue = false; 086 s_waitQueueCond.signalAll(); 087 continue; 088 } 089 } finally { 090 s_lock.unlock(); 091 } 092 Thread.currentThread().interrupt(); 093 // don't try to destroy poller, as its handle is likely no longer valid 094 wasInterrupted = true; 095 break; 096 } 097 for (VideoEvent event : events) { 098 Consumer<VideoEvent> listener; 099 s_lock.lock(); 100 try { 101 listener = s_listeners.get(event.listener); 102 } finally { 103 s_lock.unlock(); 104 } 105 if (listener != null) { 106 try { 107 listener.accept(event); 108 } catch (Throwable throwable) { 109 System.err.println( 110 "Unhandled exception during listener callback: " + throwable); 111 throwable.printStackTrace(); 112 } 113 } 114 } 115 } 116 s_lock.lock(); 117 try { 118 if (!wasInterrupted) { 119 CameraServerJNI.destroyListenerPoller(s_poller); 120 } 121 s_poller = 0; 122 } finally { 123 s_lock.unlock(); 124 } 125 }, 126 "VideoListener"); 127 s_thread.setDaemon(true); 128 s_thread.start(); 129 } 130}