Redesign some synchronization features

refs #26

webcam-capture-examples/webcam-capture-motiondetector/src/main/java/com/github/sarxos/webcam/DetectMotionExample.java

@@ -18,9 +18,6 @@
  */
 public class DetectMotionExample extends JFrame implements Runnable {
 
-	/**
-	 * 
-	 */
 	private static final long serialVersionUID = -585739158170333370L;
 
 	private static final int INTERVAL = 100; // ms

webcam-capture/src/example/java/com/github/sarxos/webcam/ConcurrentThreadsExample.java

@@ -0,0 +1,43 @@
+package com.github.sarxos.webcam;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+
+public class ConcurrentThreadsExample {
+
+	private static AtomicInteger counter = new AtomicInteger(0);
+
+	private static final class Capture extends Thread {
+
+		private static final AtomicInteger number = new AtomicInteger(0);
+
+		public Capture() {
+			super("capture-" + number.incrementAndGet());
+		}
+
+		@Override
+		public void run() {
+			while (true) {
+				Webcam.getDefault().getImage();
+				int value = counter.incrementAndGet();
+				if (value != 0 && value % 10 == 0) {
+					System.out.println(Thread.currentThread().getName() + ": Frames captured: " + value);
+				}
+			}
+		}
+	}
+
+	public static void main(String[] args) {
+
+		/**
+		 * This example will start several concurrent threads which use single
+		 * webcam instance.
+		 */
+
+		int n = Runtime.getRuntime().availableProcessors() * 4;
+		for (int i = 0; i < n; i++) {
+			System.out.println("Thread: " + i);
+			new Capture().start();
+		}
+	}
+}

webcam-capture/src/example/java/com/github/sarxos/webcam/PureDefaultDeviceExample.java

@@ -0,0 +1,45 @@
+package com.github.sarxos.webcam;
+
+import org.bridj.Pointer;
+
+import com.github.sarxos.webcam.ds.buildin.natives.Device;
+import com.github.sarxos.webcam.ds.buildin.natives.DeviceList;
+import com.github.sarxos.webcam.ds.buildin.natives.OpenIMAJGrabber;
+
+
+public class PureDefaultDeviceExample {
+
+	public static void main(String[] args) {
+
+		/**
+		 * This example show how to use native OpenIMAJ API to capture raw bytes
+		 * data as byte[] array. It also calculates current FPS.
+		 */
+
+		OpenIMAJGrabber grabber = new OpenIMAJGrabber();
+
+		Device device = null;
+		Pointer<DeviceList> devices = grabber.getVideoDevices();
+		for (Device d : devices.get().asArrayList()) {
+			device = d;
+			break;
+		}
+
+		grabber.startSession(320, 240, 30, Pointer.pointerTo(device));
+
+		long t1 = System.currentTimeMillis() / 1000;
+
+		int n = 100;
+		int i = 0;
+		do {
+			grabber.nextFrame();
+			grabber.getImage().getBytes(320 * 240 * 3); // byte[]
+		} while (++i < n);
+
+		long t2 = System.currentTimeMillis() / 1000;
+
+		System.out.println("FPS: " + ((double) n / (t2 - t1)));
+
+		grabber.stopSession();
+	}
+}

webcam-capture/src/main/java/com/github/sarxos/webcam/Webcam.java

@@ -73,12 +73,12 @@ public void run() {
 	/**
 	 * Webcam driver (LtiCivil, JMF, FMJ, JQT, OpenCV, VLCj, etc).
 	 */
-	private static WebcamDriver driver = null;
+	private static volatile WebcamDriver driver = null;
 
 	/**
 	 * Webcam discovery service.
 	 */
-	private static WebcamDiscoveryService discovery = null;
+	private static volatile WebcamDiscoveryService discovery = null;
 
 	/**
 	 * Is automated deallocation on TERM signal enabled.
@@ -331,13 +331,14 @@ public BufferedImage getImage() {
 			return null;
 		}
 
-		synchronized (this) {
-			if (!open) {
-				LOG.debug("Try to get image on closed webcam, opening it automatically");
+		if (!open) {
+			LOG.debug("Try to get image on closed webcam, opening it automatically");
+			synchronized (this) {
 				open();
 			}
-			return device.getImage();
 		}
+
+		return device.getImage();
 	}
 
 	/**
@@ -382,7 +383,7 @@ public static List<Webcam> getWebcams(long timeout) throws TimeoutException, Web
 	 * @throws TimeoutException when timeout has been exceeded
 	 * @throws WebcamException when something is wrong
 	 */
-	public static List<Webcam> getWebcams(long timeout, TimeUnit tunit) throws TimeoutException, WebcamException {
+	public static synchronized List<Webcam> getWebcams(long timeout, TimeUnit tunit) throws TimeoutException, WebcamException {
 
 		WebcamDiscoveryService discovery = getDiscoveryService();
 		List<Webcam> webcams = discovery.getWebcams(timeout, tunit);
@@ -402,6 +403,7 @@ public static List<Webcam> getWebcams(long timeout, TimeUnit tunit) throws Timeo
 	 * @see Webcam#getWebcams()
 	 */
 	public static Webcam getDefault() throws WebcamException {
+
 		try {
 			return getDefault(Long.MAX_VALUE);
 		} catch (TimeoutException e) {
@@ -507,7 +509,7 @@ public boolean removeWebcamListener(WebcamListener l) {
 	 * 
 	 * @return Webcam driver
 	 */
-	public static WebcamDriver getDriver() {
+	public static synchronized WebcamDriver getDriver() {
 
 		if (driver == null) {
 			driver = WebcamDriverUtils.findDriver(DRIVERS_LIST, DRIVERS_CLASS_LIST);
@@ -529,11 +531,14 @@ public static WebcamDriver getDriver() {
 	 * @param driver new webcam driver to be used (e.g. LtiCivil, JFM, FMJ, QTJ)
 	 * @throws IllegalArgumentException when argument is null
 	 */
-	public static void setDriver(WebcamDriver driver) {
+	public static synchronized void setDriver(WebcamDriver driver) {
+
 		if (driver == null) {
 			throw new IllegalArgumentException("Webcam driver cannot be null!");
 		}
+
 		resetDriver();
+
 		Webcam.driver = driver;
 	}
 
@@ -547,7 +552,7 @@ public static void setDriver(WebcamDriver driver) {
 	 * @param driver new video driver class to use
 	 * @throws IllegalArgumentException when argument is null
 	 */
-	public static void setDriver(Class<? extends WebcamDriver> driverClass) {
+	public static synchronized void setDriver(Class<? extends WebcamDriver> driverClass) {
 
 		resetDriver();
 
@@ -718,7 +723,7 @@ public static boolean removeDiscoveryListener(WebcamDiscoveryListener l) {
 	 * 
 	 * @return Discovery service
 	 */
-	public static WebcamDiscoveryService getDiscoveryService() {
+	public static synchronized WebcamDiscoveryService getDiscoveryService() {
 		if (discovery == null) {
 			discovery = new WebcamDiscoveryService(getDriver());
 		}

webcam-capture/src/main/java/com/github/sarxos/webcam/WebcamDiscoveryService.java

@@ -78,11 +78,7 @@ private static List<WebcamDevice> getDevices(List<Webcam> webcams) {
 		return devices;
 	}
 
-	public List<Webcam> getWebcams() throws TimeoutException {
-		return getWebcams(Webcam.getDiscoveryTimeout(), TimeUnit.MILLISECONDS);
-	}
-
-	public List<Webcam> getWebcams(long timeout, TimeUnit tunit) throws TimeoutException {
+	public synchronized List<Webcam> getWebcams(long timeout, TimeUnit tunit) throws TimeoutException {
 
 		if (timeout < 0) {
 			throw new IllegalArgumentException("Timeout cannot be negative");
@@ -162,7 +158,7 @@ public void run() {
 			List<WebcamDevice> tmpold = null;
 
 			try {
-				tmpold = getDevices(getWebcams(Webcam.getDiscoveryTimeout(), TimeUnit.MILLISECONDS));
+				tmpold = getDevices(getWebcams(Long.MAX_VALUE, TimeUnit.MILLISECONDS));
 			} catch (TimeoutException e) {
 				throw new WebcamException(e);
 			}