macOS: check that device has not been disconnected

java-does-usb/src/main/java/net/codecrete/usb/UsbDevice.java

@@ -152,6 +152,18 @@ public interface UsbDevice {
      */
     void attachStandardDrivers();
 
+    /**
+     * Indicates if the device is connected.
+     * <p>
+     * When a {@link UsbDevice} instance is initially returned by {@link Usb#getDevices()} and related methods,
+     * it is connected. When the user unplugs the device, the application can still hold on to instance of
+     * {@link UsbDevice} even though the actual USB device is gone. This method can be used to check if the
+     * device is still connected.
+     * </p>
+     * @return {@code true} if the device is connected, {@code false} if it is no longer connected
+     */
+    boolean isConnected();
+
     /**
      * Opens the device for communication.
      */

java-does-usb/src/main/java/net/codecrete/usb/common/UsbDeviceImpl.java

@@ -55,6 +55,7 @@ public abstract class UsbDeviceImpl implements UsbDevice {
     protected int deviceProtocol;
     protected Version versionUsb;
     protected Version versionDevice;
+    protected boolean connected;
 
     /**
      * Creates a new instance.
@@ -70,6 +71,7 @@ protected UsbDeviceImpl(Object id, int vendorId, int productId) {
         uniqueDeviceId = id;
         vid = vendorId;
         pid = productId;
+        connected = true;
     }
 
     @Override
@@ -157,6 +159,11 @@ public Object getUniqueId() {
         return uniqueDeviceId;
     }
 
+    @Override
+    public boolean isConnected() {
+        return connected;
+    }
+
     /**
      * Sets the class codes and version for the device descriptor.
      *

java-does-usb/src/main/java/net/codecrete/usb/macos/MacosUsbDevice.java

@@ -78,18 +78,16 @@ public class MacosUsbDevice extends UsbDeviceImpl {
     }
 
     @Override
-    public void detachStandardDrivers() {
-        if (isOpened())
-            throwException("detachStandardDrivers() must not be called while the device is open");
+    public synchronized void detachStandardDrivers() {
+        checkIsClosed("detachStandardDrivers() must not be called while the device is open");
         var ret = IoKitUsb.USBDeviceReEnumerate(device, IOKit.kUSBReEnumerateCaptureDeviceMask());
         if (ret != 0)
             throwException(ret, "detaching standard drivers failed");
     }
 
     @Override
-    public void attachStandardDrivers() {
-        if (isOpened())
-            throwException("attachStandardDrivers() must not be called while the device is open");
+    public synchronized void attachStandardDrivers() {
+        checkIsClosed("attachStandardDrivers() must not be called while the device is open");
         var ret = IoKitUsb.USBDeviceReEnumerate(device, IOKit.kUSBReEnumerateReleaseDeviceMask());
         if (ret != 0)
             throwException(ret, "attaching standard drivers failed");
@@ -100,11 +98,17 @@ public boolean isOpened() {
         return claimedInterfaces != null;
     }
 
+    private void checkIsClosed(String message) {
+        if (!connected)
+            throwException("device has been disconnected");
+        if (isOpened())
+            throwException(message);
+    }
+
     @SuppressWarnings("java:S2276")
     @Override
     public synchronized void open() {
-        if (isOpened())
-            throwException("device is already open");
+        checkIsClosed("device is already open");
 
         // open device (several retries if device has just been connected/discovered)
         var duration = System.currentTimeMillis() - discoveryTime;
@@ -161,6 +165,7 @@ public synchronized void close() {
     }
 
     synchronized void closeFully() {
+        connected = false;
         close();
         IoKitUsb.Release(device);
         device = null;
@@ -580,7 +585,7 @@ protected Transfer createTransfer() {
     }
 
     @Override
-    public void abortTransfers(UsbDirection direction, int endpointNumber) {
+    public synchronized void abortTransfers(UsbDirection direction, int endpointNumber) {
         var epInfo = getEndpointInfo(endpointNumber, direction, UsbTransferType.BULK,
                 UsbTransferType.INTERRUPT);
 
@@ -590,7 +595,7 @@ public void abortTransfers(UsbDirection direction, int endpointNumber) {
     }
 
     @Override
-    public void clearHalt(UsbDirection direction, int endpointNumber) {
+    public synchronized void clearHalt(UsbDirection direction, int endpointNumber) {
         var epInfo = getEndpointInfo(endpointNumber, direction, UsbTransferType.BULK,
                 UsbTransferType.INTERRUPT);
 

java-does-usb/src/test/java/net/codecrete/usb/special/Unplug.java

@@ -57,6 +57,27 @@ private static void onUnpluggedDevice(UsbDevice device) {
         var worker = activeDevices.remove(device);
         worker.setDisconnectTime(System.currentTimeMillis());
         worker.join();
+
+        // test handling of disconnected devices
+        new Thread(() -> {
+            sleep(2000);
+            try {
+                device.open();
+                System.err.println("Device should not be openable after disconnect");
+            } catch (UsbException e) {
+                // expected
+            }
+        }).start();
+    }
+
+    @SuppressWarnings({"SameParameterValue", "java:S2925"})
+    private static void sleep(long millis) {
+        try {
+            Thread.sleep(millis);
+
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+        }
     }
 
     static class DeviceWorker {
@@ -241,16 +262,6 @@ private void receiveEcho() {
                 logWork(1);
             }
         }
-
-        @SuppressWarnings({"SameParameterValue", "java:S2925"})
-        private static void sleep(long millis) {
-            try {
-                Thread.sleep(millis);
-
-            } catch (InterruptedException e) {
-                Thread.currentThread().interrupt();
-            }
-        }
     }
 
     static class Work {