refactor duplicated code in close method

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/CdcAcmSerialDriver.java

@@ -239,26 +239,11 @@ public class CdcAcmSerialDriver implements UsbSerialDriver {
         }
 
         @Override
-        public void close() throws IOException {
+        public void closeInt() {
-            if (mConnection == null) {
-                throw new IOException("Already closed");
-            }
-            synchronized (this) {
-                if (mUsbRequest != null)
-                    mUsbRequest.cancel();
-            }
-            mControlEndpoint = null;
-            mReadEndpoint = null;
-            mWriteEndpoint = null;
             try {
                 mConnection.releaseInterface(mControlInterface);
                 mConnection.releaseInterface(mDataInterface);
             } catch(Exception ignored) {}
-            try {
-                mConnection.close();
-            } finally {
-                mConnection = null;
-            }
         }
 
         @Override

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/Ch34xSerialDriver.java

@@ -129,23 +129,11 @@ public class Ch34xSerialDriver implements UsbSerialDriver {
 		}
 
 		@Override
-		public void close() throws IOException {
+		public void closeInt() {
-			if (mConnection == null) {
-				throw new IOException("Already closed");
-			}
-			synchronized (this) {
-				if (mUsbRequest != null)
-					mUsbRequest.cancel();
-			}
 			try {
 				for (int i = 0; i < mDevice.getInterfaceCount(); i++)
 					mConnection.releaseInterface(mDevice.getInterface(i));
 			} catch(Exception ignored) {}
-			try {
-				mConnection.close();
-			} finally {
-				mConnection = null;
-			}
 		}
 
 		private int controlOut(int request, int value, int index) {

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/CommonUsbSerialPort.java

@@ -109,7 +109,26 @@ public abstract class CommonUsbSerialPort implements UsbSerialPort {
     public abstract void open(UsbDeviceConnection connection) throws IOException;
 
     @Override
-    public abstract void close() throws IOException;
+    public void close() throws IOException {
+        if (mConnection == null) {
+            throw new IOException("Already closed");
+        }
+        synchronized (this) {
+            if (mUsbRequest != null)
+                mUsbRequest.cancel();
+        }
+        try {
+            closeInt();
+        } catch(Exception ignored) {}
+        try {
+            mConnection.close();
+        } finally {
+            mConnection = null;
+        }
+
+    }
+
+    protected abstract void closeInt();
 
     @Override
     public int read(final byte[] dest, final int timeoutMillis) throws IOException {

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/Cp21xxSerialDriver.java

@@ -166,26 +166,13 @@ public class Cp21xxSerialDriver implements UsbSerialDriver {
         }
 
         @Override
-        public void close() throws IOException {
+        public void closeInt() {
-            if (mConnection == null) {
-                throw new IOException("Already closed");
-            }
-            synchronized (this) {
-                if(mUsbRequest != null) {
-                    mUsbRequest.cancel();
-                }
-            }
             try {
                 setConfigSingle(SILABSER_IFC_ENABLE_REQUEST_CODE, UART_DISABLE);
             } catch (Exception ignored) {}
             try {
                 mConnection.releaseInterface(mDevice.getInterface(mPortNumber));
             } catch(Exception ignored) {}
-            try {
-                mConnection.close();
-            } finally {
-                mConnection = null;
-            }
         }
 
         private void setBaudRate(int baudRate) throws IOException {

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/FtdiSerialDriver.java

@@ -266,18 +266,10 @@ public class FtdiSerialDriver implements UsbSerialDriver {
         }
 
         @Override
-        public void close() throws IOException {
+        public void closeInt() {
-            if (mConnection == null) {
-                throw new IOException("Already closed");
-            }
             try {
                 mConnection.releaseInterface(mDevice.getInterface(mPortNumber));
             } catch(Exception ignored) {}
-            try {
-                mConnection.close();
-            } finally {
-                mConnection = null;
-            }
         }
 
         private int setBaudRate(int baudRate) throws IOException {

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/ProlificSerialDriver.java

@@ -338,10 +338,7 @@ public class ProlificSerialDriver implements UsbSerialDriver {
         }
 
         @Override
-        public void close() throws IOException {
+        public void closeInt() {
-            if (mConnection == null) {
-                throw new IOException("Already closed");
-            }
             try {
                 mStopReadStatusThread = true;
                 synchronized (mReadStatusThreadLock) {
@@ -354,16 +351,10 @@ public class ProlificSerialDriver implements UsbSerialDriver {
                     }
                 }
                 resetDevice();
-            } finally {
+            } catch(Exception ignored) {}
             try {
                 mConnection.releaseInterface(mDevice.getInterface(0));
             } catch(Exception ignored) {}
-                try {
-                    mConnection.close();
-                } finally {
-                    mConnection = null;
-                }
-            }
         }
 
         @Override