01. Refactored SerialInputOutputManager (#615)

Used separate threads for reading and writing, enhancing concurrency and performance.

Note: before was possible to start `SerialInputOutputManager` with `Executors.newSingleThreadExecutor().submit(ioManager)`. Now you have to use `ioManager.start()`

Author: dkaukov

usbSerialForAndroid/build.gradle

@@ -34,9 +34,10 @@ dependencies {
     implementation "androidx.annotation:annotation:1.8.0"
     testImplementation 'junit:junit:4.13.2'
     testImplementation 'org.mockito:mockito-core:5.12.0'
+    androidTestImplementation 'androidx.appcompat:appcompat:1.6.1'
     androidTestImplementation 'androidx.test:core:1.5.0'
     androidTestImplementation 'androidx.test:runner:1.5.2'
-    androidTestImplementation 'commons-net:commons-net:3.10.0'
+    androidTestImplementation 'commons-net:commons-net:3.9.0' // later version fails on old Android devices with missing java.time.Duration class
     androidTestImplementation 'org.apache.commons:commons-lang3:3.14.0'
 }
 

usbSerialForAndroid/src/androidTest/java/com/hoho/android/usbserial/DeviceTest.java

@@ -1425,19 +1425,16 @@ public void IoManager() throws Exception {
         usb.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         telnet.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         usb.ioManager.setThreadPriority(Process.THREAD_PRIORITY_DEFAULT);
+        assertEquals(SerialInputOutputManager.State.STOPPED, usb.ioManager.getState());
         usb.ioManager.start();
         usb.waitForIoManagerStarted();
-        assertTrue("iomanager thread", usb.hasIoManagerThread());
+        assertEquals(SerialInputOutputManager.State.RUNNING, usb.ioManager.getState());
+        assertTrue("iomanager thread", usb.hasIoManagerThreads());
         try {
             usb.ioManager.start();
             fail("already running error expected");
         } catch (IllegalStateException ignored) {
         }
-        try {
-            usb.ioManager.run();
-            fail("already running error expected");
-        } catch (IllegalStateException ignored) {
-        }
         try {
             usb.ioManager.setThreadPriority(Process.THREAD_PRIORITY_LOWEST);
             fail("setThreadPriority IllegalStateException expected");
@@ -1462,23 +1459,12 @@ public void IoManager() throws Exception {
         telnet.write(new byte[1]); // now uses 8 byte buffer
         usb.read(3);
 
-        // writebuffer resize
+        // small writebuffer
         try {
             usb.ioManager.writeAsync(new byte[8192]);
             fail("expected BufferOverflowException");
         } catch (BufferOverflowException ignored) {}
 
-        usb.ioManager.setWriteBufferSize(16);
-        usb.ioManager.writeAsync("1234567890AB".getBytes());
-        try {
-            usb.ioManager.setWriteBufferSize(8);
-            fail("expected BufferOverflowException");
-        } catch (BufferOverflowException ignored) {}
-        usb.ioManager.setWriteBufferSize(24); // pending date copied to new buffer
-        telnet.write("a".getBytes());
-        assertThat(usb.read(1), equalTo("a".getBytes()));
-        assertThat(telnet.read(12), equalTo("1234567890AB".getBytes()));
-
         // small readbuffer
         usb.ioManager.setReadBufferSize(8);
         Log.d(TAG, "setReadBufferSize(8)");
@@ -1490,74 +1476,31 @@ public void IoManager() throws Exception {
         telnet.write("d".getBytes());
         assertThat(usb.read(1), equalTo("d".getBytes()));
 
+        SerialInputOutputManager ioManager = usb.ioManager;
+        assertEquals(SerialInputOutputManager.State.RUNNING, usb.ioManager.getState());
         usb.close();
-        for (int i = 0; i < 100 && usb.hasIoManagerThread(); i++) {
+        for (int i = 0; i < 100 && usb.hasIoManagerThreads(); i++) {
             Thread.sleep(1);
         }
-        assertFalse("iomanager thread", usb.hasIoManagerThread());
+        assertFalse("iomanager threads", usb.hasIoManagerThreads());
+        assertNull(usb.ioManager);
+        assertEquals(SerialInputOutputManager.State.STOPPED, ioManager.getState());
         SerialInputOutputManager.DEBUG = false;
-
-        // legacy start
-        usb.open(EnumSet.of(UsbWrapper.OpenCloseFlags.NO_IOMANAGER_START)); // creates new IoManager
-        usb.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
-        telnet.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
-        usb.ioManager.setThreadPriority(Process.THREAD_PRIORITY_DEFAULT);
-        Executors.newSingleThreadExecutor().submit(usb.ioManager);
-        usb.waitForIoManagerStarted();
-        try {
-            usb.ioManager.start();
-            fail("already running error expected");
-        } catch (IllegalStateException ignored) {
-        }
     }
 
     @Test
     public void writeAsync() throws Exception {
         byte[] data, buf = new byte[]{1};
 
-        // w/o timeout: write delayed until something is read
+        // write immediately, without waiting for read
         usb.open();
         usb.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         telnet.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         usb.ioManager.writeAsync(buf);
         usb.ioManager.writeAsync(buf);
-        data = telnet.read(1);
-        assertEquals(0, data.length);
-        telnet.write(buf);
-        data = usb.read(1);
-        assertEquals(1, data.length);
         data = telnet.read(2);
         assertEquals(2, data.length);
         usb.close();
-
-        // with timeout: write after timeout
-        usb.open(EnumSet.of(UsbWrapper.OpenCloseFlags.NO_IOMANAGER_START));
-        usb.ioManager.setReadTimeout(100);
-        usb.ioManager.start();
-        usb.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
-        telnet.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
-        usb.ioManager.writeAsync(buf);
-        usb.ioManager.writeAsync(buf);
-        data = telnet.read(2);
-        assertEquals(2, data.length);
-        usb.ioManager.setReadTimeout(200);
-
-        // with internal SerialTimeoutException
-        TestBuffer tbuf = new TestBuffer(usb.writeBufferSize + 2*usb.writePacketSize);
-        byte[] pbuf1 = new byte[tbuf.buf.length - 4];
-        byte[] pbuf2 = new byte[1];
-        System.arraycopy(tbuf.buf, 0,pbuf1, 0, pbuf1.length);
-        usb.ioManager.setWriteTimeout(20); // tbuf len >= 128, needs 133msec @ 9600 baud
-        usb.setParameters(9600, 8, 1, UsbSerialPort.PARITY_NONE);
-        telnet.setParameters(9600, 8, 1, UsbSerialPort.PARITY_NONE);
-        usb.ioManager.writeAsync(pbuf1);
-        for(int i = pbuf1.length; i < tbuf.buf.length; i++) {
-            Thread.sleep(20);
-            pbuf2[0] = tbuf.buf[i];
-            usb.ioManager.writeAsync(pbuf2);
-        }
-        while(!tbuf.testRead(telnet.read(-1)))
-            ;
     }
 
     @Test

usbSerialForAndroid/src/androidTest/java/com/hoho/android/usbserial/util/UsbWrapper.java

@@ -33,6 +33,8 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 
+import androidx.core.content.ContextCompat;
+
 public class UsbWrapper implements SerialInputOutputManager.Listener {
 
     public final static int     USB_READ_WAIT = 500;
@@ -92,7 +94,7 @@ public void onReceive(Context context, Intent intent) {
             intent.setPackage(context.getPackageName());
             PendingIntent permissionIntent = PendingIntent.getBroadcast(context, 0, intent, flags);
             IntentFilter filter = new IntentFilter("com.android.example.USB_PERMISSION");
-            context.registerReceiver(usbReceiver, filter, Context.RECEIVER_NOT_EXPORTED);
+            ContextCompat.registerReceiver(context, usbReceiver, filter, Context.RECEIVER_NOT_EXPORTED);
             usbManager.requestPermission(serialDriver.getDevice(), permissionIntent);
             for(int i=0; i<5000; i++) {
                 if(granted[0] != null) break;
@@ -256,12 +258,15 @@ public void waitForIoManagerStarted() throws IOException {
         throw new IOException("IoManager not started");
     }
 
-    public boolean hasIoManagerThread() {
+    public boolean hasIoManagerThreads() {
+        int c = 0;
         for (Thread thread : Thread.getAllStackTraces().keySet()) {
-            if (thread.getName().equals(SerialInputOutputManager.class.getSimpleName()))
-                return true;
+            if (thread.getName().equals(SerialInputOutputManager.class.getSimpleName() + "_read"))
+                c += 1;
+            if (thread.getName().equals(SerialInputOutputManager.class.getSimpleName() + "_write"))
+                c += 1;
         }
-        return false;
+        return c == 2;
     }
 
     // wait full time