usb-serial-for-android: Implement timeout-handling

Since the Android USB stack and subsequently the usb-serial-for-android
driver have problems with read-timeouts, the read-timeout is now
implemented in AndroidSerial.java. Also, DC_STATUS_TIMEOUT is returned
if there are less bytes returned than expected.

Different chipsets seem to behave differently with
usb-serial-for-android. On CP210x the read blocks until there is some
data here, but on FTDI the chip seems to return whatever is currently in
the buffer (so 0 bytes if the buffer is empty). This different behaviour
should be mitigated by the changes by this commit.

Signed-off-by: Christof Arnosti <charno@charno.ch>

2 files changed, 13 insertions, 5 deletions

diff --git a/android-mobile/src/org/subsurfacedivelog/mobile/AndroidSerial.java b/android-mobile/src/org/subsurfacedivelog/mobile/AndroidSerial.java
index 59b8dc9e9..1193b0ceb 100644
--- a/android-mobile/src/org/subsurfacedivelog/mobile/AndroidSerial.java
+++ b/android-mobile/src/org/subsurfacedivelog/mobile/AndroidSerial.java
@@ -19,6 +19,7 @@ import java.util.Queue;
 import java.util.List;
 import java.util.LinkedList;
 import java.lang.Math;
+import java.util.Date;
 
 public class AndroidSerial {
 
@@ -221,17 +222,20 @@ public class AndroidSerial {
 			Log.d(TAG, "read length: " + data.length);
 
 			int toReadFromHwLength = data.length - readBuffer.size();
-
 			int arraylength = (toReadFromHwLength % 64) != 0 ? toReadFromHwLength + (64 - (toReadFromHwLength % 64)): toReadFromHwLength; // use blocks of 64 for reading
 
-			// When we don't have enough in the buffer, try to read from HW
-			if (toReadFromHwLength > 0) {
+			long startTime =  (new Date()).getTime();
+
+			// while we don't have enough in the buffer, try to read from HW until there is enough or timeout is reached.
+			while (toReadFromHwLength > 0 && (startTime + timeout > (new Date()).getTime() || timeout == 0)) {
 				// Read and append to buffer
 				byte[] readFromHwData = new byte[arraylength];
-				int actuallyReadFromHwLength = usbSerialPort.read(readFromHwData, 0); // With this it works... But the timeout is ignored! Fix this!
+				int actuallyReadFromHwLength = usbSerialPort.read(readFromHwData, 0); // This behaves differently on different chipsets. CP210x blocks, FTDI seems to return instantly.
 				for (int i = 0; i < actuallyReadFromHwLength; i++ ) {
 					readBuffer.add(readFromHwData[i]);
 				}
+				toReadFromHwLength = data.length - readBuffer.size();
+				arraylength = (toReadFromHwLength % 64) != 0 ? toReadFromHwLength + (64 - (toReadFromHwLength % 64)): toReadFromHwLength; // use blocks of 64 for reading
 			}
 
 			//Log.d(TAG, "read buffer: " + printQueue(readBuffer));
diff --git a/core/serial_usb_android.cpp b/core/serial_usb_android.cpp
index a5db132ae..8f53c56bb 100644
--- a/core/serial_usb_android.cpp
+++ b/core/serial_usb_android.cpp
@@ -141,7 +141,11 @@ static dc_status_t serial_usb_android_read(void *io, void *data, size_t size, si
 	env->GetByteArrayRegion(array, 0, retval, (jbyte *) data);
 	env->DeleteLocalRef(array);
 	TRACE (device->context, "%s: actual read size: %i", __FUNCTION__, retval);
-	return DC_STATUS_SUCCESS;
+
+	if (retval < size)
+		return DC_STATUS_TIMEOUT;
+	else
+		return DC_STATUS_SUCCESS;
 }