Fix UsbSerialTransport.read() to throw IOException on error

android/app/src/main/java/com/eddy/atomrelay/UsbSerialTransport.kt

@@ -0,0 +1,41 @@
+package com.eddy.atomrelay
+
+import android.hardware.usb.UsbConstants
+import android.hardware.usb.UsbDeviceConnection
+import android.hardware.usb.UsbEndpoint
+import org.dkaukov.esp32.io.SerialTransport
+import java.io.IOException
+
+class UsbSerialTransport(
+    private val connection: UsbDeviceConnection,
+    private val epOut: UsbEndpoint,
+    private val epIn: UsbEndpoint
+) : SerialTransport {
+
+    override fun read(buffer: ByteArray, length: Int): Int {
+        val n = connection.bulkTransfer(epIn, buffer, length, 5000)
+        if (n < 0) throw IOException("USB read failed")
+        return n
+    }
+
+    override fun write(buffer: ByteArray, length: Int) {
+        val n = connection.bulkTransfer(epOut, buffer, length, 5000)
+        if (n < 0) throw IOException("USB write failed")
+    }
+
+    override fun setControlLines(dtr: Boolean, rts: Boolean) {
+        connection.controlTransfer(
+            UsbConstants.USB_DIR_OUT or UsbConstants.USB_TYPE_CLASS or 0x01,
+            0x22,
+            (if (dtr) 0x01 else 0x00) or (if (rts) 0x02 else 0x00),
+            0,
+            null,
+            0,
+            1000
+        )
+    }
+
+    override fun readBufferSize(): Int {
+        return epIn.maxPacketSize.coerceAtLeast(64)
+    }
+}