altosdroid: protect USB read/write when connection is null

Check to see if connection is valid before attempting to read/write to
it.

Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/altosdroid/app/src/main/java/org/altusmetrum/AltosDroid/AltosUsb.java b/altosdroid/app/src/main/java/org/altusmetrum/AltosDroid/AltosUsb.java
index 35514483f026af968a6a31c13bc55f734b4a250b..ad47707d90c9706d3bba397ca384cb66dfac7974 100644 (file)
--- a/altosdroid/app/src/main/java/org/altusmetrum/AltosDroid/AltosUsb.java
+++ b/altosdroid/app/src/main/java/org/altusmetrum/AltosDroid/AltosUsb.java
@@ -210,12 +210,16 @@ public class AltosUsb extends AltosDroidLink {
        }
 
        int read(byte[] buffer, int len) {
+               if (connection == null)
+                       return 0;
                int ret = connection.bulkTransfer(in, buffer, len, -1);
                AltosDebug.debug("read(%d) = %d\n", len, ret);
                return ret;
        }
 
        int write(byte[] buffer, int len) {
+               if (connection == null)
+                       return 0;
                int ret = connection.bulkTransfer(out, buffer, len, -1);
                AltosDebug.debug("write(%d) = %d\n", len, ret);
                return ret;