From fd5a1c5b4bccaf5354b86283eedfe9255409841f Mon Sep 17 00:00:00 2001
From: nic <nic@nclm.de>
Date: Wed, 11 May 2011 11:34:47 +0200
Subject: [PATCH] - integrating comments from code review proposals
 http://code.google.com/r/sandordornbush-patches/source/detail?r=3dfdbcf78de082edb66a8994ffb604c84945df0d

---
 .../services/sensors/SensorUtils.java         | 24 +++++++++++--------
 .../services/sensors/ZephyrMessageParser.java | 19 ++++++++++-----
 2 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/MyTracks/src/com/google/android/apps/mytracks/services/sensors/SensorUtils.java b/MyTracks/src/com/google/android/apps/mytracks/services/sensors/SensorUtils.java
index 45c2364a9..7424b727c 100644
--- a/MyTracks/src/com/google/android/apps/mytracks/services/sensors/SensorUtils.java
+++ b/MyTracks/src/com/google/android/apps/mytracks/services/sensors/SensorUtils.java
@@ -30,7 +30,7 @@ public class SensorUtils {
 
   private SensorUtils() {
   }
-
+  
   /**
    * Extract one unsigned short from a big endian byte array.
    * 
@@ -66,10 +66,10 @@ public class SensorUtils {
    * @param end the position in the byte array where the payload ends
    * @return CRC8 value
    */
-  public static int getCrc8(byte[] buffer, int start, int end) {
-    int crc = 0x0;
+  public static byte getCrc8(byte[] buffer, int start, int length) {
+    byte crc = 0x0;
 
-    for (int i = start; i < (end + 1); i++) {
+    for (int i = start; i < (start + length); i++) {
       crc = crc8PushByte(crc, buffer[i]);
     }
     return crc;
@@ -81,14 +81,18 @@ public class SensorUtils {
    * @param crc int of crc value
    * @param add the next byte to add to the CRC8 calculation
    */
-  private static int crc8PushByte(int crc, byte add) {
-    int addInt = (add & 0x000000FF);
-    crc = crc ^ addInt;
+  private static byte crc8PushByte(byte crc, byte add) {
+    crc = (byte) (crc ^ add);
+    
     for (int i = 0; i < 8; i++) {
-      if ((crc & 0x00000001) != 0x00000000) {
-        crc = (crc >> 1) ^ 0x0000008C;
+      if ((crc & 0x1) != 0x0) {
+		// we have to do the OxFF mask because the right shift is
+		// supposed to shift in a 0
+    	// as crc gets implicitly casted to a
+		// signed int by >> it may be filled with 1s
+        crc = (byte) (((crc & 0xFF) >> 1) ^ 0x8C);
       } else {
-        crc = (crc >> 1);
+        crc = (byte) ((crc & 0xFF) >> 1);
       }
     }
     return crc;
diff --git a/MyTracks/src/com/google/android/apps/mytracks/services/sensors/ZephyrMessageParser.java b/MyTracks/src/com/google/android/apps/mytracks/services/sensors/ZephyrMessageParser.java
index 0808c73ca..1b86e6822 100644
--- a/MyTracks/src/com/google/android/apps/mytracks/services/sensors/ZephyrMessageParser.java
+++ b/MyTracks/src/com/google/android/apps/mytracks/services/sensors/ZephyrMessageParser.java
@@ -27,6 +27,10 @@ import com.google.android.apps.mytracks.content.Sensor;
  */
 public class ZephyrMessageParser implements MessageParser {
 
+	public static final int ZEPHYR_HXM_BYTE_STX = 0;
+	public static final int ZEPHYR_HXM_BYTE_CRC = 58;
+	public static final int ZEPHYR_HXM_BYTE_ETX = 59;
+	
   @Override
   public Sensor.SensorDataSet parseBuffer(byte[] buffer) {
     StringBuilder sb = new StringBuilder();
@@ -36,11 +40,11 @@ public class ZephyrMessageParser implements MessageParser {
     Log.w(Constants.TAG, "Got zephyr data: " + sb);
     // Heart Rate
     Sensor.SensorData.Builder heartrate = Sensor.SensorData.newBuilder()
-        .setValue(buffer[12] & 0xFF)
+        .setValue(buffer[12])
         .setState(Sensor.SensorState.SENDING);
     // Changes Nico Laum (Power and Cadence)
     Sensor.SensorData.Builder power = Sensor.SensorData.newBuilder()
-	    .setValue(buffer[11] & 0xFF)
+	    .setValue(buffer[11])
 	    .setState(Sensor.SensorState.SENDING);
     Sensor.SensorData.Builder cadence = Sensor.SensorData.newBuilder()
 	    .setValue(SensorUtils.unsignedShortToIntLittleEndian(buffer, 56) / 16)
@@ -59,10 +63,13 @@ public class ZephyrMessageParser implements MessageParser {
 
   @Override
   public boolean isValid(byte[] buffer) {
-    // Check STX, ETX and CRC Checksum
-    return buffer[0] == 0x02
-        && buffer[59] == 0x03
-        && SensorUtils.getCrc8(buffer, 3, 57) == (int) (buffer[58] & 0xFF);
+	if (buffer.length > ZEPHYR_HXM_BYTE_ETX) {
+	  // Check STX (Start of Text), ETX (End of Text) and CRC Checksum
+	  return buffer[ZEPHYR_HXM_BYTE_STX] == 0x02
+	  && buffer[ZEPHYR_HXM_BYTE_ETX] == 0x03
+	  && SensorUtils.getCrc8(buffer, 3, 55) == buffer[ZEPHYR_HXM_BYTE_CRC];
+	} else
+		return false;
   }
 
   @Override