1 files changed, 40 insertions, 0 deletions
diff --git a/src/org/traccar/helper/Crc.java b/src/org/traccar/helper/Crc.java
new file mode 100644
index 000000000..a0ad83e72
--- /dev/null
+++ b/src/org/traccar/helper/Crc.java
@@ -0,0 +1,40 @@
+/*
+ * Copyright 2012 Anton Tananaev (anton.tananaev@gmail.com)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.traccar.helper;
+
+/**
+ * CRC functions
+ */
+public class Crc {
+
+    public static int crc16Ccitt(byte[] bytes) {
+        int crc = 0xFFFF;          // initial value
+        int polynomial = 0x1021;   // 0001 0000 0010 0001 (0, 5, 12)
+
+        for (byte b : bytes) {
+            for (int i = 0; i < 8; i++) {
+                boolean bit = ((b   >> (7-i) & 1) == 1);
+                boolean c15 = ((crc >> 15    & 1) == 1);
+                crc <<= 1;
+                if (c15 ^ bit) crc ^= polynomial;
+             }
+        }
+
+        crc &= 0xffff;
+        return crc;
+    }
+
+}