aboutsummaryrefslogtreecommitdiff
path: root/src/org/traccar/helper
diff options
context:
space:
mode:
Diffstat (limited to 'src/org/traccar/helper')
-rw-r--r--src/org/traccar/helper/Crc.java40
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;
+ }
+
+}