Workaround for meiligao protocol (fix #130)

1 files changed, 50 insertions, 0 deletions

diff --git a/src/org/traccar/protocol/MeiligaoFrameDecoder.java b/src/org/traccar/protocol/MeiligaoFrameDecoder.java
new file mode 100644
index 000000000..ad1db6c89
--- /dev/null
+++ b/src/org/traccar/protocol/MeiligaoFrameDecoder.java
@@ -0,0 +1,50 @@
+/*
+ * Copyright 2013 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.protocol;
+
+import org.jboss.netty.buffer.ChannelBuffer;
+import org.jboss.netty.channel.Channel;
+import org.jboss.netty.channel.ChannelHandlerContext;
+import org.jboss.netty.handler.codec.frame.FrameDecoder;
+
+public class MeiligaoFrameDecoder extends FrameDecoder {
+    
+    private static final int MESSAGE_HEADER = 4;
+
+    @Override
+    protected Object decode(
+            ChannelHandlerContext ctx,
+            Channel channel,
+            ChannelBuffer buf) throws Exception {
+        
+        // Strip not '$' (0x24) bytes from the beginning
+        while (buf.readable() && buf.getUnsignedByte(buf.readerIndex()) != 0x24) {
+            buf.readByte();
+        }
+        
+        // Check length and return buffer
+        if (buf.readableBytes() >= MESSAGE_HEADER) {
+            int length = buf.getUnsignedShort(buf.readerIndex() + 2);
+            if (buf.readableBytes() >= length) {
+                buf.skipBytes(MESSAGE_HEADER);
+                return buf.readBytes(length - MESSAGE_HEADER);
+            }
+        }
+
+        return null;
+    }
+
+}