1 files changed, 67 insertions, 0 deletions
diff --git a/src/main/java/org/traccar/protocol/TmgFrameDecoder.java b/src/main/java/org/traccar/protocol/TmgFrameDecoder.java
new file mode 100644
index 000000000..205adaa51
--- /dev/null
+++ b/src/main/java/org/traccar/protocol/TmgFrameDecoder.java
@@ -0,0 +1,67 @@
+/*
+ * Copyright 2017 - 2018 Anton Tananaev (anton@traccar.org)
+ *
+ * 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.traccar.BaseFrameDecoder;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelHandlerContext;
+
+public class TmgFrameDecoder extends BaseFrameDecoder {
+
+    private boolean isLetter(byte c) {
+        return c >= 'a' && c <= 'z';
+    }
+
+    private int findHeader(ByteBuf buffer) {
+        int guessedIndex = buffer.indexOf(buffer.readerIndex(), buffer.writerIndex(), (byte) '$');
+        while (guessedIndex != -1 && buffer.writerIndex() - guessedIndex >= 5) {
+            if (buffer.getByte(guessedIndex + 4) == ','
+                        && isLetter(buffer.getByte(guessedIndex + 1))
+                        && isLetter(buffer.getByte(guessedIndex + 2))
+                        && isLetter(buffer.getByte(guessedIndex + 3))) {
+                return guessedIndex;
+            }
+            guessedIndex = buffer.indexOf(guessedIndex, buffer.writerIndex(), (byte) '$');
+        }
+        return -1;
+    }
+
+    @Override
+    protected Object decode(
+            ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception {
+
+        int beginIndex = findHeader(buf);
+
+        if (beginIndex >= 0) {
+
+            buf.readerIndex(beginIndex);
+
+            int endIndex = buf.indexOf(beginIndex, buf.writerIndex(), (byte) '\n');
+
+            if (endIndex >= 0) {
+                ByteBuf frame = buf.readRetainedSlice(endIndex - beginIndex);
+                buf.readByte(); // delimiter
+                return frame;
+            }
+
+        }
+
+        return null;
+    }
+
+}