Implement GL200 frame decoder

1 files changed, 96 insertions, 0 deletions

diff --git a/src/org/traccar/protocol/Gl200FrameDecoder.java b/src/org/traccar/protocol/Gl200FrameDecoder.java
new file mode 100644
index 000000000..960c3779a
--- /dev/null
+++ b/src/org/traccar/protocol/Gl200FrameDecoder.java
@@ -0,0 +1,96 @@
+/*
+ * Copyright 2017 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.jboss.netty.buffer.ChannelBuffer;
+import org.jboss.netty.channel.Channel;
+import org.jboss.netty.channel.ChannelHandlerContext;
+import org.jboss.netty.handler.codec.frame.FrameDecoder;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
+
+public class Gl200FrameDecoder extends FrameDecoder {
+
+    private static final int MINIMUM_LENGTH = 11;
+
+    private static final Set<String> BINARY_HEADERS = new HashSet<>(
+            Arrays.asList("+RSP", "+BSP", "+EVT", "+BVT", "+INF", "+BNF", "+HBD", "+CRD", "+BRD"));
+
+    public static boolean isBinary(ChannelBuffer buf) {
+        String header = buf.toString(buf.readerIndex(), 4, StandardCharsets.US_ASCII);
+        if (header.equals("+ACK")) {
+            return buf.getByte(buf.readerIndex() + header.length()) != (byte) ':';
+        } else {
+            return BINARY_HEADERS.contains(header);
+        }
+    }
+
+    @Override
+    protected Object decode(
+            ChannelHandlerContext ctx, Channel channel, ChannelBuffer buf) throws Exception {
+
+        if (buf.readableBytes() < MINIMUM_LENGTH) {
+            return null;
+        }
+
+        if (isBinary(buf)) {
+
+            int length;
+            switch (buf.toString(buf.readerIndex(), 4, StandardCharsets.US_ASCII)) {
+                case "+ACK":
+                    length = buf.getUnsignedByte(buf.readerIndex() + 6);
+                    break;
+                case "+INF":
+                case "+BNF":
+                    length = buf.getUnsignedShort(buf.readerIndex() + 7);
+                    break;
+                case "+HBD":
+                    length = buf.getUnsignedByte(buf.readerIndex() + 5);
+                    break;
+                case "+CRD":
+                case "+BRD":
+                    length = buf.getUnsignedShort(buf.readerIndex() + 6);
+                    break;
+                default:
+                    length = buf.getUnsignedShort(buf.readerIndex() + 9);
+                    break;
+            }
+
+            if (buf.readableBytes() >= length) {
+                return buf.readBytes(length);
+            }
+
+        } else {
+
+            int endIndex = buf.indexOf(buf.readerIndex(), buf.writerIndex(), (byte) '$');
+            if (endIndex < 0) {
+                endIndex = buf.indexOf(buf.readerIndex(), buf.writerIndex(), (byte) 0);
+            }
+            if (endIndex > 0) {
+                ChannelBuffer frame = buf.readBytes(endIndex - buf.readerIndex());
+                buf.readByte(); // delimiter
+                return frame;
+            }
+
+        }
+
+        return null;
+    }
+
+}