From 2204c9830058fe33a4bf426636468a9ec0749a83 Mon Sep 17 00:00:00 2001
From: Anton Tananaev <anton.tananaev@gmail.com>
Date: Mon, 27 Sep 2021 12:27:53 -0700
Subject: Add custom frame decoder

---
 .../traccar/protocol/NavtelecomFrameDecoder.java   | 75 ++++++++++++++++++++++
 .../org/traccar/protocol/NavtelecomProtocol.java   |  5 +-
 .../protocol/NavtelecomProtocolDecoder.java        |  6 +-
 3 files changed, 81 insertions(+), 5 deletions(-)
 create mode 100644 src/main/java/org/traccar/protocol/NavtelecomFrameDecoder.java

(limited to 'src/main/java/org/traccar')

diff --git a/src/main/java/org/traccar/protocol/NavtelecomFrameDecoder.java b/src/main/java/org/traccar/protocol/NavtelecomFrameDecoder.java
new file mode 100644
index 000000000..0fb82528b
--- /dev/null
+++ b/src/main/java/org/traccar/protocol/NavtelecomFrameDecoder.java
@@ -0,0 +1,75 @@
+/*
+ * Copyright 2021 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 io.netty.buffer.ByteBuf;
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelHandlerContext;
+import org.traccar.BaseFrameDecoder;
+import org.traccar.BasePipelineFactory;
+
+import java.nio.charset.StandardCharsets;
+import java.util.BitSet;
+
+public class NavtelecomFrameDecoder extends BaseFrameDecoder {
+
+    @Override
+    protected Object decode(
+            ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception {
+
+        if (buf.getByte(buf.readerIndex()) == '@') {
+
+            int length = buf.getUnsignedShortLE(12) + 12 + 2 + 2;
+            if (buf.readableBytes() >= length) {
+                return buf.readRetainedSlice(length);
+            }
+
+        } else {
+
+            NavtelecomProtocolDecoder protocolDecoder =
+                    BasePipelineFactory.getHandler(ctx.pipeline(), NavtelecomProtocolDecoder.class);
+            if (protocolDecoder == null) {
+                throw new RuntimeException("Decoder not found");
+            }
+
+            String type = buf.getCharSequence(buf.readerIndex(), 2, StandardCharsets.US_ASCII).toString();
+            BitSet bits = protocolDecoder.getBits();
+
+            if (type.equals("~A")) {
+                int count = buf.getUnsignedByte(buf.readerIndex() + 2);
+                int length = 2 + 1 + 1;
+
+                for (int i = 0; i < count; i++) {
+                    for (int j = 0; j < bits.length(); j++) {
+                        if (bits.get(j)) {
+                            length += NavtelecomProtocolDecoder.getItemLength(j + 1);
+                        }
+                    }
+                }
+
+                if (buf.readableBytes() >= length) {
+                    return buf.readRetainedSlice(length);
+                }
+            } else {
+                throw new UnsupportedOperationException("Unsupported message type: " + type);
+            }
+
+        }
+
+        return null;
+    }
+
+}
diff --git a/src/main/java/org/traccar/protocol/NavtelecomProtocol.java b/src/main/java/org/traccar/protocol/NavtelecomProtocol.java
index 24bfbf895..29ce8c41e 100644
--- a/src/main/java/org/traccar/protocol/NavtelecomProtocol.java
+++ b/src/main/java/org/traccar/protocol/NavtelecomProtocol.java
@@ -15,20 +15,17 @@
  */
 package org.traccar.protocol;
 
-import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
 import org.traccar.BaseProtocol;
 import org.traccar.PipelineBuilder;
 import org.traccar.TrackerServer;
 
-import java.nio.ByteOrder;
-
 public class NavtelecomProtocol extends BaseProtocol {
 
     public NavtelecomProtocol() {
         addServer(new TrackerServer(false, getName()) {
             @Override
             protected void addProtocolHandlers(PipelineBuilder pipeline) {
-                pipeline.addLast(new LengthFieldBasedFrameDecoder(ByteOrder.LITTLE_ENDIAN, 65535, 12, 2, 2, 0, true));
+                pipeline.addLast(new NavtelecomFrameDecoder());
                 pipeline.addLast(new NavtelecomProtocolDecoder(NavtelecomProtocol.this));
             }
         });
diff --git a/src/main/java/org/traccar/protocol/NavtelecomProtocolDecoder.java b/src/main/java/org/traccar/protocol/NavtelecomProtocolDecoder.java
index c469025c2..bdcc12c4c 100644
--- a/src/main/java/org/traccar/protocol/NavtelecomProtocolDecoder.java
+++ b/src/main/java/org/traccar/protocol/NavtelecomProtocolDecoder.java
@@ -95,7 +95,7 @@ public class NavtelecomProtocolDecoder extends BaseProtocolDecoder {
 
     private BitSet bits;
 
-    private static int getItemLength(int id) {
+    public static int getItemLength(int id) {
         Integer length = ITEM_LENGTH_MAP.get(id);
         if (length == null) {
             throw new IllegalArgumentException(String.format("Unknown item: %d", id));
@@ -103,6 +103,10 @@ public class NavtelecomProtocolDecoder extends BaseProtocolDecoder {
         return length;
     }
 
+    public BitSet getBits() {
+        return bits;
+    }
+
     private void sendResponse(
             Channel channel, SocketAddress remoteAddress, int receiver, int sender, ByteBuf content) {
         if (channel != null) {
-- 
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