1 files changed, 119 insertions, 0 deletions
diff --git a/src/org/traccar/protocol/NavisFrameDecoder.java b/src/org/traccar/protocol/NavisFrameDecoder.java
new file mode 100644
index 000000000..0146243cd
--- /dev/null
+++ b/src/org/traccar/protocol/NavisFrameDecoder.java
@@ -0,0 +1,119 @@
+/*
+ * Copyright 2019 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 io.netty.handler.codec.TooLongFrameException;
+import java.nio.charset.StandardCharsets;
+import org.traccar.BaseFrameDecoder;
+import org.traccar.BasePipelineFactory;
+
+public class NavisFrameDecoder extends BaseFrameDecoder {
+
+    private int flexDataSize; // bytes
+
+    private static final int NTCB_HEADER_LENGTH = 16;
+    private static final int NTCB_LENGTH_OFFSET = 12;
+    private static final int FLEX_HEADER_LENGTH = 2;
+    private static final int MAX_FRAME_LENGTH = 65551;
+
+    @Override
+    protected Object decode(
+            ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception {
+
+        // Check minimum length
+        if (buf.readableBytes() < 1) {
+            return null;
+        }
+
+        if (buf.readableBytes() > MAX_FRAME_LENGTH) {
+            throw new TooLongFrameException();
+        }
+
+        if (buf.getByte(buf.readerIndex()) == 0x7F) {
+            // FLEX keep alive frame
+            return buf.readRetainedSlice(1);
+        }
+
+        if (ctx != null) {
+            NavisProtocolDecoder protocolDecoder =
+                    BasePipelineFactory.getHandler(ctx.pipeline(), NavisProtocolDecoder.class);
+            if (protocolDecoder != null) {
+                flexDataSize = protocolDecoder.getFlexDataSize();
+            }
+        }
+
+        if (flexDataSize > 0) {
+            // FLEX frame
+            if (buf.readableBytes() > FLEX_HEADER_LENGTH) {
+                int length = 0;
+                String type = buf.toString(buf.readerIndex(), 2, StandardCharsets.US_ASCII);
+                switch (type) {
+                    // FLEX 1.0
+                    case "~A":
+                        length = flexDataSize  * buf.getByte(buf.readerIndex() + FLEX_HEADER_LENGTH) + 1 + 1;
+                        break;
+                    case "~T":
+                        length = flexDataSize + 4 + 1;
+                        break;
+                    case "~C":
+                        length = flexDataSize + 1;
+                        break;
+                    // FLEX 2.0 (Extra packages)
+                    case "~E":
+                        length++;
+                        for (int i = 0; i < buf.getByte(buf.readerIndex() + FLEX_HEADER_LENGTH); i++) {
+                            if (buf.readableBytes() > FLEX_HEADER_LENGTH + length + 1) {
+                                length += buf.getUnsignedShort(length + FLEX_HEADER_LENGTH) + 2;
+                            } else {
+                                return null;
+                            }
+                        }
+                        length++;
+                        break;
+                    case "~X":
+                        length = buf.getUnsignedShortLE(buf.readerIndex() + FLEX_HEADER_LENGTH) + 4 + 1;
+                        break;
+                    default:
+                        return null;
+                }
+
+                if (buf.readableBytes() >= FLEX_HEADER_LENGTH + length) {
+                    return buf.readRetainedSlice(buf.readableBytes());
+                }
+            }
+        } else {
+            // NTCB frame
+            if (buf.readableBytes() < NTCB_HEADER_LENGTH) {
+                return null;
+            }
+
+            int length = buf.getUnsignedShortLE(buf.readerIndex() + NTCB_LENGTH_OFFSET);
+            if (buf.readableBytes() >= NTCB_HEADER_LENGTH + length) {
+                return buf.readRetainedSlice(NTCB_HEADER_LENGTH + length);
+            }
+        }
+
+        return null;
+    }
+
+    public void setFlexDataSize(int flexDataSize) {
+        this.flexDataSize = flexDataSize;
+    }
+
+}