1 files changed, 81 insertions, 0 deletions
diff --git a/src/main/java/org/traccar/protocol/At2000FrameDecoder.java b/src/main/java/org/traccar/protocol/At2000FrameDecoder.java
new file mode 100644
index 000000000..5fa82a5f7
--- /dev/null
+++ b/src/main/java/org/traccar/protocol/At2000FrameDecoder.java
@@ -0,0 +1,81 @@
+/*
+ * Copyright 2016 - 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 io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelHandlerContext;
+import org.traccar.BaseFrameDecoder;
+import org.traccar.NetworkMessage;
+
+public class At2000FrameDecoder extends BaseFrameDecoder {
+
+    private static final int BLOCK_LENGTH = 16;
+    private static final int ACK_LENGTH = 496;
+
+    private boolean firstPacket = true;
+
+    private ByteBuf currentBuffer;
+    private int acknowledgedBytes;
+
+    private void sendResponse(Channel channel) {
+        if (channel != null) {
+            ByteBuf response = Unpooled.buffer(2 * BLOCK_LENGTH);
+            response.writeByte(At2000ProtocolDecoder.MSG_ACKNOWLEDGEMENT);
+            response.writeMedium(1);
+            response.writeByte(0x00); // success
+            response.writerIndex(2 * BLOCK_LENGTH);
+            channel.writeAndFlush(new NetworkMessage(response, channel.remoteAddress()));
+        }
+    }
+
+    @Override
+    protected Object decode(
+            ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception {
+
+        if (buf.readableBytes() < 5) {
+            return null;
+        }
+
+        int length;
+        if (firstPacket) {
+            firstPacket = false;
+            length = buf.getUnsignedMediumLE(buf.readerIndex() + 2);
+        } else {
+            length = buf.getUnsignedMediumLE(buf.readerIndex() + 1);
+        }
+
+        length += BLOCK_LENGTH;
+        if (length % BLOCK_LENGTH != 0) {
+            length = (length / BLOCK_LENGTH + 1) * BLOCK_LENGTH;
+        }
+
+        if ((buf.readableBytes() >= length || buf.readableBytes() % ACK_LENGTH == 0)
+                && (buf != currentBuffer || buf.readableBytes() > acknowledgedBytes)) {
+            sendResponse(channel);
+            currentBuffer = buf;
+            acknowledgedBytes = buf.readableBytes();
+        }
+
+        if (buf.readableBytes() >= length) {
+            return buf.readRetainedSlice(length);
+        }
+
+        return null;
+    }
+
+}