MaimMim Man in the middle minetest interceptor

- prototype
- between client and server, allow to capture all exchanges and potentially change them
- created to capture server maps in laby
- first test get only MapBlock, support version serialization version 28
  - prepartion for 29 with zstd but untested.

# Conflicts:
#	fetch_dependencies.sh

java/org/artisanlogiciel/games/minetest/net/IncomingSplitBuffer.java

@@ -0,0 +1,90 @@
+package org.artisanlogiciel.games.minetest.net;
+
+import org.artisanlogiciel.games.minetest.core.PacketException;
+import org.artisanlogiciel.games.minetest.core.Serialize;
+
+import java.util.ArrayList;
+
+public class IncomingSplitBuffer {
+
+    int m_seqnum;
+    int m_chunk_count;
+    int m_chunk_num;
+
+    // number of chunks
+    int m_got = 0;
+
+    NetworkPacket m_list[] = null;
+    BufferedPacket m_reassembled = null;
+
+    BufferedPacket insert(NetworkPacket networkPacket)
+            throws PacketException
+    {
+
+        byte[] buffer = networkPacket.getBuffer();
+        int length = networkPacket.getLength();
+        int offset = networkPacket.getOffset();
+
+        int type = Serialize.readU8(buffer , offset, length);
+        int seqnum = Serialize.readU16(buffer, offset + 1, length);
+        // total number of chunk
+        int chunk_count = Serialize.readU16(buffer, offset + 3, length);
+        // this chunk number
+        int chunk_num = Serialize.readU16(buffer, offset+ 5, length);
+
+        System.out.println("Split length " + length + " type " + type + " seqnum " + seqnum + " chunk_num/chunk_count " + chunk_num + "/" + chunk_count );
+
+        // move to next header
+        networkPacket.addOffset(7);
+
+        if (m_reassembled != null)
+        {
+            return m_reassembled;
+        }
+
+        if (m_list == null )
+        {
+            m_list = new NetworkPacket[chunk_count];
+        }
+
+        if ( chunk_num < chunk_count && (m_list[chunk_num] == null) )
+        {
+            m_list[chunk_num] = networkPacket;
+            m_got ++;
+        }
+        //todo seqnum
+        m_seqnum = seqnum;
+
+        // fully obtained
+        if ( m_got == chunk_count )
+        {
+            reassemble();
+        }
+
+        return m_reassembled;
+
+    }
+
+    private void reassemble()
+    {
+        // keep first header since result is a valid BufferedPacket
+        int fullLength = BufferedPacket.BASE_HEADER_SIZE;
+        for (NetworkPacket networkPacket : m_list )
+        {
+            fullLength += networkPacket.getLength() - networkPacket.getOffset();
+        }
+        byte[] reassembled = new byte[fullLength];
+        NetworkPacket first = m_list[0];
+        System.arraycopy(first.getBuffer(),0,reassembled,0,BufferedPacket.BASE_HEADER_SIZE);
+        int offset = BufferedPacket.BASE_HEADER_SIZE;
+        for (NetworkPacket networkPacket : m_list )
+        {
+            int dataLength = networkPacket.getLength() - networkPacket.getOffset();
+            System.arraycopy(networkPacket.getBuffer(), networkPacket.getOffset(),reassembled,offset,dataLength);
+            offset+=dataLength;
+        }
+        m_reassembled = new BufferedPacket(reassembled);
+
+    }
+
+}