Measure the size of map packets sent to every player.

MapPacketSize.java

package com.comphenix.example;

import java.io.DataOutputStream;
import java.io.IOException;
import java.util.ArrayDeque;
import java.util.Deque;

import net.minecraft.server.v1_5_R3.Packet;

import org.bukkit.Location;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.plugin.java.JavaPlugin;

import com.comphenix.protocol.Packets;
import com.comphenix.protocol.ProtocolLibrary;
import com.comphenix.protocol.events.ConnectionSide;
import com.comphenix.protocol.events.PacketAdapter;
import com.comphenix.protocol.events.PacketEvent;
import com.google.common.io.CountingOutputStream;
import com.google.common.io.NullOutputStream;

public class ExampleMod extends JavaPlugin {
    private Deque<Location> undo = new ArrayDeque<Location>();
    
    @Override
    public void onEnable() {
        ProtocolLibrary.getProtocolManager().addPacketListener(
            new PacketAdapter(this, ConnectionSide.SERVER_SIDE, Packets.Server.MAP_CHUNK, Packets.Server.MAP_CHUNK_BULK) {
                @Override
                public void onPacketSending(PacketEvent event) {
                    Packet packet = (Packet) event.getPacket().getHandle();
                    CountingOutputStream counting = new CountingOutputStream(new NullOutputStream());
                    
                    // Figure out the size of the packet
                    try {
                        packet.a(new DataOutputStream(counting));
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    
                    System.out.println("Size of " + packet + ": " + humanReadableByteCount(counting.getCount(), false));
                }
            }
        );
    }
    
    public static String humanReadableByteCount(long bytes, boolean si) {
        int unit = si ? 1000 : 1024;
        if (bytes < unit) return bytes + " B";
        int exp = (int) (Math.log(bytes) / Math.log(unit));
        String pre = (si ? "kMGTPE" : "KMGTPE").charAt(exp-1) + (si ? "" : "i");
        return String.format("%.1f %sB", bytes / Math.pow(unit, exp), pre);
    }
}