Add OutPacket interface and ByteBuf implementation

Replacement for LittleEndianWriter, GenericLittleEndianWriter,
and MaplePacketLittleEndianWriter.

src/main/java/net/packet/ByteBufOutPacket.java

@@ -1,11 +1,88 @@
 package net.packet;
 
 import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
+import net.jcip.annotations.NotThreadSafe;
+import net.opcodes.SendOpcode;
 
+import java.awt.*;
+
+@NotThreadSafe
 public class ByteBufOutPacket implements OutPacket {
     private final ByteBuf byteBuf;
 
-    public ByteBufOutPacket(ByteBuf byteBuf) {
+    public ByteBufOutPacket(SendOpcode op) {
+        ByteBuf byteBuf = Unpooled.buffer();
+        byteBuf.writeShortLE((short) op.getValue());
         this.byteBuf = byteBuf;
     }
+
+    public ByteBufOutPacket(SendOpcode op, int initialCapacity) {
+        ByteBuf byteBuf = Unpooled.buffer(initialCapacity);
+        byteBuf.writeShortLE((short) op.getValue());
+        this.byteBuf = byteBuf;
+    }
+
+    @Override
+    public short getHeader() {
+        return byteBuf.getShortLE(0);
+    }
+
+    @Override
+    public byte[] getBytes() {
+        // TODO implement
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public void writeByte(byte value) {
+        byteBuf.writeByte(value);
+    }
+
+    @Override
+    public void writeByte(int value) {
+        writeByte((byte) value);
+    }
+
+    @Override
+    public void writeBytes(byte[] value) {
+        byteBuf.writeBytes(value);
+    }
+
+    @Override
+    public void writeShort(short value) {
+        byteBuf.writeShortLE(value);
+    }
+
+    @Override
+    public void writeInt(int value) {
+        byteBuf.writeIntLE(value);
+    }
+
+    @Override
+    public void writeLong(long value) {
+        byteBuf.writeLongLE(value);
+    }
+
+    @Override
+    public void writeBoolean(boolean value) {
+        byteBuf.writeByte(value ? 1 : 0);
+    }
+
+    @Override
+    public void writeString(String value) {
+        writeShort((short) value.length());
+        writeBytes(value.getBytes(STRING_CHARSET));
+    }
+
+    @Override
+    public void writePoint(Point value) {
+        writeShort((short) value.getX());
+        writeShort((short) value.getY());
+    }
+
+    @Override
+    public void skip(int bytesToSkip) {
+        writeBytes(new byte[bytesToSkip]);
+    }
 }