Added boat location, and race start messages to the mock data interface

- Added proper support for signed and unsigned types. This includes automatic conversion to the correct data type (long to int, short, or byte).

- Moved code related to adding values into the byte buffer into the abstract Message class

Tags: #story[29]

src/main/java/seng302/server/messages/Message.java

@@ -1,21 +1,27 @@
 package seng302.server.messages;
 
 import java.io.DataOutputStream;
+import java.nio.ByteBuffer;
+import java.util.zip.CRC32;
 
 public abstract class Message {
-    Header header;
+    private final int CRC_SIZE = 4;
+    private Header header;
+    private ByteBuffer buffer;
+    private int bufferPosition;
+    private CRC32 crc;
 
     /**
      * @param header Set the header for this message
      */
-    public void setHeader(Header header){
+    void setHeader(Header header){
         this.header = header;
     }
 
     /**
      * @return the header specified for this message
      */
-    public Header getHeader(){
+    Header getHeader(){
         return header;
     }
 
@@ -28,4 +34,124 @@ public abstract class Message {
      * Send the message as through the outputStream
      */
     public abstract void send(DataOutputStream outputStream);
+
+    /**
+     * Allocate byte buffer to correct size
+     */
+    void allocateBuffer(){
+        buffer = ByteBuffer.allocate(Header.getSize() + getSize() + CRC_SIZE);
+        bufferPosition = 0;
+    }
+
+    /**
+     * Write the set header to the byte buffer
+     */
+    void writeHeaderToBuffer(){
+        buffer.put(getHeader().getByteBuffer());
+        bufferPosition += Header.getSize();
+        buffer.position(bufferPosition);
+    }
+
+    /**
+     * Move the buffer position by n bytes
+     * @param size Number of bytes to move the buffer by
+     */
+    private void moveBufferPositionBy(int size){
+        bufferPosition += size;
+        buffer.position(bufferPosition);
+    }
+
+    /**
+     * Put an unsigned byte in the buffer
+     */
+    void putUnsignedByte(byte b){
+        buffer.put(ByteBuffer.allocate(1).put((byte) (b & 0xff)).array());
+        moveBufferPositionBy(1);
+    }
+
+    /**
+     * Put an signed byte in the buffer
+     */
+    void putByte(byte b){
+        buffer.put(ByteBuffer.allocate(1).put(b).array());
+        moveBufferPositionBy(1);
+    }
+
+    /**
+     * Place an unsigned integer of the specified length in the buffer
+     * @param val The integer value to add (Note: This must be long due to java not supporting unsigned integers)
+     * @param size The size of the int to be added to the buffer
+     */
+    void putUnsignedInt(long val, int size){
+        if (size <= 1){
+            putUnsignedByte((byte) val);
+
+        }
+        else if (size < 4){
+            // Use short
+            buffer.put(ByteBuffer.allocate(size).putShort((short) (val & 0xffff)).array());
+            moveBufferPositionBy(size);
+        }
+        else{
+            // Use int
+            buffer.put(ByteBuffer.allocate(size).putInt((int) (val & 0xffffffffL)).array());
+            moveBufferPositionBy(size);
+        }
+    }
+
+    /**
+     * Put a signed int of a specified length in the buffer
+     * @param val The integer value to add
+     * @param size The size of the integer to be added to the buffer
+     */
+    void putInt(int val, int size){
+        if (size < 4){
+            buffer.put(ByteBuffer.allocate(size).putShort((short) val).array());
+        }
+        else{
+            buffer.put(ByteBuffer.allocate(size).putInt((short) val).array());
+        }
+        moveBufferPositionBy(size);
+    }
+
+    /**
+     * Write an array of bytes to the buffer
+     * @param bytes to write
+     */
+    void putBytes(byte[] bytes){
+        buffer.put(bytes);
+        moveBufferPositionBy(bytes.length);
+    }
+
+    /**
+     * Write a ByteBuffer of bytes to the buffer
+     * @param bytes to write
+     * @param size number of bytes
+     */
+    void putBytes(ByteBuffer bytes, int size){
+        buffer.put(bytes);
+        moveBufferPositionBy(size);
+    }
+
+
+    /**
+     * Calculate the CRC of the buffer and append it to the end of the buffer
+     */
+    void writeCRC(){
+        crc = new CRC32();
+
+        buffer.position(0);
+        crc.update(buffer.array());
+        buffer.position(bufferPosition);
+
+        putInt((int) crc.getValue(), CRC_SIZE);
+    }
+
+    /**
+     * @return The current buffer
+     */
+    public ByteBuffer getBuffer(){
+        return buffer;
+    }
+
 }