NBTOutputStream.java

package com.wasteofplastic.org.jnbt;

import java.io.Closeable;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.List;
import java.util.zip.GZIPOutputStream;

/**
 * <p>
 * This class writes <strong>NBT</strong>, or <strong>Named Binary Tag</strong>
 * <code>Tag</code> objects to an underlying <code>OutputStream</code>.
 * </p>
 * 
 * <p>
 * The NBT format was created by Markus Persson, and the specification may be
 * found at <a href="http://www.minecraft.net/docs/NBT.txt">
 * http://www.minecraft.net/docs/NBT.txt</a>.
 * </p>
 * 
 * @author Graham Edgecombe
 * 
 */
public final class NBTOutputStream implements Closeable {

    /**
     * The output stream.
     */
    private final DataOutputStream os;

    /**
     * Creates a new <code>NBTOutputStream</code>, which will write data to the
     * specified underlying output stream.
     * 
     * @param os
     *            The output stream.
     * @throws IOException
     *             if an I/O error occurs.
     */
    public NBTOutputStream(OutputStream os) throws IOException {
	this.os = new DataOutputStream(new GZIPOutputStream(os));
    }

    /**
     * Writes a tag.
     * 
     * @param tag
     *            The tag to write.
     * @throws IOException
     *             if an I/O error occurs.
     */
    public void writeTag(Tag tag) throws IOException {
	int type = NBTUtils.getTypeCode(tag.getClass());
	String name = tag.getName();
	byte[] nameBytes = name.getBytes(NBTConstants.CHARSET);

	os.writeByte(type);
	os.writeShort(nameBytes.length);
	os.write(nameBytes);

	if (type == NBTConstants.TYPE_END) {
	    throw new IOException("Named TAG_End not permitted.");
	}

	writeTagPayload(tag);
    }

    /**
     * Writes tag payload.
     * 
     * @param tag
     *            The tag.
     * @throws IOException
     *             if an I/O error occurs.
     */
    private void writeTagPayload(Tag tag) throws IOException {
	int type = NBTUtils.getTypeCode(tag.getClass());
	switch (type) {
	case NBTConstants.TYPE_END:
	    writeEndTagPayload((EndTag) tag);
	    break;
	case NBTConstants.TYPE_BYTE:
	    writeByteTagPayload((ByteTag) tag);
	    break;
	case NBTConstants.TYPE_SHORT:
	    writeShortTagPayload((ShortTag) tag);
	    break;
	case NBTConstants.TYPE_INT:
	    writeIntTagPayload((IntTag) tag);
	    break;
	case NBTConstants.TYPE_LONG:
	    writeLongTagPayload((LongTag) tag);
	    break;
	case NBTConstants.TYPE_FLOAT:
	    writeFloatTagPayload((FloatTag) tag);
	    break;
	case NBTConstants.TYPE_DOUBLE:
	    writeDoubleTagPayload((DoubleTag) tag);
	    break;
	case NBTConstants.TYPE_BYTE_ARRAY:
	    writeByteArrayTagPayload((ByteArrayTag) tag);
	    break;
	case NBTConstants.TYPE_STRING:
	    writeStringTagPayload((StringTag) tag);
	    break;
	case NBTConstants.TYPE_LIST:
	    writeListTagPayload((ListTag) tag);
	    break;
	case NBTConstants.TYPE_COMPOUND:
	    writeCompoundTagPayload((CompoundTag) tag);
	    break;
	default:
	    throw new IOException("Invalid tag type: " + type + ".");
	}
    }

    /**
     * Writes a <code>TAG_Byte</code> tag.
     * 
     * @param tag
     *            The tag.
     * @throws IOException
     *             if an I/O error occurs.
     */
    private void writeByteTagPayload(ByteTag tag) throws IOException {
	os.writeByte(tag.getValue());
    }

    /**
     * Writes a <code>TAG_Byte_Array</code> tag.
     * 
     * @param tag
     *            The tag.
     * @throws IOException
     *             if an I/O error occurs.
     */
    private void writeByteArrayTagPayload(ByteArrayTag tag) throws IOException {
	byte[] bytes = tag.getValue();
	os.writeInt(bytes.length);
	os.write(bytes);
    }

    /**
     * Writes a <code>TAG_Compound</code> tag.
     * 
     * @param tag
     *            The tag.
     * @throws IOException
     *             if an I/O error occurs.
     */
    private void writeCompoundTagPayload(CompoundTag tag) throws IOException {
	for (Tag childTag : tag.getValue().values()) {
	    writeTag(childTag);
	}
	os.writeByte((byte) 0); // end tag - better way?
    }

    /**
     * Writes a <code>TAG_List</code> tag.
     * 
     * @param tag
     *            The tag.
     * @throws IOException
     *             if an I/O error occurs.
     */
    private void writeListTagPayload(ListTag tag) throws IOException {
	Class<? extends Tag> clazz = tag.getType();
	List<Tag> tags = tag.getValue();
	int size = tags.size();

	os.writeByte(NBTUtils.getTypeCode(clazz));
	os.writeInt(size);
	for (int i = 0; i < size; i++) {
	    writeTagPayload(tags.get(i));
	}
    }

    /**
     * Writes a <code>TAG_String</code> tag.
     * 
     * @param tag
     *            The tag.
     * @throws IOException
     *             if an I/O error occurs.
     */
    private void writeStringTagPayload(StringTag tag) throws IOException {
	byte[] bytes = tag.getValue().getBytes(NBTConstants.CHARSET);
	os.writeShort(bytes.length);
	os.write(bytes);
    }

    /**
     * Writes a <code>TAG_Double</code> tag.
     * 
     * @param tag
     *            The tag.
     * @throws IOException
     *             if an I/O error occurs.
     */
    private void writeDoubleTagPayload(DoubleTag tag) throws IOException {
	os.writeDouble(tag.getValue());
    }

    /**
     * Writes a <code>TAG_Float</code> tag.
     * 
     * @param tag
     *            The tag.
     * @throws IOException
     *             if an I/O error occurs.
     */
    private void writeFloatTagPayload(FloatTag tag) throws IOException {
	os.writeFloat(tag.getValue());
    }

    /**
     * Writes a <code>TAG_Long</code> tag.
     * 
     * @param tag
     *            The tag.
     * @throws IOException
     *             if an I/O error occurs.
     */
    private void writeLongTagPayload(LongTag tag) throws IOException {
	os.writeLong(tag.getValue());
    }

    /**
     * Writes a <code>TAG_Int</code> tag.
     * 
     * @param tag
     *            The tag.
     * @throws IOException
     *             if an I/O error occurs.
     */
    private void writeIntTagPayload(IntTag tag) throws IOException {
	os.writeInt(tag.getValue());
    }

    /**
     * Writes a <code>TAG_Short</code> tag.
     * 
     * @param tag
     *            The tag.
     * @throws IOException
     *             if an I/O error occurs.
     */
    private void writeShortTagPayload(ShortTag tag) throws IOException {
	os.writeShort(tag.getValue());
    }

    /**
     * Writes a <code>TAG_Empty</code> tag.
     * 
     * @param tag
     *            The tag.
     * @throws IOException
     *             if an I/O error occurs.
     */
    private void writeEndTagPayload(EndTag tag) {
	/* empty */
    }

    @Override
    public void close() throws IOException {
	os.close();
    }

}