FastAsyncWorldEdit/src/org/jnbt/NBTInputStream.java

package org.jnbt;

/*
 * JNBT License
 * 
 * Copyright (c) 2010 Graham Edgecombe
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 *     * Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *       
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *       
 *     * Neither the name of the JNBT team nor the names of its
 *       contributors may be used to endorse or promote products derived from
 *       this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE. 
 */

import java.io.Closeable;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.zip.GZIPInputStream;

/**
 * <p>This class reads <strong>NBT</strong>, or
 * <strong>Named Binary Tag</strong> streams, and produces an object graph of
 * subclasses of the <code>Tag</code> object.</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 NBTInputStream implements Closeable {
	
	/**
	 * The data input stream.
	 */
	private final DataInputStream is;
	
	/**
	 * Creates a new <code>NBTInputStream</code>, which will source its data
	 * from the specified input stream.
	 * @param is The input stream.
	 * @throws IOException if an I/O error occurs.
	 */
	public NBTInputStream(InputStream is) throws IOException {
		this.is = new DataInputStream(new GZIPInputStream(is));
	}
	
	/**
	 * Reads an NBT tag from the stream.
	 * @return The tag that was read.
	 * @throws IOException if an I/O error occurs.
	 */
	public Tag readTag() throws IOException {
		return readTag(0);
	}
	
	/**
	 * Reads an NBT from the stream.
	 * @param depth The depth of this tag.
	 * @return The tag that was read.
	 * @throws IOException if an I/O error occurs.
	 */
	private Tag readTag(int depth) throws IOException {
		int type = is.readByte() & 0xFF;
				
		String name;
		if(type != NBTConstants.TYPE_END) {
			int nameLength = is.readShort() & 0xFFFF;
			byte[] nameBytes = new byte[nameLength];
			is.readFully(nameBytes);
			name = new String(nameBytes, NBTConstants.CHARSET);
		} else {
			name = "";
		}
		
		return readTagPayload(type, name, depth);
	}

	/**
	 * Reads the payload of a tag, given the name and type.
	 * @param type The type.
	 * @param name The name.
	 * @param depth The depth.
	 * @return The tag.
	 * @throws IOException if an I/O error occurs.
	 */
	private Tag readTagPayload(int type, String name, int depth) throws IOException {
		switch(type) {
		case NBTConstants.TYPE_END:
			if(depth == 0) {
				throw new IOException("TAG_End found without a TAG_Compound/TAG_List tag preceding it.");
			} else {
				return new EndTag();
			}
		case NBTConstants.TYPE_BYTE:
			return new ByteTag(name, is.readByte());
		case NBTConstants.TYPE_SHORT:
			return new ShortTag(name, is.readShort());
		case NBTConstants.TYPE_INT:
			return new IntTag(name, is.readInt());
		case NBTConstants.TYPE_LONG:
			return new LongTag(name, is.readLong());
		case NBTConstants.TYPE_FLOAT:
			return new FloatTag(name, is.readFloat());
		case NBTConstants.TYPE_DOUBLE:
			return new DoubleTag(name, is.readDouble());
		case NBTConstants.TYPE_BYTE_ARRAY:
			int length = is.readInt();
			byte[] bytes = new byte[length];
			is.readFully(bytes);
			return new ByteArrayTag(name, bytes);
		case NBTConstants.TYPE_STRING:
			length = is.readShort();
			bytes = new byte[length];
			is.readFully(bytes);
			return new StringTag(name, new String(bytes, NBTConstants.CHARSET));
		case NBTConstants.TYPE_LIST:
			int childType = is.readByte();
			length = is.readInt();
			
			List<Tag> tagList = new ArrayList<Tag>();
			for(int i = 0; i < length; i++) {
				Tag tag = readTagPayload(childType, "", depth + 1);
				if(tag instanceof EndTag) {
					throw new IOException("TAG_End not permitted in a list.");
				}
				tagList.add(tag);
			}
			
			return new ListTag(name, NBTUtils.getTypeClass(childType), tagList);
		case NBTConstants.TYPE_COMPOUND:
			Map<String, Tag> tagMap = new HashMap<String, Tag>();
			while(true) {
				Tag tag = readTag(depth + 1);
				if(tag instanceof EndTag) {
					break;
				} else {
					tagMap.put(tag.getName(), tag);
				}
			}
			
			return new CompoundTag(name, tagMap);
		default:
			throw new IOException("Invalid tag type: " + type + ".");
		}
	}

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

}