DemoInputBuffer.java

/*
  DemoInputBuffer.java

  (c) 2012-2014 Edward Swartz

  All rights reserved. This program and the accompanying materials
  are made available under the terms of the Eclipse Public License v1.0
  which accompanies this distribution, and is available at
  http://www.eclipse.org/legal/epl-v10.html
 */
package v9t9.engine.demos.format;

import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;

import v9t9.common.demos.DemoFormat;
import v9t9.engine.demos.stream.BaseDemoInputBuffer;

/**
 * @author ejs
 *
 */
public class DemoInputBuffer extends BaseDemoInputBuffer {
	private byte[] buffer;
	private int length;
	private int index;
	private final int code;
	
	class Utf8InputStream extends InputStream {

		@Override
		public int read() throws IOException {
			if (index >= length)
				return -1;
			return buffer[index++] & 0xff;
		}
		
	}
	
	private Utf8InputStream utf8Is = new Utf8InputStream();
	
	public DemoInputBuffer(InputStream is, 
			int code,
			String identifier)  {
		super(is, identifier);
		this.code = code;
	}
	
	public String getIdentifier() {
		return label;
	}

	public int getCode() {
		return code;
	}
	

	@Override
	public void refill() throws IOException {
		length = DemoFormat.readVariableLengthNumber(is);
		
		if (buffer == null || length > buffer.length)
			buffer = new byte[length];
		
		int read = is.read(buffer, 0, length);
		if (read != length)
			throw newBufferException("short read of " + read + ", expected " + length);
		
		index = 0;
	}



	/* (non-Javadoc)
	 * @see v9t9.engine.demos.stream.IDemoInputBuffer#getEffectivePos()
	 */
	@Override
	public long getEffectivePos() {
		return startPos + index;
	}

	@Override
	public boolean isAvailable() {
		return index < length;
	}

	@Override
	public int read() throws IOException {
		if (index >= length)
			throw new EOFException();
		return buffer[index++] & 0xff; 
	}

	@Override
	public byte[] readRest() {
		byte[] data = new byte[length - index];
		System.arraycopy(buffer, index, data, 0, length - index);
		index = length;
		return data;
	}

	@Override
	public byte[] readData(int chunkLength) throws IOException {
		if (index + chunkLength > length) {
			throw newBufferException("short data block in " + label + "; expected " + chunkLength +
					", only have " + (length - index));
		}
		
		byte[] data = new byte[chunkLength];
		System.arraycopy(buffer, index, data, 0, chunkLength);
		
		index += chunkLength;
		return data;
	}
	
	public int readVar() throws IOException {
		return DemoFormat.readVariableLengthNumber(utf8Is);
	}
	
}