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package it.unimi.dsi.fastutil.io;

/*		 
 * Copyright (C) 2005-2015 Sebastiano Vigna
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License. 
 */

import it.unimi.dsi.fastutil.bytes.ByteArrays;

import java.io.IOException;

/** Simple, fast byte-array output stream that exposes the backing array.
 *
 * {@link java.io.ByteArrayOutputStream} is nice, but to get its content you
 * must generate each time a new object. This doesn't happen here.
 *
 * This class will automatically enlarge the backing array, doubling its
 * size whenever new space is needed. The {@link #reset()} method will
 * mark the content as empty, but will not decrease the capacity: use 
 * {@link #trim()} for that purpose.
 *
 * @author Sebastiano Vigna
 */

public class FastByteArrayOutputStream extends MeasurableOutputStream implements RepositionableStream {

	/** The array backing the output stream. */
	public final static int DEFAULT_INITIAL_CAPACITY = 16;

	/** The array backing the output stream. */
	public byte[] array;

	/** The number of valid bytes in {@link #array}. */
	public int length;

	/** The current writing position. */
	private int position;

	/** Creates a new array output stream with an initial capacity of {@link #DEFAULT_INITIAL_CAPACITY} bytes. */
	public FastByteArrayOutputStream() {
		this( DEFAULT_INITIAL_CAPACITY );
	}

	/** Creates a new array output stream with a given initial capacity.
	 *
	 * @param initialCapacity the initial length of the backing array.
	 */
	public FastByteArrayOutputStream( final int initialCapacity ) {
		array = new byte[ initialCapacity ];
	}

	/** Creates a new array output stream wrapping a given byte array.
	 *
	 * @param a the byte array to wrap.
	 */
	public FastByteArrayOutputStream( final byte[] a ) {
		array = a;
	}

	/** Marks this array output stream as empty. */
	public void reset() {
		length = 0;
		position = 0;
	}

	/** Ensures that the length of the backing array is equal to {@link #length}. */
	public void trim() {
		array = ByteArrays.trim( array, length );
	}

	public void write( final int b ) {
		if ( position >= array.length ) array = ByteArrays.grow( array, position + 1, length );
		array[ position++ ] = (byte)b;
		if ( length < position ) length = position;
	}

	public void write( final byte[] b, final int off, final int len ) throws IOException {
		ByteArrays.ensureOffsetLength( b, off, len );
		if ( position + len > array.length ) array = ByteArrays.grow( array, position + len, position );
		System.arraycopy( b, off, array, position, len );
		if ( position + len > length ) length = position += len;
	}

	public void position( long newPosition ) {
		if ( position > Integer.MAX_VALUE ) throw new IllegalArgumentException( "Position too large: " + newPosition );
		position = (int)newPosition;
	}

	public long position() {
		return position;
	}

	@Override
	public long length() throws IOException {
		return length;
	}
}