/*
 * Copyright 2012 Takao Nakaguchi
 *
 * 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.
 */
package org.trie4j.util;

import java.io.Serializable;
import java.util.Arrays;

public class FastBitSet implements Serializable, BitSet{
	public FastBitSet() {
	}

	public FastBitSet(int bitSize){
		bytes = new byte[bitSize / 8 + 1];
	}

	@Override
	public String toString() {
		StringBuilder b = new StringBuilder();
		int n = Math.min(size, 32);
		for(int i = 0; i < n; i++){
			b.append((bytes[(i / 8)] & (0x80 >> (i % 8))) != 0 ? "1" : "0");
		}
		return b.toString();
	}

	@Override
	public int size(){
		return size;
	}

	public byte[] getBytes(){
		return bytes;
	}

	@Override
	public boolean get(int index){
		return (bytes[index / 8] & (0x80 >> (index % 8))) != 0;
	}

	public void set(int index){
		if(size <= index){
			if(index / 8 >= bytes.length){
				extend(index);
			}
			size = index + 1;
		}
		bytes[index / 8] |= 0x80 >> (index % 8);
	}

	public void unset(int index){
		if(size <= index){
			if(index / 8 >= bytes.length){
				extend(index);
			}
			size = index + 1;
		}
		bytes[index / 8] &= ~(0x80 >> (index % 8));
	}

	public void unsetIfLE(int index){
		if(size <= index){
			if(index / 8 >= bytes.length){
				extend(index);
			}
			size = index + 1;
		}
	}

	public void ensureCapacity(int index){
		if((index / 8) >= bytes.length){
			extend(index);
		}
	}

	public void trimToSize(){
		int sz = size / 8 + 1;
		if(bytes.length > sz){
			bytes = Arrays.copyOf(bytes, sz);
		}
	}

	private void extend(int index){
		bytes = Arrays.copyOf(bytes,
				Math.max(index / 8 + 1, (int)(bytes.length * 1.5))
				);
	}

	private int size;
	private byte[] bytes = {};
	private static final long serialVersionUID = -3346250300546707823L;
}