/*
 * Copyright (C) 2009, Google Inc.
 * Copyright (C) 2008, Marek Zawirski <marek.zawirski@gmail.com>
 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
 * Copyright (C) 2013, Robin Rosenberg
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * 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 Eclipse Foundation, Inc. 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 OWNER 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.
 */

package org.eclipse.jgit.treewalk.filter;

import org.eclipse.jgit.util.RawParseUtils;

Specialized set for byte arrays, interpreted as strings for use in Group. Most methods assume the hash is already know and therefore requires the caller to supply it beforehand. The implementation is a loose derivative of ObjectIdSubclassMap. 

The class is only intended for use by PathFilterGroup.

The arrays stored may not be changed after adding.
/**
 * Specialized set for byte arrays, interpreted as strings for use in
 * {@link PathFilterGroup.Group}. Most methods assume the hash is already know
 * and therefore requires the caller to supply it beforehand. The implementation
 * is a loose derivative of ObjectIdSubclassMap.
 * <p>
 * The class is only intended for use by PathFilterGroup.
 * <p>
 * The arrays stored may not be changed after adding.
 */
class ByteArraySet {

	private int size;

	private int grow;

	private int mask;

	private byte[][] table;

	
Create an empty set.
Params:
capacity – /**
	 * Create an empty set.
	 *
	 * @param capacity
	 */
	ByteArraySet(int capacity) {
		initTable(1 << Integer.highestOneBit((capacity * 2) - 1));
	}

	private byte[] get(byte[] toFind, int length, int hash) {
		final int msk = mask;
		int i = hash & msk;
		final byte[][] tbl = table;
		byte[] obj;

		while ((obj = tbl[i]) != null) {
			if (equals(obj, toFind, length))
				return obj;
			i = (i + 1) & msk;
		}
		return null;
	}

	private static boolean equals(byte[] storedObj, byte[] toFind, int length) {
		if (storedObj.length != length || toFind.length < length)
			return false;
		for (int i = 0; i < length; ++i) {
			if (storedObj[i] != toFind[i])
				return false;
		}
		return true;
	}

	
Returns true if this set contains the specified array.
Params:
toFind – 
           array to find.
length – 
           The number of bytes in toFind that are used
hash – 
           pre-computed hash of toFind
Returns:
true if the mapping exists for this byte array; false otherwise./**
	 * Returns true if this set contains the specified array.
	 *
	 * @param toFind
	 *            array to find.
	 * @param length
	 *            The number of bytes in toFind that are used
	 * @param hash
	 *            pre-computed hash of toFind
	 * @return true if the mapping exists for this byte array; false otherwise.
	 */
	boolean contains(byte[] toFind, int length, int hash) {
		return get(toFind, length, hash) != null;
	}

	
Store a byte array for future lookup.
 Stores newValue, but only if it does not already exist in the set. Callers can tell if the value is new by checking the return value with reference equality: 
byte[] obj = ...;
boolean wasNew = map.addIfAbsent(array, length, hash) == array;

Params:
newValue – 
           the array to store by reference if the length is the same as
           the length parameter
length – 
           The number of bytes in newValue that are used
hash – 
           pre-computed hash of toFind
Returns:
newValue if stored, or the prior value already stored and that would have been returned had the caller used get(newValue) first./**
	 * Store a byte array for future lookup.
	 * <p>
	 * Stores {@code newValue}, but only if it does not already exist in the
	 * set. Callers can tell if the value is new by checking the return value
	 * with reference equality:
	 *
	 * <pre>
	 * byte[] obj = ...;
	 * boolean wasNew = map.addIfAbsent(array, length, hash) == array;
	 * </pre>
	 *
	 * @param newValue
	 *            the array to store by reference if the length is the same as
	 *            the length parameter
	 * @param length
	 *            The number of bytes in newValue that are used
	 * @param hash
	 *            pre-computed hash of toFind
	 * @return {@code newValue} if stored, or the prior value already stored and
	 *         that would have been returned had the caller used
	 *         {@code get(newValue)} first.
	 */
	byte[] addIfAbsent(final byte[] newValue, int length, int hash) {
		final int msk = mask;
		int i = hash & msk;
		final byte[][] tbl = table;
		byte[] obj;

		while ((obj = tbl[i]) != null) {
			if (equals(obj, newValue, length))
				return obj;
			i = (i + 1) & msk;
		}

		byte[] valueToInsert = copyIfNotSameSize(newValue, length);
		if (++size == grow) {
			grow();
			insert(valueToInsert, hash);
		} else
			tbl[i] = valueToInsert;
		return valueToInsert;
	}

	private static byte[] copyIfNotSameSize(byte[] newValue, int length) {
		if (newValue.length == length)
			return newValue;
		byte[] ret = new byte[length];
		System.arraycopy(newValue, 0, ret, 0, length);
		return ret;
	}

	
Returns:
number of arrays in the set/**
	 * @return number of arrays in the set
	 */
	int size() {
		return size;
	}

	
Returns:
true if size() is 0./** @return true if {@link #size()} is 0. */
	boolean isEmpty() {
		return size == 0;
	}

	private void insert(byte[] newValue, int hash) {
		final int msk = mask;
		int j = hash & msk;
		final byte[][] tbl = table;
		while (tbl[j] != null)
			j = (j + 1) & msk;
		tbl[j] = newValue;
	}

	private Hasher hasher = new Hasher(null, 0);

	private void grow() {
		final byte[][] oldTable = table;
		final int oldSize = table.length;

		initTable(oldSize << 1);
		for (int i = 0; i < oldSize; i++) {
			final byte[] obj = oldTable[i];
			if (obj != null) {
				hasher.init(obj, obj.length);
				insert(obj, hasher.hash());
			}
		}
	}

	private void initTable(int sz) {
		if (sz < 2)
			sz = 2;
		grow = sz >> 1;
		mask = sz - 1;
		table = new byte[sz][];
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public String toString() {
		StringBuilder sb = new StringBuilder();
		sb.append('[');
		for (byte[] b : table) {
			if (b == null)
				continue;
			if (sb.length() > 1)
				sb.append(" , "); //$NON-NLS-1$
			sb.append('"');
			sb.append(RawParseUtils.decode(b));
			sb.append('"');
			sb.append('(');
			sb.append(chainlength(b));
			sb.append(')');
		}
		sb.append(']');
		return sb.toString();
	}

	private int chainlength(byte[] b) {
		Hasher h = new Hasher(b, b.length);
		int hash = h.hash();
		final int msk = mask;
		int i = hash & msk;
		final byte[][] tbl = table;
		byte[] obj;

		int n = 0;
		while ((obj = tbl[i]) != null) {
			if (equals(obj, b, b.length))
				return n;
			i = (i + 1) & msk;
			++n;
		}
		return -1;
	}

	
An incremental hash function.
/**
	 * An incremental hash function.
	 */
	static class Hasher {
		private int hash;

		private int pos;

		private byte[] data;

		private int length;

		Hasher(byte[] data, int length) {
			init(data, length);
		}

		void init(byte[] d, int l) {
			this.data = d;
			this.length = l;
			pos = 0;
			hash = 0;
		}

		int hash() {
			while (pos < length)
				hash = hash * 31 + data[pos++];
			return hash;
		}

		int nextHash() {
			for (;;) {
				hash = hash * 31 + data[pos];
				++pos;
				if (pos == length || data[pos] == '/')
					return hash;
			}
		}

		int getHash() {
			return hash;
		}

		boolean hasNext() {
			return pos < length;
		}

		public int length() {
			return pos;
		}

		@Override
		public String toString() {
			StringBuilder sb = new StringBuilder();
			for (int i = 0; i < pos; ++i)
				sb.append((char) data[i]);
			sb.append(" | "); //$NON-NLS-1$
			for (int i = pos; i < length; ++i)
				sb.append((char) data[i]);
			return sb.toString();
		}
	}

	byte[][] toArray() {
		byte[][] ret = new byte[size][];
		int i = 0;
		for (byte[] entry : table) {
			if (entry != null)
				ret[i++] = entry;
		}
		return ret;
	}

}