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eXist-db NoSQL Database Core
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/*
 * eXist-db Open Source Native XML Database
 * Copyright (C) 2001 The eXist-db Authors
 *
 * [email protected]
 * http://www.exist-db.org
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */
package org.exist.collections;

/**
 * URI to represent a Collection path internally in eXist
 * */
public class CollectionURI {

    public final static char FRAGMENT_SEPARATOR = '/';

    private char[] uri = null;
    private int length = 0;

    private int hash; // Default to 0

    public CollectionURI(String path) {
        append(path);
    }

    public CollectionURI(CollectionURI other) {
        this.uri = new char[other.uri.length];
        System.arraycopy(other.uri, 0, this.uri, 0, other.length);
        this.length = other.length;
        this.hash = other.hash;
    }

    public void append(final String segment) {
        int startOffset = 0;
        if (segment.charAt(0) == FRAGMENT_SEPARATOR) {
            startOffset = 1;
        }
        if(uri == null) {
            uri = new char[segment.length() + 1 - startOffset];
            uri[0] = FRAGMENT_SEPARATOR;
            segment.getChars(startOffset, segment.length(), uri, 1);
        } else {
            char[] newURI = new char[length + 1 + segment.length() - startOffset];
            System.arraycopy(uri, 0, newURI, 0, length);
            newURI[length] = FRAGMENT_SEPARATOR;
            segment.getChars(startOffset, segment.length(), newURI, length+1);
            uri = newURI;
        }
        length += segment.length() + 1 - startOffset;
        //reset the cache
        hash = 0;
    }

    public void removeLastSegment() {
        char c;
        int pos = length - 1;
        while ((c = uri[pos]) != FRAGMENT_SEPARATOR) {
            pos--;
        }
        length = pos;
        //reset the cache
        hash = 0;
    }

    public String toString() {
        return new String(uri, 0, length);
    }

    /**
     * Copied from java.lang.String.hashCode();
     * 
     * Returns a hash code for this string. The hash code for a
     * String object is computed as
     *      * s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
     * 
     * using int arithmetic, where s[i] is the
     * ith character of the string, n is the length of
     * the string, and ^ indicates exponentiation.
     * (The hash value of the empty string is zero.)
     *
     * @return  a hash code value for this object.
     */
    public int hashCode() {
        int h = hash;
        if (h == 0) {
            int off = 0;
            for (int i = 0; i < length; i++) {
                h = 31*h + uri[off++];
            }
            hash = h;
        }
        return h;
    }

    public boolean equals(Object object) {
        if (object instanceof CollectionURI) {
            final CollectionURI otherCollectionURI = (CollectionURI)object;
            if (this.length == otherCollectionURI.length) {
                int pos = length - 1;
                while (pos > -1) {
                    if (this.uri[pos] != otherCollectionURI.uri[pos--])
                        {return false;}
                }
                return true;
            }
        }
        return false;
    }

}