/*
* eXist Open Source Native XML Database
* Copyright (C) 2001-06 The eXist Project
* http://exist-db.org
*
* This program 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
* of the License, or (at your option) any later version.
*
* This program 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 St, Fifth Floor, Boston, MA 02110-1301 USA
*
* $Id$
*/
package org.exist.numbering;
import java.io.IOException;
import org.exist.security.MessageDigester;
import org.exist.storage.io.VariableByteInput;
import org.exist.storage.io.VariableByteOutputStream;
/**
* Represents a node id in the form of a dynamic level number (DLN). DLN's are
* hierarchical ids, which borrow from Dewey's decimal classification. Examples for
* node ids: 1, 1.1, 1.2, 1.2.1, 1.2.2, 1.3. In this case, 1 represents the root node, 1.1 is
* the first node on the second level, 1.2 the second, and so on.
*
* To support efficient insertion of new nodes between existing nodes, we use the
* concept of sublevel ids. Between two nodes 1.1 and 1.2, a new node can be inserted
* as 1.1/1, where the / is the sublevel separator. The / does not start a new level. 1.1 and
* 1.1/1 are thus on the same level of the tree.
*
* In the binary encoding, the '.' is represented by a 0-bit while '/' is written as a 1-bit.
*/
public class DLN extends DLNBase implements NodeId {
/**
* Constructs a new DLN with a single id with value 1.
*
*/
public DLN() {
this(1);
}
/**
* Constructs a new DLN by parsing the string argument.
* In the string, levels are separated by a '.', sublevels by
* a '/'. For example, '1.2/1' or '1.2/1.2' are valid ids.
*
* @param s
*/
public DLN(final String s) {
bits = new byte[1];
final StringBuilder buf = new StringBuilder(16);
boolean subValue = false;
for(int p = 0; p < s.length(); p++) {
final char ch = s.charAt(p);
if(ch == '.' || ch == '/') {
addLevelId(Integer.parseInt(buf.toString()), subValue);
subValue = ch == '/';
buf.setLength(0);
} else {
buf.append(ch);
}
}
if(buf.length() > 0) {
addLevelId(Integer.parseInt(buf.toString()), subValue);
}
}
/**
* Constructs a new DLN, using the passed id as its
* single level value.
*
* @param id
*/
public DLN(final int id) {
bits = new byte[1];
addLevelId(id, false);
}
/**
* Constructs a new DLN by copying the data of the
* passed DLN.
*
* @param other
*/
public DLN(final DLN other) {
super(other);
}
/**
* Reads a DLN from the given byte[].
*
* @param units number of bits to read
* @param data the byte[] to read from
* @param startOffset the start offset to start reading at
*/
public DLN(final int units, final byte[] data, final int startOffset) {
super(units, data, startOffset);
}
/**
* Reads a DLN from the given {@link VariableByteInput} stream.
*
* @see #write(VariableByteOutputStream)
* @param is
* @throws IOException
*/
public DLN(final short bitCnt, final VariableByteInput is) throws IOException {
super(bitCnt, is);
}
public DLN(final byte prefixLen, final DLN previous, final short bitCnt, final VariableByteInput is) throws IOException {
super(prefixLen, previous, bitCnt, is);
}
/**
* Create a new DLN by copying nbits bits from the given
* byte[].
*
* @param data
* @param nbits
*/
protected DLN(final byte[] data, final int nbits) {
super(data, nbits);
}
/**
* Returns a new DLN representing the first child
* node of this node.
*
* @return new child node id
*/
@Override
public NodeId newChild() {
final DLN child = new DLN(this);
child.addLevelId(1, false);
return child;
}
/**
* Returns a new DLN representing the next following
* sibling of this node.
*
* @return new sibling node id.
*/
@Override
public NodeId nextSibling() {
final DLN sibling = new DLN(this);
sibling.incrementLevelId();
return sibling;
}
@Override
public NodeId precedingSibling() {
final DLN sibling = new DLN(this);
sibling.decrementLevelId();
return sibling;
}
@Override
public NodeId getChild(final int child) {
final DLN nodeId = new DLN(this);
nodeId.addLevelId(child, false);
return nodeId;
}
@Override
public NodeId insertNode(final NodeId right) {
final DLN rightNode = (DLN) right;
if (right == null) {
return nextSibling();
}
final int lastLeft = lastLevelOffset();
final int lastRight = rightNode.lastLevelOffset();
final int lenLeft = getSubLevelCount(lastLeft);
final int lenRight = rightNode.getSubLevelCount(lastRight);
final DLN newNode;
if(lenLeft > lenRight) {
newNode = new DLN(this);
newNode.incrementLevelId();
} else if(lenLeft < lenRight) {
newNode = (DLN) rightNode.insertBefore();
} else {
newNode = new DLN(this);
newNode.addLevelId(1, true);
}
return newNode;
}
@Override
public NodeId insertBefore() {
final int lastPos = lastFieldPosition();
final int lastId = getLevelId(lastPos);
final DLN newNode = new DLN(this);
//System.out.println("insertBefore: " + newNode.toString() + " = " + newNode.bitIndex);
if (lastId == 1) {
newNode.setLevelId(lastPos, 0);
newNode.addLevelId(35, true);
} else {
newNode.setLevelId(lastPos, lastId - 1);
newNode.compact();
//System.out.println("newNode: " + newNode.toString() + " = " + newNode.bitIndex + "; last = " + lastPos);
}
return newNode;
}
@Override
public NodeId append(final NodeId otherId) {
final DLN other = (DLN) otherId;
final DLN newId = new DLN(this);
int offset = 0;
while(offset <= other.bitIndex) {
boolean subLevel = false;
if (offset > 0) {
subLevel = ((other.bits[offset >> UNIT_SHIFT] & (1 << ((7 - offset++) & 7))) != 0);
}
final int id = other.getLevelId(offset);
newId.addLevelId(id, subLevel);
offset += DLNBase.getUnitsRequired(id) * BITS_PER_UNIT;
}
return newId;
}
/**
* Returns a new DLN representing the parent of the
* current node. If the current node is the root element
* of the document, the method returns
* {@link NodeId#DOCUMENT_NODE}. If the current node
* is the document node, null is returned.
*
* @see NodeId#getParentId()
*/
@Override
public NodeId getParentId() {
if(this == DOCUMENT_NODE) {
return null;
}
final int last = lastLevelOffset();
if (last == 0) {
return DOCUMENT_NODE;
}
return new DLN(bits, last - 1);
}
@Override
public boolean isDescendantOf(final NodeId ancestor) {
final DLN other = (DLN) ancestor;
return startsWith(other) && bitIndex > other.bitIndex
&& isLevelSeparator(other.bitIndex + 1);
}
@Override
public boolean isDescendantOrSelfOf(final NodeId other) {
final DLN ancestor = (DLN) other;
return startsWith(ancestor) &&
(bitIndex == ancestor.bitIndex || isLevelSeparator((ancestor).bitIndex + 1));
}
@Override
public boolean isChildOf(final NodeId parent) {
final DLN other = (DLN) parent;
if(!startsWith(other)) {
return false;
}
final int levels = getLevelCount(other.bitIndex + 2);
return levels == 1;
}
@Override
public int computeRelation(final NodeId ancestor) {
final DLN other = (DLN) ancestor;
if (other == NodeId.DOCUMENT_NODE) {
return getLevelCount(0) == 1 ? IS_CHILD : IS_DESCENDANT;
}
if (startsWith(other)) {
if (bitIndex == other.bitIndex) {
return IS_SELF;
}
if (bitIndex > other.bitIndex && isLevelSeparator(other.bitIndex + 1)) {
if (getLevelCount(other.bitIndex + 2) == 1) {
return IS_CHILD;
}
return IS_DESCENDANT;
}
}
return -1;
}
@Override
public boolean isSiblingOf(final NodeId sibling) {
final NodeId parent = getParentId();
return sibling.isChildOf(parent);
}
/**
* Returns the level within the document tree at which
* this node occurs.
*/
@Override
public int getTreeLevel() {
return getLevelCount(0);
}
@Override
public boolean equals(final NodeId other) {
return super.equals((DLNBase) other);
}
@Override
public int compareTo(final NodeId otherId) {
if(otherId == null) {
return 1;
}
final DLN other = (DLN) otherId;
final int a1len = bits.length;
final int a2len = other.bits.length;
final int limit = a1len <= a2len ? a1len : a2len;
final byte[] obits = other.bits;
for(int i = 0; i < limit; i++) {
final byte b1 = bits[i];
final byte b2 = obits[i];
if(b1 != b2) {
return (b1 & 0xFF) - (b2 & 0xFF);
}
}
return (a1len - a2len);
}
@Override
public boolean after(final NodeId other, final boolean isFollowing) {
if (compareTo(other) > 0) {
if (isFollowing) {
return !isDescendantOf(other);
}
return true;
}
return false;
}
@Override
public boolean before(final NodeId other, final boolean isPreceding) {
if (compareTo(other) < 0) {
if (isPreceding) {
return !other.isDescendantOf(this);
}
return true;
}
return false;
}
/**
* Write the node id to a {@link VariableByteOutputStream}.
*
* @param os
* @throws IOException
*/
@Override
public void write(final VariableByteOutputStream os) throws IOException {
os.writeShort((short) units());
os.write(bits, 0, bits.length);
}
@Override
public NodeId write(final NodeId prevId, final VariableByteOutputStream os) throws IOException {
int i = 0;
if(prevId != null) {
final DLN previous = (DLN) prevId;
final int len = Math.min(bits.length, previous.bits.length);
for( ; i < len; i++) {
final byte b = bits[i];
if (b != previous.bits[i]) {
break;
}
}
}
os.writeByte((byte) i);
os.writeShort((short) units());
os.write(bits, i, bits.length - i);
return this;
}
public static void main(final String[] args) {
final DLN left1 = new DLN("5.6.2.6");
final DLN left2 = new DLN("5.6.2.7");
final DLN right = new DLN("5.6.2.7.1");
final byte[] nodeIdData1 = new byte[left1.size()];
left1.serialize(nodeIdData1, 0);
System.out.println(left1.units() + ": " +left1 + ": " + MessageDigester.byteArrayToHex(nodeIdData1) + Integer.toHexString(left1.units()));
final byte[] nodeIdData2 = new byte[left2.size()];
left2.serialize(nodeIdData2, 0);
System.out.println(left2.units() + ": " + left2 + ": " + MessageDigester.byteArrayToHex(nodeIdData2) + Integer.toHexString(left2.units()));
final byte[] nodeIdData3 = new byte[right.size()];
right.serialize(nodeIdData3, 0);
System.out.println(right.units() + ": " + right + ": " + MessageDigester.byteArrayToHex(nodeIdData3) + Integer.toHexString(right.units()));
}
}