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/*
* OutputStack.java July 2006
*
* Copyright (C) 2006, Niall Gallagher
*
* 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.simpleframework.xml.stream;
import java.util.Iterator;
import java.util.ArrayList;
import java.util.Set;
/**
* The OutputStack is used to keep track of the nodes
* that have been written to the document. This ensures that when
* nodes are written to the XML document that the writer can tell
* whether a child node for a given OutputNode can be
* created. Each created node is pushed, and popped when ended.
*
* @author Niall Gallagher
*
* @see org.simpleframework.xml.stream.OutputNode
*/
class OutputStack extends ArrayList {
/**
* Represents the set of nodes that have not been committed.
*/
private final Set active;
/**
* Constructor for the OutputStack object. This is
* used to create a stack that can be used to keep track of the
* elements that have been written to the XML document.
*/
public OutputStack(Set active) {
this.active = active;
}
/**
* This is used to remove the OutputNode from the
* top of the output stack. This is used when an element has been
* ended and the output writer wants to block child creation.
*
* @return this returns the node from the top of the stack
*/
public OutputNode pop() {
int size = size();
if(size <= 0) {
return null;
}
return purge(size - 1);
}
/**
* This is used to acquire the OutputNode from the
* top of the output stack. This is used when the writer wants to
* determine the current element written to the XML document.
*
* @return this returns the node from the top of the stack
*/
public OutputNode top() {
int size = size();
if(size <= 0) {
return null;
}
return get(size - 1);
}
/**
* This is used to acquire the OutputNode from the
* bottom of the output stack. This is used when the writer wants
* to determine the root element for the written XML document.
*
* @return this returns the node from the bottom of the stack
*/
public OutputNode bottom() {
int size = size();
if(size <= 0) {
return null;
}
return get(0);
}
/**
* This method is used to add an OutputNode to the
* top of the stack. This is used when an element is written to
* the XML document, and allows the writer to determine if a
* child node can be created from a given output node.
*
* @param value this is the output node to add to the stack
*/
public OutputNode push(OutputNode value) {
active.add(value);
add(value);
return value;
}
/**
* The purge method is used to purge a match from
* the provided position. This also ensures that the active set
* has the node removed so that it is no longer relevant.
*
* @param index the index of the node that is to be removed
*
* @return returns the node removed from the specified index
*/
public OutputNode purge(int index) {
OutputNode node = remove(index);
if(node != null){
active.remove(node);
}
return node;
}
/**
* This is returns an Iterator that is used to loop
* through the ouptut nodes from the top down. This allows the
* node writer to determine what Mode should be used
* by an output node. This reverses the iteration of the list.
*
* @return returns an iterator to iterate from the top down
*/
public Iterator iterator() {
return new Sequence();
}
/**
* The is used to order the OutputNode objects from
* the top down. This is basically used to reverse the order of
* the linked list so that the stack can be iterated within a
* for each loop easily. This can also be used to remove a node.
*
* @author Niall Gallagher
*/
private class Sequence implements Iterator {
/**
* The cursor used to acquire objects from the stack.
*/
private int cursor;
/**
* Constructor for the Sequence object. This is
* used to position the cursor at the end of the list so the
* last inserted output node is the first returned from this.
*/
public Sequence() {
this.cursor = size();
}
/**
* Returns the OutputNode object at the cursor
* position. If the cursor has reached the start of the list
* then this returns null instead of the first output node.
*
* @return this returns the node from the cursor position
*/
public OutputNode next() {
if(hasNext()) {
return get(--cursor);
}
return null;
}
/**
* This is used to determine if the cursor has reached the
* start of the list. When the cursor reaches the start of
* the list then this method returns false.
*
* @return this returns true if there are more nodes left
*/
public boolean hasNext() {
return cursor > 0;
}
/**
* Removes the match from the cursor position. This also
* ensures that the node is removed from the active set so
* that it is not longer considered a relevant output node.
*/
public void remove() {
purge(cursor);
}
}
}