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/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.apache.ws.security.util;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import java.util.ArrayList;
/**
* The abstraction this class provides is a push down stack of variable
* length frames of prefix to namespace mappings. Used for keeping track
* of what namespaces are active at any given point as an XML document is
* traversed or produced.
*
* From a performance point of view, this data will both be modified frequently
* (at a minimum, there will be one push and pop per XML element processed),
* and scanned frequently (many of the "good" mappings will be at the bottom
* of the stack). The one saving grace is that the expected maximum
* cardinalities of the number of frames and the number of total mappings
* is only in the dozens, representing the nesting depth of an XML document
* and the number of active namespaces at any point in the processing.
*
* Accordingly, this stack is implemented as a single array, will null
* values used to indicate frame boundaries.
*
* @author James Snell
* @author Glen Daniels ([email protected])
* @author Sam Ruby ([email protected])
*/
public class NSStack {
protected static Log log =
LogFactory.getLog(NSStack.class.getName());
private Mapping[] stack;
private int top = 0;
private int iterator = 0;
private int currentDefaultNS = -1;
// invariant member variable to track low-level logging requirements
// we cache this once per instance lifecycle to avoid repeated lookups
// in heavily used code.
private final boolean traceEnabled = log.isTraceEnabled();
public NSStack() {
stack = new Mapping[32];
stack[0] = null;
}
/**
* Create a new frame at the top of the stack.
*/
public void push() {
top++;
if (top >= stack.length) {
Mapping newstack[] = new Mapping[stack.length * 2];
System.arraycopy(stack, 0, newstack, 0, stack.length);
stack = newstack;
}
if (traceEnabled)
log.trace("NSPush (" + stack.length + ")");
stack[top] = null;
}
/**
* Remove the top frame from the stack.
*/
public void pop() {
clearFrame();
top--;
// If we've moved below the current default NS, figure out the new
// default (if any)
if (top < currentDefaultNS) {
// Reset the currentDefaultNS to ignore the frame just removed.
currentDefaultNS = top;
while (currentDefaultNS > 0) {
if (stack[currentDefaultNS] != null &&
stack[currentDefaultNS].getPrefix().length() == 0)
break;
currentDefaultNS--;
}
}
if (top == 0) {
if (traceEnabled)
log.trace("NSPop (empty)");
return;
}
if (traceEnabled) {
log.trace("NSPop (" + stack.length + ")");
}
}
/**
* Return a copy of the current frame. Returns null if none are present.
*/
public ArrayList cloneFrame() {
if (stack[top] == null) return null;
ArrayList clone = new ArrayList();
for (Mapping map = topOfFrame(); map != null; map = next()) {
clone.add(map);
}
return clone;
}
/**
* Remove all mappings from the current frame.
*/
private void clearFrame() {
while (stack[top] != null) top--;
}
/**
* Reset the embedded iterator in this class to the top of the current
* (i.e., last) frame. Note that this is not threadsafe, nor does it
* provide multiple iterators, so don't use this recursively. Nor
* should you modify the stack while iterating over it.
*/
public Mapping topOfFrame() {
iterator = top;
while (stack[iterator] != null) iterator--;
iterator++;
return next();
}
/**
* Return the next namespace mapping in the top frame.
*/
public Mapping next() {
if (iterator > top) {
return null;
} else {
return stack[iterator++];
}
}
/**
* Add a mapping for a namespaceURI to the specified prefix to the top
* frame in the stack. If the prefix is already mapped in that frame,
* remap it to the (possibly different) namespaceURI.
*/
public void add(String namespaceURI, String prefix) {
int idx = top;
try {
// Replace duplicate prefixes (last wins - this could also fault)
for (int cursor = top; stack[cursor] != null; cursor--) {
if (stack[cursor].getPrefix().equals(prefix)) {
stack[cursor].setNamespaceURI(namespaceURI);
idx = cursor;
return;
}
}
push();
stack[top] = new Mapping(namespaceURI, prefix);
idx = top;
} finally {
// If this is the default namespace, note the new in-scope
// default is here.
if (prefix.length() == 0) {
currentDefaultNS = idx;
}
}
}
/**
* Return an active prefix for the given namespaceURI. NOTE : This
* may return null even if the namespaceURI was actually mapped further
* up the stack IF the prefix which was used has been repeated further
* down the stack. I.e.:
*
*
*
* *here's where we're looking*
*
*
*
* If we look for a prefix for "namespace" at the indicated spot, we won't
* find one because "pre" is actually mapped to "otherNamespace"
*/
public String getPrefix(String namespaceURI, boolean noDefault) {
if ((namespaceURI == null) || (namespaceURI.equals("")))
return null;
int hash = namespaceURI.hashCode();
// If defaults are OK, and the given NS is the current default,
// return "" as the prefix to favor defaults where possible.
if (!noDefault && currentDefaultNS > 0 && stack[currentDefaultNS] != null &&
namespaceURI.equals(stack[currentDefaultNS].getNamespaceURI()))
return "";
for (int cursor = top; cursor > 0; cursor--) {
Mapping map = stack[cursor];
if (map == null) continue;
if (map.getNamespaceHash() == hash &&
map.getNamespaceURI().equals(namespaceURI)) {
String possiblePrefix = map.getPrefix();
if (noDefault && possiblePrefix.length() == 0) continue;
// now make sure that this is the first occurance of this
// particular prefix
int ppHash = possiblePrefix.hashCode();
for (int cursor2 = top; true; cursor2--) {
if (cursor2 == cursor) return possiblePrefix;
map = stack[cursor2];
if (map == null) continue;
if (ppHash == map.getPrefixHash() &&
possiblePrefix.equals(map.getPrefix()))
break;
}
}
}
return null;
}
/**
* Return an active prefix for the given namespaceURI, including
* the default prefix ("").
*/
public String getPrefix(String namespaceURI) {
return getPrefix(namespaceURI, false);
}
/**
* Given a prefix, return the associated namespace (if any).
*/
public String getNamespaceURI(String prefix) {
if (prefix == null)
prefix = "";
int hash = prefix.hashCode();
for (int cursor = top; cursor > 0; cursor--) {
Mapping map = stack[cursor];
if (map == null) continue;
if (map.getPrefixHash() == hash && map.getPrefix().equals(prefix))
return map.getNamespaceURI();
}
return null;
}
/**
* Produce a trace dump of the entire stack, starting from the top and
* including frame markers.
*/
public void dump(String dumpPrefix) {
for (int cursor = top; cursor > 0; cursor--) {
Mapping map = stack[cursor];
if (map == null) {
log.trace(dumpPrefix + "stackFrame00");
} else {
log.trace(dumpPrefix + map.getNamespaceURI() + " -> " + map.getPrefix());
}
}
}
}
