001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the "License");
007 * you may not use this file except in compliance with the License.
008 * You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018 /*
019 * $Id: ElemContext.java 468654 2006-10-28 07:09:23Z minchau $
020 */
021 package org.apache.xml.serializer;
022
023 /**
024 * This class is a stack frame that consists of
025 * information about the element currently being processed
026 * by a serializer. Consider this example:
027 * <pre>
028 * <A>
029 * <B1>
030 * </B1>
031 * <B2>
032 * </B2>
033 * <A>
034 * </pre>
035 *
036 * A stack frame will be pushed for "A" at depth 1,
037 * then another one for "B1" at depth 2.
038 * Then "B1" stackframe is popped. When the stack frame for "B2" is
039 * pushed, this implementation re-uses the old stack fram object used
040 * by "B1" to be efficient at not creating too many of these object.
041 *
042 * This is by no means a public class, and neither are its fields or methods,
043 * they are all helper fields for a serializer.
044 *
045 * The purpose of this class is to be more consistent with pushing information
046 * when a new element is being serialized and more quickly restoring the old
047 * information about the parent element with a simple pop() when the
048 * child element is done. Previously there was some redundant and error-prone
049 * calculations going on to retore information.
050 *
051 * @xsl.usage internal
052 */
053 final class ElemContext
054 {
055 // Fields that form the context of the element
056
057 /**
058 * The nesting depth of the element inside other elements.
059 */
060 final int m_currentElemDepth;
061
062 /** HTML field, the element description of the HTML element */
063 ElemDesc m_elementDesc = null;
064
065 /**
066 * The local name of the element.
067 */
068 String m_elementLocalName = null;
069
070 /**
071 * The fully qualified name of the element (with prefix, if any).
072 */
073 String m_elementName = null;
074
075 /**
076 * The URI of the element.
077 * If this value is null it means that the URI is not yet determined
078 * for the element. Valid values are the empty string "", meaning
079 * that it is in no namespace, or a string of non-zero length.
080 */
081 String m_elementURI = null;
082
083 /** If the element is in the cdata-section-names list
084 * then the value is true. If it is true the text children of the element
085 * should be output in CDATA section blocks.
086 */
087 boolean m_isCdataSection;
088
089 /** True if the current element has output escaping disabled.
090 * This is true for SCRIPT and STYLE elements.
091 */
092 boolean m_isRaw = false;
093
094 /** The next element "stack frame". This value will only be
095 * set once as deeper stack frames are not deleted when popped off,
096 * but are rather re-used when a push is required.
097 *
098 * This makes for very fast pushing and popping of stack frames
099 * because very few stack frame objects are ever created, they are
100 * mostly re-used. This re-use saves object creation but it also means
101 * that connections between the frames via m_next and m_prev
102 * never changes either. Just the contents of the frames change
103 * as they are re-used. Only the reference to the current stack frame, which
104 * is held by the serializer is changed via a quick pop() or push().
105 */
106 private ElemContext m_next;
107
108 /** The previous element "stack frame". */
109 final ElemContext m_prev;
110
111 /**
112 * Set to true when a start tag is started, or open, but not all the
113 * attributes or namespace information is yet collected.
114 */
115 boolean m_startTagOpen = false;
116
117 /**
118 * Constructor to create the root of the element contexts.
119 *
120 */
121 ElemContext()
122 {
123 // this assignment means can never pop this context off
124 m_prev = this;
125 // depth 0 because it doesn't correspond to any element
126 m_currentElemDepth = 0;
127 }
128
129 /**
130 * Constructor to create the "stack frame" for a given element depth.
131 *
132 * This implementation will re-use the context at each depth. If
133 * a documents deepest element depth is N then there will be (N+1)
134 * such objects created, no more than that.
135 *
136 * @param previous The "stack frame" corresponding to the new
137 * elements parent element.
138 */
139 private ElemContext(final ElemContext previous)
140 {
141 m_prev = previous;
142 m_currentElemDepth = previous.m_currentElemDepth + 1;
143 }
144
145 /**
146 * Pop the current "stack frame".
147 * @return Returns the parent "stack frame" of the one popped.
148 */
149 final ElemContext pop()
150 {
151 /* a very simple pop. No clean up is done of the deeper
152 * stack frame. All deeper stack frames are still attached
153 * but dormant, just waiting to be re-used.
154 */
155 return this.m_prev;
156 }
157
158 /**
159 * This method pushes an element "stack frame"
160 * but with no initialization of values in that frame.
161 * This method is used for optimization purposes, like when pushing
162 * a stack frame for an HTML "IMG" tag which has no children and
163 * the stack frame will almost immediately be popped.
164 */
165 final ElemContext push()
166 {
167 ElemContext frame = this.m_next;
168 if (frame == null)
169 {
170 /* We have never been at this depth yet, and there is no
171 * stack frame to re-use, so we now make a new one.
172 */
173 frame = new ElemContext(this);
174 this.m_next = frame;
175 }
176 /*
177 * We shouldn't need to set this true because we should just
178 * be pushing a dummy stack frame that will be instantly popped.
179 * Yet we need to be ready in case this element does have
180 * unexpected children.
181 */
182 frame.m_startTagOpen = true;
183 return frame;
184 }
185
186 /**
187 * Push an element context on the stack. This context keeps track of
188 * information gathered about the element.
189 * @param uri The URI for the namespace for the element name,
190 * can be null if it is not yet known.
191 * @param localName The local name of the element (no prefix),
192 * can be null.
193 * @param qName The qualified name (with prefix, if any)
194 * of the element, this parameter is required.
195 */
196 final ElemContext push(
197 final String uri,
198 final String localName,
199 final String qName)
200 {
201 ElemContext frame = this.m_next;
202 if (frame == null)
203 {
204 /* We have never been at this depth yet, and there is no
205 * stack frame to re-use, so we now make a new one.
206 */
207 frame = new ElemContext(this);
208 this.m_next = frame;
209 }
210
211 // Initialize, or reset values in the new or re-used stack frame.
212 frame.m_elementName = qName;
213 frame.m_elementLocalName = localName;
214 frame.m_elementURI = uri;
215 frame.m_isCdataSection = false;
216 frame.m_startTagOpen = true;
217
218 // is_Raw is already set in the HTML startElement() method
219 // frame.m_isRaw = false;
220 return frame;
221 }
222 }