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Java > Open Source Codes > org > apache > xalan > xsltc > compiler > Pattern


1 /*
2  * Copyright 2001-2004 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 /*
17  * $Id: Pattern.java,v 1.4 2004/02/16 22:24:29 minchau Exp $
18  */
19
20 package org.apache.xalan.xsltc.compiler;
21
22 import org.apache.xalan.xsltc.compiler.util.ClassGenerator;
23 import org.apache.xalan.xsltc.compiler.util.MethodGenerator;
24 import org.apache.xalan.xsltc.compiler.util.Type;
25 import org.apache.xalan.xsltc.compiler.util.TypeCheckError;
26
27 /**
28  * @author Jacek Ambroziak
29  * @author Santiago Pericas-Geertsen
30  */
31 public abstract class Pattern extends Expression {
32     /**
33      * Returns the type of a pattern, which is always a <code>NodeType</code>.
34      * A <code>NodeType</code> has a number of subtypes defined by
35      * <code>NodeType._type</code> corresponding to each type of node.
36      */
37     public abstract Type typeCheck(SymbolTable stable) throws TypeCheckError;
38
39     /**
40      * Translate this node into JVM bytecodes. Patterns are translated as
41      * boolean expressions with true/false lists. Before calling
42      * <code>translate</code> on a pattern, make sure that the node being
43      * matched is on top of the stack. After calling <code>translate</code>,
44      * make sure to backpatch both true and false lists. True lists are the
45      * default, in the sense that they always <em>"fall through"</em>. If this
46      * is not the intended semantics (e.g., see
47      * {@link org.apache.xalan.xsltc.compiler.AlternativePattern#translate()})
48      * then a GOTO must be appended to the instruction list after calling
49      * <code>translate</code>.
50      */
51     public abstract void translate(ClassGenerator classGen,
52                    MethodGenerator methodGen);
53
54     /**
55      * Returns the priority of this pattern (section 5.5 in the XSLT spec).
56      */
57     public abstract double getPriority();
58 }
59
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