1 /*
   2  * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package jdk.nashorn.internal.ir;
  27 
  28 import jdk.nashorn.internal.codegen.types.Type;
  29 import jdk.nashorn.internal.ir.visitor.NodeVisitor;
  30 
  31 /**
  32  * A wrapper for an expression that is in a position to be a join predecessor.
  33  */
  34 public class JoinPredecessorExpression extends Expression implements JoinPredecessor {
  35     private static final long serialVersionUID = 1L;
  36 
  37     private final Expression expression;
  38     private final LocalVariableConversion conversion;
  39 
  40     /**
  41      * A no-arg constructor does not wrap any expression on its own, but can be used as a place to contain a local
  42      * variable conversion in a place where an expression can otherwise stand.
  43      */
  44     public JoinPredecessorExpression() {
  45         this(null);
  46     }
  47 
  48     /**
  49      * A constructor for wrapping an expression and making it a join predecessor. Typically used on true and false
  50      * subexpressions of the ternary node as well as on the operands of short-circuiting logical expressions {@code &&}
  51      * and {@code ||}.
  52      * @param expression the expression to wrap
  53      */
  54     public JoinPredecessorExpression(final Expression expression) {
  55         this(expression, null);
  56     }
  57 
  58     private JoinPredecessorExpression(final Expression expression, final LocalVariableConversion conversion) {
  59         super(expression == null ? 0L : expression.getToken(), expression == null ? 0 : expression.getStart(), expression == null ? 0 : expression.getFinish());
  60         this.expression = expression;
  61         this.conversion = conversion;
  62     }
  63 
  64     @Override
  65     public JoinPredecessor setLocalVariableConversion(final LexicalContext lc, final LocalVariableConversion conversion) {
  66         if(conversion == this.conversion) {
  67             return this;
  68         }
  69         return new JoinPredecessorExpression(expression, conversion);
  70     }
  71 
  72     @Override
  73     public Type getType() {
  74         return expression.getType();
  75     }
  76 
  77     @Override
  78     public boolean isAlwaysFalse() {
  79         return expression != null && expression.isAlwaysFalse();
  80     }
  81 
  82     @Override
  83     public boolean isAlwaysTrue() {
  84         return expression != null && expression.isAlwaysTrue();
  85     }
  86 
  87     /**
  88      * Returns the underlying expression.
  89      * @return the underlying expression.
  90      */
  91     public Expression getExpression() {
  92         return expression;
  93     }
  94 
  95     /**
  96      * Sets the underlying expression.
  97      * @param expression the new underlying expression
  98      * @return this or modified join predecessor expression object.
  99      */
 100     public JoinPredecessorExpression setExpression(final Expression expression) {
 101         if(expression == this.expression) {
 102             return this;
 103         }
 104         return new JoinPredecessorExpression(expression, conversion);
 105     }
 106 
 107     @Override
 108     public LocalVariableConversion getLocalVariableConversion() {
 109         return conversion;
 110     }
 111 
 112     @Override
 113     public Node accept(final NodeVisitor<? extends LexicalContext> visitor) {
 114         if(visitor.enterJoinPredecessorExpression(this)) {
 115             final Expression expr = getExpression();
 116             return visitor.leaveJoinPredecessorExpression(expr == null ? this : setExpression((Expression)expr.accept(visitor)));
 117         }
 118         return this;
 119     }
 120 
 121     @Override
 122     public void toString(final StringBuilder sb, final boolean printType) {
 123         if(expression != null) {
 124             expression.toString(sb, printType);
 125         }
 126         if(conversion != null) {
 127             conversion.toString(sb);
 128         }
 129     }
 130 
 131 }