com.nginious.http.xsp.expr.AndOperator.java Source code

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Here is the source code for com.nginious.http.xsp.expr.AndOperator.java

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/**
 * Copyright 2012 NetDigital Sweden AB
 *
 * 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 com.nginious.http.xsp.expr;

import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;

/**
 * A boolean operator which evaluates two other values. This operator evaluates to
 * true if both of the values evaluate to true.
 * 
 * @author Bojan Pisler, NetDigital Sweden AB
 *
 */
public class AndOperator extends BooleanOperator {

    /**
     * Constructs a new and operator with the two specified values.
     * 
     * @param value1 the left side value
     * @param value2 the right side value
     */
    public AndOperator(Value value1, Value value2) {
        super(value1, value2);
    }

    /**
     * Evaluates this and operator which returns true if both the left side
     * and the right side value evaluates to <code>true</code>.
     * 
     * @return <code>true</code> if both values evaluate to </code>true</code>,
     *    otherwise <code>false</code>
     */
    protected boolean getBooleanValue() {
        return value1.getBooleanValue() && value2.getBooleanValue();
    }

    /**
     * Creates bytecode for evaluating this and operator. The bytecode is generated using
     * the specified method visitor. The result of the evaluation produces the specified
     * type.
     * 
     * @param visitor the method visitor
     * @param type the type
     */
    void compile(MethodVisitor visitor, Type type) {
        Label labelFalse = new Label();
        Label labelEnd = new Label();

        // Test first value
        value1.compile(visitor, type);
        visitor.visitInsn(Opcodes.ICONST_1);
        visitor.visitJumpInsn(Opcodes.IF_ICMPNE, labelFalse);

        // Test second value
        value2.compile(visitor, type);
        visitor.visitInsn(Opcodes.ICONST_1);
        visitor.visitJumpInsn(Opcodes.IF_ICMPNE, labelFalse);

        // True
        visitor.visitLdcInsn(true);
        visitor.visitJumpInsn(Opcodes.GOTO, labelEnd);

        // False
        visitor.visitLabel(labelFalse);
        visitor.visitLdcInsn(false);

        visitor.visitLabel(labelEnd);
    }

    /**
     * Returns a description of this and operator.
     * 
     * @return description of this and operator
     */
    public String toString() {
        return "(" + this.value1 + " && " + this.value2 + ")";
    }
}