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

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Here is the source code for com.nginious.http.xsp.expr.LessEqualsOperator.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 comparison operator which checks if the left side argument value is less than or equals to
 * the right side argument value.
 * 
 * @author Bojan Pisler, NetDigital Sweden AB
 *
 */
public class LessEqualsOperator extends ComparisonOperator {

    /**
     * Constructs a new less than or equals operator with the specified two argument values.
     * 
     * @param value1 the left side argument value
     * @param value2 the right side argument value
     * @throws ExpressionException if any of the two argument values are not numeric
     */
    public LessEqualsOperator(Value value1, Value value2) throws ExpressionException {
        super(value1, value2);

        if (value1.getType() == Type.STRING || value2.getType() == Type.STRING) {
            throw new ExpressionException("Can't use less than or equals operator with strings");
        }
    }

    /**
     * Evaluates this less than or equals operator.
     * 
     * @return <code>true</code> if the left side argument value is less than or equals
     * to the right side argument value, <code>false</code> otherwise
     */
    @SuppressWarnings("incomplete-switch")
    protected boolean getBooleanValue() {
        Type type = resolveType(this.value1, this.value2);

        switch (type) {
        case INT:
            return value1.getIntValue() <= value2.getIntValue();

        case DOUBLE:
            return value1.getDoubleValue() <= value2.getDoubleValue();
        }

        return false;
    }

    /**
     * Creates bytecode for evaluating this operator. The bytecode is generated using
     * the specified method visitor and for the specified type.
     * 
     * @param visitor the methos visitor
     * @param type the type
     */
    @SuppressWarnings("incomplete-switch")
    void compile(MethodVisitor visitor, Type type) {
        Type subType = resolveType(this.value1, this.value2);

        switch (subType) {
        case INT:
            compileInt(visitor);
            break;

        case DOUBLE:
            compileDouble(visitor);
            break;
        }
    }

    /**
     * Creates bytecode for evaluating the argument values as integers. The bytecode
     * is generated using the specified method visitor.
     * 
     * @param visitor the method visitor
     */
    private void compileInt(MethodVisitor visitor) {
        Label labelFalse = new Label();
        Label labelEnd = new Label();

        value2.compile(visitor, Type.INT);
        value1.compile(visitor, Type.INT);

        visitor.visitJumpInsn(Opcodes.IF_ICMPLT, labelFalse);

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

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

        visitor.visitLabel(labelEnd);
    }

    /**
     * Creates bytecode for evaluating the argument values as doubles. The bytecode
     * is generated using the specified method visitor.
     * 
     * @param visitor the method visitor
     */
    private void compileDouble(MethodVisitor visitor) {
        Label labelFalse = new Label();
        Label labelEnd = new Label();

        value2.compile(visitor, Type.DOUBLE);
        value1.compile(visitor, Type.DOUBLE);

        visitor.visitInsn(Opcodes.DCMPL);
        visitor.visitJumpInsn(Opcodes.IFLT, labelFalse);

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

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

        visitor.visitLabel(labelEnd);
    }
}