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

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Here is the source code for com.nginious.http.xsp.expr.MinFunction.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.MethodVisitor;
import org.objectweb.asm.Opcodes;

/**
 * A math function which returns the lowest of two value argumrnyd. Below is an example which 
 * evaluates to 4.
 * 
 * <pre>
 * min(4, 6)
 * </pre>
 * 
 * @author Bojan Pisler, NetDigital Sweden AB
 *
 */
public class MinFunction extends Function {

    private Value value1;

    private Value value2;

    /**
     * Constructs a new min function which returns the smallest of the two specified
     * values.
     * 
     * @param value1 the first value
     * @param value2 the second value
     */
    public MinFunction(Value value1, Value value2) {
        super();
        this.value1 = value1;
        this.value2 = value2;
    }

    /**
     * Returns the default type produced by this function when evaluated. The default type
     * depends on the argument value types to this function. If both argument values are
     * integers then this function returns an integer, otherwise it returns a double.
     * 
     * @return the type returned by this function
     */
    protected Type getType() {
        return resolveType(this.value1, this.value2);
    }

    /**
     * Evaluates this function which returns the lowest of the two argument values.
     * 
     * @return the result of evaluating this function
     */
    @SuppressWarnings("incomplete-switch")
    protected Value evaluate() {
        Type type = resolveType(this.value1, this.value2);
        Value returnValue = null;

        switch (type) {
        case DOUBLE:
            returnValue = new DoubleValue(Math.min(value1.getDoubleValue(), value2.getDoubleValue()));
            break;

        case INT:
            returnValue = new IntegerValue(Math.min(value1.getIntValue(), value2.getIntValue()));
            break;
        }

        return returnValue;
    }

    /**
     * Evaluates this function and returns the lowest value as an integer.
     * 
     * @return the integer result of evaluating this function
     */
    protected int getIntValue() {
        return Math.min(value1.getIntValue(), value2.getIntValue());
    }

    /**
     * Evaluates this function and returns the lowest value as a double.
     * 
     * @return the double result of evaluating this function
     */
    protected double getDoubleValue() {
        return Math.min(value1.getDoubleValue(), value2.getDoubleValue());
    }

    /**
     * Evaluates this function and returns the lowest value converted to a string.
     * 
     * @return the string result of evaluating this function
     */
    @SuppressWarnings("incomplete-switch")
    protected String getStringValue() {
        Type type = resolveType(this.value1, this.value2);
        String value = null;

        switch (type) {
        case DOUBLE:
            value = Double.toString(Math.min(value1.getDoubleValue(), value2.getDoubleValue()));
            break;

        case INT:
            value = Integer.toString(Math.min(value1.getIntValue(), value2.getIntValue()));
            break;
        }

        return value;
    }

    /**
     * Evaluates this function and returns the lowest value converted to a boolean.
     * 
     * @return <code>true</code> if the lowest value is different from 0.0d, <code>false</code>
     *    otherwise
     */
    protected boolean getBooleanValue() {
        return getDoubleValue() != 0.0d;
    }

    /**
     * Creates bytecode for evaluating this function. The bytecode is generated using the
     * specified method visitor. The generated bytecode produces a result of the specified
     * type.
     * 
     * @param visitor the method visitor
     * @param type the type
     */
    void compile(MethodVisitor visitor, Type type) {
        type = resolveType(this.value1, this.value2);
        value1.compile(visitor, type);
        value2.compile(visitor, type);
        visitor.visitMethodInsn(Opcodes.INVOKESTATIC, "java/lang/Math", "min",
                type == Type.DOUBLE ? "(DD)D" : "(II)I");
    }
}