src/main/java/freemarker/core/NumericalOutput.java

/*
 * Copyright (c) 2003 The Visigoth Software Society. All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Visigoth Software Society (http://www.visigoths.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
 *
 * 4. Neither the name "FreeMarker", "Visigoth", nor any of the names of the 
 *    project contributors may be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact visigoths@visigoths.org.
 *
 * 5. Products derived from this software may not be called "FreeMarker" or "Visigoth"
 *    nor may "FreeMarker" or "Visigoth" appear in their names
 *    without prior written permission of the Visigoth Software Society.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE VISIGOTH SOFTWARE SOCIETY OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Visigoth Software Society. For more
 * information on the Visigoth Software Society, please see
 * http://www.visigoths.org/
 */

package freemarker.core;

import java.io.IOException;
import java.text.NumberFormat;
import java.util.Locale;

import freemarker.template.TemplateException;

/**
 * An instruction that outputs the value of a numerical expression.
 * @author <a href="mailto:jon@revusky.com">Jonathan Revusky</a>
 */
final class NumericalOutput extends TemplateElement {

    private final Expression expression;
    private final boolean hasFormat;
    private final int minFracDigits;
    private final int maxFracDigits;
    private volatile FormatHolder formatCache; // creating new NumberFormat is slow operation

    NumericalOutput(Expression expression) {
        this.expression = expression;
        hasFormat = false;
        this.minFracDigits = 0;
        this.maxFracDigits = 0;
    }

    NumericalOutput(Expression expression,
                    int minFracDigits,
                    int maxFracDigits) 
    {
        this.expression = expression;
        hasFormat = true;
        this.minFracDigits = minFracDigits;
        this.maxFracDigits = maxFracDigits;
    }

    void accept(Environment env) throws TemplateException, IOException 
    {
        Number num = expression.evalToNumber(env);
        
        FormatHolder fmth = formatCache;  // atomic sampling
        if (fmth == null || !fmth.locale.equals(env.getLocale())) {
            synchronized(this) {
                fmth = formatCache;
                if (fmth == null || !fmth.locale.equals(env.getLocale())) {
                    NumberFormat fmt = NumberFormat.getNumberInstance(env.getLocale());
                    if (hasFormat) {
                        fmt.setMinimumFractionDigits(minFracDigits);
                        fmt.setMaximumFractionDigits(maxFracDigits);
                    } else {
                        fmt.setMinimumFractionDigits(0);
                        fmt.setMaximumFractionDigits(50);
                    }
                    fmt.setGroupingUsed(false);
                    formatCache = new FormatHolder(fmt, env.getLocale());
                    fmth = formatCache;
                }
            }
        }
        // We must use Format even if hasFormat == false.
        // Some locales may use non-Arabic digits, thus replacing the
        // decimal separator in the result of toString() is not enough.
        env.getOut().write(fmth.format.format(num));
    }

    protected String dump(boolean canonical) {
        StringBuffer buf = new StringBuffer("#{");
        buf.append(expression.getCanonicalForm());
        if (hasFormat) {
            buf.append(" ; ");
            buf.append("m");
            buf.append(minFracDigits);
            buf.append("M");
            buf.append(maxFracDigits);
        }
        buf.append("}");
        return buf.toString();
    }
    
    String getNodeTypeSymbol() {
        return "#{...}";
    }

    boolean heedsOpeningWhitespace() {
        return true;
    }

    boolean heedsTrailingWhitespace() {
        return true;
    }
    
    private static class FormatHolder {
        final NumberFormat format;
        final Locale locale;
        
        FormatHolder(NumberFormat format, Locale locale) {
            this.format = format;
            this.locale = locale;
        }
    }

    int getParameterCount() {
        return 3;
    }

    Object getParameterValue(int idx) {
        switch (idx) {
        case 0: return expression;
        case 1: return new Integer(minFracDigits);
        case 2: return new Integer(maxFracDigits);
        default: throw new IndexOutOfBoundsException();
        }
    }

    ParameterRole getParameterRole(int idx) {
        switch (idx) {
        case 0: return ParameterRole.CONTENT;
        case 1: return ParameterRole.MINIMUM_DECIMALS;
        case 2: return ParameterRole.MAXIMUM_DECIMALS;
        default: throw new IndexOutOfBoundsException();
        }
    }
}