Subversion Repositories mkgmap

/*
 * Copyright (C) 2012.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 3 or
 * version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 */

package uk.me.parabola.mkgmap.osmstyle.function;

import java.util.HashMap;
import java.util.Map;

/**
 * A factory for style functions.
 * @author WanMil
 */
public class FunctionFactory {

        // cache for style functions
        // use a thread local so that there is one cache per thread to ensure thread safety of the StyleFunction objects
        private static final ThreadLocal<Map<String, StyleFunction>> cache = new ThreadLocal<Map<String, StyleFunction>>() {
                protected Map<String, StyleFunction> initialValue() {
                        return new HashMap<String, StyleFunction>();
                }
        };

        /**
         * Retrieves a style function with the given name. The cache stores one instance
         * per thread only to ensure thread safety.
         * @param name the style function name
         * @return the style function instance or <code>null</code> if there is no such function
         */
        public static StyleFunction getCachedFunction(String name) {
                // check if the cache contains a function with the given name
                StyleFunction function = cache.get().get(name);
               
                if (function == null) {
                        // the function need to be instantiated
                        function = createFunction(name);
                       
                        // put the function into the cache for later usage
                        if (function != null) {
                                cache.get().put(name, function);
                        }
                }
               
                return function;
        }
       
       
        /**
         * Returns a new instance of a style function with the given name.
         * @param name the style function name
         * @return the style function instance or <code>null</code> if there is no such function
         */
        public static StyleFunction createFunction(String name) {
                if ("length".equals(name)) {
                        return new LengthFunction();
                }
                if ("is_closed".equals(name)) {
                        return new IsClosedFunction();
                }
                if ("is_complete".equals(name)) {
                        return new IsCompleteFunction();
                }
                return null;
        }
}