modules/luni/src/main/java/org/apache/harmony/luni/util/MsgHelp.java

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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 org.apache.harmony.luni.util;


import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Locale;
import java.util.MissingResourceException;
import java.util.ResourceBundle;

import org.apache.harmony.kernel.vm.VM;

/**
 * This class contains helper methods for loading resource bundles and
 * formatting external message strings.
 */

public final class MsgHelp {

	/**
	 * Generates a formatted text string given a source string containing
	 * "argument markers" of the form "{argNum}" where each argNum must be in
	 * the range 0..9. The result is generated by inserting the toString of each
	 * argument into the position indicated in the string.
	 * <p>
	 * To insert the "{" character into the output, use a single backslash
	 * character to escape it (i.e. "\{"). The "}" character does not need to be
	 * escaped.
	 * 
	 * @param format
	 *            String the format to use when printing.
	 * @param args
	 *            Object[] the arguments to use.
	 * @return String the formatted message.
	 */
	public static String format(String format, Object[] args) {
		StringBuilder answer = new StringBuilder(format.length()
				+ (args.length * 20));
		String[] argStrings = new String[args.length];
		for (int i = 0; i < args.length; ++i) {
			if (args[i] == null)
				argStrings[i] = "<null>";
			else
				argStrings[i] = args[i].toString();
		}
		int lastI = 0;
		for (int i = format.indexOf('{', 0); i >= 0; i = format.indexOf('{',
				lastI)) {
			if (i != 0 && format.charAt(i - 1) == '\\') {
				// It's escaped, just print and loop.
				if (i != 1)
					answer.append(format.substring(lastI, i - 1));
				answer.append('{');
				lastI = i + 1;
			} else {
				// It's a format character.
				if (i > format.length() - 3) {
					// Bad format, just print and loop.
					answer.append(format.substring(lastI, format.length()));
					lastI = format.length();
				} else {
					int argnum = (byte) Character.digit(format.charAt(i + 1),
							10);
					if (argnum < 0 || format.charAt(i + 2) != '}') {
						// Bad format, just print and loop.
						answer.append(format.substring(lastI, i + 1));
						lastI = i + 1;
					} else {
						// Got a good one!
						answer.append(format.substring(lastI, i));
						if (argnum >= argStrings.length)
							answer.append("<missing argument>");
						else
							answer.append(argStrings[argnum]);
						lastI = i + 3;
					}
				}
			}
		}
		if (lastI < format.length())
			answer.append(format.substring(lastI, format.length()));
		return answer.toString();
	}

	/**
	 * Changes the locale of the messages.
	 * 
	 * @param locale
	 *            Locale the locale to change to.
	 */
	static public ResourceBundle setLocale(final Locale locale,
			final String resource) {
		try {
			final ClassLoader loader = VM.bootCallerClassLoader();
			return (ResourceBundle) AccessController
					.doPrivileged(new PrivilegedAction<Object>() {
						public Object run() {
							return ResourceBundle.getBundle(resource, locale,
									loader != null ? loader : ClassLoader.getSystemClassLoader());
						}
					});
		} catch (MissingResourceException e) {
		}
		return null;
	}
}