001/****************************************************************
002 * Licensed to the Apache Software Foundation (ASF) under one   *
003 * or more contributor license agreements.  See the NOTICE file *
004 * distributed with this work for additional information        *
005 * regarding copyright ownership.  The ASF licenses this file   *
006 * to you under the Apache License, Version 2.0 (the            *
007 * "License"); you may not use this file except in compliance   *
008 * with the License.  You may obtain a copy of the License at   *
009 *                                                              *
010 *   http://www.apache.org/licenses/LICENSE-2.0                 *
011 *                                                              *
012 * Unless required by applicable law or agreed to in writing,   *
013 * software distributed under the License is distributed on an  *
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
015 * KIND, either express or implied.  See the License for the    *
016 * specific language governing permissions and limitations      *
017 * under the License.                                           *
018 ****************************************************************/
019
020package org.apache.james.mime4j.util;
021
022import java.nio.charset.Charset;
023import java.nio.charset.IllegalCharsetNameException;
024import java.nio.charset.UnsupportedCharsetException;
025
026/**
027 * Utility class for working with character sets.
028 */
029public class CharsetUtil {
030
031    /** carriage return - line feed sequence */
032    public static final String CRLF = "\r\n";
033
034    /** US-ASCII CR, carriage return (13) */
035    public static final int CR = '\r';
036
037    /** US-ASCII LF, line feed (10) */
038    public static final int LF = '\n';
039
040    /** US-ASCII SP, space (32) */
041    public static final int SP = ' ';
042
043    /** US-ASCII HT, horizontal-tab (9) */
044    public static final int HT = '\t';
045
046    public static final Charset US_ASCII = Charset.forName("US-ASCII");
047
048    public static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");
049
050    public static final Charset UTF_8 = Charset.forName("UTF-8");
051
052    public static final Charset DEFAULT_CHARSET = US_ASCII;
053
054    /**
055     * Returns <code>true</code> if the specified character falls into the US
056     * ASCII character set (Unicode range 0000 to 007f).
057     *
058     * @param ch
059     *            character to test.
060     * @return <code>true</code> if the specified character falls into the US
061     *         ASCII character set, <code>false</code> otherwise.
062     */
063    public static boolean isASCII(char ch) {
064        return (0xFF80 & ch) == 0;
065    }
066
067    /**
068     * Returns <code>true</code> if the specified string consists entirely of
069     * US ASCII characters.
070     *
071     * @param s
072     *            string to test.
073     * @return <code>true</code> if the specified string consists entirely of
074     *         US ASCII characters, <code>false</code> otherwise.
075     */
076    public static boolean isASCII(final String s) {
077        if (s == null) {
078            throw new IllegalArgumentException("String may not be null");
079        }
080        final int len = s.length();
081        for (int i = 0; i < len; i++) {
082            if (!isASCII(s.charAt(i))) {
083                return false;
084            }
085        }
086        return true;
087    }
088
089    /**
090     * Returns <code>true</code> if the specified character is a whitespace
091     * character (CR, LF, SP or HT).
092     *
093     * @param ch
094     *            character to test.
095     * @return <code>true</code> if the specified character is a whitespace
096     *         character, <code>false</code> otherwise.
097     */
098    public static boolean isWhitespace(char ch) {
099        return ch == SP || ch == HT || ch == CR || ch == LF;
100    }
101
102    /**
103     * Returns <code>true</code> if the specified string consists entirely of
104     * whitespace characters.
105     *
106     * @param s
107     *            string to test.
108     * @return <code>true</code> if the specified string consists entirely of
109     *         whitespace characters, <code>false</code> otherwise.
110     */
111    public static boolean isWhitespace(final String s) {
112        if (s == null) {
113            throw new IllegalArgumentException("String may not be null");
114        }
115        final int len = s.length();
116        for (int i = 0; i < len; i++) {
117            if (!isWhitespace(s.charAt(i))) {
118                return false;
119            }
120        }
121        return true;
122    }
123
124    /**
125     * Returns a {@link Charset} instance if character set with the given name
126     * is recognized and supported by Java runtime. Returns <code>null</code>
127     * otherwise.
128     * <p/>
129     * This method is a wrapper around {@link Charset#forName(String)} method
130     * that catches {@link IllegalCharsetNameException} and
131     *  {@link UnsupportedCharsetException} and returns <code>null</code>.
132     */
133    public static Charset lookup(final String name) {
134        if (name == null) {
135            return null;
136        }
137        try {
138            return Charset.forName(name);
139        } catch (IllegalCharsetNameException ex) {
140            return null;
141        } catch (UnsupportedCharsetException ex) {
142            return null;
143        }
144    }
145
146 }