001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one or more
003 *  contributor license agreements.  See the NOTICE file distributed with
004 *  this work for additional information regarding copyright ownership.
005 *  The ASF licenses this file to You under the Apache License, Version 2.0
006 *  (the "License"); you may not use this file except in compliance with
007 *  the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 *  Unless required by applicable law or agreed to in writing, software
012 *  distributed under the License is distributed on an "AS IS" BASIS,
013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 *  See the License for the specific language governing permissions and
015 *  limitations under the License.
016 */
017
018package org.apache.commons.compress.archivers.zip;
019
020import static java.nio.charset.StandardCharsets.UTF_8;
021
022import java.nio.ByteBuffer;
023import java.nio.charset.Charset;
024import java.nio.charset.UnsupportedCharsetException;
025
026/**
027 * Static helper functions for robustly encoding file names in ZIP files.
028 */
029public abstract class ZipEncodingHelper {
030
031
032    /**
033     * name of the encoding UTF-8
034     */
035    static final String UTF8 = "UTF8";
036
037    /**
038     * the encoding UTF-8
039     */
040    static final ZipEncoding UTF8_ZIP_ENCODING = getZipEncoding(UTF8);
041
042    /**
043     * Instantiates a ZIP encoding. An NIO based character set encoder/decoder will be returned.
044     * As a special case, if the character set is UTF-8, the nio encoder will be configured  replace malformed and
045     * unmappable characters with '?'. This matches existing behavior from the older fallback encoder.
046     * <p>
047     *     If the requested character set cannot be found, the platform default will
048     *     be used instead.
049     * </p>
050     * @param name The name of the ZIP encoding. Specify {@code null} for
051     *             the platform's default encoding.
052     * @return A ZIP encoding for the given encoding name.
053     */
054    public static ZipEncoding getZipEncoding(final String name) {
055        Charset cs = Charset.defaultCharset();
056        if (name != null) {
057            try {
058                cs = Charset.forName(name);
059            } catch (final UnsupportedCharsetException e) { // NOSONAR we use the default encoding instead
060            }
061        }
062        final boolean useReplacement = isUTF8(cs.name());
063        return new NioZipEncoding(cs, useReplacement);
064    }
065
066    static ByteBuffer growBufferBy(final ByteBuffer buffer, final int increment) {
067        buffer.limit(buffer.position());
068        buffer.rewind();
069
070        final ByteBuffer on = ByteBuffer.allocate(buffer.capacity() + increment);
071
072        on.put(buffer);
073        return on;
074    }
075
076    /**
077     * Returns whether a given encoding is UTF-8. If the given name is null, then check the platform's default encoding.
078     *
079     * @param charsetName If the given name is null, then check the platform's default encoding.
080     */
081    static boolean isUTF8(final String charsetName) {
082        final String actual = charsetName != null ? charsetName : Charset.defaultCharset().name();
083        if (UTF_8.name().equalsIgnoreCase(actual)) {
084            return true;
085        }
086        return UTF_8.aliases().stream().anyMatch(alias -> alias.equalsIgnoreCase(actual));
087    }
088}