    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
    026import org.apache.commons.compress.utils.CharsetNames;
    027import org.apache.commons.compress.utils.Charsets;
    028
    029/**
    030 * Static helper functions for robustly encoding file names in ZIP files.
    031 */
    032public abstract class ZipEncodingHelper {
    033
    034    /**
    035     * UTF-8.
    036     */
    037    static final ZipEncoding ZIP_ENCODING_UTF_8 = getZipEncoding(CharsetNames.UTF_8);
    038
    039    /**
    040     * Instantiates a ZIP encoding. An NIO based character set encoder/decoder will be returned.
    041     * As a special case, if the character set is UTF-8, theNIOencoder will be configured  replace malformed and
    042     * unmappable characters with '?'. This matches existing behavior from the older fallback encoder.
    043     * <p>
    044     *     If the requested character set cannot be found, the platform default will
    045     *     be used instead.
    046     * </p>
    047     * @param name The name of the ZIP encoding. Specify {@code null} for
    048     *             the platform's default encoding.
    049     * @return A ZIP encoding for the given encoding name.
    050     */
    051    public static ZipEncoding getZipEncoding(final String name) {
    052        Charset cs = Charset.defaultCharset();
    053        try {
    054            cs = Charsets.toCharset(name);
    055        } catch (final UnsupportedCharsetException ignore) { // NOSONAR we use the default encoding instead
    056        }
    057        final boolean useReplacement = isUTF8(cs.name());
    058        return new NioZipEncoding(cs, useReplacement);
    059    }
    060
    061    static ByteBuffer growBufferBy(final ByteBuffer buffer, final int increment) {
    062        buffer.limit(buffer.position());
    063        buffer.rewind();
    064
    065        final ByteBuffer on = ByteBuffer.allocate(buffer.capacity() + increment);
    066
    067        on.put(buffer);
    068        return on;
    069    }
    070
    071    /**
    072     * Tests whether a given encoding is UTF-8. If the given name is null, then check the platform's default encoding.
    073     *
    074     * @param charsetName If the given name is null, then check the platform's default encoding.
    075     */
    076    static boolean isUTF8(final String charsetName) {
    077        final String actual = charsetName != null ? charsetName : Charset.defaultCharset().name();
    078        if (UTF_8.name().equalsIgnoreCase(actual)) {
    079            return true;
    080        }
    081        return UTF_8.aliases().stream().anyMatch(alias -> alias.equalsIgnoreCase(actual));
    082    }
    083}