    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}