    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 */
    018
    019package org.apache.commons.compress.archivers.zip;
    020
    021import static java.nio.charset.StandardCharsets.UTF_8;
    022
    023import java.nio.ByteBuffer;
    024import java.nio.charset.Charset;
    025import java.nio.charset.UnsupportedCharsetException;
    026
    027/**
    028 * Static helper functions for robustly encoding file names in ZIP files.
    029 */
    030public abstract class ZipEncodingHelper {
    031
    032
    033    /**
    034     * name of the encoding UTF-8
    035     */
    036    static final String UTF8 = "UTF8";
    037
    038    /**
    039     * the encoding UTF-8
    040     */
    041    static final ZipEncoding UTF8_ZIP_ENCODING = getZipEncoding(UTF8);
    042
    043    /**
    044     * Instantiates a ZIP encoding. An NIO based character set encoder/decoder will be returned.
    045     * As a special case, if the character set is UTF-8, the nio encoder will be configured  replace malformed and
    046     * unmappable characters with '?'. This matches existing behavior from the older fallback encoder.
    047     * <p>
    048     *     If the requested character set cannot be found, the platform default will
    049     *     be used instead.
    050     * </p>
    051     * @param name The name of the ZIP encoding. Specify {@code null} for
    052     *             the platform's default encoding.
    053     * @return A ZIP encoding for the given encoding name.
    054     */
    055    public static ZipEncoding getZipEncoding(final String name) {
    056        Charset cs = Charset.defaultCharset();
    057        if (name != null) {
    058            try {
    059                cs = Charset.forName(name);
    060            } catch (final UnsupportedCharsetException e) { // NOSONAR we use the default encoding instead
    061            }
    062        }
    063        final boolean useReplacement = isUTF8(cs.name());
    064        return new NioZipEncoding(cs, useReplacement);
    065    }
    066
    067    static ByteBuffer growBufferBy(final ByteBuffer buffer, final int increment) {
    068        buffer.limit(buffer.position());
    069        buffer.rewind();
    070
    071        final ByteBuffer on = ByteBuffer.allocate(buffer.capacity() + increment);
    072
    073        on.put(buffer);
    074        return on;
    075    }
    076
    077    /**
    078     * Returns whether a given encoding is UTF-8. If the given name is null, then check the platform's default encoding.
    079     *
    080     * @param charsetName If the given name is null, then check the platform's default encoding.
    081     */
    082    static boolean isUTF8(final String charsetName) {
    083        final String actual = charsetName != null ? charsetName : Charset.defaultCharset().name();
    084        if (UTF_8.name().equalsIgnoreCase(actual)) {
    085            return true;
    086        }
    087        return UTF_8.aliases().stream().anyMatch(alias -> alias.equalsIgnoreCase(actual));
    088    }
    089}