    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 java.nio.ByteBuffer;
    022import java.nio.charset.Charset;
    023import java.nio.charset.StandardCharsets;
    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    /**
    067     * Returns whether a given encoding is UTF-8. If the given name is null, then check the platform's default encoding.
    068     *
    069     * @param charsetName If the given name is null, then check the platform's default encoding.
    070     */
    071    static boolean isUTF8(String charsetName) {
    072        if (charsetName == null) {
    073            // check platform's default encoding
    074            charsetName = Charset.defaultCharset().name();
    075        }
    076        if (StandardCharsets.UTF_8.name().equalsIgnoreCase(charsetName)) {
    077            return true;
    078        }
    079        for (final String alias : StandardCharsets.UTF_8.aliases()) {
    080            if (alias.equalsIgnoreCase(charsetName)) {
    081                return true;
    082            }
    083        }
    084        return false;
    085    }
    086
    087    static ByteBuffer growBufferBy(final ByteBuffer buffer, final int increment) {
    088        buffer.limit(buffer.position());
    089        buffer.rewind();
    090
    091        final ByteBuffer on = ByteBuffer.allocate(buffer.capacity() + increment);
    092
    093        on.put(buffer);
    094        return on;
    095    }
    096}