/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.commons.compress.compressors.xz;

import java.util.HashMap;
import java.util.Map;
import org.apache.commons.compress.compressors.FileNameUtil;

Utility code for the xz compression format.
@ThreadSafe
Since:
1.4/**
 * Utility code for the xz compression format.
 * @ThreadSafe
 * @since 1.4
 */
public class XZUtils {

    private static final FileNameUtil fileNameUtil;

    
XZ Header Magic Bytes begin a XZ file.
This is a copy of org.tukaani.xz.XZ.HEADER_MAGIC in XZ for Java version 1.5.
/**
     * XZ Header Magic Bytes begin a XZ file.
     *
     * <p>This is a copy of {@code org.tukaani.xz.XZ.HEADER_MAGIC} in
     * XZ for Java version 1.5.</p>
     */
    private static final byte[] HEADER_MAGIC = {
        (byte) 0xFD, '7', 'z', 'X', 'Z', '\0'
    };

    enum CachedAvailability {
        DONT_CACHE, CACHED_AVAILABLE, CACHED_UNAVAILABLE
    }

    private static volatile CachedAvailability cachedXZAvailability;

    static {
        final Map<String, String> uncompressSuffix = new HashMap<>();
        uncompressSuffix.put(".txz", ".tar");
        uncompressSuffix.put(".xz", "");
        uncompressSuffix.put("-xz", "");
        fileNameUtil = new FileNameUtil(uncompressSuffix, ".xz");
        cachedXZAvailability = CachedAvailability.DONT_CACHE;
        try {
            Class.forName("org.osgi.framework.BundleEvent");
        } catch (final Exception ex) {
            setCacheXZAvailablity(true);
        }
    }

    
Private constructor to prevent instantiation of this utility class. /** Private constructor to prevent instantiation of this utility class. */
    private XZUtils() {
    }

    
Checks if the signature matches what is expected for a .xz file.
This is more or less a copy of the version found in XZCompressorInputStream but doesn't depend on the presence of XZ for Java.
Params:
signature –     the bytes to check
length –        the number of bytes to check
Returns:
 true if signature matches the .xz magic bytes, false otherwise
Since:
1.9/**
     * Checks if the signature matches what is expected for a .xz file.
     *
     * <p>This is more or less a copy of the version found in {@link
     * XZCompressorInputStream} but doesn't depend on the presence of
     * XZ for Java.</p>
     *
     * @param   signature     the bytes to check
     * @param   length        the number of bytes to check
     * @return  true if signature matches the .xz magic bytes, false otherwise
     * @since 1.9
     */
    public static boolean matches(final byte[] signature, final int length) {
        if (length < HEADER_MAGIC.length) {
            return false;
        }

        for (int i = 0; i < HEADER_MAGIC.length; ++i) {
            if (signature[i] != HEADER_MAGIC[i]) {
                return false;
            }
        }

        return true;
    }

    
Are the classes required to support XZ compression available?
Since:
1.5
Returns:
true if the classes required to support XZ compression are available/**
     * Are the classes required to support XZ compression available?
     * @since 1.5
     * @return true if the classes required to support XZ compression are available
     */
    public static boolean isXZCompressionAvailable() {
        final CachedAvailability cachedResult = cachedXZAvailability;
        if (cachedResult != CachedAvailability.DONT_CACHE) {
            return cachedResult == CachedAvailability.CACHED_AVAILABLE;
        }
        return internalIsXZCompressionAvailable();
    }

    private static boolean internalIsXZCompressionAvailable() {
        try {
            XZCompressorInputStream.matches(null, 0);
            return true;
        } catch (final NoClassDefFoundError error) {
            return false;
        }
    }

    
Detects common xz suffixes in the given filename.
Params:
filename – name of a file
Returns:
true if the filename has a common xz suffix, false otherwise/**
     * Detects common xz suffixes in the given filename.
     *
     * @param filename name of a file
     * @return {@code true} if the filename has a common xz suffix,
     *         {@code false} otherwise
     */
    public static boolean isCompressedFilename(final String filename) {
        return fileNameUtil.isCompressedFilename(filename);
    }

    
Maps the given name of a xz-compressed file to the name that the
file should have after uncompression. Commonly used file type specific
suffixes like ".txz" are automatically detected and
correctly mapped. For example the name "package.txz" is mapped to
"package.tar". And any filenames with the generic ".xz" suffix
(or any other generic xz suffix) is mapped to a name without that
suffix. If no xz suffix is detected, then the filename is returned
unmapped.
Params:
filename – name of a file
Returns:
name of the corresponding uncompressed file/**
     * Maps the given name of a xz-compressed file to the name that the
     * file should have after uncompression. Commonly used file type specific
     * suffixes like ".txz" are automatically detected and
     * correctly mapped. For example the name "package.txz" is mapped to
     * "package.tar". And any filenames with the generic ".xz" suffix
     * (or any other generic xz suffix) is mapped to a name without that
     * suffix. If no xz suffix is detected, then the filename is returned
     * unmapped.
     *
     * @param filename name of a file
     * @return name of the corresponding uncompressed file
     */
    public static String getUncompressedFilename(final String filename) {
        return fileNameUtil.getUncompressedFilename(filename);
    }

    
Maps the given filename to the name that the file should have after
compression with xz. Common file types with custom suffixes for
compressed versions are automatically detected and correctly mapped.
For example the name "package.tar" is mapped to "package.txz". If no
custom mapping is applicable, then the default ".xz" suffix is appended
to the filename.
Params:
filename – name of a file
Returns:
name of the corresponding compressed file/**
     * Maps the given filename to the name that the file should have after
     * compression with xz. Common file types with custom suffixes for
     * compressed versions are automatically detected and correctly mapped.
     * For example the name "package.tar" is mapped to "package.txz". If no
     * custom mapping is applicable, then the default ".xz" suffix is appended
     * to the filename.
     *
     * @param filename name of a file
     * @return name of the corresponding compressed file
     */
    public static String getCompressedFilename(final String filename) {
        return fileNameUtil.getCompressedFilename(filename);
    }

    
Whether to cache the result of the XZ for Java check.
This defaults to false in an OSGi environment and true otherwise.
Params:
doCache – whether to cache the result
Since:
1.9/**
     * Whether to cache the result of the XZ for Java check.
     *
     * <p>This defaults to {@code false} in an OSGi environment and {@code true} otherwise.</p>
     * @param doCache whether to cache the result
     * @since 1.9
     */
    public static void setCacheXZAvailablity(final boolean doCache) {
        if (!doCache) {
            cachedXZAvailability = CachedAvailability.DONT_CACHE;
        } else if (cachedXZAvailability == CachedAvailability.DONT_CACHE) {
            final boolean hasXz = internalIsXZCompressionAvailable();
            cachedXZAvailability = hasXz ? CachedAvailability.CACHED_AVAILABLE // NOSONAR
                : CachedAvailability.CACHED_UNAVAILABLE;
        }
    }

    // only exists to support unit tests
    static CachedAvailability getCachedXZAvailability() {
        return cachedXZAvailability;
    }
}