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Apache Commons Compress software defines an API for working with
compression and archive formats. These include: bzip2, gzip, pack200,
lzma, xz, Snappy, traditional Unix Compress, DEFLATE, DEFLATE64, LZ4,
Brotli, Zstandard and ar, cpio, jar, tar, zip, dump, 7z, arj.
/*
* 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;
import org.apache.commons.compress.utils.OsgiUtils;
/**
* 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 {@code org.tukaani.xz.XZ.HEADER_MAGIC} in
* XZ for Java version 1.5.
*/
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 uncompressSuffix = new HashMap<>();
uncompressSuffix.put(".txz", ".tar");
uncompressSuffix.put(".xz", "");
uncompressSuffix.put("-xz", "");
fileNameUtil = new FileNameUtil(uncompressSuffix, ".xz");
cachedXZAvailability = CachedAvailability.DONT_CACHE;
setCacheXZAvailablity(!OsgiUtils.isRunningInOsgiEnvironment());
}
/** 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 {@link
* XZCompressorInputStream} but doesn't depend on the presence of
* XZ for Java.
*
* @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
* @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) { // NOSONAR
return false;
}
}
/**
* Detects common xz suffixes in the given file name.
*
* @param fileName name of a file
* @return {@code true} if the file name 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 file names 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 file name 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 file name 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 file name.
*
* @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 {@code false} in an OSGi environment and {@code true} otherwise.
* @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;
}
}