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 * distributed with this work for additional information
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 * 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
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 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
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 * KIND, either express or implied.  See the License for the
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package org.apache.commons.compress.compressors.lzma;

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

Utility code for the lzma compression format.
@ThreadSafe
Since:1.10
/** * Utility code for the lzma compression format. * @ThreadSafe * @since 1.10 */
public class LZMAUtils { private static final FileNameUtil fileNameUtil;
LZMA Header Magic Bytes begin a LZMA file.
/** * LZMA Header Magic Bytes begin a LZMA file. */
private static final byte[] HEADER_MAGIC = { (byte) 0x5D, 0, 0 }; enum CachedAvailability { DONT_CACHE, CACHED_AVAILABLE, CACHED_UNAVAILABLE } private static volatile CachedAvailability cachedLZMAAvailability; static { final Map<String, String> uncompressSuffix = new HashMap<>(); uncompressSuffix.put(".lzma", ""); uncompressSuffix.put("-lzma", ""); fileNameUtil = new FileNameUtil(uncompressSuffix, ".lzma"); cachedLZMAAvailability = CachedAvailability.DONT_CACHE; try { Class.forName("org.osgi.framework.BundleEvent"); } catch (final Exception ex) { // NOSONAR setCacheLZMAAvailablity(true); } }
Private constructor to prevent instantiation of this utility class.
/** Private constructor to prevent instantiation of this utility class. */
private LZMAUtils() { }
Checks if the signature matches what is expected for a .lzma file.
Params:
  • signature – the bytes to check
  • length – the number of bytes to check
Returns: true if signature matches the .lzma magic bytes, false otherwise
/** * Checks if the signature matches what is expected for a .lzma file. * * @param signature the bytes to check * @param length the number of bytes to check * @return true if signature matches the .lzma magic bytes, false otherwise */
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 LZMA compression available?
Returns:true if the classes required to support LZMA compression are available
/** * Are the classes required to support LZMA compression available? * @return true if the classes required to support LZMA * compression are available */
public static boolean isLZMACompressionAvailable() { final CachedAvailability cachedResult = cachedLZMAAvailability; if (cachedResult != CachedAvailability.DONT_CACHE) { return cachedResult == CachedAvailability.CACHED_AVAILABLE; } return internalIsLZMACompressionAvailable(); } private static boolean internalIsLZMACompressionAvailable() { try { LZMACompressorInputStream.matches(null, 0); return true; } catch (final NoClassDefFoundError error) { // NOSONAR return false; } }
Detects common lzma suffixes in the given file name.
Params:
  • fileName – name of a file
Returns:true if the file name has a common lzma suffix, false otherwise
/** * Detects common lzma suffixes in the given file name. * * @param fileName name of a file * @return {@code true} if the file name has a common lzma suffix, * {@code false} otherwise */
public static boolean isCompressedFilename(final String fileName) { return fileNameUtil.isCompressedFilename(fileName); }
Maps the given name of a lzma-compressed file to the name that the file should have after uncompression. Any file names with the generic ".lzma" suffix (or any other generic lzma suffix) is mapped to a name without that suffix. If no lzma suffix is detected, then the file name is returned unmapped.
Params:
  • fileName – name of a file
Returns:name of the corresponding uncompressed file
/** * Maps the given name of a lzma-compressed file to the name that * the file should have after uncompression. Any file names with * the generic ".lzma" suffix (or any other generic lzma suffix) * is mapped to a name without that suffix. If no lzma 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 lzma.
Params:
  • fileName – name of a file
Returns:name of the corresponding compressed file
/** * Maps the given file name to the name that the file should have after * compression with lzma. * * @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 LZMA check.

This defaults to false in an OSGi environment and true otherwise.

Params:
  • doCache – whether to cache the result
/** * Whether to cache the result of the LZMA check. * * <p>This defaults to {@code false} in an OSGi environment and {@code true} otherwise.</p> * @param doCache whether to cache the result */
public static void setCacheLZMAAvailablity(final boolean doCache) { if (!doCache) { cachedLZMAAvailability = CachedAvailability.DONT_CACHE; } else if (cachedLZMAAvailability == CachedAvailability.DONT_CACHE) { final boolean hasLzma = internalIsLZMACompressionAvailable(); cachedLZMAAvailability = hasLzma ? CachedAvailability.CACHED_AVAILABLE // NOSONAR : CachedAvailability.CACHED_UNAVAILABLE; } } // only exists to support unit tests static CachedAvailability getCachedLZMAAvailability() { return cachedLZMAAvailability; } }