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<?xml version="1.0"?>
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<document xmlns="http://maven.apache.org/XDOC/2.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/XDOC/2.0 https://maven.apache.org/xsd/xdoc-2.0.xsd">
<properties>
<title>Known Limitations and Problems</title>
</properties>
<body>
<section name="General">
<p>
This page lists the known limitations and problems of Apache
Commons Compress™ grouped by the archiving/compression
format they apply to.
</p>
<ul>
<li>Several implementations of decompressors and unarchivers will
invoke <a
href="https://docs.oracle.com/javase/10/docs/api/java/io/InputStream.html#skip(long)"><code>skip</code></a>
on the underlying <code>InputStream</code> which may throw an
<code>IOException</code> in some stream implementations. One
known case where this happens is when using
<code>System.in</code> as input. If you encounter an
exception with a message like "Illegal seek" we recommend you
wrap your stream in a <code>SkipShieldingInputStream</code>
from our utils package before passing it to Compress.</li>
<li>Commons Compress prior to 1.21 cannot be built on JDK 14 or newer.</li>
</ul>
</section>
<section name="7Z">
<ul>
<li>the format requires the otherwise optional <a
href="https://tukaani.org/xz/java.html">XZ for Java</a>
library.</li>
<li>only <code>File</code>s are supported as input/output,
not streams. Starting with Compress 1.13
<code>SeekableByteChannel</code> is supported as well.</li>
<li>In Compress 1.7
<code>ArchiveStreamFactory</code> will not auto-detect 7z
archives, starting with 1.8 it will throw a
<code>StreamingNotSupportedException</code> when reading from
a 7z archive.</li>
<li>Encryption, solid compression and header compression
are only supported when reading archives</li>
<li>Commons Compress 1.12 and earlier didn't support writing
LZMA.</li>
<li>Several of the "methods" supported by 7z are not
implemented in Compress.</li>
<li>No support for writing multi-volume archives. Such
archives can be read by simply concatenating the parts, for
example by using
<code>MultiReadOnlySeekableByteChannel</code>.</li>
<li>Support for some BCJ filters and the DELTA filter has
been added with Compress 1.8. Because of a known bug in
version 1.4 of the <a
href="https://tukaani.org/xz/java.html">XZ for Java</a>
library, archives using BCJ filters will cause an
<code>AssertionError</code> when read. If you need support
for BCJ filters you must use XZ for Java 1.5 or later.</li>
</ul>
</section>
<section name="AR">
<ul>
<li>AR archives can not contain directories - this is a
limitation of the format rather than one of Compress'
implementation.</li>
<li>file names longer than 16 characters are only fully
supported using the BSD dialect, the GNU/SRV4 dialect is only
supported when reading archives.</li>
</ul>
</section>
<section name="ARJ">
<ul>
<li>read-only support</li>
<li>no support for compression, encryption or multi-volume
archives</li>
</ul>
</section>
<section name="Brotli">
<ul>
<li>the format requires the otherwise optional <a
href="https://github.com/google/brotli">Google Brotli dec</a>
library.</li>
<li>read-only support</li>
<li><code>CompressorStreamFactory</code> is not able to auto-detect
streams using Brotli compression.</li>
</ul>
</section>
<section name="BZIP2">
<p>Versions of Compress prior to 1.4.1 are vulnerable to a
possible denial of service attack, see the <a
href="security.html">Security Reports</a> page for details.</p>
</section>
<section name="CPIO">
<p>We are not aware of any problems.</p>
</section>
<section name="DEFLATE">
<ul>
<li><code>CompressorStreamFactory</code> is not able to auto-detect
streams using DEFLATE compression.</li>
</ul>
</section>
<section name="DEFLATE64">
<ul>
<li><code>CompressorStreamFactory</code> is not able to auto-detect
streams using DEFLATE64 compression.</li>
<li>read-only support</li>
</ul>
</section>
<section name="DUMP">
<ul>
<li>read-only support</li>
<li>only the new-fs format is supported</li>
<li>the only compression algorithm supported is zlib</li>
</ul>
</section>
<section name="GZIP">
<p>We are not aware of any problems.</p>
</section>
<section name="JAR">
<p>JAR archives are special ZIP archives, all limitations of <a
href="#ZIP">ZIP</a> apply to JAR as well.</p>
<ul>
<li><code>ArchiveStreamFactory</code> cannot tell JAR
archives from ZIP archives and will not auto-detect
JARs.</li>
<li>Compress doesn't provide special access to the archive's
MANIFEST</li>
</ul>
</section>
<section name="LZ4">
<ul>
<li>In theory LZ4 compressed streams can contain literals and
copies of arbitrary length while Commons Compress only
supports sizes up to 2<sup>63</sup> - 1 (i.e. ≈ 9.2
EB).</li>
</ul>
</section>
<section name="LZMA">
<ul>
<li>the format requires the otherwise optional <a
href="https://tukaani.org/xz/java.html">XZ for Java</a>
library.</li>
<li>Commons Compress 1.12 and earlier only support reading
the format</li>
</ul>
</section>
<section name="PACK200">
<ul>
<li><p>Pack200 support in Commons Compress prior to 1.21 relies on the
<code>Pack200</code> class of the Java classlib. Java 14
removed support and thus Pack200 will not work at all when
running on Java 14 or later.</p>
<p>Starting with Commons Compress 1.21 the classlib
implementation is no longer used at all, instead Commons
Compress contains the pack200 code of the retired Apache
Harmony™ project.</p></li>
</ul>
</section>
<section name="SNAPPY">
<ul>
<li>Commons Compress 1.13 and earlier only support reading
the format</li>
</ul>
</section>
<section name="TAR">
<ul>
<li>sparse files could not be read in version prior to
Compress 1.20</li>
<li>sparse files can not be written</li>
<li>only a subset of the GNU and POSIX extensions are
supported</li>
<li>In Compress 1.6 <code>TarArchiveInputStream</code> could
fail to read the full contents of an entry unless the stream
was wrapped in a buffering stream.</li>
</ul>
</section>
<section name="XZ">
<ul>
<li>the format requires the otherwise optional <a
href="https://tukaani.org/xz/java.html">XZ for Java</a>
library.</li>
</ul>
</section>
<section name="Z">
<ul>
<li>Prior to Compress 1.8.1
<code>CompressorStreamFactory</code> was not able to
auto-detect streams using .Z compression.</li>
<li>read-only support</li>
</ul>
</section>
<section name="ZIP">
<ul>
<li><code>ZipArchiveInputStream</code> is limited and may
even return false contents in some cases, use
<code>ZipFile</code> whenever possible. See <a
href="zip.html#ZipArchiveInputStream_vs_ZipFile">the ZIP
documentation page</a> for details. This limitation is a
result of streaming data vs using random access and not a
limitation of Compress' specific implementation.</li>
<li>only a subset of compression methods are supported,
including the most common STORED and DEFLATEd. IMPLODE,
SHRINK, DEFLATE64 and BZIP2 support is read-only.</li>
<li>no support for encryption</li>
<li>no support for multi-volume archives prior to Compress 1.20</li>
<li>It is currently not possible to write split archives with
more than 64k segments. When creating split archives with more
than 100 segments you will need to adjust the file names as
<code>ZipArchiveOutputStream</code> assumes extensions will be
three characters long.</li>
<li>In versions prior to Compress 1.6
<code>ZipArchiveEntries</code> read from an archive will
contain non-zero millisecond values when using Java 8 or later rather
than the expected two-second granularity.</li>
<li>Compress 1.7 has a known bug where the very first entry
of an archive will not be read correctly by
<code>ZipArchiveInputStream</code> if it used the STORED
method.</li>
<li><code>ZipArchiveEntry#getLastModifiedDate</code> uses
<code>ZipEntry#getTime</code> under the covers which may
return different times for the same archive when using
different versions of Java.</li>
<li>In versions of Compress prior to 1.16 a specially crafted
ZIP archive can be used to cause an infinite loop inside of
Compress' extra field parser used by the <code>ZipFile</code>
and <code>ZipArchiveInputStream</code> classes. This can be
used to mount a denial of service attack against services
that use Compress' zip package. See the <a
href="security.html">Security Reports</a> page for
details.</li>
</ul>
</section>
<section name="Zstandard">
<ul>
<li>the format requires the otherwise optional <a
href="https://github.com/luben/zstd-jni">Zstandard JNI</a>
library.</li>
</ul>
</section>
</body>
</document>
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