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<?xml version="1.0"?>
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<document>
<properties>
<title>Commons Compress Examples</title>
<author email="dev@commons.apache.org">Commons Documentation Team</author>
</properties>
<body>
<section name="Examples">
<subsection name="Archivers and Compressors">
<p>Commons Compress calls all formats that compress a single
stream of data compressor formats while all formats that
collect multiple entries inside a single (potentially
compressed) archive are archiver formats.</p>
<p>The compressor formats supported are gzip, bzip2, xz, lzma,
Pack200, DEFLATE and Z, the archiver formats are 7z, ar, arj,
cpio, dump, tar and zip. Pack200 is a special case as it can
only compress JAR files.</p>
<p>We currently only provide read support for arj,
dump and Z. arj can only read uncompressed archives, 7z can read
archives with many compression and encryption algorithms
supported by 7z but doesn't support encryption when writing
archives.</p>
</subsection>
<subsection name="Common Notes">
<p>The stream classes all wrap around streams provided by the
calling code and they work on them directly without any
additional buffering. On the other hand most of them will
benefit from buffering so it is highly recommended that
users wrap their stream
in <code>Buffered<em>(In|Out)</em>putStream</code>s before
using the Commons Compress API.</p>
</subsection>
<subsection name="Factories">
<p>Compress provides factory methods to create input/output
streams based on the names of the compressor or archiver
format as well as factory methods that try to guess the
format of an input stream.</p>
<p>To create a compressor writing to a given output by using
the algorithm name:</p>
<source><![CDATA[
CompressorOutputStream gzippedOut = new CompressorStreamFactory()
.createCompressorOutputStream(CompressorStreamFactory.GZIP, myOutputStream);
]]></source>
<p>Make the factory guess the input format for a given
archiver stream:</p>
<source><![CDATA[
ArchiveInputStream input = new ArchiveStreamFactory()
.createArchiveInputStream(originalInput);
]]></source>
<p>Make the factory guess the input format for a given
compressor stream:</p>
<source><![CDATA[
CompressorInputStream input = new CompressorStreamFactory()
.createCompressorInputStream(originalInput);
]]></source>
<p>Note that there is no way to detect the lzma format so only
the two-arg version of
<code>createCompressorInputStream</code> can be used. Prior
to Compress 1.9 the .Z format hasn't been auto-detected
either.</p>
</subsection>
<subsection name="Unsupported Features">
<p>Many of the supported formats have developed different
dialects and extensions and some formats allow for features
(not yet) supported by Commons Compress.</p>
<p>The <code>ArchiveInputStream</code> class provides a method
<code>canReadEntryData</code> that will return false if
Commons Compress can detect that an archive uses a feature
that is not supported by the current implementation. If it
returns false you should not try to read the entry but skip
over it.</p>
</subsection>
<subsection name="Concatenated Streams">
<p>For the bzip2, gzip and xz formats a single compressed file
may actually consist of several streams that will be
concatenated by the command line utilities when decompressing
them. Starting with Commons Compress 1.4 the
<code>*CompressorInputStream</code>s for these formats support
concatenating streams as well, but they won't do so by
default. You must use the two-arg constructor and explicitly
enable the support.</p>
</subsection>
<subsection name="ar">
<p>In addition to the information stored
in <code>ArchiveEntry</code> a <code>ArArchiveEntry</code>
stores information about the owner user and group as well as
Unix permissions.</p>
<p>Adding an entry to an ar archive:</p>
<source><![CDATA[
ArArchiveEntry entry = new ArArchiveEntry(name, size);
arOutput.putArchiveEntry(entry);
arOutput.write(contentOfEntry);
arOutput.closeArchiveEntry();
]]></source>
<p>Reading entries from an ar archive:</p>
<source><![CDATA[
ArArchiveEntry entry = (ArArchiveEntry) arInput.getNextEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
arInput.read(content, offset, content.length - offset);
}
]]></source>
<p>Traditionally the AR format doesn't allow file names longer
than 16 characters. There are two variants that circumvent
this limitation in different ways, the GNU/SRV4 and the BSD
variant. Commons Compress 1.0 to 1.2 can only read archives
using the GNU/SRV4 variant, support for the BSD variant has
been added in Commons Compress 1.3. Commons Compress 1.3
also optionally supports writing archives with file names
longer than 16 characters using the BSD dialect, writing
the SVR4/GNU dialect is not supported.</p>
<p>It is not possible to detect the end of an AR archive in a
reliable way so <code>ArArchiveInputStream</code> will read
until it reaches the end of the stream or fails to parse the
stream's content as AR entries.</p>
</subsection>
<subsection name="cpio">
<p>In addition to the information stored
in <code>ArchiveEntry</code> a <code>CpioArchiveEntry</code>
stores various attributes including information about the
original owner and permissions.</p>
<p>The cpio package supports the "new portable" as well as the
"old" format of CPIO archives in their binary, ASCII and
"with CRC" variants.</p>
<p>Adding an entry to a cpio archive:</p>
<source><![CDATA[
CpioArchiveEntry entry = new CpioArchiveEntry(name, size);
cpioOutput.putArchiveEntry(entry);
cpioOutput.write(contentOfEntry);
cpioOutput.closeArchiveEntry();
]]></source>
<p>Reading entries from an cpio archive:</p>
<source><![CDATA[
CpioArchiveEntry entry = cpioInput.getNextCPIOEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
cpioInput.read(content, offset, content.length - offset);
}
]]></source>
<p>Traditionally CPIO archives are written in blocks of 512
bytes - the block size is a configuration parameter of the
<code>Cpio*Stream</code>'s constuctors. Starting with version
1.5 <code>CpioArchiveInputStream</code> will consume the
padding written to fill the current block when the end of the
archive is reached. Unfortunately many CPIO implementations
use larger block sizes so there may be more zero-byte padding
left inside the original input stream after the archive has
been consumed completely.</p>
</subsection>
<subsection name="dump">
<p>In addition to the information stored
in <code>ArchiveEntry</code> a <code>DumpArchiveEntry</code>
stores various attributes including information about the
original owner and permissions.</p>
<p>As of Commons Compress 1.3 only dump archives using the
new-fs format - this is the most common variant - are
supported. Right now this library supports uncompressed and
ZLIB compressed archives and can not write archives at
all.</p>
<p>Reading entries from an dump archive:</p>
<source><![CDATA[
DumpArchiveEntry entry = dumpInput.getNextDumpEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
dumpInput.read(content, offset, content.length - offset);
}
]]></source>
<p>Prior to version 1.5 <code>DumpArchiveInputStream</code>
would close the original input once it had read the last
record. Starting with version 1.5 it will not close the
stream implicitly.</p>
</subsection>
<subsection name="tar">
<p>The TAR package has a <a href="tar.html">dedicated
documentation page</a>.</p>
<p>Adding an entry to a tar archive:</p>
<source><![CDATA[
TarArchiveEntry entry = new TarArchiveEntry(name);
entry.setSize(size);
tarOutput.putArchiveEntry(entry);
tarOutput.write(contentOfEntry);
tarOutput.closeArchiveEntry();
]]></source>
<p>Reading entries from an tar archive:</p>
<source><![CDATA[
TarArchiveEntry entry = tarInput.getNextTarEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
tarInput.read(content, offset, content.length - offset);
}
]]></source>
</subsection>
<subsection name="zip">
<p>The ZIP package has a <a href="zip.html">dedicated
documentation page</a>.</p>
<p>Adding an entry to a zip archive:</p>
<source><![CDATA[
ZipArchiveEntry entry = new ZipArchiveEntry(name);
entry.setSize(size);
zipOutput.putArchiveEntry(entry);
zipOutput.write(contentOfEntry);
zipOutput.closeArchiveEntry();
]]></source>
<p><code>ZipArchiveOutputStream</code> can use some internal
optimizations exploiting <code>SeekableByteChannel</code> if it
knows it is writing to a seekable output rather than a non-seekable
stream. If you are writing to a file, you should use the
constructor that accepts a <code>File</code> or
<code>SeekableByteChannel</code> argument rather
than the one using an <code>OutputStream</code> or the
factory method in <code>ArchiveStreamFactory</code>.</p>
<p>Reading entries from an zip archive:</p>
<source><![CDATA[
ZipArchiveEntry entry = zipInput.getNextZipEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
zipInput.read(content, offset, content.length - offset);
}
]]></source>
<p>Reading entries from an zip archive using the
recommended <code>ZipFile</code> class:</p>
<source><![CDATA[
ZipArchiveEntry entry = zipFile.getEntry(name);
InputStream content = zipFile.getInputStream(entry);
try {
READ UNTIL content IS EXHAUSTED
} finally {
content.close();
}
]]></source>
<p>Reading entries from an in-memory zip archive using
<code>SeekableInMemoryByteChannel</code> and <code>ZipFile</code> class:</p>
<source><![CDATA[
byte[] inputData; // zip archive contents
SeekableInMemoryByteChannel inMemoryByteChannel = new SeekableInMemoryByteChannel(inputData);
ZipFile zipFile = new ZipFile(inMemoryByteChannel);
ZipArchiveEntry archiveEntry = zipFile.getEntry("entryName");
InputStream inputStream = zipFile.getInputStream(archiveEntry);
inputStream.read() // read data from the input stream
]]></source>
<p>Creating a zip file with multiple threads:</p>
A simple implementation to create a zip file might look like this:
<source>
public class ScatterSample {
ParallelScatterZipCreator scatterZipCreator = new ParallelScatterZipCreator();
ScatterZipOutputStream dirs = ScatterZipOutputStream.fileBased(File.createTempFile("scatter-dirs", "tmp"));
public ScatterSample() throws IOException {
}
public void addEntry(ZipArchiveEntry zipArchiveEntry, InputStreamSupplier streamSupplier) throws IOException {
if (zipArchiveEntry.isDirectory() &amp;&amp; !zipArchiveEntry.isUnixSymlink())
dirs.addArchiveEntry(ZipArchiveEntryRequest.createZipArchiveEntryRequest(zipArchiveEntry, streamSupplier));
else
scatterZipCreator.addArchiveEntry( zipArchiveEntry, streamSupplier);
}
public void writeTo(ZipArchiveOutputStream zipArchiveOutputStream)
throws IOException, ExecutionException, InterruptedException {
dirs.writeTo(zipArchiveOutputStream);
dirs.close();
scatterZipCreator.writeTo(zipArchiveOutputStream);
}
}
</source>
</subsection>
<subsection name="jar">
<p>In general, JAR archives are ZIP files, so the JAR package
supports all options provided by the ZIP package.</p>
<p>To be interoperable JAR archives should always be created
using the UTF-8 encoding for file names (which is the
default).</p>
<p>Archives created using <code>JarArchiveOutputStream</code>
will implicitly add a <code>JarMarker</code> extra field to
the very first archive entry of the archive which will make
Solaris recognize them as Java archives and allows them to
be used as executables.</p>
<p>Note that <code>ArchiveStreamFactory</code> doesn't
distinguish ZIP archives from JAR archives, so if you use
the one-argument <code>createArchiveInputStream</code>
method on a JAR archive, it will still return the more
generic <code>ZipArchiveInputStream</code>.</p>
<p>The <code>JarArchiveEntry</code> class contains fields for
certificates and attributes that are planned to be supported
in the future but are not supported as of Compress 1.0.</p>
<p>Adding an entry to a jar archive:</p>
<source><![CDATA[
JarArchiveEntry entry = new JarArchiveEntry(name, size);
entry.setSize(size);
jarOutput.putArchiveEntry(entry);
jarOutput.write(contentOfEntry);
jarOutput.closeArchiveEntry();
]]></source>
<p>Reading entries from an jar archive:</p>
<source><![CDATA[
JarArchiveEntry entry = jarInput.getNextJarEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
jarInput.read(content, offset, content.length - offset);
}
]]></source>
</subsection>
<subsection name="7z">
<p>Note that Commons Compress currently only supports a subset
of compression and encryption algorithms used for 7z archives.
For writing only uncompressed entries, LZMA, LZMA2, BZIP2 and
Deflate are supported - reading also supports
AES-256/SHA-256.</p>
<p>Multipart archives are not supported at all.</p>
<p>7z archives can use multiple compression and encryption
methods as well as filters combined as a pipeline of methods
for its entries. Prior to Compress 1.8 you could only specify
a single method when creating archives - reading archives
using more than one method has been possible before. Starting
with Compress 1.8 it is possible to configure the full
pipeline using the <code>setContentMethods</code> method of
<code>SevenZOutputFile</code>. Methods are specified in the
order they appear inside the pipeline when creating the
archive, you can also specify certain parameters for some of
the methods - see the Javadocs of
<code>SevenZMethodConfiguration</code> for details.</p>
<p>When reading entries from an archive the
<code>getContentMethods</code> method of
<code>SevenZArchiveEntry</code> will properly represent the
compression/encryption/filter methods but may fail to
determine the configuration options used. As of Compress 1.8
only the dictionary size used for LZMA2 can be read.</p>
<p>Currently solid compression - compressing multiple files
as a single block to benefit from patterns repeating accross
files - is only supported when reading archives. This also
means compression ratio will likely be worse when using
Commons Compress compared to the native 7z executable.</p>
<p>Reading or writing requires a
<code>SeekableByteChannel</code> that will be obtained
transparently when reading from or writing to a file. The
class
<code>org.apache.commons.compress.utils.SeekableInMemoryByteChannel</code>
allows you to read from or write to an in-memory archive.</p>
<p>Adding an entry to a 7z archive:</p>
<source><![CDATA[
SevenZOutputFile sevenZOutput = new SevenZOutputFile(file);
SevenZArchiveEntry entry = sevenZOutput.createArchiveEntry(fileToArchive, name);
sevenZOutput.putArchiveEntry(entry);
sevenZOutput.write(contentOfEntry);
sevenZOutput.closeArchiveEntry();
]]></source>
<p>Uncompressing a given 7z archive (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
SevenZFile sevenZFile = new SevenZFile(new File("archive.7z"));
SevenZArchiveEntry entry = sevenZFile.getNextEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
sevenZFile.read(content, offset, content.length - offset);
}
]]></source>
<p>Uncompressing a given in-memory 7z archive:</p>
<source><![CDATA[
byte[] inputData; // 7z archive contents
SeekableInMemoryByteChannel inMemoryByteChannel = new SeekableInMemoryByteChannel(inputData);
SevenZFile sevenZFile = new SevenZFile(inMemoryByteChannel);
SevenZArchiveEntry entry = sevenZFile.getNextEntry();
sevenZFile.read(); // read current entry's data
]]></source>
</subsection>
<subsection name="arj">
<p>Note that Commons Compress doesn't support compressed,
encrypted or multi-volume ARJ archives, yet.</p>
<p>Uncompressing a given arj archive (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
ArjArchiveEntry entry = arjInput.getNextEntry();
byte[] content = new byte[entry.getSize()];
LOOP UNTIL entry.getSize() HAS BEEN READ {
arjInput.read(content, offset, content.length - offset);
}
]]></source>
</subsection>
<subsection name="bzip2">
<p>Note that <code>BZipCompressorOutputStream</code> keeps
hold of some big data structures in memory. While it is
recommended for <em>any</em> stream that you close it as soon as
you no longer need it, this is even more important
for <code>BZipCompressorOutputStream</code>.</p>
<p>Uncompressing a given bzip2 compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.bz2"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
BZip2CompressorInputStream bzIn = new BZip2CompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = bzIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
bzIn.close();
]]></source>
<p>Compressing a given file using bzip2 (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.tar"));
OutputStream fout = Files.newOutputStream(Paths.get("archive.tar.gz"));
BufferedOutputStream out = new BufferedInputStream(out);
BZip2CompressorOutputStream bzOut = new BZip2CompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
bzOut.write(buffer, 0, n);
}
bzOut.close();
in.close();
]]></source>
</subsection>
<subsection name="gzip">
<p>The implementation of the DEFLATE/INFLATE code used by this
package is provided by the <code>java.util.zip</code> package
of the Java class library.</p>
<p>Uncompressing a given gzip compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.gz"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
GZipCompressorInputStream gzIn = new GZipCompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = gzIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
gzIn.close();
]]></source>
<p>Compressing a given file using gzip (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.tar"));
OutputStream fout = Files.newOutputStream(Paths.get("archive.tar.gz"));
BufferedOutputStream out = new BufferedInputStream(out);
GZipCompressorOutputStream gzOut = new GZipCompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
gzOut.write(buffer, 0, n);
}
gzOut.close();
in.close();
]]></source>
</subsection>
<subsection name="Pack200">
<p>The Pack200 package has a <a href="pack200.html">dedicated
documentation page</a>.</p>
<p>The implementation of this package is provided by
the <code>java.util.zip</code> package of the Java class
library.</p>
<p>Uncompressing a given pack200 compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.pack"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.jar"));
Pack200CompressorInputStream pIn = new Pack200CompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = pIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
pIn.close();
]]></source>
<p>Compressing a given jar using pack200 (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.jar"));
OutputStream fout = Files.newOutputStream(Paths.get("archive.pack"));
BufferedOutputStream out = new BufferedInputStream(out);
Pack200CompressorOutputStream pOut = new Pack200CompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
pOut.write(buffer, 0, n);
}
pOut.close();
in.close();
]]></source>
</subsection>
<subsection name="XZ">
<p>The implementation of this package is provided by the
public domain <a href="http://tukaani.org/xz/java.html">XZ
for Java</a> library.</p>
<p>When you try to open an XZ stream for reading using
<code>CompressorStreamFactory</code>, Commons Compress will
check whether the XZ for Java library is available. Starting
with Compress 1.9 the result of this check will be cached
unless Compress finds OSGi classes in its classpath. You can
use <code>XZUtils#setCacheXZAvailability</code> to overrride
this default behavior.</p>
<p>Uncompressing a given XZ compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.xz"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
XZCompressorInputStream xzIn = new XZCompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = xzIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
xzIn.close();
]]></source>
<p>Compressing a given file using XZ (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.tar"));
OutputStream fout = Files.newOutputStream(Paths.get("archive.tar.xz"));
BufferedOutputStream out = new BufferedInputStream(out);
XZCompressorOutputStream xzOut = new XZCompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
xzOut.write(buffer, 0, n);
}
xzOut.close();
in.close();
]]></source>
</subsection>
<subsection name="Z">
<p>Uncompressing a given Z compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.Z"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
ZCompressorInputStream zIn = new ZCompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = zIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
zIn.close();
]]></source>
</subsection>
<subsection name="lzma">
<p>The implementation of this package is provided by the
public domain <a href="http://tukaani.org/xz/java.html">XZ
for Java</a> library.</p>
<p>Uncompressing a given lzma compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.lzma"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
LZMACompressorInputStream lzmaIn = new LZMACompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = xzIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
lzmaIn.close();
]]></source>
<p>Compressing a given file using lzma (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.tar"));
OutputStream fout = Files.newOutputStream(Paths.get("archive.tar.lzma"));
BufferedOutputStream out = new BufferedInputStream(out);
LZMACompressorOutputStream lzOut = new LZMACompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
lzOut.write(buffer, 0, n);
}
lzOut.close();
in.close();
]]></source>
</subsection>
<subsection name="DEFLATE">
<p>The implementation of the DEFLATE/INFLATE code used by this
package is provided by the <code>java.util.zip</code> package
of the Java class library.</p>
<p>Uncompressing a given DEFLATE compressed file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("some-file"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
DeflateCompressorInputStream defIn = new DeflateCompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = defIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
defIn.close();
]]></source>
<p>Compressing a given file using DEFLATE (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.tar"));
OutputStream fout = Files.newOutputStream(Paths.get("some-file"));
BufferedOutputStream out = new BufferedInputStream(out);
DeflateCompressorOutputStream defOut = new DeflateCompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
defOut.write(buffer, 0, n);
}
defOut.close();
in.close();
]]></source>
</subsection>
<subsection name="Snappy">
<p>There are two different "formats" used for <a
href="https://github.com/google/snappy/">Snappy</a>, one only
contains the raw compressed data while the other provides a
higher level "framing format" - Commons Compress offers two
different stream classes for reading either format.</p>
<p>Starting with 1.12 we've added support for different
dialects of the framing format that can be specified when
constructing the stream. The <code>STANDARD</code> dialect
follows the "framing format" specification while the
<code>IWORK_ARCHIVE</code> dialect can be used to parse IWA
files that are part of Apple's iWork 13 format. If no dialect
has been specified, <code>STANDARD</code> is used. Only the
<code>STANDARD</code> format can be detected by
<code>CompressorStreamFactory</code>.</p>
<p>Uncompressing a given framed Snappy file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.sz"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
FramedSnappyCompressorInputStream zIn = new FramedSnappyCompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = zIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
zIn.close();
]]></source>
<p>Compressing a given file using framed Snappy (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.tar"));
OutputStream fout = Files.newOutputStream(Paths.get("archive.tar.sz"));
BufferedOutputStream out = new BufferedInputStream(out);
FramedSnappyCompressorOutputStream snOut = new FramedSnappyCompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
snOut.write(buffer, 0, n);
}
snOut.close();
in.close();
]]></source>
</subsection>
<subsection name="LZ4">
<p>There are two different "formats" used for <a
href="http://lz4.github.io/lz4/">lz4</a>. The format called
"block format" only contains the raw compressed data while the
other provides a higher level "frame format" - Commons
Compress offers two different stream classes for reading or
writing either format.</p>
<p>Uncompressing a given frame LZ4 file (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream fin = Files.newInputStream(Paths.get("archive.tar.lz4"));
BufferedInputStream in = new BufferedInputStream(fin);
OutputStream out = Files.newOutputStream(Paths.get("archive.tar"));
FramedLZ4CompressorInputStream zIn = new FramedLZ4CompressorInputStream(in);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = zIn.read(buffer))) {
out.write(buffer, 0, n);
}
out.close();
zIn.close();
]]></source>
<p>Compressing a given file using the LZ4 frame format (you would
certainly add exception handling and make sure all streams
get closed properly):</p>
<source><![CDATA[
InputStream in = Files.newInputStream(Paths.get("archive.tar"));
OutputStream fout = Files.newOutputStream(Paths.get("archive.tar.lz4"));
BufferedOutputStream out = new BufferedInputStream(out);
FramedLZ4CompressorOutputStream lzOut = new FramedLZ4CompressorOutputStream(out);
final byte[] buffer = new byte[buffersize];
int n = 0;
while (-1 != (n = in.read(buffer))) {
lzOut.write(buffer, 0, n);
}
lzOut.close();
in.close();
]]></source>
</subsection>
<subsection name="Extending Commons Compress">
<p>
Starting in release 1.13, it is now possible to add Compressor- and ArchiverStream implementations using the
Java's <a href="https://docs.oracle.com/javase/7/docs/api/java/util/ServiceLoader.html">ServiceLoader</a>
mechanism.
</p>
</subsection>
<subsection name="Extending Commons Compress Compressors">
<p>
To provide your own compressor, you must make available on the classpath a file called
<code>META-INF/services/org.apache.commons.compress.compressors.CompressorStreamProvider</code>.
</p>
<p>
This file MUST contain one fully-qualified class name per line.
</p>
<p>
For example:
</p>
<pre>org.apache.commons.compress.compressors.TestCompressorStreamProvider</pre>
<p>
This class MUST implement the Commons Compress interface
<a href="apidocs/org/apache/commons/compress/compressors/CompressorStreamProvider.html">org.apache.commons.compress.compressors.CompressorStreamProvider</a>.
</p>
</subsection>
<subsection name="Extending Commons Compress Archivers">
<p>
To provide your own compressor, you must make available on the classpath a file called
<code>META-INF/services/org.apache.commons.compress.archivers.ArchiveStreamProvider</code>.
</p>
<p>
This file MUST contain one fully-qualified class name per line.
</p>
<p>
For example:
</p>
<pre>org.apache.commons.compress.archivers.TestArchiveStreamProvider</pre>
<p>
This class MUST implement the Commons Compress interface
<a href="apidocs/org/apache/commons/compress/archivers/ArchiveStreamProvider.html">org.apache.commons.compress.archivers.ArchiveStreamProvider</a>.
</p>
</subsection>
</section>
</body>
</document>