com.fitbur.apache.commons.compress.compressors.pack200.package.html Maven / Gradle / Ivy
Provides stream classes for compressing and decompressing
streams using the Pack200 algorithm used to compress Java
archives.
The streams of this package only work on JAR archives, i.e. a
{@link
org.apache.commons.compress.compressors.pack200.Pack200CompressorOutputStream
Pack200CompressorOutputStream} expects to be wrapped around a
stream that a valid JAR archive will be written to and a {@link
org.apache.commons.compress.compressors.pack200.Pack200CompressorInputStream
Pack200CompressorInputStream} provides a stream to read from a
JAR archive.
JAR archives compressed with Pack200 will in general be
different from the original archive when decompressed again.
For details see
the API
documentation of Pack200.
The streams of this package work on non-deflated streams,
i.e. archives like those created with the --no-gzip
option of the JDK's pack200 command line tool. If
you want to work on deflated streams you must use an additional
stream layer - for example by using Apache Commons Compress'
gzip package.
The Pack200 API provided by the Java class library doesn't lend
itself to real stream
processing. Pack200CompressorInputStream will
uncompress its input immediately and then provide
an InputStream to a cached result.
Likewise Pack200CompressorOutputStream will not
write anything to the given OutputStream
until finish or close is called - at
which point the cached output written so far gets
compressed.
Two different caching modes are available - "in memory", which
is the default, and "temporary file". By default data is cached
in memory but you should switch to the temporary file option if
your archives are really big.
Given there always is an intermediate result
the getBytesRead and getCount methods
of Pack200CompressorInputStream are meaningless
(read from the real stream or from the intermediate result?)
and always return 0.
During development of the initial version several attempts have
been made to use a real streaming API based for example
on Piped(In|Out)putStream or explicit stream
pumping like Commons Exec's InputStreamPumper but
they have all failed because they rely on the output end to be
consumed completely or else the (un)pack will block
forever. Especially for Pack200InputStream it is
very likely that it will be wrapped in
a ZipArchiveInputStream which will never read the
archive completely as it is not interested in the ZIP central
directory data at the end of the JAR archive.