Hi, all:
I tried to use gzip to decompress a file of about 350 M bytes, it took about
45 min, does anyone know what else decompresison utilities which are faster?
I can suffer a bit compression ratio degradation.
Thanks.
Xuedong
Compression is a very wide ranging subject. I don’t know
the details of how “gzip” works, but it most likely creates
a Hoffman encoding table. This method finds the most common
bytes, and encodes them as the smallest bit streams. This is
a very good way to compress data of unknown distribution.
On the other hand, it is hard to make it very fast as it
has to decend a tree when decoding.
If you know something about your data, you might be able
to construct your own compression program with better
results. For example if you know that your data has a
lot of repeating strings, such a Zeros, a simple
run-length limited scheme may provide better compression,
and run faster.
Also be aware of any built in limitations. For example,
how long does it take to write out a 350Meg file on
your system.
Previously, Xuedong Chen wrote in qdn.public.qnxrtp.os:
Hi, all:
I tried to use gzip to decompress a file of about 350 M bytes, it took about
45 min, does anyone know what else decompresison utilities which are faster?
I can suffer a bit compression ratio degradation.Thanks.
Xuedong
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–
Mitchell Schoenbrun --------- maschoen@pobox.com
On Mon, 18 Jun 2001 21:35:52 -0700, “Xuedong Chen”
<Xuedong.Chen@IGT.com> wrote:
Hi, all:
I tried to use gzip to decompress a file of about 350 M bytes, it took about
45 min, does anyone know what else decompresison utilities which are faster?
I can suffer a bit compression ratio degradation.Thanks.
I’ve seen unarj somwhere, staff.qnx.com/~jfehr/repository?
Also, gzip has -1 and -9 parameters (compress faster/compress
better). If you have more than one disk, try to decompress from one to
the other. I wonder whether inflating/deflating could be used here.
ako
Xuedong
I too am in the process of adding compression to my QNX programs. I have
been experimenting with various programs and searching the 'net for all
things compression. The most promising tools that I’ve found are LZO and
zlib. LZO is significantly faster and actually bills itself as a real-time
decompressor; its decompression is extremely fast (the author claims about
1/3 the speed of a memcpy() ). The web site says the “fast” algorithm will
compress ~5MB/second on a Pentium 133, but I believe that that number is
buffer to buffer. It favors speed over compression ratios, although its
compression ratios are quite good and you can tune it to your application.
The source compiled flawlessly on my RTP and created a library with a number
of compression/decompression routines available. Assembly routines for x86
and ANSI C routines for all are both included. Pretty slick so far.
LZO:
http://wildsau.idv.uni-linz.ac.at/mfx/lzo.html
zlib:
http://www.gzip.org/zlib/
Hope that helps.
Jason A. Farqué
CDI at http://www.pigging.com/
“Xuedong Chen” <Xuedong.Chen@IGT.com> wrote in message
news:9gmk9b$8ti$1@inn.qnx.com…
Hi, all:
I tried to use gzip to decompress a file of about 350 M bytes, it took
about
45 min, does anyone know what else decompresison utilities which are
faster?
I can suffer a bit compression ratio degradation.Thanks.
Xuedong
Great! Thank You.
“Jason A. Farque’” <jasonf@pigging.com> wrote in message
news:9gnrj6$2u8$1@inn.qnx.com…
I too am in the process of adding compression to my QNX programs. I have
been experimenting with various programs and searching the 'net for all
things compression. The most promising tools that I’ve found are LZO and
zlib. LZO is significantly faster and actually bills itself as a
real-time
decompressor; its decompression is extremely fast (the author claims about
1/3 the speed of a memcpy() ). The web site says the “fast” algorithm
will
compress ~5MB/second on a Pentium 133, but I believe that that number is
buffer to buffer. It favors speed over compression ratios, although its
compression ratios are quite good and you can tune it to your application.
The source compiled flawlessly on my RTP and created a library with a
number
of compression/decompression routines available. Assembly routines for
x86
and ANSI C routines for all are both included. Pretty slick so far.
LZO:
http://wildsau.idv.uni-linz.ac.at/mfx/lzo.htmlzlib:
http://www.gzip.org/zlib/Hope that helps.
Jason A. Farqué
CDI at > http://www.pigging.com/
“Xuedong Chen” <> Xuedong.Chen@IGT.com> > wrote in message
news:9gmk9b$8ti$> 1@inn.qnx.com> …
Hi, all:I tried to use gzip to decompress a file of about 350 M bytes, it took
about
45 min, does anyone know what else decompresison utilities which are
faster?
I can suffer a bit compression ratio degradation.Thanks.
Xuedong
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