Re: Java text compression

From:
Eric Sosman <esosman@ieee-dot-org.invalid>
Newsgroups:
comp.lang.java.programmer
Date:
Sun, 18 Nov 2007 15:16:22 -0500
Message-ID:
<Wr2dnb4OMr84AN3anZ2dnUVZ_vumnZ2d@comcast.com>
Chris wrote:

What's the fastest way to compress/decompress text?


     If you're really interested in "the fastest way" to the
exclusion of all other concerns, then don't compress at all.
Bingo! Problem solved!

     You might be happier with a compression scheme that did
a little better at reducing the size of the data, but now you
can't get a sensible answer until you describe the trade-offs
you're willing to make. For example, if you were offered a
compression scheme that ran ten percent faster than your current
method but emitted fifteen percent more data, would you take it
or reject it?

We're doing that over really large datasets in our app. We're currently
converting char arrays to byte arrays using our own UTF-8 conversion
code, and then compressing the bytes using java.util.zip. The code is
pretty old.

I don't like this two-step process, and the profiler shows that this is
a bottleneck in our app.

Is anyone aware of any code that compresses chars directly? Perhaps a
third-party library that does it faster?


     How badly do you need your own idiosyncratic UTF-8 conversion?
If you can use standard methods, consider wrapping the compressed
streams, somewhat like

    Writer w = new OutputStreamWriter(
        new GZIPOutputStream(...));
    w.write("Hello, world!");

    BufferedReader r = new BufferedReader(
        new InputStreamReader(
            new GZIPInputStream(...)));
    String s = r.readLine();

     You'll have to make your own assessment of the speeds and the
degree of compression.

In our particular situation, decompression speed is a lot more important
than compression speed.


     "You'll have to make your own assessment ..."

--
Eric Sosman
esosman@ieee-dot-org.invalid

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