Re: Data Compression

[Jacco van Schaik <jacco@nlr.nl>]

On Mon, 31 Jan 2000, Jerome Kaidor wrote:

>    When you use a compressor like gzip, you tell it:
> 
>   "Here is a file, or data area for you to compress.  Here's where it
> starts, here's how long it is.  Put the compressed version over there.  Come
> back when you're through."
> 
>    Whereas with my compressor, you'd say:
> 
>    "I want you to start creating some compressed data for me."
>              ( compressor returns a 'handle' for use in subsequent calls )
>    "Here's a kilobyte"
>    "Here's five hundred thirty  three more bytes"
>    "Here's another byte"
>    "Here's another hundred bytes"
>              .
>              .
>              .   
>    "OK, there's no more bytes.  Finish it up!"

Actually, the zlib library that (as far as I know) forms the basis for
gzip does just that.

There are functions like gzread(), gzwrite(), gzprintf() and gzgets()
that are equivalent to the corresponding system functions. When reading,
it automatically detects whether the input is compressed, so you can use
these functions to read both compressed and uncompressed data. See
/usr/include/zlib.h on your Linux box for more info.

Groeten,				- Jacco

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