Compression - Re: Random access to content of archived files without extraction

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Re: Random access to content of archived files without extraction - how? compression

Paul Marquess

2006-07-01, 6:55 pm

Mark Adler wrote:

> Claudio Grondi wrote:
>
> It can certainly be done, but I don't know of any off-the-shelf code to
> do it, at least not in the sense you describe. I wrote some example
> code in the zlib distribution showing how it can be done with zlib,
> examples/zran.c, that you can look at. For any scheme, what you do is
> build a random access index that provides the information that allows
> you to a) figure out about where an uncompressed offset is in the
> compressed data, and b) allow you to start decompressing some short
> distance before that location to get your data. A parameter of the
> process is how far apart the index points be and still give you the
> speed of random access you want.

Is it possible to do what zran does on the compression phase? If so, is
there any example code?

Paul

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