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From: eg (egoots_at_[hidden])
Date: 2006-11-29 21:56:07


Hi all,

I'm new to the iostreams library. It looks pretty cool.
We have a bunch of existing objects which already have interfaces for
reading and writing their state to a stream, e.g.
MyWrite(std::ostream &out) and MyRead(std::istream &in)

I've convinced myself I can filter these with iostreams, as I prototyped
setting up a filtering stream with an existing gzip_compressor() filter,
then reversed it with a gzip_decompressor(). Nice.

Now, what I want to do is write my own filter, and thought that a
symmetric_filter met my needs based on the description. Unfortunately,
there are no simple examples in the tutorial section, and the
documentation seems a bit weaker in this area. As a first kick at the
can, reading the zlib/bzip implementations is a bit dense to pick out
the nuances.

Does anyone have an identity_filter example (based on symmetric_filter)
that just copies input to output characters?

... or given some dumb c function like the following, how to construct a
symmetric_filter using it.

my_dumb_crypt(char* in, char* out, char *pwd, int len)
{
   for (int i=0; i < len; ++i) // assumes in, out, and pwd are len long
     out[i] = in[i] ^ pwd[i];

}

Thanks.
eg


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