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From Alexei Kosut <>
Subject Re: filter API spec
Date Tue, 02 Sep 1997 18:40:41 GMT
On Tue, 2 Sep 1997, Dean Gaudet wrote:

> I haven't read this completely yet, but it looks like you're missing
> writev() -- it's needed for performance (avoiding user-to-user copies).
> Without it you can't implement chunking as a filter as efficiently as I
> presently have.

But BUFF doesn't provide writev now, except internally to how it does
chunking. And as I understand writev, you couldn't use it if there are
filters stacked below chunking, and if there weren't, we'd use the
existing approach (which does use writev).

> write() functions must take const void *, they should not modify data --
> consider mmap()d files. 

Good point.

> Multiple layers of buffers is dangerous, but this is really an
> implementation detail in each filter.  Filters should be able to
> completely disable buffering. 

I suppose - which way, though? Do they disable buffering in their own
BUFF, or the one they sit on top of?. Why are multiple layers of buffers
dangerous, anyhow?

-- Alexei Kosut <>

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