RE: [PATCH] splice support #2

[Linus Torvalds <torvalds@osdl.org>]

On Fri, 31 Mar 2006, Hua Zhong wrote:
> 
> If I understand correctly:
> 
> splice is one fd in, one fd out

Yes, and one of the fd's have to be a pipe.

> tee is one fd in, two fd out (and I'd assume the "one fd in" would always be
> a pipe)

Actually, all three of them would have to be pipes. The tee() thing has to 
push to both sources in a "synchronized" manner, so it can't just take 
arbitrary file descriptors that it doesn't know the exact buffering rules 
for.

(Otherwise you wouldn't need "tee()" at all - you could have a "splice()" 
that just takes several output fd's).

> How about one fd in, N fd out? Do you then stack the tee calls using
> temporary pipes?

I didn't write the tee() logic, but making it 1:N instead of 1:2 is not 
conceptually a problem at all. The exact system call interface might limit 
it some way, of course. 

		Linus
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