Re: Fwd: Concatenated input streams

From: Gavin Lambert (boost_at_[hidden])
Date: 2022-03-08 03:58:11

On 8/03/2022 16:00, Robert Dodier wrote:
> I'm interested in working with an input stream which comprises
> multiple input streams. The resulting stream comprises all of the
> input from the first stream (until EOF), then all of the input from
> the second, etc. For what it's worth, such an input stream is called a
> concatenated input stream in at least one other context (namely Common
> Lisp).
> 
> The input streams in question are file input streams, although
> conceptually I don't know if that changes anything. I am hoping to
> find something equivalent to
> 
> $ cat file1 file2 file3 ... > alldata
> 
> and then reading alldata.
> 
> Is there a Boost class which implements such a thing? I know that this
> is a pretty simple concept, and therefore it's just a small matter of
> programming, but I'm hoping that someone has already worked out the
> details.

It's not streams, but you might find this (and related) of interest (in 
particular the scatter/gather section right at the bottom):

 
https://www.boost.org/doc/libs/1_78_0/doc/html/boost_asio/reference/buffer.html

Having said that, while ASIO does provide file streams as well, this is 
sort of opposite to your use case, and it doesn't directly address what 
you're looking for.  Still, it would be possible to use similar 
techniques to write your own multi-stream that could be read as if it 
were one stream.

Although writing ASIO integrations is not for the faint of heart, so 
this is likely overkill unless you're already wanting to mix in ASIO for 
other reasons.