Convert output range to input range

[John Chapman]

On Saturday, 17 March 2018 at 17:16:40 UTC, David Nadlinger wrote:
> On Friday, 16 March 2018 at 07:57:04 UTC, John Chapman wrote:
>> I need to write to a range created with outputRangeObject, 
>> then read from it. Is there a way to convert it to an input 
>> range?
>
> Could you illustrate your problem a bit further?

I'm trying to replace the old std.streams in my app with ranges. 
I'm interfacing with a networking library to which I supply a 
callback that when invoked provides the requested data. I write 
that data to an output range, but later on I need to read that 
data from the range too - which of course you can't do.

So what I'm looking for is the range-based equivalent of a 
MemoryStream.