Re: Better way to fill Storage_IO?

[Per Sandberg <per.s.sandberg@bahnhof.se>]

To emulate a stream on "any" locatoion
https://github.com/persan/a-stream-tools
/P


On 17/05/2021 22:48, Michael Hardeman wrote:
> On Monday, May 17, 2021 at 4:20:14 PM UTC-4, Dmitry A. Kazakov wrote:
>> On 2021-05-17 21:14, Simon Wright wrote:
>>> Michael Hardeman <mhard...@gmail.com> writes:
>>>
>>>> So I've been messing around with the new Ada 2020 package
>>>> Ada.Streams.Storage.Bounded/Unbounded; and if I'm understand it
>>>> correctly it allows you to treat your program's memory like a stream
>>>> without having to open file descriptors (which should make it
>>>> faster?). That seems like a powerful abstraction to me and a great
>>>> addition to the language.
>> 1. It was always possible, since Ada 95, actually. So it is not that
>> great addition.
>>
>> 2. The package as described is not a replacement for I/O, because it
>> lacks blocking/synchronization and because it does not work between
>> processes. E.g. at the end of the stream Read must rather block for an
>> incoming Write. Both are quite possible to implement though.
>>
>> A great addition would be properly tagged protected objects and tasks. A
>> blocking stream cannot support timed entry call syntax like this:
>>
>> select
>> S := String'Input (Pipe'Access); -- This is not Ada!
>> or delay 1.0;
>> raise Timed_Out;
>> end select;
>>
>> And note another problem. Entries do not work with indefinite objects.
>> You cannot return String from an entry call.
>>
>> And yet another problem, you cannot use returned objects in many places,
>> like in an entry call above.
>>>> I was wondering if we could find a better way to fill the stream other
>>>> than writing the variables into it? Can anyone figure out a good way
>>>> to just stream a variable's bytes directly?
>> Allocators, of course. I am using both allocators and memory-mapped
>> streams (though of a greater variety, e.g. for blocked exchange,
>> encryption, interporcess communication).
>>> This *is* the way to just stream the variable's bytes directly. What
>>> sort of syntax were you hoping for?
>> Both allocators and streams require explicit specification of the type.
>> Clearly, that is a way around multiple dispatch, but it is way too
>> heavy. Access to stream is no more necessary in 'Input. It was not
>> necessary when it was introduced in Ada 95. The Rosen's trick allows
>> circumvent in- parameter modes, when necessary.
>>
>> -- 
>> Regards,
>> Dmitry A. Kazakov
>> http://www.dmitry-kazakov.de
> 
> Hey Dmitry,
> 
>> Allocators, of course. I am using both allocators and memory-mapped
>> streams (though of a greater variety, e.g. for blocked exchange,
>> encryption, interporcess communication).
> 
> Could you show me an example of how I could do this with allocators?
>