some problems for an introductory python test

[Dennis Lee Bieber]

On Sun, 15 Aug 2021 00:15:58 -0300, Hope Rouselle <hrouselle at jevedi.com>
declaimed the following:

	Giganews seems to have just vomited up three days worth of traffic...

>Dennis Lee Bieber <wlfraed at ix.netcom.com> writes:
>
>>
>> 	Granted, the fact that the Amiga used a shared common address space for
>> all running applications made IPC quite easy -- one looked up the
>> application message port, then added a small packet to the linked list
>> associated with the port. That small packet basically held the address of
>> the message port for returning data, and the address of the data being
>> passed. The closet thing I've seen to that capability on systems with
>> process-isolated virtual memory is (Open)VMS "mailbox" structures. The
>> difference being that the entire data had to be written (QIO) to the
>> mailbox, and the receiver had to read (another QIO call) the message --
>> this allowed the address space to change.
>>
>> 	I've not seen anything equivalent in my light perusal of the Win32 API
>> (the various guide books aren't layed out in any way to be a reference),
>> and Linux seems to use UNIX sockets for IPC... No way to search for a
>> connection point by name...
>
>I don't know anything about Amiga, REXX et cetera, so I might be totall
>off here. But since you spoke of your perusal of the Win32 API, let me
>add a tiny bit.  I gave myself a quick tour through the Win32 API using
>Pavel Yosifovich's book ``Windows 10 System Programming''.  It's a two
>volume work.  The thing that impressed me the most was the many ways to
>do the IPC.  The purpose the work is clearly to show what is available
>and it it probably does the job well.  (I ignored Windows for most of my
>life and now I decided to take a look at it.  I don't feel it has much
>of the elegance of UNIX.  It's what it is.)

	For a book that was published only a year ago -- it seems to be hard to
find... Amazon has v1, but not v2.

	I have the "Windows Internals 6th" both volumes.

	The closet those get to IPC is something called ALPC -- and that is
declared to be internal only, not available to third party programmers.

	"Programming Windows 6th" is focused on using C# (which, for the most
part, means using the "managed" API, not the Win32 API directly).

	"Mailslots" (I'm using Google to find Windows IPC options) initially
sound close to Amiga message ports... Except there is no status return
inherent to the system; Amiga messages contain a return address so a
program can wait for the status of processing by the destination address.
They also don't qualify as VMS mailboxes as there can only be one reader
(the creator of the mailslot). VMS mailboxes allow multiple writers and/or
multiple readers.

	"File mapping" doesn't provide any form of queuing -- multiple
"writers" would require manually implementing some protocol to track "next
available space" in the mapped file. It would allow bidirectional message
passing, but again that requires some rather nasty overhead information
(when is the return status valid -- it is presumed the client wanting the
return status would get it from the same memory space as the message it
sent, and that space can't be reused until the client explicitly frees it
-- again by some overhead protocol changing headers of free space.

	"Data Copy" also sounds close to Amiga message ports (closer than
"Mailslots"), but the online documentation doesn't indicate if it queues
messages. The documentation doesn't illustrate HOW to return TRUE or FALSE
(processed/rejected). It advices that the receiver should treat the data as
read-only -- though I have to wonder if it /could/ write a return status
into the same message structure before "returning TRUE".

	Named Pipes and Sockets both have the "tied to endpoints" problem, and
in the case of Pipes, may only allow one sender to connect at a time
(sockets are also one connection, but normally the receivers spawns a
thread for each active connection and the connections are made using
different allocated sockets).



-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
	wlfraed at ix.netcom.com    http://wlfraed.microdiversity.freeddns.org/