[Info-vax] Returning data from Cobol AST routine.

[Dave Froble]

On 9/21/2021 9:53 PM, Arne Vajhøj wrote:
> On 9/21/2021 9:46 PM, Dave Froble wrote:
>> On 9/21/2021 5:13 PM, Jan-Erik Söderholm wrote:
>>> But my guess is that, if you queue QIOs from multiple sources, the AST
>>> routine must have some way to tell which source it was that trigged
>>> the AST. Say you make (made up example, not part of our current target)
>>> 10 QIO calls having the address of the same AST routine in the calls,
>>> each QIO reading from its own TNA device, you need to know in the AST
>>> routine which TNA device (like 10 different production machines) it
>>> was that sent something.
>>
>> That sounds like a real headache.  Perhaps event flags would help.  I
>> tend to avoid event flags.
>>
>>> I have probably not read enough aboit AST and QUI calls yet...
>>
>> ASTs can be fun.  I try to use them to set flags or cancel I/O.
>> Cancelling an I/O causes a completion of an async read.  I feel that
>> if I try to get "tricky", I'll outsmart myself,
>
> That is why I suggested a message queue instead of mailboxes,
> $QIO(W) and AST's.

You'd still have to check the message periodically.  Testing a flag, and 
already having the message in a buffer, should be more efficient.

> Way less options for experiencing "unexpected features".
>
> Arne


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David Froble                       Tel: 724-529-0450
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