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Re: Delayed "printf"

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Am 25.04.2017 um 02:42 schrieb Tim Wescott:
> I don't like putting "printf" in fast tasks for obvious reasons -- even 
> with infinite spooling, it can take time to process a format string.  In 
> my usual context, this can result in audible sounds from motors when I 
> print some bit of debugging information from a high-priority task.  The 
> problem can't be alleviated by spooling the output of the printf, because 
> it's the execution time of the printf itself that's the problem.
> 
> Just how dumb is it to have "printf" queue up the format string AND the 
> parameters into a buffer, to be printed out in some low-priority task?

The first question to ask is: do you really need a full-blown 'printf'?
Or do you just need something that expands '%d' and/or '%x', '%s', and
that's it? Such a function can be implemented in a screenful of code,
using a 'putchar' function as the back-end, which in turn writes into an
asynchronous buffer.

Such a function is fast so you might get away with it. Compared to
'printf', it lacks locking and synchronisation with the rest of stdio,
and it also doesn't need the bajillions of ifs which 'printf' uses to
implement left/right-pad, pad-with-zero, float, thousands-separators, etc.

If you wish to keep using a 'printf'-style interface and just stash away
the parameters, you'd still need to pre-parse the format string and I'd
guess that doesn't save much compared to actually formatting.

I worked with such a 'printf' workalike function in the past and had no
problems using it from things like audio DMA interrupts.

Another question to ask is whether you want to log essays like "foo is
not recognized as an internal or external command, operable program or
batch file. Try reinstalling the application if the program persists",
or just brief messages like "foo: file not found". :-)


  Stefan

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Thread

Delayed "printf" Tim Wescott <seemywebsite@myfooter.really> - 2017-04-24 19:42 -0500
  Re: Delayed "printf" Don Y <blockedofcourse@foo.invalid> - 2017-04-24 18:51 -0700
    Re: Delayed "printf" Tim Wescott <tim@seemywebsite.com> - 2017-04-24 21:54 -0500
      Re: Delayed "printf" Don Y <blockedofcourse@foo.invalid> - 2017-04-24 21:27 -0700
  Re: Delayed "printf" Paul Rubin <no.email@nospam.invalid> - 2017-04-24 19:53 -0700
  Re: Delayed "printf" Clifford Heath <no.spam@please.net> - 2017-04-25 13:01 +1000
    Re: Delayed "printf" Theo Markettos <theom+news@chiark.greenend.org.uk> - 2017-04-25 18:51 +0100
      Re: Delayed "printf" Clifford Heath <no.spam@please.net> - 2017-04-26 12:59 +1000
        Re: Delayed "printf" Theo Markettos <theom+news@chiark.greenend.org.uk> - 2017-04-26 13:24 +0100
  Re: Delayed "printf" Robert Wessel <robertwessel2@yahoo.com> - 2017-04-25 00:19 -0500
    Re: Delayed "printf" David Brown <david.brown@hesbynett.no> - 2017-04-25 10:44 +0200
      Re: Delayed "printf" Robert Wessel <robertwessel2@yahoo.com> - 2017-04-25 09:22 -0500
        Re: Delayed "printf" David Brown <david.brown@hesbynett.no> - 2017-04-25 16:37 +0200
    Re: Delayed "printf" Tim Wescott <tim@seemywebsite.com> - 2017-04-25 10:49 -0500
  Re: Delayed "printf" Jack <jack4747@gmail.com> - 2017-04-24 23:33 -0700
  Re: Delayed "printf" Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-04-25 08:09 +0100
  Re: Delayed "printf" John Devereux <john@devereux.me.uk> - 2017-04-25 08:14 +0100
  Re: Delayed "printf" David Brown <david.brown@hesbynett.no> - 2017-04-25 10:58 +0200
  Re: Delayed "printf" Stefan Reuther <stefan.news@arcor.de> - 2017-04-25 18:46 +0200
  Re: Delayed "printf" Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2017-04-25 21:03 +0200
  Re: Delayed "printf" Tim Wescott <seemywebsite@myfooter.really> - 2017-04-25 16:11 -0500
    Re: Delayed "printf" Les Cargill <lcargill99@comcast.com> - 2017-04-25 17:28 -0500
    Re: Delayed "printf" Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-04-26 10:03 +0300
  Re: Delayed "printf" Dave Nadler <drn@nadler.com> - 2017-04-25 14:31 -0700
  Re: Delayed "printf" Les Cargill <lcargill99@comcast.com> - 2017-04-25 17:25 -0500
  Re: Delayed "printf" mac <acolvin@efunct.com> - 2017-04-26 17:22 +0000
    Re: Delayed "printf" Grant Edwards <invalid@invalid.invalid> - 2017-04-26 17:37 +0000
      Re: Delayed "printf" Grant Edwards <invalid@invalid.invalid> - 2017-04-26 17:38 +0000

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