Re: pgnuplot.exe flow control

[Hans-Bernhard B. <HBB...@t-...>]

Tait wrote:

> I can tell Perl to autoflush, but I still have the
> problem that Perl is too fast for pgnuplot. Is there any way for the data
> provider (the thing dumping into the pipe) to know when pgnuplot/gnuplot
> is ready for more input?

I have no idea how Perl might do this.  On the C side of things, what 
would be needed is blocking I/O.  In short, the program calling pgnuplot 
would have to *wait* for pgnuplot.  The low-level pipe functions in 
Win32, CreatePipe() used with ReadFile()/WriteFile(), claim to use 
blocking I/O, whereas the top-level <stdio.h> function _popen() 
apparently fails to block.  The mid-range functions 
_pipe()/_read()/_write() claim they block, too.

So the behaviour of scripting tools like Perl would depend on the way 
they run their pipes.

>> The wgnuplot_pipes.exe is entirely different from the pgnuplot
>> It allows that
>>     plot '< awk -f awkscript.awk'
> 
> Is there a reason why the wgnuplot_pipes behavior is not simply the 
> default in wgnuplot.exe?

To support opening pipes, wgnuplot_pipes keeps an open console.  Among 
other things, this means that if you start it from a cmd.exe session, 
you don't get the prompt back until wgnuplot_pipes ends.