[Kde-java] KProgressTest program

[KJ P]

Hello Richard

>This is an interesting difference between C++ and java arrays. In the C++
>example 
>'sizeof(javaToQtTypeSignatureMap)/sizeof(*javaToQtTypeSignatureMap)',
>sizeof() is a compile time thing. So the expression should be evaluated at
>compile time by gcc, and just map onto a constant (maybe I'm wrong and it
>isn't..). In java, array sizes are a runtime thing, which allows it to 
>check
>array bounds at runtime.
Thank you for my C++ refresher/lesson again.  The stuff you forget when you 
do not use it for a long time.  I had forgotten about java having the 
arraybounds check at runtime.  If I remember correctly it was a compile time 
flag that was passed to the compiler to turn runtime checking on.  I could 
be wrong.  Corrections are welcome from you experts.

Regards


Kenneth

>From: Richard Dale <Richard_Dale@tipitina.demon.co.uk>
>Reply-To: kde-java@kde.org
>To: kde-java@kde.org
>Subject: Re: [Kde-java] KProgressTest program
>Date: Fri, 1 Mar 2002 13:40:50 +0000
>
>On Friday 01 March 2002 10:21 am, Kevin Krammer wrote:
> > Richard Dale wrote:
> > > string concatenation really - can't see the point. Perhaps the best
> > > thing is to remove KProcess from the bindings, as there doesn't seem
> > > to be anything particularly KDE-specific about starting a process. Is
> > > there a Java System.exec() or similar that could be used instead?
> >
> > There is such a method in java.lang.Runtime
> > http://java.sun.com/products/jdk/1.2/docs/api/index.html
> >
> > Runtime rt = Runtime.getRuntime();
> > Process proc = rt.exec(commandString);
>Thanks! What I like about Java is that you feel you know it before you've
>written any code. I can guess there'll be something called 'blah 
>blah.exec()'
>somewhere - and sure enough you java experts point out the above example of
>exec(). Which to me looks pretty neat - easier to use than KProcess?
>
>On Friday 01 March 2002 9:50 am, KJ P wrote:
> > >particularly KDE-specific about starting a process. Is there a Java
> > >System.exec() or similar that could be used instead?
> >
> > Yes I agree.  What I liked about KProcess was that you could start a
> > process and block or not block.  The signals for when a process is 
>finished
> > I thought was good as well.  The System.exec() will work of course.
>Perhaps we can put some kind of KDE api layer on top of Runtime.exec() with
>slot/signal notification and blocking/unblocking, rather than adapt the C++
>specific KProcess class.
>
> > >Yes, the Qt examples are a good test for the bindings - I've fixed 
>quite a
> > >lot
> > >of bugs.
> >
> > I can tell.  I will be trying them out this weekend.
>Good - the more testing the better.. I've got drag and drop working now, so
>KScribble should drag and drop, I think that was the only thing that wasn't
>working properly.
>
> >
> > I know it probably means nothing at all but while looking at the code of
> > JavaSlot.cpp I thought that instead of testing the index <
> > sizeof(javaToQtTypeSignatureMap)/sizeof(*javaToQtTypeSignatureMap) each 
>and
> > every time would it not be better to assign the length of the table to a
> > variable and test against the variable instead of calculating every time 
>as
> > in the following:
> >
> > const char *
> > JavaSlot::javaToQtSlotType(const char * javaTypeSignature, const char *
> > signalString)
> > {
> >    int lenghtOfTable =
> > sizeof(javaToQtTypeSignatureMap)/sizeof(*javaToQtTypeSignatureMap)
> >
> >         for (   unsigned int index = 0;
> >                         index < lengthOfTable;
> >                         index++ )
> >         {
> >                 if (    strcmp(javaTypeSignature,
> > javaToQtTypeSignatureMap[index][0]) == 0
> >                                 && (    signalString == 0
> >
> > QObject::checkConnectArgs(signalString, (const QObject *) 0,
> > javaToQtTypeSignatureMap[index][1]) ) )
> >                 {
> >                         return javaToQtTypeSignatureMap[index][1];
> >                 }
> >         }
> >
> >         // If no matching C++ type signature is found, then just return 
>the
> > java one
> >         return javaTypeSignature;
> > }
> >
> > I am not taking pot shots at the code it is just something that popped 
>out
> > at me while looking.  In c++ maybe it does not mean anything, it is just
> > something I try to do in java programs to save some cpu cycles.  As the
> > table grows in length this might help.
>Pot shots are most welcome - keep reviewing the code!.
>
>This is an interesting difference between C++ and java arrays. In the C++
>example 
>'sizeof(javaToQtTypeSignatureMap)/sizeof(*javaToQtTypeSignatureMap)',
>sizeof() is a compile time thing. So the expression should be evaluated at
>compile time by gcc, and just map onto a constant (maybe I'm wrong and it
>isn't..). In java, array sizes are a runtime thing, which allows it to 
>check
>array bounds at runtime.
>
>On the other hand, I don't believe in optimization without measurement. So 
>to
>justify any change to a working method, I think we should profile the code 
>to
>see if a significant time was spent in JavaSlot::javaToQtSlotType().
>
>-- Richard
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