RE: Prototype Calls

[Joel Cochran <jrc@xxxxxxxxxx>]

On Fri, 2004-11-05 at 16:03, Bob Cozzi wrote:
> Oh man Joel! This is why people have trouble understanding the APIs and
> prototypes. 
> Your example passes the full 3000 bytes as the command string every time.
> That is not necessary. 
> Working with your code, it would be "better" to have it as follows:
> 
>   d sysCommand      pr                  extpgm('QCMDEXC')
> >>d commandString               3000    const   OPTIONS(*VARSIZE)
>   d commandLength                 15  5 const
> >>d QcmdCmd         s           3000    VARYING
> >>d QcmdLength      s             10I 0
> 
> Defining QcmdLength this way means you never have to do anything other
> than use the parameter name (assuming you populate and use QcmdCmd...)
> 
> EX:
>     c                   Eval      QcmdCmd = 'RMVLIBLE LIB(CVTSPLV4R1)'
>   >>c                   CallP(E)  sysCommand( QcmdCmd : %len(qcmdcmd) )
> 
> Summary of changes:
> Add OPTIONS(*VARSIZE) to the commandString parameter.
> Add VARYING to the CL variable that contains the command to be run.
> Change the data type of the QcmdLength variable to 10I0. Since CommandLength
> is "const" the compiler will convert the Int4 value into a 15P5 value
> automatically (the pleasure of prototyping correctly!).
> Changed the 2nd parm value of the CALLP to sysCommand to be the current
> length of the no variable length string.
> 
> -Bob Cozzi

Thanks Bob,  

I got this example several years ago and never really re-examined it. 
And to think at the time I was just happy it worked! :-)

Actually, doing it this way, would we even need to define QcmdLength? 
It isn't used for anything since we are passing %len( QcmdCmd )...

d sysCommand      pr                  extpgm('QCMDEXC')
d commandString               3000    const   OPTIONS(*VARSIZE)
d commandLength                 15  5 const
d QcmdCmd         s           3000    VARYING

EX:
    c                   Eval      QcmdCmd = 'RMVLIBLE LIB(CVTSPLV4R1)'
   c                   CallP(E)  sysCommand( QcmdCmd : %len(qcmdcmd) )

It never occurred to me to use *VARSIZE variables.  I am a big fan of varying 
strings, so I should have done this sooner.  As always, thanks for the tips!


Joel
http://www.rpgnext.com