Re: [tcljava-user] Advice Porting Tcl C API Tcl_CreateObjCommand to TclJava tcl.lang.Interp#createCommand

[Tom P. <tpo...@ny...>]

Hi Brian,

There's not ClientData in JTcl/Jacl, because Java already gives you
that functionality for free, just for having Java classes.  Writing
a JTcl extension in Java requires that you implement the tcl.lang.Command
interface; your actual classes can have any amount of private data
per command class.  Of course you'll need a constructor that provides
or creates your private data, but that can happen once when you load
your package.

Many of the builtin command implementations use some private data,
but mostly these are constants ("private static final ....").  There's
no reason these can't be ordinary Java class fields.

Also check out tcl.lang.cmd.AfterCmd.java.  It uses the
interp AssocData, you can see how that's done.



Here's a sample using the 'hyde' extension, and the Java code
that it produces:

-----------------------------------------------
package require hyde
hyde::configure -debug 1
hyde::jcommand lastInvoked -auxmethods {
    // some private data
    private int lastInvokedSeconds;

    // constructor for this command (hyde adds the "Cmd" suffix)
    public lastInvokedCmd () {
        getSeconds();
    }

    // a helper method
    private void getSeconds() {
        lastInvokedSeconds = (int) (System.currentTimeMillis() / 1000);
    }

} -body {
    // body of our command, just return the last invoked time
    interp.setResult(lastInvokedSeconds);

    // set the time for the next invocation
    getSeconds();
}
-----------------------------------------------




Here's the Java code that hyde produces, compiles,
and creates into a Tcl command:

-----------------------------------------------
package hyde;
import tcl.lang.*;
public class lastInvokedCmd
    implements Command  {


    // some private data
    private int lastInvokedSeconds;

    // constructor for this command (hyde adds the "Cmd" suffix)
    public lastInvokedCmd () {
        getSeconds();
    }

    // a helper method
    private void getSeconds() {
        lastInvokedSeconds = (int) (System.currentTimeMillis() / 1000);
    }





  public void
  cmdProc (Interp interp, TclObject argv[])
    throws TclException {


    // body of our command, just return the last invoked time
    interp.setResult(lastInvokedSeconds);

    // set the time for the next invocation
    getSeconds();


  }
}
-----------------------------------------------



Now, try out our new 'lastInvoked' command:


proc testLastInvoked {} {
  puts "time now is [clock format [clock seconds]]"
  lastInvoked
  after 5000
  puts "   it's now [clock format [clock seconds]], \
       but the last time invoked was [clock format [lastInvoked]]"
}
testLastInvoked


==> time now is Mon May 02 20:47:41 MDT 2016
==>    it's now Mon May 02 20:47:46 MDT 2016, but the last time invoked was Mon May 02 20:47:41 MDT 2016




Good luck,
Tom




On Fri, Apr 29, 2016 at 03:40:31PM +0000, Brian Brooks (US) wrote:
> We're porting a TCL-based C app to Java using TclJava (technically, jtcl).
> 
> We have a lot of TCL commands written in C which utilize the ClientData passed to Tcl_CreateObjCommand https://www.tcl.tk/man/tcl/TclLib/CrtObjCmd.htm.
> 
> TclJava lacks command ClientData support.  So I'm trying to come up with an alternative that works with TclJava tcl.lang.Interp#createCommand http://tcljava.sourceforge.net/docs/TclJavaLib/createCmd.htm.
> 
> A couple of Intra-Process-Communication approaches I've considering:
> 1. Use AssocData http://tcljava.sourceforge.net/docs/TclJavaLib/AssocData.htm.
> 2. Use a Java class static member (guarded for thread-safety) e.g. 
> 
> Package org.myorg.myprod;
> 
> public class GlobalData {
>     public static Map<String,Object> clientData = new HashMap<>();
> }
> 
> We have hundreds of TCL scripts which already use these commands, so altering the scripts to pass the "ClientData" as command arguments isn't really an option.
> 
> Has anyone already successfully solved this problem?  Are there examples of how to do this already?  Any advice?
> 
> Sincerely,
> Brian Brooks
> Sr Software Engineer
> Duluth, GA 30096
> 
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-- 
Tom Poindexter
tpo...@ny...