Hello all,
again this nasty Java -> Octave connection.
I also want to embed Octave into a Java program and call Octave functions
from Java.
Initially I started with programming an execution engine which starts
octave.exe and connected to its standard input and output pipes. This
concept works (in the meantime I also found two solutions which implement
the same technique) but is somewhat ugly and inefficient due to conversions
to and from strings
What I tried now was to call the Octave DLLs (Windows platform) directly via
a C wrapper and using JNI.
This technique provides a very elegant solution and I have used this in the
past to call C and FORTRAN codes from Java. I want to define some global
variables, set the values from Java, execute some user supplied functions
and finally return the results (global variables set inside the user
functions) to Java.
Now with the Octrave DLLs I stumbled across a problem.
To study the interface to ther DLLs I started with a C++ program.
Basically I used the following logic:
//-----------------------------
// start and initialize Octave (once, then keep it alive)
char * pArgs[] = {"octave.exe","--path", "C:\\Programme\\Octave", "--norc",
NULL};
int iRet = octave_main (4 pArgs, true);
//-----------------------------
// execute some commands
std::string s = std::string("global Output;\nglobal
Input;\nInput=12;\nOutput=2*Input;\n");
octave_value x = eval_string (s, false, parse_status);
// examine the returned "x" with x.isnumeric() etc. works when code is in an
executable (.exe) file
// what does the follwing code do? It works, but where is the variable in
Octave?
set_global_value (std::string(cName), val);
octave_value vReturn = get_global_value (std::string(cName));
// the variable has the correct value, but is_globally_visible
(std::string(Name)) returns false...
// what does global mean here?
// terminate Octave
do_octave_atexit();
//-----------------------------
All this works well when I have the code inside an executable C++ program
(MSVC8.0).
So far so good.
Now for the interface via JNI I have to put this into a DLL which provides a
thin layer between Java objects and the C interface to Octave.
If I put the same code inside a DLL I can initialize Octave, but the
eval_string () and other functions doe not work - they seem to do nothing.
I found can do somethings with set_global_value () and get_global_value (),
but this is not enough and also these "global" values seem to be something
else than global variables in Octave.
Anyway, I see that eval_string() seems to work when called from a C
executable, but not when I call it from a DLL. Could this have something to
do with i/o streams which are different in a DLL and in an EXE?
Any ideas where to look and how to test?
Thank You,
Martin
--
View this message in context:
http://www.nabble.com/Java-package-tp15052296p19308994.html
Sent from the octave-dev mailing list archive at Nabble.com.
-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
Octave-dev mailing list
Octave-dev@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/octave-dev
