Re: [xmlvm-dev] Native methods in the C backend

[Paul P. <bay...@gm...>]

FYI - daemon threads are now implemented, so if you update, applications
will now terminate appropriately.

Thanks,
Paul

On Wed, Aug 3, 2011 at 11:07 AM, Arno Puder <ar...@pu...> wrote:

>
> I suggest you write yourself a little shell script based on the
> instructions I mentioned in my last message.
>
> Arno
>
>
> On 8/3/11 9:01 AM, Shai wrote:
> > Thanks Arno that explains allot.
> > How do I add this to the build process at least for now (until there is
> > a more official plugin architecture)?
> > Do I just place the file in the native directory and recompile xmlvm?
> > Do I need to list it somewhere in the build process?
> >
> > Thanks,
> > Shai.
> >
> > ------------------------------------------------------------------------
> > *From:* Arno Puder <ar...@pu...>
> > *To:* "Xml...@li..."
> > <Xml...@li...>
> > *Sent:* Wednesday, August 3, 2011 6:30 PM
> > *Subject:* [xmlvm-dev] Native methods in the C backend
> >
> >
> > there was a question on the mailing list regarding the native interface
> > for the C backend. While XMLVM already makes extensive use of the native
> > interface when cross-compiling Apache Harmony, we have not exposed this
> > functionality in a proper way for applications. However, here a little
> > how-to showing how this can be done. 'Proper' support would just do a
> > better job at integrating the following steps into the XMLVM toolchain,
> > but the basic principles would remain the same.
> >
> > Consider the following class NativeTest. The idea is to provide an
> > implementation for nativeMethod() that prints out the array and then
> > calls back to a Java method:
> >
> > package xmlvm;
> >
> > public class NativeTest {
> >
> > native void nativeMethod(int[] intArray);
> >
> > void methodToBeCalledFromNative() {
> > System.out.println("Hello from methodToBeCalledFromNative()");
> > }
> >
> > public static void main(String[] args) {
> > int intArray[] = {2, 4, 6, 8};
> > NativeTest instance = new NativeTest();
> > instance.nativeMethod(intArray);
> > }
> > }
> >
> > javac NativeTest.java
> > xmlvm --in=NativeTest.class --out=out --target=posix
> > mv out/src/xmlvm.m out/src/xmlvm.c
> > xmlvm --in=NativeTest.class --out=native \
> > --target=gen-c-wrappers --gen-native-skeletons
> > # Ignore the error that the last command will generate. This command
> > # will generate a skeleton file for nativeMethod().
> > # In file native/native_xmlvm_NativeTest.c out/src/ inject the following
> > code:
> >
> > //XMLVM_BEGIN_NATIVE[xmlvm_NativeTest_nativeMethod___int_1ARRAY]
> > xmlvm_NativeTest* thiz = me;
> > printf("Hello from nativeMethod()\n");
> > org_xmlvm_runtime_XMLVMArray* intArray = n1;
> > JAVA_ARRAY_INT* data = (JAVA_ARRAY_INT*)
> > intArray->fields.org_xmlvm_runtime_XMLVMArray.array_;
> > int length = intArray->fields.org_xmlvm_runtime_XMLVMArray.length_;
> > for (int i = 0; i < length; i++) {
> > printf("%d, ", data[i]);
> > }
> > printf("\n");
> > #ifdef XMLVM_VTABLE_IDX_xmlvm_NativeTest_methodToBeCalledFromNative__
> > VTABLE_PTR func =
> >
> thiz->tib->vtable[XMLVM_VTABLE_IDX_xmlvm_NativeTest_methodToBeCalledFromNative__];
> > (*(void (*)(JAVA_OBJECT)) func)(me);
> > #else
> > xmlvm_NativeTest_methodToBeCalledFromNative__(me);
> > #endif
> > //XMLVM_END_NATIVE
> >
> > cp native/native_xmlvm_NativeTest.c out/src/
> > cd out/dist/
> > make
> > ./build/out
> >
> > A few comments: the purpose of the special comment markers
> > //XMLVM_BEGIN_* and //XMLVM_END_NATIVE is to clearly distinguish between
> > generated portions of the file (outside the special markers) and
> > injected code (inside the markers). When the skeleton is regenerated via
> > --gen-native-skeletons (e.g., because of new added native methods in
> > NativeTest), the injected code will be automatically migrated.
> >
> > Another comment regarding the ominous #ifdef: XMLVM performs various
> > optimizations on the generated C code. If a method is never overridden
> > in an application, XMLVM will not put it in the vtable of the class. The
> > #ifdef will be true iff the method in question was overridden. In this
> > case the method needs to be called via the vtable (the funky looking
> > function pointer). If the #ifdef is false, it means the method was never
> > overridden in the application and can therefore be called directly.
> >
> > Note that the application does not terminate. That is because the
> > garbage collection thread is not yet a daemon thread and therefore
> > blocks termination of the application. This will be fixed.
> >
> > Hope this helps,
> > Arno
> >
> >
> ------------------------------------------------------------------------------
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> >
> >
> >
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