"John Keiser" <[EMAIL PROTECTED]> writes:
> Comments?
I don't particularly like the template idea -- mainly because Java
doesn't support the notion of templates. It's not nicely abstracted,
and it leaves room for error.
So, here's a new proposal, based on interface dispatch. Tell me what
you think. :)
VM dependent classes delegate calls to interfaces defined in package
"gnu.vm". These interfaces must be implemented by a VM in order for
it to work with GNU Classpath. Implementations of "gnu.vm" are housed
in a packaged called "gnu.vm.<VIRTUAL_MACHINE_NAME>", where
<VIRTUAL_MACHINE_NAME> is the name of the virtual machine.
For example, here's the full source code for gnu.vm.Runtime:
public interface gnu.vm.Runtime {
public void exit(int status);
public void runFinalizersOnExit();
public void gc();
public void runFinalization();
public void traceInstructions(boolean on);
public void traceMethodCalls(boolean on);
}
Here's a segment of GNU Classpath's java.lang.Runtime:
public class Runtime extends Object {
static gnu.vm.Runtime run = new gnu.vm.VIRTUAL_MACHINE_NAME.Runtime();
public void exit(int status) {
run.exit(status);
}
}
At compile time, VIRTUAL_MACHINE_NAME is resolved to the correct class
name through the use of the C preprocessor. The value of
VIRTUAL_MACHINE_NAME is determined via autoconf.
So for Japhar, a stack trace might look like:
1: gnu.vm.japhar.Runtime.exit(0)
0: java.lang.Runtime.exit(0)
Using an interface dispatch scheme results in an extra Java function
call for each VM specific call. This allows freedom in the VM
specific code, as it has been abstracted from GNU Classpath. The VM
specific code is free to do anything that it so desires. For example,
there's no requirement for the native code in the VM classes to be
JNI. The extra layer of abstraction allows each VM to live in its own
separate namespace, unaffected by changes to non gnu.vm classes.
Let's say for instance your name begins with a "J", and ends with
"ohn". You might not like the _one_ extra function call overhead. No
problem, just write a bytecode muncher which inlines all the VM
specific code into the core Java classes after compilation of GNU
Classpath.
Comments?
--
Paul Fisher * [EMAIL PROTECTED]
