[Aegisvm-devel] aegis patches

[Justin B. <jus...@ya...>]

Hello all,

I've got a working version of aegis that is based on
older sources, and to which I've made some
modifications. I've tried to incorporate these changes
into the latest development source code. I think I've
got everything right but it's possible I've missed
something new. All of this code works with my version.

As well as fixing various minor typos and removing
some compilation warnings under my compiler, the
changes can be summarized as follows:

1) JNI additions, which were heavily based on code
from Gildas Bazin. These implement
New<PrimitiveType>Array(),
Get<PrimitiveType>ArrayRegion and
Set<PrimitiveType>ArrayRegion, as well as
GetObjectArrayElement.

Files affected: jni.c, jni.h

2) Invocation of static native methods changed to pass
class as second parameter, as per the Java Native
Interface Specification 1.1, Ch 2, Section Native
Method Arguments. Previously only the JNIEnv pointer
was being passed to static native methods. This
required changing all the built-in static native
methods' prototypes.

Files affected: invoke.c, jni.c, prepare.c, jpr/ff.c,
jpr/ff.h

3) Dynamic expansion of the internal heap used by java
programs, by using an algorithm that grows the heap at
garbage collection time. Maximum and minimum limits
can be set, as well as a maximum number of garbage
collection executions before growing. There are surely
other ways of making the heap dynamic (probably by
re-implementing the gc), but this method allows the
garbage collector to largely remain intact. 

In this algorithm, the heap is seperated into two
sections. When the garbage collector copies from one
to another (thus performing the garbage collection by
only copying valid pointers), and it finds that there
isn't enough space left over in the heap afterwards,
it re-allocates a larger memory slice for the target
section of the heap, effectively growing it. (The next
garbage collection the other section grows also).

Files Affected: gc.h, gc.c, builtin.c 


3) Implemented updated java/lang/String and
java/lang/StringBuffer support, allowing sharing of
backing arrays whenever reasonable. These were taken
from the GNU classpath project, and modified.
StringBuffer is essentially the same, with only one
added check to ensure that large backing arrays are
not hanging around needlessly. String is a mix of
(mostly) GNU's String, aegis' String, and some other
additions. These changes were made mostly because of
internal aegis dependence upon the format of string
class. Notably, the StringHashTable has been retained
from aegis' version, and the ToUpperCase/toLowerCase()
functions were modified. These changes at times
provide a big improvement in efficiency and space
usage. Note: the GNU StringBuffer class can be used
unchanged. The Error.java I submit IS the GNU class.

Files affected: java/lang/String.java,
java/lang/StringBuffer.java, java/lang/Error.java,
gc.c, jni.c, builtin.c, object.h, resolve.c

A zip of the diffs is attached. I think aegis is well
written and hope these changes will prove useful to
it's further development. Please let me know if there
are any problems or if you have questions.

-Justin Briggs


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