java/docs/object-layout.txt

Object layout for Java objects and array objects
------------------------------------------------

1) objects

    Need extensible header for the use of:

    a) VM: locking, hashing, dynamic type checking, virtual function
           invocation.

    b) GC: garbage collection (can be the reference count for a
           reference counting garbage collector)

    obj_t : { <header_t>, <field_t1>, <field_t2>, ..., <field_tN> }

    +--------+ <-- pointer to object
    | header |
    +--------+
    | field1 |
    +--------+
    | field2 |
    +--------+
    | ...... |
    +--------+
    | fieldN |
    +--------+

2) arrays

    +--------+ <-- pointer to array object
    |  len   |
    +--------+
    | header |
    +--------+
    | obj_t* |
    +--------+
    | ...... |
    +--------+
    | ...... |
    +--------+

    array_object_t : { uint, <header_t>, [ 0 x <obj_t>* ] }


Type information for java objects
---------------------------------

VM_Class object for each class. This object needs at least the
following fields:

a) pointer to VM_Class object of its super class
b) list of interfaces implemented
c) list of field descriptors
d) list of methods (static, constructor, virtual, finalizer)
e) list of attributes (constant value, code, exceptions, inner
classes, synthetic, source file, line number table, local variable
table, deprecated)

We would most likely need a method dispatch table as well (vtable).