nitvm: Clean the code and add an absolute offset for methods and attributes.

This offset will be used to implement object-mechanisms by direct access

Signed-off-by: Julien Pagès <julien.projet@gmail.com>

diff --git a/src/vm.nit b/src/vm.nit
index 9e9c778..067c962 100644 (file)
--- a/src/vm.nit
+++ b/src/vm.nit
@@ -41,7 +41,7 @@ class VirtualMachine super NaiveInterpreter
        # Perfect hashing and perfect numbering
        var ph: Perfecthashing = new Perfecthashing
 
-       # Handles memory and garbage collection
+       # Handles memory allocated in C
        var memory_manager: MemoryManager = new MemoryManager
 
        # The unique instance of the `MInit` value
@@ -336,9 +336,9 @@ redef class MClass
                var nb_methods = new Array[Int]
                var nb_attributes = new Array[Int]
 
-               # Absolute offset of the beginning of the attributes table
+               # Absolute offset of attribute from the beginning of the attributes table
                var offset_attributes = 0
-               # Absolute offset of the beginning of the methods table
+               # Absolute offset of method from the beginning of the methods table
                var offset_methods = 0
 
                for parent in superclasses do
@@ -350,9 +350,7 @@ redef class MClass
 
                        for p in parent.intro_mproperties(none_visibility) do
                                if p isa MMethod then methods += 1
-                               if p isa MAttribute then
-                                       attributes += 1
-                               end
+                               if p isa MAttribute then attributes += 1
                        end
 
                        ids.push(parent.vtable.id)
@@ -411,11 +409,13 @@ redef class MClass
                        if p isa MMethod then
                                self_methods += 1
                                p.offset = relative_offset_meth
+                               p.absolute_offset = offset_methods + relative_offset_meth
                                relative_offset_meth += 1
                        end
                        if p isa MAttribute then
                                nb_introduced_attributes += 1
                                p.offset = relative_offset_attr
+                               p.absolute_offset = offset_attributes + relative_offset_attr
                                relative_offset_attr += 1
                        end
                end
@@ -432,8 +432,8 @@ redef class MClass
                update_positions(offset_attributes, offset_methods, self)
 
                # Since we have the number of attributes for each class, calculate the delta
-               var d = calculate_delta(nb_attributes_total)
-               vtable.internal_vtable = v.memory_manager.init_vtable(ids_total, nb_methods_total, d, vtable.mask)
+               var deltas = calculate_delta(nb_attributes_total)
+               vtable.internal_vtable = v.memory_manager.init_vtable(ids_total, nb_methods_total, deltas, vtable.mask)
        end
 
        # Fill the vtable with methods of `self` class
@@ -558,13 +558,20 @@ redef class MClass
 end
 
 redef class MAttribute
-       # Represents the relative offset of this attribute in the runtime instance
+       # Relative offset of this attribute in the runtime instance
+       # (beginning of the block of its introducing class)
        var offset: Int
+
+       # Absolute offset of this attribute in the runtime instance (beginning of the attribute table)
+       var absolute_offset: Int
 end
 
 redef class MMethod
-       # Represents the relative offset of this attribute in the runtime instance
+       # Relative offset of this method in the virtual table (from the beginning of the block)
        var offset: Int
+
+       # Absolute offset of this method in the virtual table (from the beginning of the vtable)
+       var absolute_offset: Int
 end
 
 # Redef MutableInstance to improve implementation of attributes in objects