def gen_method(info, method_obj):
node = method_obj.node
assert node.name in 'MethodDeclaration'
# Preprocessing:
# Assign frame pointer offsets to each parameter and local variable
# declaration node.
param_start_index = len(node.find_child('Parameters').children) + 1
for decl in node.find_child('Parameters').children:
decl.frame_offset = param_start_index
param_start_index -= 1
local_var_start_index = -1
num_vars = 0
all_local_decls = list(node.select(['LocalVariableDeclaration']))
for decl in all_local_decls:
decl.frame_offset = local_var_start_index
local_var_start_index -= 1
num_vars += 1
output = []
# Preamble for method.
output.append(method_obj.node.label + ':')
# save ebp & esp
output.extend([
"push ebp",
"mov ebp, esp",
])
# make room for local vars in the stack
output.append("sub esp, %d" % (num_vars*4))
body = node[4] # MethodBody
if len(body.children) != 0:
output.extend(statement.gen_block(info, body[0], method_obj))
# restore ebp & esp
output.extend([
"END~%s:" % (method_obj.node.label),
"mov esp, ebp",
"pop ebp",
"ret"
])
return output
def gen_constructor(info, constructor_obj):
node = constructor_obj.node
assert node.name == 'ConstructorDeclaration'
# Preprocessing:
# Assign frame pointer offsets to each parameter and local variable
# declaration node.
param_start_index = len(node.find_child('Parameters').children) + 1
for decl in node.find_child('Parameters').children:
decl.frame_offset = param_start_index
param_start_index -= 1
local_var_start_index = -1
num_vars = 0
all_local_decls = list(node.select(['LocalVariableDeclaration']))
for decl in all_local_decls:
decl.frame_offset = local_var_start_index
local_var_start_index -= 1
num_vars += 1
output = []
# Preamble for constructor.
output.append(constructor_obj.node.label + ':')
# save ebp & esp
output.extend([
"push ebp",
"mov ebp, esp",
])
# make room for local vars in the stack
output.append("sub esp, %d" % (num_vars*4))
# Call superclass default constructor if this is not java.lang.Object.
if info.class_obj.name != 'java.lang.Object':
this_offset = (len(constructor_obj.params) * 4) + 8
output.append('mov eax, %d' % this_offset)
output.append('mov eax, [eax+ebp]')
output.append('push eax')
superclass = info.class_obj.extends.name
superclass_simple = superclass.split('.')[-1]
superclass_label = 'CONSTRUCTOR~%s.%s~' % (superclass, superclass_simple)
output.append('call %s' % superclass_label)
output.append('add esp, 4')
# Initialize instance fields.
for member in info.class_obj.declare:
if isinstance(member, class_hierarchy.Field) == False:
continue
field_obj = member
field_node = field_obj.node
if 'Static' not in field_obj.mods and \
len(field_node[3].children) == 1: # Initializer
# Evaluate initializer.
output.extend(expression.gen_expr(info, field_node[3][0], constructor_obj))
# Get the address of 'this'.
this_offset = (len(constructor_obj.params) * 4) + 8
output.append('mov ebx, ebp')
output.append('add ebx, %d' % this_offset)
output.append('mov ebx, [ebx]')
# Assign to field offset.
receiver_type = info.class_obj.name
field_name = field_obj.name
field_offset = info.get_field_offset_from_field_name(receiver_type, field_name)
field_offset += 12
output.append('mov [ebx+%d], eax' % field_offset)
body = node # ConstructorBody
if len(body.children) != 0:
output.extend(statement.gen_block(info, body[3], constructor_obj))
# restore ebp & esp
output.extend([
"END~%s:" % (constructor_obj.node.label),
"mov esp, ebp",
"pop ebp",
"ret"
])
return output
