def ret(class_name, command_number):
output = COMMENT.format(command='return', name='', arg='')
output += READ.format(address='LCL')
output += STORE.format(address='ENDFRAME')
output += _set_address_from_endframe(RETURN_ADDRESS,
OFFSET_ENDFRAME[RETURN_ADDRESS])
output += READ_AND_DECREMENT_SP
output += ADDRESS.format(address='ARG')
output += FOLLOW_POINTER
output += WRITE_TO_MEMORY_FROM_REGISTER
output += READ.format(address='ARG')
output += 'D=D+1\n'
output += STORE.format(address='SP')
for address in ['THAT', 'THIS', 'ARG', 'LCL']:
output += _set_address_from_endframe(address, OFFSET_ENDFRAME[address])
output += ADDRESS.format(address=RETURN_ADDRESS)
output += FOLLOW_POINTER
output += JUMP
return output
def push(class_name, command_number, memory_segment, value):
address_offset = int(value)
output = COMMENT.format(command='push', name=memory_segment, arg=value)
output += ADDRESS.format(
address=_get_base_address(class_name, memory_segment, address_offset))
if memory_segment == 'constant':
output += LOAD_VALUE_TO_REGISTER
elif memory_segment == 'static':
output += FOLLOW_POINTER
output += LOAD_VALUE_TO_REGISTER
else:
if memory_segment in MEMORY_SEGMENT_ADDRESSES:
output += FOLLOW_POINTER
# could be 'temp' or 'pointer'
if address_offset != 0:
output += _increment_memory(address_offset)
output += FOLLOW_POINTER
output += LOAD_VALUE_TO_REGISTER
output += WRITE_AND_INCREMENT_SP
return output
def call(class_name, command_number, function_name, argument_num):
output = COMMENT.format(command='call',
name=function_name,
arg=argument_num)
argument_num = int(argument_num)
return_address = RETURN_ADDRESS_LABEL.format(class_name=class_name,
command_number=command_number)
output += ADDRESS.format(address=return_address)
output += LOAD_VALUE_TO_REGISTER
output += WRITE_AND_INCREMENT_SP
for address in ['LCL', 'ARG', 'THIS', 'THAT']:
output += READ.format(address=address)
output += WRITE_AND_INCREMENT_SP
output += READ.format(address='SP')
output += SUBTRACT.format(value=5)
if argument_num > 0:
output += SUBTRACT.format(value=argument_num)
output += STORE.format(address='ARG')
output += READ.format(address='SP')
output += STORE.format(address='LCL')
output += GOTO.format(address=function_name)
output += LABEL.format(address=return_address)
return output
def bootstrap():
output = COMMENT.format(command='bootstrap', name='', arg='')
output += ADDRESS.format(address='256')
output += LOAD_VALUE_TO_REGISTER
output += STORE.format(address='SP')
output += call('bootstrap', 0, 'Sys.init', 0)
return output
def function(class_name, command_number, function_name, local_variable_num):
output = COMMENT.format(command='function',
name=function_name,
arg=local_variable_num)
local_variable_num = int(local_variable_num)
output += LABEL.format(address=function_name)
for i in range(0, local_variable_num):
output += ADDRESS.format(address='0')
output += LOAD_VALUE_TO_REGISTER
output += WRITE_AND_INCREMENT_SP
return output
def pop(class_name, command_number, memory_segment, value):
address_offset = int(value)
output = COMMENT.format(command='pop',
name=memory_segment,
arg=address_offset)
output += READ_AND_DECREMENT_SP
output += ADDRESS.format(
address=_get_base_address(class_name, memory_segment, address_offset))
if memory_segment == 'static':
output += WRITE_TO_MEMORY_FROM_REGISTER
else:
if memory_segment == 'pointer':
output += WRITE_TO_MEMORY_FROM_REGISTER
elif memory_segment in MEMORY_SEGMENT_ADDRESSES:
output += FOLLOW_POINTER
# could be 'temp' or 'pointer'
if address_offset != 0:
output += _increment_memory(address_offset)
output += WRITE_TO_MEMORY_FROM_REGISTER
return output
def if_goto(class_name, command_number, label_name):
output = COMMENT.format(command='if-goto', name=label_name, arg='')
output += READ_AND_DECREMENT_SP
output += ADDRESS.format(address=label_name)
output += JUMP_IF_NOT
return output