def _prepare_for_binary():
"""
Loads the first 2 entries of stack to D and M
"""
return (load_stack_head_to_D() +
'@SP\n' +
'A=M-1\n')
def return_handler():
frame_address_pointer = 'R13' # NOQA temp address used to store the base frame address
continue_address_pointer = 'R14' # NOQA temp address used to store the address of
return ('// return\n'
'@LCL\n'
'D=M\n'
'@{}\n'.format(frame_address_pointer) +
'M=D\n' # NOQA Store in frame_address_pointer (temp) the value of LCL (head of stack at beginning of call execution)
'@5\n'
'D=D-A\n' # D now holds the address of return pointer
'A=D\n'
'D=M\n'
'@{}\n'.format(continue_address_pointer) +
'M=D\n' + # NOQA Store continuation_address in continue_address_pointer (return address was previously set in call_handler)
load_stack_head_to_D() +
'@ARG\n'
'A=M\n'
'M=D\n' # Set ARG [0] to return value of function
'D=A+1\n' # Next stack head should be the value of ARG[0] + 1
'@SP\n'
'M=D\n' # NOQA Set stack head to point to one address above where we store the returned value
'@{}\n'.format(frame_address_pointer) +
'A=M-1\n'
'D=M\n'
'@THAT\n'
'M=D\n' # Set the caller's THAT to its previous value
'@2\n'
'D=A\n'
'@{}\n'.format(frame_address_pointer) +
'D=M-D\n'
'A=D\n'
'D=M\n'
'@THIS\n'
'M=D\n' # Set the caller's THIS to its previous value
'@3\n'
'D=A\n'
'@{}\n'.format(frame_address_pointer) +
'D=M-D\n'
'A=D\n'
'D=M\n'
'@ARG\n'
'M=D\n' # Set the caller's ARG to its previous value
'@4\n'
'D=A\n'
'@{}\n'.format(frame_address_pointer) +
'D=M-D\n'
'A=D\n'
'D=M\n'
'@LCL\n'
'M=D\n' # Set the caller's LCL to its previous value
'@{}\n'.format(continue_address_pointer) +
'A=M\n' # Load the return address to continue executing caller
'0;JMP\n'
)
def _from_stack_to_memory_transporter(segment, index):
return ('// pop from stack to segment {} {} \n'.format(segment, index) +
'@{}\n'.format(index) +
'D=A\n' +
'@{}\n'.format(segment) +
'D=D+M\n' +
'@R13\n' +
'M=D\n' + # Store memory index where we want to store in R13
load_stack_head_to_D() +
'@R13\n' +
'A=M\n' +
'M=D\n')
def _from_stack_to_static_transporter(index, file):
return ('// pop from statck to static {}\n'.format(index) +
load_stack_head_to_D() + '@{}_{}\n'.format(file, index) + 'M=D')
def _from_stack_to_register_transporter(register):
return ('// pop from stack to register {}\n'.format(register) +
load_stack_head_to_D() + '@{}\n'.format(register) + 'M=D')
def _from_stack_to_memory_transporter(segment, index):
return ('// pop from stack to segment {} {} \n'.format(segment, index) +
'@{}\n'.format(index) + 'D=A\n' + '@{}\n'.format(segment) +
'D=D+M\n' + '@R13\n' +
'M=D\n' + # Store memory index where we want to store in R13
load_stack_head_to_D() + '@R13\n' + 'A=M\n' + 'M=D\n')
def _from_stack_to_static_transporter(index, file):
return ('// pop from statck to static {}\n'.format(index) +
load_stack_head_to_D() +
'@{}_{}\n'.format(file, index) +
'M=D')
def _from_stack_to_register_transporter(register):
return ('// pop from stack to register {}\n'.format(register) +
load_stack_head_to_D() +
'@{}\n'.format(register) +
'M=D')
def if_goto_handler(label):
return ('// goto handler {}\n'.format(label) +
load_stack_head_to_D() +
'@{}\n'.format(label) +
'D;JNE\n')
def if_goto_handler(label):
return ('// goto handler {}\n'.format(label) + load_stack_head_to_D() +
'@{}\n'.format(label) + 'D;JNE\n')