class CompilationEngine(object):
# the destination file for writing
destination_file = None
# the tokenizer for the input file
tokenizer = None
# symbol table
symbol_table = None
# vm writer
vm_writer = None
# the class name
class_name = ""
# indicies for if and while loops
# start at -1 because we increment before use
while_index = -1
if_index = -1
# the constructor for compiling a single class
# the next method to be called after construction must be compile_class
# source_filename must be a single file, not a directory
def __init__(self, source_filename):
# destination filename
# if the original extension was .jack, then make the extension .vm
# if the original extension was not .jack, then append .vm
if source_filename.lower().endswith(".jack"):
destination_filename = source_filename[:-5] + ".vm"
else:
destination_filename = source_filename + ".vm"
# open the destination filename for writing
self.destination_file = open(destination_filename, 'w')
# create a tokenizer for the input file
self.tokenizer = JackTokenizer(source_filename)
# create the symbol table
self.symbol_table = SymbolTable()
# create the vm writer
self.vm_writer = VMWriter(self.destination_file)
# compiles a complete class and closes the output file
def compile_class(self):
# class keyword
tt, t = self._token_next(True, "KEYWORD", "class")
# name of class
tt, t = self._token_next(True, "IDENTIFIER")
self.class_name = t
# open brace
tt, t = self._token_next(True, "SYMBOL", "{")
# one or more variable declarations
self.tokenizer.advance()
while True:
tt, t = self._token_next(False)
if tt == "KEYWORD" and t in ["field", "static"]:
self.compile_class_var_dec()
else:
# stop trying to process variable declarations
break
# one or more subroutine declarations
while True:
tt, t = self._token_next(False)
if tt == "KEYWORD" and t in ["constructor", "function", "method"]:
self.compile_subroutine()
else:
# stop trying to process functions
break
# close brace
# do not advance because we already advanced upon exiting the last loop
tt, t = self._token_next(False, "SYMBOL", "}")
# done with compilation; close the output file
self.destination_file.close()
# compiles a static declaration or field declaration
def compile_class_var_dec(self):
# compile the variable declaration
# False means this is a class (not a subroutine)
self.compile_var_dec(False)
# compiles a complete method, function, or constructor
def compile_subroutine(self):
# start of subroutine
self.symbol_table.start_subroutine()
# constructor, function, or method keyword
tt, type = self._token_next(False, "KEYWORD")
# type of the return value
# can be either keyword (void) or an identifier (any type)
tt, t = self._token_next(True)
# name of the method/function/constructor
tt, name = self._token_next(True)
name = self.class_name + "." + name
# if the type is a method, "define" this as an argument, so the other
# argument indexes work correctly
if type == "method":
self.symbol_table.define("this", self.class_name, SymbolTable.ARG)
# opening parenthesis
tt, t = self._token_next(True, "SYMBOL", "(")
# arguments
self.tokenizer.advance()
self.compile_parameter_list()
# closing parenthesis
tt, t = self._token_next(False, "SYMBOL", ")")
# opening brace
tt, t = self._token_next(True, "SYMBOL", "{")
# variable declarations
self.tokenizer.advance()
while True:
tt, t = self._token_next(False)
if tt == "KEYWORD" and t == "var":
self.compile_var_dec()
else:
# stop trying to process variable declarations
break
# write the function
num_locals = self.symbol_table.var_count(self.symbol_table.VAR)
self.vm_writer.write_function(name, num_locals)
# write any special code at the top of the function
if type == "constructor":
# code to allocate memory and set "this"
size = self.symbol_table.var_count(self.symbol_table.FIELD)
self.vm_writer.write_push(self.vm_writer.CONST, size)
self.vm_writer.write_call("Memory.alloc", 1)
self.vm_writer.write_pop(self.vm_writer.POINTER, 0)
elif type == "function":
# nothing special
pass
elif type == "method":
# put argument 0 into pointer 0 (this)
self.vm_writer.write_push(self.vm_writer.ARG, 0)
self.vm_writer.write_pop(self.vm_writer.POINTER, 0)
else:
print "WARNING: Expected constructor, function, or name; got", type
# statements
self.compile_statements()
# closing brace
tt, t = self._token_next(False, "SYMBOL", "}")
self.tokenizer.advance()
# compiles a (possibly empty) parameter list, not including the enclosing
# parentheses
def compile_parameter_list(self):
# check for empty list
tt, t = self._token_next(False)
if tt == "SYMBOL" and t == ")":
# the parameter list was empty; do not process any more
pass
else:
# there are things in the parameter list
while True:
# keyword (variable type)
tt, type = self._token_next(False)
# identifier (variable name)
tt, name = self._token_next(True)
# the kind is always an arg, since these are all parameters to the
# function
kind = SymbolTable.ARG
# define the variable in the symbol table
self.symbol_table.define(name, type, kind)
# possible comma
tt, t = self._token_next(True)
if tt != "SYMBOL" or t != ",":
# not a comma; stop processing parameters
break
self.tokenizer.advance()
# compiles a var declaration
# if subroutine is true, only the var keyword can be used
# if subroutine is false, only the static and field keywords can be used
def compile_var_dec(self, subroutine=True):
# the keyword to start the declaration
tt, kind = self._token_next(False, "KEYWORD")
# check for required types
if subroutine:
if kind == "var":
kind = SymbolTable.VAR
else:
print "WARNING: expecting var, but received %s" % (str(kind))
else:
if kind == "static":
kind = SymbolTable.STATIC
elif kind == "field":
kind = SymbolTable.FIELD
else:
print "WARNING: expecting static or field, but received %s" % (str(kind))
# type of the declaration
# could be an identifier or a keyword (int, etc)
tt, type = self._token_next(True)
# name of the declaration
tt, name = self._token_next(True, "IDENTIFIER")
# define the variable in the symbol table
self.symbol_table.define(name, type, kind)
# can support more than one identifier name, to declare more than one
# variable, separated by commas; process the 2nd-infinite variables
self.tokenizer.advance()
while True:
tt, t = self._token_next(False)
if tt == "SYMBOL" and t == ",":
# another variable name follows
tt, name = self._token_next(True, "IDENTIFIER")
# define the variable in the symbol table
self.symbol_table.define(name, type, kind)
self.tokenizer.advance()
else:
# no more variable names
break
# should be on the semicolon at the end of the line
tt, t = self._token_next(False, "SYMBOL", ";")
self.tokenizer.advance()
# compiles a sequence of statements, not including the enclosing {}
def compile_statements(self):
while True:
tt, t = self._token_next(False)
if tt == "KEYWORD" and t in ["do", "let", "while", "return", "if"]:
# call compile_t, where t is the type of compilation we want
token = getattr(self, "compile_" + t)()
else:
# not a statement; stop processing statements
break
# compiles a do statement
def compile_do(self):
# do keyword
tt, t = self._token_next(False, "KEYWORD", "do")
# subroutine call
self.tokenizer.advance()
self.compile_subroutine_call()
# do statements do not have a return value, so eliminate the return
# off of the stack
self.vm_writer.write_pop(self.vm_writer.TEMP, 0)
# semicolon
tt, t = self._token_next(False, "SYMBOL", ";")
self.tokenizer.advance()
# compiles a let statement
def compile_let(self):
# let keyword
tt, t = self._token_next(False, "KEYWORD", "let")
# variable name
tt, name = self._token_next(True, "IDENTIFIER")
# possible brackets for array
tt, t = self._token_next(True)
if tt == "SYMBOL" and t == "[":
# array - write operation
array = True
# compile the offset expression
self.tokenizer.advance()
self.compile_expression()
# write the base address onto the stack
segment, index = self._resolve_symbol(name)
self.vm_writer.write_push(segment, index)
# add base and offset
self.vm_writer.write_arithmetic("add")
# we cannot yet put the result into pointer 1, since the read
# operation (which hasn't been parsed/computed yet) may use pointer 1
# to read from an arrya value
# closing bracket
tt, t = self._token_next(False, "SYMBOL", "]")
# advance to the next token, since we are expected to be on the = for
# the next line
self.tokenizer.advance()
else:
array = False
# equals sign
tt, t = self._token_next(False, "SYMBOL", "=")
# expression
self.tokenizer.advance()
self.compile_expression()
if array:
# our stack now looks like this:
# TOP OF STACK
# computed result to store
# address in which value should be stored
# ... previous stuff ...
# pop the computed value to temp 0
self.vm_writer.write_pop(self.vm_writer.TEMP, 0)
# pop the array address to pointer 1 (that)
self.vm_writer.write_pop(self.vm_writer.POINTER, 1)
# put the computed value back onto the stack
self.vm_writer.write_push(self.vm_writer.TEMP, 0)
# pop to the variable name or the array reference
self.vm_writer.write_pop(self.vm_writer.THAT, 0)
else:
# not an array - pop the expression to the variable
segment, index = self._resolve_symbol(name)
self.vm_writer.write_pop(segment, index)
# semicolon
tt, t = self._token_next(False, "SYMBOL", ";")
self.tokenizer.advance()
# compiles a while statement
def compile_while(self):
# labels for this while loop
self.while_index += 1
while_start = "WHILE_START_%d" % (self.while_index)
while_end = "WHILE_END_%d" % (self.while_index)
# while keyword
tt, t = self._token_next(False, "KEYWORD", "while")
# opening parenthesis
tt, t = self._token_next(True, "SYMBOL", "(")
# label for the start of the while statement
self.vm_writer.write_label(while_start)
# the expression that is the condition of the while statement
self.tokenizer.advance()
self.compile_expression()
# the closing parenthesis
tt, t = self._token_next(False, "SYMBOL", ")")
# the result of the evaluation is now on the stack
# if false, then goto to the end of the loop
# to do this, negate and then call if-goto
self.vm_writer.write_arithmetic("not")
self.vm_writer.write_if(while_end)
# the opening brace
tt, t = self._token_next(True, "SYMBOL", "{")
# the statments that is the body of the while loop
self.tokenizer.advance()
self.compile_statements()
# the closing brace
tt, t = self._token_next(False, "SYMBOL", "}")
# after the last statement of the while loop
# need to jump back up to the top of the loop to evaluate again
self.vm_writer.write_goto(while_start)
# label at the end of the loop
self.vm_writer.write_label(while_end)
self.tokenizer.advance()
# compiles a return statement
def compile_return(self):
# return keyword
tt, t = self._token_next(False, "KEYWORD", "return")
# possible expression to return
tt, t = self._token_next(True)
if tt != "SYMBOL" and t != ";":
self.compile_expression()
else:
# no return expression; return 0
self.vm_writer.write_push(self.vm_writer.CONST, 0)
# ending semicolon
tt, t = self._token_next(False, "SYMBOL", ";")
self.vm_writer.write_return()
self.tokenizer.advance()
# compiles a if statement, including a possible trailing else clause
def compile_if(self):
# it is more efficient in an if-else case to have the else portion first
# in the code when testing, but we use the less-efficient but
# easier-to-write true-false pattern here
# labels for this if statement
self.if_index += 1
if_false = "IF_FALSE_%d" % (self.if_index)
if_end = "IF_END_%d" % (self.if_index)
# if keyword
tt, t = self._token_next(False, "KEYWORD", "if")
# opening parenthesis
tt, t = self._token_next(True, "SYMBOL", "(")
# expression of if statement
self.tokenizer.advance()
self.compile_expression()
# closing parenthesis
tt, t = self._token_next(False, "SYMBOL", ")")
# the result of the evaluation is now on the stack
# if false, then goto the false label
# if true, fall through to executing code
# if there is no else, then false and end are the same, but having two
# labels does not increase code size
self.vm_writer.write_arithmetic("not")
self.vm_writer.write_if(if_false)
# opening brace
tt, t = self._token_next(True, "SYMBOL", "{")
# statements for true portion
self.tokenizer.advance()
self.compile_statements()
# closing brace
tt, t = self._token_next(False, "SYMBOL", "}")
tt, t = self._token_next(True)
if tt == "KEYWORD" and t == "else":
# else statement exists
# goto the end of the if statement at the end of the true portion
self.vm_writer.write_goto(if_end)
# label for the start of the false portion
self.vm_writer.write_label(if_false)
# opening brace
tt, t = self._token_next(True, "SYMBOL", "{")
# statements
self.tokenizer.advance()
self.compile_statements()
# closing brace
tt, t = self._token_next(False, "SYMBOL", "}")
# end label
self.vm_writer.write_label(if_end)
# advance tokenizer only if we are in the else, since otherwise the
# token was advanced by the else check
self.tokenizer.advance()
else:
# no else portion; only put in a label for false, since end is not
# used
self.vm_writer.write_label(if_false)
# compiles an expression (one or more terms connected by operators)
def compile_expression(self):
# the first term
self.compile_term()
# finish any number of operators followed by terms
while True:
tt, t = self._token_next(False)
if tt == "SYMBOL" and t in "+-*/&|<>=":
# found an operator
# postfix order - add the next term and then do the operator
# the next term
self.tokenizer.advance()
self.compile_term()
# the operator
if t == "+":
self.vm_writer.write_arithmetic("add")
if t == "-":
self.vm_writer.write_arithmetic("sub")
if t == "=":
self.vm_writer.write_arithmetic("eq")
if t == ">":
self.vm_writer.write_arithmetic("gt")
if t == "<":
self.vm_writer.write_arithmetic("lt")
if t == "&":
self.vm_writer.write_arithmetic("and")
if t == "|":
self.vm_writer.write_arithmetic("or")
if t == "*":
self.vm_writer.write_call("Math.multiply", 2)
if t == "/":
self.vm_writer.write_call("Math.divide", 2)
else:
# no term found; done parsing the expression
break
# compiles a term
# this routine is faced with a slight difficulty when trying to decide
# between some of the alternative parsing rules. specifically, if the
# current token is an identifier, the routine must distinguish between a
# variable, an array entry, and a subroutine call. a single lookahead token,
# which may be one of [, (, or ., suffices to distinguish between the three
# possibilities. any other token is not part of this term and should not
# be advanced over.
def compile_term(self):
# a term: integer_constant | string_constant | keyword_constant |
# varname | varname[expression] | subroutine_call | (expression) |
# unary_op term
tt, t = self._token_next(False)
if tt == "INT_CONST":
self.vm_writer.write_push(self.vm_writer.CONST, t)
# advance for the next statement
self.tokenizer.advance()
elif tt == "STRING_CONST":
# after this portion is run, a pointer to a string should be on the
# stack
# we create a new string of a certain size and then append characters
# one by one; each append operation returns the pointer to the same
# string
# create the string
# string is a len, data tuple; not null-terminated
size = len(t)
self.vm_writer.write_push(self.vm_writer.CONST, size)
self.vm_writer.write_call("String.new", 1)
# append each character
for char in t:
self.vm_writer.write_push(self.vm_writer.CONST, ord(char))
self.vm_writer.write_call("String.appendChar", 2)
# advance for the next statement
self.tokenizer.advance()
elif tt == "KEYWORD":
if t == "true":
# true is -1, which is 0 negated
self.vm_writer.write_push(self.vm_writer.CONST, 0)
self.vm_writer.write_arithmetic("not")
elif t == "false" or t == "null":
self.vm_writer.write_push(self.vm_writer.CONST, 0)
elif t == "this":
self.vm_writer.write_push(self.vm_writer.POINTER, 0)
# advance for the next statement
self.tokenizer.advance()
elif tt == "SYMBOL" and t == "(":
# ( expression )
# parse the expression
self.tokenizer.advance()
self.compile_expression()
# closing parenthesis
tt, t = self._token_next(False, "SYMBOL", ")")
# advance for the next statement
self.tokenizer.advance()
elif tt == "SYMBOL" and t in "-~":
# unary_op term
# postfix order - add the next term and then do the operator
# parse the rest of the term
self.tokenizer.advance()
self.compile_term()
# write the unary operation
if t == "-":
self.vm_writer.write_arithmetic("neg")
elif t == "~":
self.vm_writer.write_arithmetic("not")
elif tt == "IDENTIFIER":
# varname, varname[expression], subroutine_call
# do not write the identifer yet
# get the next bit of the expression
# if it is a [, then array; if it is a ( or ., then subroutine call
# if none of above, then pass over
tt2, t2 = self._token_next(True)
if tt2 == "SYMBOL" and t2 in "(.":
# subroutine call
# back up and then compile the subroutine call
self.tokenizer.retreat()
self.compile_subroutine_call()
elif tt2 == "SYMBOL" and t2 == "[":
# array - read operation
# write the base address onto the stack
segment, index = self._resolve_symbol(t)
self.vm_writer.write_push(segment, index)
# compile the offset expression
self.tokenizer.advance()
self.compile_expression()
# add base and offset
self.vm_writer.write_arithmetic("add")
# put the resulting address into pointer 1 (that)
self.vm_writer.write_pop(self.vm_writer.POINTER, 1)
# read from that 0 onto the stack
self.vm_writer.write_push(self.vm_writer.THAT, 0)
# closing bracket
tt, t = self._token_next(False, "SYMBOL", "]")
# advance for the next statement
self.tokenizer.advance()
else:
# none of above - just a single identifier
segment, index = self._resolve_symbol(t)
self.vm_writer.write_push(segment, index)
else:
# unknown
print "WARNING: Unknown term expression object:", tt, t
# compiles a (possible empty) comma-separated list of expressions
def compile_expression_list(self):
num_args = 0
# check for empty list
tt, t = self._token_next(False)
if tt == "SYMBOL" and t == ")":
# the parameter list was empty; do not process any more
pass
else:
# there are things in the parameter list
while True:
# expression to pass
self.compile_expression()
num_args += 1
# possible comma
tt, t = self._token_next(False)
if tt == "SYMBOL" and t == ",":
self.tokenizer.advance()
else:
# not a comma; stop processing parameters
break
return num_args
# compiles a subroutine call
# two cases:
# - subroutineName(expressionList)
# - (class|var).subroutineName(expressionList)
def compile_subroutine_call(self):
# first part of name
tt, name1 = self._token_next(False, "IDENTIFIER")
# a dot and another name may exist, or it could be a parenthesis
name2 = None
tt, t = self._token_next(True)
if tt == "SYMBOL" and t == ".":
# the name after the dot
tt, name2 = self._token_next(True, "IDENTIFIER")
# advance so that we are on the parenthesis
self.tokenizer.advance()
# determine if this is a method call
# three possibilities
# - class.func() - function call
# - var.func() - method call
# - func() - method call on current object
if self.symbol_table.contains(name1):
method_call = True
local_call = False
elif name2 == None:
method_call = True
local_call = True
else:
method_call = False
# if a method call, push variable name1
# this a method call if the symbol table contains name1 and name2 exists
# OR name1 is a method in the current object
if method_call and local_call:
# push the current object onto the stack as a hidden argument
self.vm_writer.write_push(self.vm_writer.POINTER, 0)
elif method_call and not local_call:
# push the variable onto the stack as a hidden argument
segment, index = self._resolve_symbol(name1)
self.vm_writer.write_push(segment, index)
# opening parenthesis
tt, t = self._token_next(False, "SYMBOL", "(")
# expression list
self.tokenizer.advance()
num_args = self.compile_expression_list()
# closing parenthesis
tt, t = self._token_next(False, "SYMBOL", ")")
# write the call
if method_call and local_call:
# methd + <blank>
# get the name of the vm function to call
classname = self.class_name
vm_function_name = classname + "." + name1
# increase arguments by 1, since there is the hidden "this"
num_args += 1
# make the call
self.vm_writer.write_call(vm_function_name, num_args)
elif method_call and not local_call:
# variable name + method
# get the name of the vm function to call
classname = self.symbol_table.get(name1)[1]
vm_function_name = classname + "." + name2
# increase arguments by 1, since there is the hidden "this"
num_args += 1
# make the call
self.vm_writer.write_call(vm_function_name, num_args)
else:
# get the name of the vm function to call
vm_function_name = name1 + "." + name2
# make the call
self.vm_writer.write_call(vm_function_name, num_args)
self.tokenizer.advance()
# returns the token_type and token of the next token after advancing the
# tokenizer before reading if advance is True
def _token_next(self, advance=False, expected_type=None, expected_value=None):
# advance the tokenizer, if requested
if advance:
self.tokenizer.advance()
# get the token type and the token itself
token_type = self.tokenizer.token_type()
token = str(getattr(self.tokenizer, token_type.lower())())
if expected_type and token_type != expected_type:
print "WARNING: Type", token_type, "found; expected", expected_type
import traceback, sys
traceback.print_stack()
sys.exit(1)
if expected_value and token != expected_value:
print "WARNING: Value", token, "found; expected", expected_value
import traceback, sys
traceback.print_stack()
sys.exit(1)
return token_type, token
# convets a symbol table type into a segment type
def _type_to_segment(self, type):
if type == self.symbol_table.STATIC:
return self.vm_writer.STATIC
elif type == self.symbol_table.FIELD:
return self.vm_writer.THIS
elif type == self.symbol_table.ARG:
return self.vm_writer.ARG
elif type == self.symbol_table.VAR:
return self.vm_writer.LOCAL
else:
print "ERROR: Bad type %s" % (str(type))
# resolves the symbol from the symbol table
# the segment and index is returned as a 2-tuple
def _resolve_symbol(self, name):
kind, type, index = self.symbol_table.get(name)
return self._type_to_segment(kind), index
class CompilationEngine():
'''
Parses a stream of jack tokens recursively.
'''
def __init__(self, tokenizer):
self._name = tokenizer.get_filename().replace('.jack','')
# tokenizer for input
self._tokenizer = tokenizer
# symbol table
self._symbols = SymbolTable()
# vm output fiole
self._writer = VMWriter(self._name + '.vm')
# Input should be a tokenized .jack file containing one class
assert self._tokenizer.has_more_tokens()
self._tokenizer.advance()
self._class = None
self._subroutine = None
self._counter = 0
self.compile_class()
self.close()
def change_name(self, name):
self._name = name
def get_name(self, name):
return self._name
def get_token(self):
return self._tokenizer._token
def get_type(self):
return self._tokenizer._type
def close(self):
# close the output file at the end
self._writer.close()
def compile_class(self):
# 'class' className '{' classVarDec* subroutineDec* '}'
# keyword - class
assert self._tokenizer.keyword() == 'class'
self._tokenizer.advance()
# identifier - className
assert self._tokenizer.identifier()
self._class = self._tokenizer.identifier()
self._tokenizer.advance()
# sybmol - '{'
assert self._tokenizer.symbol() == '{', "expected '{' but got " + self.get_token()
self._tokenizer.advance()
# classVarDec*
while self._tokenizer.is_valid_class_variable():
self.compile_class_var()
# subroutineBody*
while self._tokenizer.is_valid_subroutine():
self.compile_subroutine()
# sybmol - '}'
assert self._tokenizer.symbol() == '}', "expected '}' but got " + self.get_token()
self._tokenizer.advance()
# assuming .jack file is properly formatted, there should be no more tokens
assert not self._tokenizer.has_more_tokens()
def compile_class_var(self):
# ('static'|'field') type varName (',' varName)* ';'
assert self._tokenizer.is_valid_class_variable()
# keyword - 'static' or 'field'
temp_kind = self._tokenizer.get_token()
self._tokenizer.advance()
# type - 'int' or 'char' or 'boolean' or className
assert self._tokenizer.is_valid_type()
temp_type = self._tokenizer.get_token()
self._tokenizer.advance()
# identifier - varName
assert self._tokenizer.identifier()
temp_name = self._tokenizer.get_token()
self._symbols.define(temp_name, temp_type, temp_kind)
self._tokenizer.advance()
# recursively check for (',' varName)* structure
while self._tokenizer.symbol() == ',':
self._tokenizer.advance()
# identifier - varName
assert self._tokenizer.identifier()
temp_name = self._tokenizer.get_token()
self._symbols.define(temp_name, temp_type, temp_kind)
# symbol - ',' or ';'
self._tokenizer.advance()
# next token should be a ';'
assert self._tokenizer.symbol() == ';', "expected ';' but got " + self.get_token()
self._tokenizer.advance()
def compile_subroutine(self):
# ('constructor'|'method'|'function') ('void'| type) subroutineName '(' parameterList ')' subroutineBody
assert self._tokenizer.is_valid_subroutine()
self._symbols.start_subroutine()
# keyword - constructor or method or function
self._subroutine = self._tokenizer.get_token()
if self._subroutine == 'method':
# in the case of method, add 'this' to symbol table
self._symbols.define('this', self._class, 'argument')
self._tokenizer.advance()
# keyword - type or void
assert self._tokenizer.is_valid_subroutine_type()
self._tokenizer.advance()
# identifier - subroutineName
assert self._tokenizer.identifier()
temp_name = self._tokenizer.identifier()
self._tokenizer.advance()
# symbol - '('
assert self._tokenizer.symbol() == '('
self._tokenizer.advance()
# parameterList
if self._tokenizer.is_valid_type():
self.compile_parameter_list()
# symbol - '('
assert self._tokenizer.symbol() == ')'
self._tokenizer.advance()
temp_name = self._class + '.' + temp_name
# symbol - '{'
assert self._tokenizer.symbol() == '{'
# subroutineBody
self.compile_subroutine_body(temp_name)
self._writer.write_comment('end subroutine ' + temp_name)
def compile_parameter_list(self):
# ( (type varName) (',' type varName)* )?
# only called if non-empty parameter list
assert self._tokenizer.is_valid_type()
# type - int or char or boolean or className
temp_type = self._tokenizer.get_token()
self._tokenizer.advance()
# identifier - varName
assert self._tokenizer.identifier()
temp_name = self._tokenizer.get_token()
self._symbols.define(temp_name, temp_type, 'argument')
self._tokenizer.advance()
while self._tokenizer.symbol() == ',':
# symbol - ','
self._tokenizer.advance()
assert self._tokenizer.is_valid_type()
# type - int or char or boolean or className
temp_type = self._tokenizer.get_token()
self._tokenizer.advance()
# identifier - varName
assert self._tokenizer.identifier()
temp_name = self._tokenizer.get_token()
self._symbols.define(temp_name, temp_type, 'argument')
self._tokenizer.advance()
# symbol - ')'
assert self._tokenizer.symbol() == ')'
def compile_subroutine_body(self, name):
# '{' varDec* statements '}'
# symbol - '{'
assert self._tokenizer.symbol() == '{'
self._tokenizer.advance()
# varDec
num_locals = 0
while self._tokenizer.keyword() == 'var':
# remember that compiling variables writes NO vm code
num_locals += self.compile_var()
self._writer.write_function(name, num_locals)
if self._subroutine == 'method':
# set this, in the case of a method
self._writer.write_push('argument',0)
self._writer.write_pop('pointer',0)
elif self._subroutine == 'constructor':
# allocate object
self._writer.write_object_alloc(self._symbols.var_count('field'))
# statements
self.compile_statements()
# symbol - '{'
assert self._tokenizer.symbol() == '}'
self._tokenizer.advance()
def compile_var(self):
# 'var' type varName (',' varName)* ';'
assert self._tokenizer.is_valid_variable()
# keyword - 'var'
self._tokenizer.advance()
# type - int or char or boolean or className
assert self._tokenizer.is_valid_type()
temp_type = self._tokenizer.get_token()
self._tokenizer.advance()
# identifier - varName
assert self._tokenizer.identifier()
temp_name = self._tokenizer.get_token()
self._symbols.define(temp_name, temp_type, 'local')
num_locals = 1
self._tokenizer.advance()
while self._tokenizer.symbol() == ',':
# symbol - ','
self._tokenizer.advance()
# identifier - varName
assert self._tokenizer.identifier()
temp_name = self._tokenizer.get_token()
self._symbols.define(temp_name, temp_type, 'local')
num_locals += 1
self._tokenizer.advance()
# symbol - ';'
assert self._tokenizer.symbol() == ';'
self._tokenizer.advance()
return num_locals
def compile_statements(self):
# statement*
while self._tokenizer.is_valid_statement():
if self._tokenizer.keyword() == 'let':
# letStatement
self.compile_let()
elif self._tokenizer.keyword() == 'if':
# ifStatement
self.compile_if()
elif self._tokenizer.keyword() == 'while':
# whileStatement
self.compile_while()
elif self._tokenizer.keyword() == 'do':
# doStatement
self.compile_do()
elif self._tokenizer.keyword() == 'return':
# returnStatement
self.compile_return()
# symbol - '}'
assert self._tokenizer.symbol() == '}'
def compile_let(self):
# 'let' varName ('[' expression ']')? '=' expression ';'
# keyword - 'let'
assert self._tokenizer.keyword() == 'let'
self._tokenizer.advance()
# identifier - varName
assert self._tokenizer.identifier()
if self._tokenizer.peek() == '=':
# varName '=' expression ';'
var_kind = self._symbols.kind_of(self._tokenizer.identifier())
var_index = self._symbols.index_of(self._tokenizer.identifier())
self._tokenizer.advance()
# next token is '='
self._tokenizer.advance()
# evaluate RHS expression, pop into variable
self.compile_expression()
if var_kind == 'field':
self._writer.write_pop('this', var_index)
else:
self._writer.write_pop(var_kind, var_index)
# expression ends with a ';'
assert self._tokenizer.symbol() == ';', "expected ';' but got " + self.get_token()
self._tokenizer.advance()
elif self._tokenizer.peek() == '[':
# varName '[' expression ']' '=' expression ';'
# write base address to stack
self._writer.write_push(self._symbols.kind_of(self._tokenizer.identifier()),
self._symbols.index_of(self._tokenizer.identifier()))
self._tokenizer.advance()
# symbol - '['
self._tokenizer.advance()
# expression - represents array index
self.compile_expression()
# base address + array index
self._writer.write_arithmetic('add')
# symbol - '['
assert self._tokenizer.symbol() == ']'
self._tokenizer.advance()
# symbol - '='
assert self._tokenizer.symbol() == '='
self._tokenizer.advance()
# expression
self.compile_expression()
# pop RHS value into temp segment
self._writer.write_pop('temp', 1)
# align that with array[i]
self._writer.write_pop('pointer', 1)
# push value of RHS expression onto stack
self._writer.write_push('temp', 1)
# pop value into correct array index
self._writer.write_pop('that', 0)
# symbol - ';'
assert self._tokenizer.symbol() == ';', "expected ';' but got " + self.get_token()
self._tokenizer.advance()
def compile_if(self):
# 'if' '(' expression ')' ('else' '{' statements '}')?
# keyword - if
assert self._tokenizer.keyword() == 'if'
self._writer.write_comment('if statement')
self._tokenizer.advance()
# symbol - (
assert self._tokenizer.symbol() == '(', "expected '(' but got " + self.get_token()
self._tokenizer.advance()
# expression
self.compile_expression()
self._writer.write_arithmetic('not')
label_num = str(self._counter)
self._counter += 1
self._writer.write_if('ELSE'+label_num)
# symbol - )
assert self._tokenizer.symbol() == ')', "expected '(' but got " + self.get_token()
self._tokenizer.advance()
# symbol - '{'
assert self._tokenizer.symbol() == '{'
self._tokenizer.advance()
# statements
self.compile_statements()
# symbol - '}'
assert self._tokenizer.symbol() == '}'
self._tokenizer.advance()
self._writer.write_goto('IF'+label_num)
self._writer.write_label('ELSE'+label_num)
# check for else
if self._tokenizer.keyword() == 'else':
# 'else' '{' statements '}'
# keyword - 'else'
self._tokenizer.advance()
# symbol - '{'
assert self._tokenizer.symbol() == '{', "expected '{' but got " + self.get_token()
self._tokenizer.advance()
# statements
self.compile_statements()
# symbol - '}'
assert self._tokenizer.symbol() == '}', "expected '}' but got " + self.get_token()
self._tokenizer.advance()
self._writer.write_label('IF'+label_num)
def compile_while(self):
# 'while' '(' expression ')' '{' statements '}'
# keyword - 'while'
assert self._tokenizer.keyword() == 'while'
# labels for ifgoto and goto vm commands
label_num = str(self._counter)
self._counter += 1
self._tokenizer.advance()
# symbol - '('
assert self._tokenizer.symbol() == '('
self._tokenizer.advance()
self._writer.write_label('WHILE'+label_num)
# expression
self.compile_expression()
self._writer.write_arithmetic('not')
self._writer.write_if('ELSE'+label_num)
# symbol - ')'
assert self._tokenizer.symbol() == ')'
self._tokenizer.advance()
# symbol - '{'
assert self._tokenizer.symbol() == '{'
self._tokenizer.advance()
# statements
self.compile_statements()
self._writer.write_goto('WHILE'+label_num)
self._writer.write_label('ELSE'+label_num)
# symbol - '}'
assert self._tokenizer.symbol() == '}'
self._tokenizer.advance()
def compile_do(self):
# 'do' subroutineCall ';'
assert self._tokenizer.keyword() == 'do'
# keyword - 'do'
self._tokenizer.advance()
# identifier - subroutineCall
assert self._tokenizer.identifier()
# outer subroutine must be void function
self.compile_subroutine_call()
# symbol - ';'
assert self._tokenizer.symbol() == ';'
# discard void function default return value
self._writer.write_pop('temp',0)
self._tokenizer.advance()
def compile_return(self):
# 'return' expression? ';'
# keyword - 'return'
assert self._tokenizer.keyword() == 'return'
self._writer.write_comment('return statement')
self._tokenizer.advance()
# expression?
if self._tokenizer.symbol() == ';':
# symbol - ';' (void function)
self._writer.write_push('constant', 0)
self._tokenizer.advance()
else:
# expression (not void)
self.compile_expression()
# symbol - ';'
assert self._tokenizer.symbol() == ';'
self._tokenizer.advance()
self._writer.write_return()
def compile_expression(self):
# term (op term)*
# term
self.compile_term()
# check for op
while self._tokenizer.is_valid_operator():
# op
temp_op = self._tokenizer.symbol()
self._tokenizer.advance()
# term
self.compile_term()
# write operator vm command, postfix order
self._writer.write_operator(temp_op)
def compile_term(self):
# integerConstant | stringConstant | keywordConstant | varName |
# varName '[' expression']' | subroutineCall | '(' expression ')' | unaryOp term
if self._tokenizer.int_value() is not None:
# integerConstant
self._writer.write_push('constant', self._tokenizer.int_value())
self._tokenizer.advance()
elif self._tokenizer.string_value() is not None:
# stringConstant
self._writer.write_string_constant(self._tokenizer.string_value())
self._tokenizer.advance()
elif self._tokenizer.keyword() is not None:
# keywordConstant
self._writer.write_keyword_constant(self._tokenizer.keyword())
self._tokenizer.advance()
elif self._tokenizer.symbol() == '(':
# '(' expression ')'
self._tokenizer.advance()
self.compile_expression()
assert self._tokenizer.symbol() == ')'
self._tokenizer.advance()
elif self._tokenizer.is_valid_unary():
# unaryOp term
temp_op = self._tokenizer.symbol()
self._tokenizer.advance()
# term
self.compile_term()
# write operator vm command, postfix order
self._writer.write_unary(temp_op)
elif self._tokenizer.identifier() and self._tokenizer.peek() == '[':
# varName '[' expression']'
# process array name, push associated value onto stack
self._writer.write_push(self._symbols.kind_of(self._tokenizer.identifier()),
self._symbols.index_of(self._tokenizer.identifier()))
self._tokenizer.advance()
# process [ symbol
self._tokenizer.advance()
# expects expression, value is pushed onto the stack
self.compile_expression()
# setup pointer to array element
self._writer.write_operator('+')
self._writer.write_pop('pointer', 1)
# push array value onto stack
self._writer.write_push('that', 0)
# expects closing square bracket
assert self._tokenizer.symbol() == ']'
self._tokenizer.advance()
elif self._tokenizer.identifier() and self._tokenizer.peek() in ['(','.']:
# subroutineCall
self.compile_subroutine_call()
elif self._symbols.exists(self._tokenizer.identifier()):
# varName
var_name = self._tokenizer.identifier()
var_kind = self._symbols.kind_of(var_name)
var_index = self._symbols.index_of(var_name)
if var_kind == 'field':
# push field var onto stack
self._writer.write_push('this', var_index)
else:
self._writer.write_push(var_kind, var_index)
self._tokenizer.advance()
else:
assert False, "unknown token: " + self.get_token() + " with type " + self.get_type()
def compile_subroutine_call(self):
# subroutineName '(' expressionList ')'| (className | varName) '.' subroutineName '(' expressionList ')'
assert self._tokenizer.identifier() and self._tokenizer.peek() in ['(','.']
if self._tokenizer.identifier() and self._tokenizer.peek() == '(':
# subroutineName '(' expressionList ')'
# method (in current class)
temp_name = self._class + '.' + self._tokenizer.identifier()
self._tokenizer.advance()
# symbol - '('
self._tokenizer.advance()
# push this onto the stack
self._writer.write_push('pointer',0)
temp_nargs = 1
# expressionList
temp_nargs += self.compile_expression_list()
self._writer.write_call(temp_name, temp_nargs)
# symbol - ')'
assert self._tokenizer.symbol() == ')'
self._tokenizer.advance()
elif self._symbols.exists(self._tokenizer.identifier()) and self._tokenizer.peek() == '.':
# varName '.' subroutineName '(' expressionList ')'
# varName (object)
temp_name = self._tokenizer.identifier()
# push object address onto stack, this is an implicit argument
if self._symbols.kind_of(temp_name) == 'field':
self._writer.write_push('this',
self._symbols.index_of(temp_name))
else:
self._writer.write_push(self._symbols.kind_of(temp_name),
self._symbols.index_of(temp_name))
# change name to class name
temp_name = self._symbols.type_of(temp_name)
temp_nargs = 1
self._tokenizer.advance()
# symbol - '.'
temp_name += self._tokenizer.get_token()
self._tokenizer.advance()
# subroutineName
assert self._tokenizer.identifier()
temp_name += self._tokenizer.identifier()
self._tokenizer.advance()
# symbol - '('
assert self._tokenizer.symbol() == '('
self._tokenizer.advance()
# expressionList
temp_nargs += self.compile_expression_list()
self._writer.write_call(temp_name, temp_nargs)
# symbol - '('
assert self._tokenizer.symbol() == ')'
self._tokenizer.advance()
elif self._tokenizer.identifier() and self._tokenizer.peek() == '.':
# className . subroutineName '(' expressionList ')'
# className
temp_name = self._tokenizer.identifier()
self._tokenizer.advance()
# symbol - '.'
temp_name += self._tokenizer.get_token()
self._tokenizer.advance()
# subroutineName
assert self._tokenizer.identifier(), print(self._tokenizer._tokens)
temp_name += self._tokenizer.identifier()
self._tokenizer.advance()
# symbol - '('
assert self._tokenizer.symbol() == '('
self._tokenizer.advance()
# expressionList
temp_nargs = self.compile_expression_list()
self._writer.write_call(temp_name, temp_nargs)
# symbol - ')'
assert self._tokenizer.symbol() == ')'
self._tokenizer.advance()
def compile_expression_list(self):
# (expression ( ',' expression)* )?
temp_nargs = 0
while self._tokenizer.symbol() != ')':
self.compile_expression()
temp_nargs += 1
if self._tokenizer.symbol() == ',':
# there is another expression in the list
self._tokenizer.advance()
return temp_nargs
