class Engine(object):
def __init__(self, tokens, filepath):
# compilation engine init
self.lex = tokens
self.symbols = SymbolTable()
self.vm = VMWriter(filepath)
self.compile_class()
self.vm.closeout()
# Routines to advance the token
def _require(self, tok, val=None):
lextok, lexval = self._advance()
if tok != lextok or tok in (T_KEYWORD, T_SYM) and val != lexval:
raise Exception(self._require_failed_msg(tok, val))
else:
return lexval
def _require_failed_msg(self, tok, val):
if val is None:
val = token_list[tok]
return 'Expected: {0}, {1} \ntoken is: {2}'.format(tok, val, self.lex.tokens)
def _advance(self):
return self.lex.advance()
def vm_function_name(self):
return self._cur_class + '.' + self._cur_subroutine
def vm_push_variable(self, name):
(type, kind, index) = self.symbols.lookup(name)
self.vm.write_push(segments[kind], index)
def vm_pop_variable(self, name):
(type, kind, index) = self.symbols.lookup(name)
self.vm.write_pop(segments[kind], index)
def load_this_ptr(self, kwd):
if kwd == KW_METHOD:
self.vm.push_arg(0)
self.vm.pop_this_ptr() # set up 'this' pointer to point to new object
elif kwd == KW_CONSTRUCTOR:
self.vm.push_const(self.symbols.var_count(SK_FIELD)) # object size
self.vm.write_call('Memory.alloc', 1)
self.vm.pop_this_ptr() # set up 'this' pointer to point to new object
def write_func_decl(self, kwd):
self.vm.write_function(self.vm_function_name(), self.symbols.var_count(SK_VAR))
self.load_this_ptr(kwd)
def write_string_const_init(self, val):
self.vm.push_const(len(val))
self.vm.write_call('String.new', 1) # String.new(len(str))
for c in val:
self.vm.push_const(ord(c))
self.vm.write_call('String.appendChar', 2) # String.appendChar(nextchar)
label_num = 0
def new_label(self):
self.label_num += 1
return 'label' + str(self.label_num)
# ------------- verify part ----------------
def _is_token(self, tok, val=None):
lextok, lexval = self.lex.peek()
return val == None and lextok == tok or (lextok, lexval) == (tok, val)
def _is_keyword(self, *keywords):
lextok, lexval = self.lex.peek()
return lextok == T_KEYWORD and lexval in keywords
def _is_sym(self, symbols):
lextok, lexval = self.lex.peek()
return lextok == T_SYM and lexval in symbols
# Variable declarations
def _is_class_var_dec(self):
return self._is_keyword(KW_STATIC, KW_FIELD)
def _is_type(self):
return self._is_token(T_ID) or self._is_keyword(KW_INT, KW_CHAR, KW_BOOLEAN)
# Subroutine declarations
def _is_subroutine(self):
return self._is_keyword(KW_CONSTRUCTOR, KW_FUNCTION, KW_METHOD)
def _is_var_dec(self):
return self._is_keyword(KW_VAR)
def _is_let(self):
return self._is_keyword(KW_LET)
def _is_if(self):
return self._is_keyword(KW_IF)
def _is_while(self):
return self._is_keyword(KW_WHILE)
def _is_do(self):
return self._is_keyword(KW_DO)
def _is_return(self):
return self._is_keyword(KW_RETURN)
def _is_statement(self):
return self._is_let() or self._is_if() or self._is_while() or self._is_do() or self._is_return()
def _is_const(self):
return self._is_token(T_NUM) or self._is_token(T_STR) or self._is_keyword_constant()
def _is_keyword_constant(self):
return self._is_keyword(KW_TRUE, KW_FALSE, KW_NULL, KW_THIS)
def _is_op(self):
return self._is_sym('+-*/&|<>=')
def _is_unary_op(self):
return self._is_sym('-~')
def _is_var_name(self):
return self._is_token(T_ID)
def _is_builtin_type(self, type):
return type in [KW_INT, KW_CHAR, KW_BOOLEAN, KW_VOID]
def _is_term(self):
return self._is_const() or self._is_var_name() or self._is_sym('(') or self._is_unary_op()
# --------------- compile part -----------------
# Parser and compile Jack code
# class: 'class' className '{' classVarDec* subroutineDec* '}'
def compile_class(self):
self._require(T_KEYWORD, KW_CLASS)
self.compile_class_name()
self._require(T_SYM, '{')
while self._is_class_var_dec():
self.compile_class_var_dec()
while self._is_subroutine():
self.compile_subroutine()
self._require(T_SYM, '}')
# className: identifier
def compile_class_name(self):
self._cur_class = self.compile_var_name() # Class names don't have to go into the symbol table
# type varName (',' varName)* ';'
def _compile_dec(self, kind):
type = self.compile_type()
name = self.compile_var_name()
self.symbols.define(name, type, kind)
while self._is_sym(','):
self._advance()
name = self.compile_var_name()
self.symbols.define(name, type, kind)
self._require(T_SYM, ';')
def compile_type(self):
"""
type: 'int' | 'char' | 'boolean' | className
"""
if self._is_type():
return self._advance()[1]
else:
raise ValueError(self._require_failed_msg(*self.lex.peek()))
# classVarDec: {'static'|'field'} type varName (',' varName)* ';'
def compile_class_var_dec(self):
tok, kwd = self._advance() # static | field
self._compile_dec(kwd_to_kind[kwd])
# varName: identifier
def compile_var_name(self):
return self._require(T_ID)
# subroutineDec: ('constructor'|'function'|'method') ('void'|type)
# subroutineName '(' parameterList ')' subroutineBody
def compile_subroutine(self):
tok, kwd = self._advance()
type = self.compile_void_or_type()
self.compile_subroutine_name()
self.symbols.start_subroutine()
if kwd == KW_METHOD:
self.symbols.define('this', self._cur_class, SK_ARG)
self._require(T_SYM, '(')
self.compile_parameter_list()
self._require(T_SYM, ')')
self.compile_subroutine_body(kwd)
# 'void' | type
def compile_void_or_type(self):
if self._is_keyword(KW_VOID):
return self._advance()[1]
else:
return self.compile_type()
# subroutineName: identifier
def compile_subroutine_name(self):
self._cur_subroutine = self.compile_var_name() # subroutine names don't have to go in the symbol table
# parameterList: (parameter (',' parameter)*)?
def compile_parameter_list(self):
if self._is_type():
self.compile_parameter()
while self._is_sym(','):
self._advance()
self.compile_parameter()
# parameter: type varName
def compile_parameter(self):
if self._is_type():
type = self.compile_type()
name = self.compile_var_name()
self.symbols.define(name, type, SK_ARG)
# subroutineBody: '{' varDec* statements '}'
def compile_subroutine_body(self, kwd):
self._require(T_SYM, '{')
while self._is_var_dec():
self.compile_var_dec()
self.write_func_decl(kwd)
self.compile_statements()
# varDec: 'var' type varName (',' varName)* ';'
def compile_var_dec(self):
self._require(T_KEYWORD, KW_VAR)
return self._compile_dec(SK_VAR)
# statement: statement*
def compile_statements(self):
while self._is_statement():
self._compile_statement()
# statement: letStatement | ifStatement | whileStatement | doStatement | returnStatement
def _compile_statement(self):
if self._is_let():
self.compile_let()
elif self._is_if():
self.compile_if()
elif self._is_while():
self.compile_while()
elif self._is_do():
self.compile_do()
elif self._is_return():
self.compile_return()
# letStatement: 'let' varName ('[' expression ']')? '=' expression ';'
def compile_let(self):
self._require(T_KEYWORD, KW_LET)
name = self.compile_var_name()
subscript = self._is_sym('[')
if subscript:
self.compile_base_plus_index(name) # calculate base+index
self._require(T_SYM, '=')
self.compile_expression() # calculate expression to assign
self._require(T_SYM, ';')
if subscript:
self.pop_array_element() # *(base+index) = expr
else:
self.vm_pop_variable(name) # pop value directly into variable
def pop_array_element(self):
self.vm.pop_temp(TEMP_ARRAY) # Pop expr value to temp register
self.vm.pop_that_ptr() # Pop base+index into 'that' register
self.vm.push_temp(TEMP_ARRAY) # Push expr back onto stack
self.vm.pop_that() # Pop value into *(base+index)
# ('[' expression ']')?
def compile_base_plus_index(self, name):
self.vm_push_variable(name) # push array ptr onto stack
self._advance()
self.compile_expression() # push index onto stack
self._require(T_SYM, ']')
self.vm.write_vm_cmd('add') # base+index - leave on the stack for later
def compile_expression(self):
self.compile_term()
# Doesn't handle normal order of operations - just left to right for now
while self._is_op():
op = self._advance()
self.compile_term()
self.vm.write_vm_cmd(vm_cmds[op[1]]) # op
# term: integerConstant | stringConstant | keywordConstant | varName
# | varName '[' expression ']' | subroutineCall | '(' expression ')'
# | unaryOp term
def compile_term(self):
if self._is_const():
self.compile_const()
elif self._is_sym('('):
self._advance()
self.compile_expression() # VM code to evaluate expression
self._require(T_SYM, ')')
elif self._is_unary_op():
tok, op = self._advance()
self.compile_term()
self.vm.write_vm_cmd(vm_unary_cmds[op]) # op
elif self._is_var_name():
tok, name = self._advance()
if self._is_sym('['):
self.compile_array_subscript(name) # VM code for array subscript
elif self._is_sym('(.'):
self.compile_subroutine_call(name) # VM code for subroutine call
else:
self.vm_push_variable(name) # push variable on stack
# integerConstant | stringConstant | keywordConstant
def compile_const(self):
tok, val = self._advance()
if tok == T_NUM:
self.vm.push_const(val) # push constant val
elif tok == T_STR:
self.write_string_const_init(val) # initialize string & push str addr
elif tok == T_KEYWORD:
self.compile_kwd_const(val) # push TRUE, FALSE, NULL etc.
# '[' expression ']'
def compile_array_subscript(self, name):
self.vm_push_variable(name) # push array ptr onto stack
self._require(T_SYM, '[')
self.compile_expression() # push index onto stack
self._require(T_SYM, ']')
self.vm.write_vm_cmd('add') # base+index
self.vm.pop_that_ptr() # pop into 'that' ptr
self.vm.push_that() # push *(base+index) onto stack
# subroutineCall: subroutineName '(' expressionList ')'
# | (className | varName) '.' subroutineName '(' expressionList ')'
def compile_subroutine_call(self, name):
(type, kind, index) = self.symbols.lookup(name)
if self._is_sym('.'):
num_args, name = self.compile_dotted_subroutine_call(name, type)
else:
num_args = 1
self.vm.push_this_ptr()
name = self._cur_class+'.'+name
self._require(T_SYM, '(')
num_args += self.compile_expr_list() # VM code to push arguments
self._require(T_SYM, ')')
self.vm.write_call(name, num_args) # call name num_args
# keywordConstant: 'true' | 'false' | 'null' | 'this'
def compile_kwd_const(self, kwd):
if kwd == KW_THIS:
self.vm.push_this_ptr()
elif kwd == KW_TRUE:
self.vm.push_const(1)
self.vm.write_vm_cmd('neg')
else: # KW_FALSE or KW_NULL
self.vm.push_const(0)
def compile_dotted_subroutine_call(self, name, type):
num_args = 0
obj_name = name
self._advance()
name = self.compile_var_name()
if self._is_builtin_type(type): # e.g. int.func(123) not allowed
ValueError('Cannot use "." operator on builtin type')
elif type == None: # Calling using class name
name = obj_name+'.'+name
else: # Calling using object variable name
num_args = 1
self.vm_push_variable(obj_name) # push object ptr onto stack
name = self.symbols.type_of(obj_name)+'.'+name
return num_args, name
# expressionList: (expression (',' expression)*)?
def compile_expr_list(self):
num_args = 0
if self._is_term():
self.compile_expression()
num_args = 1
while self._is_sym(','):
self._advance()
self.compile_expression()
num_args += 1
return num_args
# ifStatement: 'if' '(' expression ')' '{' statements '}'
# ('else' '{' statements '}')?
def compile_if(self):
self._require(T_KEYWORD, KW_IF)
end_label = self.new_label()
self._compile_cond_expression_statements(end_label) # VM code for condition and if statements
if self._is_keyword(KW_ELSE):
self._advance()
self._require(T_SYM, '{')
self.compile_statements() # VM code for else statements
self._require(T_SYM, "}")
self.vm.write_label(end_label) # label end_label
# '(' expression ')' '{' statements '}'
def _compile_cond_expression_statements(self, label):
self._require(T_SYM, '(')
self.compile_expression()
self._require(T_SYM, ')')
self.vm.write_vm_cmd('not') # ~(cond)
notif_label = self.new_label()
self.vm.write_if(notif_label) # if-goto notif_label
self._require(T_SYM, '{')
self.compile_statements() # VM code for if statements
self._require(T_SYM, '}')
self.vm.write_goto(label) # goto label
self.vm.write_label(notif_label)# label notif_label
# whileStatement: 'while' '(' expression ')' '{' statements '}'
def compile_while(self):
self._require(T_KEYWORD, KW_WHILE)
top_label = self.new_label()
self.vm.write_label(top_label) # label top_label
self._compile_cond_expression_statements(top_label) # VM code for condition and while statements
# do_statement: 'do' subroutineCall ';'
def compile_do(self):
self._require(T_KEYWORD, KW_DO)
name = self._require(T_ID)
self.compile_subroutine_call(name) # VM code for subroutine call
self.vm.pop_temp(TEMP_RETURN) # Pop return value and discard
self._require(T_SYM, ';')
# returnStatement: 'return' expression? ';'
def compile_return(self):
self._require(T_KEYWORD, KW_RETURN)
if not self._is_sym(';'):
self.compile_expression() # VM code for return expression if any
else:
self.vm.push_const(0) # push 0 if not returning a value
self._require(T_SYM, ';')
self.vm.write_return() # return
