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Copy pathinterpreter.py
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757 lines (696 loc) · 29.1 KB
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"""
PC-BASIC - interpreter.py
BASIC interpreter
(c) 2013--2023 Rob Hagemans
This file is released under the GNU GPL version 3 or later.
"""
import struct
from .base import error
from .base import tokens as tk
from .base.tokens import DIGITS
from .base import codestream
from . import values
class Interpreter(object):
"""BASIC interpreter."""
def __init__(
self, queues, console, cursor, files, sound,
values, memory, program, parser, basic_events
):
"""Initialise interpreter."""
self._queues = queues
self._basic_events = basic_events
self._values = values
self._memory = memory
self._scalars = memory.scalars
self._console = console
self._cursor = cursor
self._files = files
self._sound = sound
# program buffer
self._program = program
self._program_code = program.bytecode
# direct line buffer
self.direct_line = codestream.TokenisedStream()
self.current_statement = 0
# statement syntax parser
self.parser = parser
# line number tracing
self.tron = False
# pointer position: False for direct line, True for program
self.run_mode = False
# clear stacks
self.clear_stacks_and_pointers()
self._init_error_trapping()
self.error_num = 0
self.error_pos = 0
self.set_pointer(False, 0)
# interpreter is waiting for INPUT or LINE INPUT
self.input_mode = False
# interpreter is executing a command (needs console)
self.set_parse_mode(False)
# additional operations on program step (debugging)
self.step = lambda token: None
def __getstate__(self):
"""Pickle."""
pickle_dict = self.__dict__.copy()
# functions can't be pickled
pickle_dict['step'] = None
return pickle_dict
def __setstate__(self, pickle_dict):
"""Unpickle."""
self.__dict__.update(pickle_dict)
self.step = lambda token: None
# go to start of statement on resume
ins = self.get_codestream()
ins.seek(self.current_statement)
if not self.parser.redo_on_break:
# parse line number or : at start of statement
if ins.read(1) in tk.END_LINE:
# line number marker, new statement
token = ins.read(4)
ins.skip_to(tk.END_STATEMENT)
def _init_error_trapping(self):
"""Initialise error trapping."""
# True if error handling in progress
self.error_handle_mode = False
# statement pointer, run mode of error for RESUME
self.error_resume = None
# pointer to error trap
self.on_error = None
def parse(self):
"""Parse from the current pointer in current codestream."""
while True:
# update what basic events need to be handled
self._queues.set_basic_event_handlers(self._basic_events.enabled)
# check input and BASIC events. may raise Break, Reset or Exit
self._queues.check_events()
try:
self.handle_basic_events()
ins = self.get_codestream()
self.current_statement = ins.tell()
c = ins.skip_blank_read()
# parse line number or : at start of statement
if c in tk.END_LINE:
# line number marker, new statement
token = ins.read(4)
# end of program or truncated file
if token[:2] == b'\0\0' or len(token) < 4:
if c == b'\0' and self.error_resume:
# unfinished error handler: no RESUME (don't trap this)
self.error_handle_mode = True
# get line number right
raise error.BASICError(error.NO_RESUME, ins.tell()-len(token)-2)
# stream has ended
self.set_pointer(False)
return
if self.tron:
linenum = struct.unpack_from('<H', token, 2)
self._console.write(b'[%i]' % linenum)
self.step(token)
elif c not in (b':', tk.THEN, tk.ELSE, tk.GOTO):
# new statement or branch of an IF statement allowed, nothing else
raise error.BASICError(error.STX)
self.parser.parse_statement(ins)
except error.BASICError as e:
self.trap_error(e)
def loop(self):
"""Run commands until control returns to user."""
if not self.parse_mode:
return
try:
# parse until break or end
self.parse()
except error.Break as e:
self._sound.stop_all_sound()
self._handle_break(e)
# move pointer to the start of direct line (for both on and off!)
self.set_pointer(False, 0)
# return control to user
self.set_parse_mode(False)
def set_parse_mode(self, on):
"""Enter or exit parse mode."""
self.parse_mode = on
self._cursor.set_direct(not on)
def _handle_break(self, e):
"""Handle a Break event."""
# print ^C at current position
if not self.input_mode and not e.stop:
self._console.write(b'^C')
# if we're in a program, save pointer
pos = -1
if self.run_mode:
pos = self.current_statement
if self.parser.redo_on_break:
self.stop_pos = pos
else:
self._program.bytecode.skip_to(tk.END_STATEMENT)
self.stop_pos = self._program.bytecode.tell()
self.parser.redo_on_break = False
if self.error_handle_mode:
e.trapped_error_num = self.error_num
# when the error is trapped, error position shifts to start of line
line = self._program.get_line_number(self.error_pos)
if 0 <= line <= 65535:
e.trapped_error_pos = self._program.line_numbers[line]
else:
e.trapped_error_pos = self.error_pos
#self.error_handle_mode = False
# ensure we can handle the break like an error
e.err = 0
e.pos = pos
raise e
###########################################################################
# clear state
def clear(self):
"""Clear all to be cleared for CLEAR statement."""
# clear last error number (ERR) and line number (ERL)
self.error_num, self.error_pos = 0, 0
# disable error trapping
self._init_error_trapping()
# disable all event trapping (resets PEN to OFF too)
self._basic_events.reset()
# CLEAR also dumps for_next and while_wend stacks
self.for_stack = []
self.while_stack = []
# reset stop/cont
self.stop_pos = None
# reset the DATA pointer
self.data_pos = 0
def clear_stacks_and_pointers(self):
"""Initialise the stacks and pointers for a new program."""
# reset loop stacks
self._clear_stacks()
# reset program pointer
self._program_code.seek(0)
# reset stop/cont
self.stop_pos = None
# reset data reader
self.data_pos = 0
def _clear_stacks(self):
"""Clear loop and jump stacks."""
# stop running if we were
self.set_pointer(False)
self.gosub_stack = []
self.for_stack = []
self.while_stack = []
###########################################################################
# event and error handling
def handle_basic_events(self):
"""Jump to user-defined event subs if events triggered."""
if self._basic_events.suspend_all or not self.run_mode:
return
for event in self._basic_events.enabled:
if (event.triggered and not event.stopped and event.gosub is not None):
# release trigger
event.triggered = False
# stop this event while handling it
event.stopped = True
# execute 'ON ... GOSUB' subroutine;
# attach handler to allow un-stopping event on RETURN
self.jump_sub(event.gosub, event)
def trap_error(self, e):
"""Handle a BASIC error through trapping."""
if e.pos is None:
if self.run_mode:
e.pos = self._program_code.tell()-1
else:
e.pos = -1
self.error_num = e.err
self.error_pos = e.pos
# don't jump if we're already busy handling an error
if self.on_error is not None and self.on_error != 0 and not self.error_handle_mode:
self.error_resume = self.current_statement, self.run_mode
self.jump(self.on_error)
self.error_handle_mode = True
self._basic_events.suspend_all = True
else:
self.error_handle_mode = False
self.set_pointer(False)
raise e
def erl_(self, args):
"""ERL: get line number of last error."""
list(args)
if self.error_pos == 0:
pos = 0
elif self.error_pos == -1:
pos = 65535
else:
pos = self._program.get_line_number(self.error_pos)
return self._values.new_single().from_int(pos)
def err_(self, args):
"""ERR: get error code of last error."""
list(args)
return self._values.new_integer().from_int(self.error_num)
###########################################################################
# jumps
def set_pointer(self, new_runmode, pos=None):
"""Set program pointer to the given codestream and position."""
# flush lpt1 on entering interactive mode
if self.run_mode and not new_runmode:
self._files.lpt1_file.do_print()
self.run_mode = new_runmode
# events are active in run mode
if new_runmode:
self._queues.set_basic_event_handlers(self._basic_events.enabled)
else:
self._queues.set_basic_event_handlers([])
# keep the sound engine on to avoid delays in run mode
self._sound.persist(new_runmode)
# suppress cassette messages in run mode
self._files.get_device(b'CAS1:').quiet(new_runmode)
codestream = self.get_codestream()
if pos is not None:
# jump to position, if given
codestream.seek(pos)
else:
# position at end - don't execute anything unless we jump
codestream.seek(0, 2)
def get_codestream(self):
"""Get the current codestream."""
return self._program_code if self.run_mode else self.direct_line
def jump(self, jumpnum, err=error.UNDEFINED_LINE_NUMBER):
"""Execute jump for a GOTO or RUN instruction."""
if jumpnum is None:
self.set_pointer(True, 0)
else:
try:
# jump to target
self.set_pointer(True, self._program.line_numbers[jumpnum])
except KeyError:
raise error.BASICError(err)
def jump_sub(self, jumpnum, handler=None):
"""Execute jump for a GOSUB."""
# set return position
pos = self.get_codestream().tell()
# record run mode before executing self.jump, as that sets the runmode to True
run_mode = self.run_mode
self.jump(jumpnum)
self.gosub_stack.append((pos, run_mode, handler))
def goto_(self, args):
"""GOTO: jump to line number."""
self.jump(*args)
def gosub_(self, args):
"""GOSUB: jump to subroutine."""
self.jump_sub(*args)
def return_(self, args):
"""Execute jump for a RETURN."""
jumpnum, = args
try:
pos, orig_runmode, handler = self.gosub_stack.pop()
except IndexError:
raise error.BASICError(error.RETURN_WITHOUT_GOSUB)
# returning from ON (event) GOSUB, re-enable event
if handler:
# if stopped explicitly using STOP, we wouldn't have got here;
# if STOP is run inside the trap, no effect. OFF in trap: event off.
handler.stopped = False
if jumpnum is None:
# go back to position of GOSUB
self.set_pointer(orig_runmode, pos)
# ignore rest of statement ('GOSUB 100 LAH' works just fine..)
# but NOT if we jumped for an event, as we might have jumped from anywhere!
if not handler:
self.get_codestream().skip_to(tk.END_STATEMENT)
else:
# jump to specified line number
self.jump(jumpnum)
###########################################################################
# branches
def if_(self, args):
"""IF: branching statement."""
# get condition
# avoid overflow: don't use bools.
then_branch = not values.to_single(next(args)).is_zero()
# cofunction only parses the branch we need
# cofunction checks for line number
branch = args.send(then_branch)
# and completes
list(args)
# we may have a line number immediately after THEN or ELSE
if branch is not None:
self.jump(branch)
# note that any :ELSE block encountered will be ignored automatically
# since standalone ELSE is a no-op to end of line
def on_jump_(self, args):
"""ON GOTO/GOSUB: calculated jump."""
onvar = values.to_int(next(args))
error.range_check(0, 255, onvar)
jump_type = next(args)
# only parse jumps (and errors!) up to our choice
i = -1
for i, jumpnum in enumerate(args):
if i == onvar-1:
# we counted the right number of commas, then didn't find a line number
if jumpnum is None:
raise error.BASICError(error.STX)
if jump_type == tk.GOTO:
self.jump(jumpnum)
elif jump_type == tk.GOSUB:
self.jump_sub(jumpnum)
return
###########################################################################
# loops
def for_(self, args):
"""Initialise a FOR loop."""
# read variable
varname = self._memory.complete_name(next(args))
vartype = varname[-1:]
start = values.to_type(vartype, next(args)).clone()
# only raised after the TO has been parsed
if vartype in (values.STR, values.DBL):
raise error.BASICError(error.TYPE_MISMATCH)
stop = values.to_type(vartype, next(args)).clone()
step = next(args)
if step is not None:
step = values.to_type(vartype, step).clone()
list(args)
if step is None:
# convert 1 to vartype
step = self._values.from_value(1, varname[-1:])
ins = self.get_codestream()
# find NEXT
forpos, nextpos = self._find_next(ins, varname)
# initialise loop variable
self._scalars.set(varname, start)
# obtain a view of the loop variable
self.for_stack.append((varname, stop, step, step.sign(), forpos, nextpos,))
# empty loop: jump to NEXT without executing block
if (start.gt(stop) if step.sign() >= 0 else stop.gt(start)):
ins.seek(nextpos)
self.iterate_loop()
def _find_next(self, ins, varname):
"""Helper function for FOR: find matching NEXT."""
endforpos = ins.tell()
ins.skip_block(tk.FOR, tk.NEXT, allow_comma=True)
if ins.skip_blank() not in (tk.NEXT, b','):
# FOR without NEXT marked with FOR line number
ins.seek(endforpos)
raise error.BASICError(error.FOR_WITHOUT_NEXT)
comma = (ins.read(1) == b',')
# check var name for NEXT
# no-var only allowed in standalone NEXT
if ins.skip_blank() not in tk.END_STATEMENT:
varname2 = self._memory.complete_name(self.parser.parse_name(ins))
else:
varname2 = None
# get position and line number just after the matching variable in NEXT
nextpos = ins.tell()
if (comma or varname2) and varname2 != varname:
# NEXT without FOR marked with NEXT line number, while we're only at FOR
raise error.BASICError(error.NEXT_WITHOUT_FOR)
ins.seek(endforpos)
return endforpos, nextpos
def next_(self, args):
"""Iterate a loop (NEXT)."""
for varname in args:
# increment counter, check condition
if self.iterate_loop(varname):
break
def iterate_loop(self, varname=None):
"""Iterate a loop (NEXT)."""
ins = self.get_codestream()
# record the location after the variable
pos = ins.tell()
# find the matching NEXT record
num = len(self.for_stack)
for depth in range(num):
varname2, stop, step, sgn, forpos, nextpos = self.for_stack[-depth-1]
if pos == nextpos:
if varname is not None and varname2 != self._memory.complete_name(varname):
# check once more for matches
# it has been checked at FOR, but DEFtypes may have changed.
raise error.BASICError(error.NEXT_WITHOUT_FOR)
# only drop NEXT record if we've found a matching one
self.for_stack = self.for_stack[:len(self.for_stack)-depth]
break
else:
raise error.BASICError(error.NEXT_WITHOUT_FOR)
# increment counter
counter_view = self._scalars.view(varname2)
counter_view.iadd(step)
# check condition
loop_ends = counter_view.gt(stop) if sgn > 0 else stop.gt(counter_view)
if loop_ends:
self.for_stack.pop()
else:
ins.seek(forpos)
return not loop_ends
def while_(self, args):
"""WHILE: enter while-loop."""
list(args)
ins = self.get_codestream()
# find matching WEND
whilepos, wendpos = self._find_wend(ins)
self.while_stack.append((whilepos, wendpos))
self._check_while_condition(ins, whilepos)
def _find_wend(self, ins):
"""Helper function for WHILE: find matching WEND."""
# just after WHILE token
whilepos = ins.tell()
ins.skip_block(tk.WHILE, tk.WEND)
if ins.read(1) != tk.WEND:
# WHILE without WEND
ins.seek(whilepos)
raise error.BASICError(error.WHILE_WITHOUT_WEND)
ins.skip_to(tk.END_STATEMENT)
wendpos = ins.tell()
ins.seek(whilepos)
return whilepos, wendpos
def _check_while_condition(self, ins, whilepos):
"""Check condition of while-loop."""
ins.seek(whilepos)
# WHILE condition is zero?
if not values.pass_number(self.parser.parse_expression(ins)).is_zero():
# statement start is before WHILE token
self.current_statement = whilepos-2
ins.require_end()
else:
# ignore rest of line and jump to WEND
_, wendpos = self.while_stack.pop()
ins.seek(wendpos)
def wend_(self, args):
"""WEND: iterate while-loop."""
list(args)
ins = self.get_codestream()
pos = ins.tell()
while True:
if not self.while_stack:
# WEND without WHILE
raise error.BASICError(error.WEND_WITHOUT_WHILE)
whilepos, wendpos = self.while_stack[-1]
if pos == wendpos:
break
# not the expected WEND, we must have jumped out
self.while_stack.pop()
self._check_while_condition(ins, whilepos)
###########################################################################
# DATA utilities
def restore_(self, args):
"""Reset data pointer (RESTORE) """
datanum = next(args)
if datanum is None:
self.data_pos = 0
else:
try:
self.data_pos = self._program.line_numbers[datanum]
except KeyError:
raise error.BASICError(error.UNDEFINED_LINE_NUMBER)
list(args)
def read_(self, args):
"""READ: read values from DATA statement."""
data_error = False
for name, indices in args:
name = self._memory.complete_name(name)
current = self._program_code.tell()
self._program_code.seek(self.data_pos)
if self._program_code.peek() in tk.END_STATEMENT:
# initialise - find first DATA
self._program_code.skip_to_token(tk.DATA,)
if self._program_code.read(1) not in (tk.DATA, b','):
self._program_code.seek(current)
raise error.BASICError(error.OUT_OF_DATA)
self._program_code.skip_blank()
if name[-1:] == values.STR:
# for unquoted strings, payload starts at the first non-empty character
address = self._program_code.tell_address()
word = self._program_code.read_to((b',', b'"',) + tk.END_STATEMENT)
if self._program_code.peek() == b'"':
if word == b'':
# nothing before the quotes, so this is a quoted string literal
# string payload starts after quote
address = self._program_code.tell_address() + 1
word = self._program_code.read_string().strip(b'"')
else:
# complete unquoted string literal
word += self._program_code.read_string()
if (self._program_code.skip_blank() not in (tk.END_STATEMENT + (b',',))):
raise error.BASICError(error.STX)
else:
word = word.strip(self._program_code.blanks)
value = self._values.from_str_at(word, address)
else:
word = self._program_code.read_number()
value = self._values.from_repr(word, allow_nonnum=False)
# anything after the number is a syntax error, but assignment has taken place)
if (self._program_code.skip_blank() not in (tk.END_STATEMENT + (b',',))):
data_error = True
# restore to current program location
# to ensure any other errors in set_variable get the correct line number
data_pos = self._program_code.tell()
self._program_code.seek(current)
self._memory.set_variable(name, indices, value=value)
if data_error:
self._program_code.seek(self.data_pos)
raise error.BASICError(error.STX)
else:
self.data_pos = data_pos
###########################################################################
# COMMON
def gather_commons(self):
"""Get all COMMON declarations."""
common_scalars = set()
common_arrays = set()
current = self._program_code.tell()
self._program_code.seek(0)
while self._program_code.skip_to_token(tk.COMMON):
self._program_code.read(len(tk.COMMON))
self._add_common_vars(common_scalars, common_arrays)
self._program_code.seek(current)
return common_scalars, common_arrays
def _parse_common_args(self, ins):
"""Parse COMMON syntax."""
if ins.skip_blank() in tk.END_STATEMENT:
return
while True:
name = self.parser.parse_name(ins)
bracket = ins.skip_blank_read_if((b'(', b'['))
if bracket:
# a literal is allowed but ignored;
# for sqare brackets, it's a syntax error if omitted
if (bracket == b'[') or ins.peek() in set(DIGITS) | set(tk.NUMBER):
x = self.parser.expression_parser.read_number_literal(ins)
ins.require_read((b')', b']'))
# entries with square brackets are completely ignored!
if bracket != b'[':
yield name, bracket
if not ins.skip_blank_read_if((b',',)):
break
ins.require_end()
def _add_common_vars(self, common_scalars, common_arrays):
"""COMMON: define variables to be preserved on CHAIN."""
common_vars = list(self._parse_common_args(self._program_code))
common_scalars.update(
self._memory.complete_name(name)
for name, brackets in common_vars if not brackets
)
common_arrays.update(
self._memory.complete_name(name)
for name, brackets in common_vars if brackets
)
###########################################################################
# callbacks
def error_(self, args):
"""ERROR: simulate an error condition."""
errn, = args
errn = values.to_int(errn)
error.range_check(1, 255, errn)
raise error.BASICError(errn)
def stop_(self, args):
"""STOP: break program execution and return to interpreter."""
list(args)
raise error.Break(stop=True)
def cont_(self, args):
"""CONT: continue STOPped or ENDed execution."""
list(args)
if self.stop_pos is None:
raise error.BASICError(error.CANT_CONTINUE)
else:
self.set_pointer(True, self.stop_pos)
# IN GW-BASIC, weird things happen if you do GOSUB nn :PRINT "x"
# and there's a STOP in the subroutine.
# CONT then continues and the rest of the original line is executed, printing x
# However, CONT:PRINT triggers a bug
# - a syntax error in a nonexistant line number is reported.
# CONT:PRINT "y" results in neither x nor y being printed.
# if a command is executed before CONT, x is not printed.
# It would appear that GW-BASIC only partially overwrites the line buffer and
# then jumps back to the original return location!
# in this implementation, the CONT command will fully overwrite the line buffer
# so x is not printed.
def tron_(self, args):
"""TRON: trace on."""
list(args)
self.tron = True
def troff_(self, args):
"""TROFF: trace off."""
list(args)
self.tron = False
def on_error_goto_(self, args):
"""ON ERROR GOTO: define error trapping routine."""
linenum, = args
if linenum != 0 and linenum not in self._program.line_numbers:
raise error.BASICError(error.UNDEFINED_LINE_NUMBER)
self.on_error = linenum
# pause soft-handling math errors so that we can catch them
self._values.error_handler.suspend(linenum != 0)
# ON ERROR GOTO 0 in error handler
if self.on_error == 0 and self.error_handle_mode:
# re-raise the error so that execution stops
raise error.BASICError(self.error_num, self.error_pos)
def resume_(self, args):
"""RESUME: resume program flow after error-trap."""
if self.error_resume is None:
# unset error handler
self.on_error = 0
raise error.BASICError(error.RESUME_WITHOUT_ERROR)
# parse arguments
where, = args
start_statement, runmode = self.error_resume
self.error_num = 0
self.error_handle_mode = False
self.error_resume = None
self._basic_events.suspend_all = False
if not where:
# RESUME or RESUME 0
self.set_pointer(runmode, start_statement)
elif where == tk.NEXT:
# RESUME NEXT
self.set_pointer(runmode, start_statement)
self.get_codestream().skip_to(tk.END_STATEMENT, break_on_first_char=False)
else:
# RESUME n
self.jump(where)
def def_fn_(self, args):
"""DEF FN: define a function."""
fnname, = args
fnname = self._memory.complete_name(fnname)
# don't allow DEF FN in direct mode, as we point to the code in the stored program
# this is raised before further syntax errors
if not self.run_mode:
raise error.BASICError(error.ILLEGAL_DIRECT)
# arguments and expression are being read and parsed by UserFunctionManager
self.parser.user_functions.define(fnname, self._program_code)
def llist_(self, args):
"""LLIST: output program lines to LPT1: """
line_range, = args
for l in self._program.list_lines(*line_range):
self._files.lpt1_file.write_line(l)
# return to direct mode
self.set_pointer(False)
def renum_(self, args):
"""RENUM: renumber program line numbers."""
new, old, step = args
new, old = self._program.explicit_lines(new, old)
if step is not None and step < 1:
raise error.BASICError(error.IFC)
old_to_new = self._program.renum(self._console, new, old, step)
# stop running if we were
# reset loop stacks
self._clear_stacks()
# renumber error handler
if self.on_error:
self.on_error = old_to_new[self.on_error]
# renumber event traps
for handler in self._basic_events.all:
if handler.gosub:
handler.set_jump(old_to_new[handler.gosub])