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import argparse
import sys
import time
import token
import tokenize
import traceback
from abc import abstractmethod
from typing import Any, Callable, cast, Dict, Optional, Tuple, Type, TypeVar
from pegen.tokenizer import exact_token_types
from pegen.tokenizer import Mark
from pegen.tokenizer import Tokenizer
T = TypeVar("T")
P = TypeVar("P", bound="Parser")
F = TypeVar("F", bound=Callable[..., Any])
def logger(method: F) -> F:
"""For non-memoized functions that we want to be logged.
(In practice this is only non-leader left-recursive functions.)
"""
method_name = method.__name__
def logger_wrapper(self: P, *args: object) -> T:
if not self._verbose:
return method(self, *args)
argsr = ",".join(repr(arg) for arg in args)
fill = " " * self._level
print(f"{fill}{method_name}({argsr}) .... (looking at {self.showpeek()})")
self._level += 1
tree = method(self, *args)
self._level -= 1
print(f"{fill}... {method_name}({argsr}) --> {tree!s:.200}")
return tree
logger_wrapper.__wrapped__ = method # type: ignore
return cast(F, logger_wrapper)
def memoize(method: F) -> F:
"""Memoize a symbol method."""
method_name = method.__name__
def memoize_wrapper(self: P, *args: object) -> T:
mark = self.mark()
key = mark, method_name, args
# Fast path: cache hit, and not verbose.
if key in self._cache and not self._verbose:
tree, endmark = self._cache[key]
self.reset(endmark)
return tree
# Slow path: no cache hit, or verbose.
verbose = self._verbose
argsr = ",".join(repr(arg) for arg in args)
fill = " " * self._level
if key not in self._cache:
if verbose:
print(f"{fill}{method_name}({argsr}) ... (looking at {self.showpeek()})")
self._level += 1
tree = method(self, *args)
self._level -= 1
if verbose:
print(f"{fill}... {method_name}({argsr}) -> {tree!s:.200}")
endmark = self.mark()
self._cache[key] = tree, endmark
else:
tree, endmark = self._cache[key]
if verbose:
print(f"{fill}{method_name}({argsr}) -> {tree!s:.200}")
self.reset(endmark)
return tree
memoize_wrapper.__wrapped__ = method # type: ignore
return cast(F, memoize_wrapper)
def memoize_left_rec(method: Callable[[P], Optional[T]]) -> Callable[[P], Optional[T]]:
"""Memoize a left-recursive symbol method."""
method_name = method.__name__
def memoize_left_rec_wrapper(self: P) -> Optional[T]:
mark = self.mark()
key = mark, method_name, ()
# Fast path: cache hit, and not verbose.
if key in self._cache and not self._verbose:
tree, endmark = self._cache[key]
self.reset(endmark)
return tree
# Slow path: no cache hit, or verbose.
verbose = self._verbose
fill = " " * self._level
if key not in self._cache:
if verbose:
print(f"{fill}{method_name} ... (looking at {self.showpeek()})")
self._level += 1
# For left-recursive rules we manipulate the cache and
# loop until the rule shows no progress, then pick the
# previous result. For an explanation why this works, see
# https://github.com/PhilippeSigaud/Pegged/wiki/Left-Recursion
# (But we use the memoization cache instead of a static
# variable; perhaps this is similar to a paper by Warth et al.
# (http://web.cs.ucla.edu/~todd/research/pub.php?id=pepm08).
# Prime the cache with a failure.
self._cache[key] = None, mark
lastresult, lastmark = None, mark
depth = 0
if verbose:
print(f"{fill}Recursive {method_name} at {mark} depth {depth}")
while True:
self.reset(mark)
result = method(self)
endmark = self.mark()
depth += 1
if verbose:
print(
f"{fill}Recursive {method_name} at {mark} depth {depth}: {result!s:.200} to {endmark}"
)
if not result:
if verbose:
print(f"{fill}Fail with {lastresult!s:.200} to {lastmark}")
break
if endmark <= lastmark:
if verbose:
print(f"{fill}Bailing with {lastresult!s:.200} to {lastmark}")
break
self._cache[key] = lastresult, lastmark = result, endmark
self.reset(lastmark)
tree = lastresult
self._level -= 1
if verbose:
print(f"{fill}{method_name}() -> {tree!s:.200} [cached]")
if tree:
endmark = self.mark()
else:
endmark = mark
self.reset(endmark)
self._cache[key] = tree, endmark
else:
tree, endmark = self._cache[key]
if verbose:
print(f"{fill}{method_name}() -> {tree!s:.200} [fresh]")
if tree:
self.reset(endmark)
return tree
memoize_left_rec_wrapper.__wrapped__ = method # type: ignore
return memoize_left_rec_wrapper
class Parser:
"""Parsing base class."""
def __init__(self, tokenizer: Tokenizer, *, verbose: bool = False):
self._tokenizer = tokenizer
self._verbose = verbose
self._level = 0
self._cache: Dict[Tuple[Mark, str, Tuple[Any, ...]], Tuple[Any, Mark]] = {}
# Pass through common tokenizer methods.
# TODO: Rename to _mark and _reset.
self.mark = self._tokenizer.mark
self.reset = self._tokenizer.reset
@abstractmethod
def start(self) -> Any:
pass
def showpeek(self) -> str:
tok = self._tokenizer.peek()
return f"{tok.start[0]}.{tok.start[1]}: {token.tok_name[tok.type]}:{tok.string!r}"
@memoize
def name(self) -> Optional[tokenize.TokenInfo]:
tok = self._tokenizer.peek()
if tok.type == token.NAME:
return self._tokenizer.getnext()
return None
@memoize
def number(self) -> Optional[tokenize.TokenInfo]:
tok = self._tokenizer.peek()
if tok.type == token.NUMBER:
return self._tokenizer.getnext()
return None
@memoize
def string(self) -> Optional[tokenize.TokenInfo]:
tok = self._tokenizer.peek()
if tok.type == token.STRING:
return self._tokenizer.getnext()
return None
@memoize
def op(self) -> Optional[tokenize.TokenInfo]:
tok = self._tokenizer.peek()
if tok.type == token.OP:
return self._tokenizer.getnext()
return None
@memoize
def expect(self, type: str) -> Optional[tokenize.TokenInfo]:
tok = self._tokenizer.peek()
if tok.string == type:
return self._tokenizer.getnext()
if type in exact_token_types:
if tok.type == exact_token_types[type]:
return self._tokenizer.getnext()
if type in token.__dict__:
if tok.type == token.__dict__[type]:
return self._tokenizer.getnext()
if tok.type == token.OP and tok.string == type:
return self._tokenizer.getnext()
return None
def positive_lookahead(self, func: Callable[..., T], *args: object) -> T:
mark = self.mark()
ok = func(*args)
self.reset(mark)
return ok
def negative_lookahead(self, func: Callable[..., object], *args: object) -> bool:
mark = self.mark()
ok = func(*args)
self.reset(mark)
return not ok
def make_syntax_error(self, filename: str = "<unknown>") -> SyntaxError:
tok = self._tokenizer.diagnose()
return SyntaxError(
"pegen parse failure", (filename, tok.start[0], 1 + tok.start[1], tok.line)
)
def simple_parser_main(parser_class: Type[Parser]) -> None:
argparser = argparse.ArgumentParser()
argparser.add_argument(
"-v",
"--verbose",
action="count",
default=0,
help="Print timing stats; repeat for more debug output",
)
argparser.add_argument(
"-q", "--quiet", action="store_true", help="Don't print the parsed program"
)
argparser.add_argument("filename", help="Input file ('-' to use stdin)")
args = argparser.parse_args()
verbose = args.verbose
verbose_tokenizer = verbose >= 3
verbose_parser = verbose == 2 or verbose >= 4
t0 = time.time()
filename = args.filename
if filename == "" or filename == "-":
filename = "<stdin>"
file = sys.stdin
else:
file = open(args.filename)
try:
tokengen = tokenize.generate_tokens(file.readline)
tokenizer = Tokenizer(tokengen, verbose=verbose_tokenizer)
parser = parser_class(tokenizer, verbose=verbose_parser)
tree = parser.start()
try:
if file.isatty():
endpos = 0
else:
endpos = file.tell()
except IOError:
endpos = 0
finally:
if file is not sys.stdin:
file.close()
t1 = time.time()
if not tree:
err = parser.make_syntax_error(filename)
traceback.print_exception(err.__class__, err, None)
sys.exit(1)
if not args.quiet:
print(tree)
if verbose:
dt = t1 - t0
diag = tokenizer.diagnose()
nlines = diag.end[0]
if diag.type == token.ENDMARKER:
nlines -= 1
print(f"Total time: {dt:.3f} sec; {nlines} lines", end="")
if endpos:
print(f" ({endpos} bytes)", end="")
if dt:
print(f"; {nlines / dt:.0f} lines/sec")
else:
print()
print("Caches sizes:")
print(f" token array : {len(tokenizer._tokens):10}")
print(f" cache : {len(parser._cache):10}")
## print_memstats()
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