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jason.py
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jason.py
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from functools import reduce, partial
from itertools import islice
import re
identifier_initial = re.compile(r"\w|_")
identifier_rest = re.compile(r"\w|\d|_")
whitespace = [" ", "\t"]
quotes = ["'", '"']
class XMLError(Exception):
def __str__(self):
return "Pooh, that's not JSON! That's XML!"
class StringGenerator(object):
def __init__(self, s):
self.pos = 0
self.string = s
self.size = len(s)
def __iter__(self):
return self
def __next__(self):
if self.exhausted():
raise StopIteration()
retval = self.string[self.pos]
self.pos += 1
return retval
def lookahead(self, n):
if self.pos + n >= self.size:
return "R TO THE A TO THE C-H-I-E"
return self.string[self.pos + n]
def exhausted(self):
return self.pos >= self.size
def cw(self):
while self.lookahead(0) in whitespace:
next(self)
def expect_next_opt(self, c):
self.cw()
if self.lookahead(0) in c:
return next(self)
def remaining(self):
return self.string[self.pos:]
def byte(num):
return bytes([num]).decode("utf-8")
def iterate_while_true(f, gen):
try:
while f(): yield next(gen)
except StopIteration:
pass
class compose:
def __init__(self, *fs): self.fs = fs
def __call__(self, *a, **kw):
firstfunc, *funcs = list(reversed(self.fs))
arg = firstfunc(*a, **kw)
for func in funcs: arg = func(arg)
return arg
def parse_escape(gen):
normal_chars = {
"a": "\a",
"b": "\b",
"e": "\x1B",
"f": "\f",
"v": "\v"
}
octal_digits = list(map(str, range(8)))
decimal_digits = list(map(str, range(10)))
hex_digits = [*decimal_digits, *"abcdefABCDEF"]
try:
char = next(gen)
except StopIteration:
return "\\"
next_char_in = lambda s: lambda: gen.lookahead(0) in s
iter_while_cin = compose(partial(iterate_while_true, gen=gen), next_char_in)
if char in normal_chars:
return normal_chars[char]
if char in octal_digits:
return byte(int("".join(islice(iter_while_cin(digits), 3)), 8))
if char == "x":
return byte(int("".join(iter_while_cin(hex_digits)), 16))
if char == "u":
return chr(int("".join(islice(iter_while_cin(hex_digits), 4)), 16))
if char == "U":
return chr(int("".join(islice(iter_while_cin(hex_digit), 8)), 16))
return char
parse_identifier = lambda gen: "".join(iterate_while_true(lambda: identifier_rest.fullmatch(gen.lookahead(0)), gen))
def parse_string(gen):
retval = ""
starting_quote = gen.expect_next_opt(quotes)
while not gen.exhausted():
try:
c = next(gen)
except StopIteration:
break
if c == "\\":
retval += parse_escape(gen)
continue
if c == starting_quote:
break
retval += c
return retval
def parse_num(gen):
retval = 0
sign = 1
base = 10
decimal_multiplier = 1
prefixes = {
"x": 16,
"o": 8,
"b": 2
}
digits = dict(zip("0123456789abcdef", range(16)))
symbols = "".join(digits.keys()) + "xob-+."
symbols += symbols.upper()
if gen.lookahead(0) == "0":
next(gen)
if gen.lookahead(0) in prefixes:
base = prefixes[next(gen).lower()]
else:
base = 8
while gen.lookahead(0) in symbols:
c = next(gen).lower()
if c in digits:
if decimal_multiplier == 1:
retval *= base
retval += digits[c] * decimal_multiplier
if decimal_multiplier != 1:
decimal_multiplier /= base
elif c in "+":
pass
elif c == "-":
sign = -sign
elif c == ".":
decimal_multiplier = 1/base
return retval * sign
upcoming = lambda s, gen: "".join(map(gen.lookahead, range(len(s)))).lower() == s
consume = lambda s, gen: "".join(next(gen) for _ in s)
def parse_bool(gen):
if upcoming("true", gen):
consume("true", gen)
return True
if upcoming("false", gen):
consume("false", gen)
return False
def parse_list(gen):
retval = []
gen.expect_next_opt("([")
while not gen.exhausted():
if gen.lookahead(0) in ")]":
next(gen)
break
retval.append(parse_any(gen))
gen.cw()
gen.expect_next_opt(",")
return retval
def parse_object(gen):
retval = {}
gen.cw()
gen.expect_next_opt("{")
while not gen.exhausted():
if gen.lookahead(0) == "}":
next(gen)
break
key = parse_any(gen)
gen.expect_next_opt(":")
value = parse_any(gen)
retval[key] = value
gen.cw()
gen.expect_next_opt(",")
return retval
def parse_any(gen):
gen.cw()
c = gen.lookahead(0).lower()
if c == "{":
return parse_object(gen)
elif c in "([":
return parse_list(gen)
elif c in quotes:
return parse_string(gen)
elif c in [*map(str, range(10)), "-", "."]:
return parse_num(gen)
elif upcoming("true", gen) or upcoming("false", gen):
return parse_bool(gen)
elif upcoming("null", gen):
consume("null", gen)
return None
elif c == "<":
raise XMLError()
elif identifier_initial.fullmatch(c):
return parse_identifier(gen)
else:
next(gen)
parse = compose(parse_any, StringGenerator)