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# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
# Licensed to PSF under a Contributor Agreement.
# Extended to handle raw and unicode literals by Georg Brandl.
"""Safely evaluate Python string literals without using eval()."""
from __future__ import print_function
import re
from six import text_type
simple_escapes = {"a": "\a",
"b": "\b",
"f": "\f",
"n": "\n",
"r": "\r",
"t": "\t",
"v": "\v",
"'": "'",
'"': '"',
"\\": "\\"}
def convert_hex(x, n):
if len(x) < n+1:
raise ValueError("invalid hex string escape ('\\%s')" % x)
try:
return int(x[1:], 16)
except ValueError:
raise ValueError("invalid hex string escape ('\\%s')" % x)
def escape(m):
all, tail = m.group(0, 1)
assert all.startswith("\\")
esc = simple_escapes.get(tail)
if esc is not None:
return esc
elif tail.startswith("x"):
return chr(convert_hex(tail, 2))
elif tail.startswith('u'):
return unichr(convert_hex(tail, 4))
elif tail.startswith('U'):
return unichr(convert_hex(tail, 8))
elif tail.startswith('N'):
import unicodedata
try:
return unicodedata.lookup(tail[1:-1])
except KeyError:
raise ValueError("undefined character name %r" % tail[1:-1])
else:
try:
return chr(int(tail, 8))
except ValueError:
raise ValueError("invalid octal string escape ('\\%s')" % tail)
def escaperaw(m):
all, tail = m.group(0, 1)
if tail.startswith('u'):
return unichr(convert_hex(tail, 4))
elif tail.startswith('U'):
return unichr(convert_hex(tail, 8))
else:
return all
escape_re = re.compile(r"\\(\'|\"|\\|[abfnrtv]|x.{0,2}|[0-7]{1,3})")
uni_escape_re = re.compile(r"\\(\'|\"|\\|[abfnrtv]|x.{0,2}|[0-7]{1,3}|"
r"u[0-9a-fA-F]{0,4}|U[0-9a-fA-F]{0,8}|N\{.+?\})")
def evalString(s, encoding=None):
regex = escape_re
repl = escape
if encoding and not isinstance(s, text_type):
s = s.decode(encoding)
if s.startswith('u') or s.startswith('U'):
regex = uni_escape_re
s = s[1:]
if s.startswith('r') or s.startswith('R'):
repl = escaperaw
s = s[1:]
assert s.startswith("'") or s.startswith('"'), repr(s[:1])
q = s[0]
if s[:3] == q*3:
q = q*3
assert s.endswith(q), repr(s[-len(q):])
assert len(s) >= 2*len(q)
s = s[len(q):-len(q)]
return regex.sub(repl, s)
def test():
for i in range(256):
c = chr(i)
s = repr(c)
e = evalString(s)
if e != c:
print(i, c, s, e)
if __name__ == "__main__":
test()
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