#
#
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import re
from .base import ValuesMixin
from .validator import ValueValidator
[docs]
class ChunkedValueValidator(ValueValidator):
'''
Validates values for TXT/SPF-style chunked strings: present,
ASCII-only, with no unescaped or double-escaped ``;`` characters.
'''
_unescaped_semicolon_re = re.compile(r'\w;')
_double_escaped_semicolon_re = re.compile(r'\\\\;')
[docs]
def validate(self, value_cls, data, _type):
if not data:
return ['missing value(s)']
elif not isinstance(data, (list, tuple)):
data = (data,)
reasons = []
for value in data:
if self._unescaped_semicolon_re.search(value):
reasons.append(f'unescaped ; in "{value}"')
if self._double_escaped_semicolon_re.search(value):
reasons.append(f'double escaped ; in "{value}"')
try:
value.encode('ascii')
except UnicodeEncodeError:
reasons.append(f'non ASCII character in "{value}"')
return reasons
chunked_value_validator = ChunkedValueValidator(
'chunked-value-rfc', sets={'legacy', 'strict'}
)
[docs]
class _ChunkedValuesMixin(ValuesMixin):
CHUNK_SIZE = 255
[docs]
def chunked_value(self, value):
value = value.replace('"', '\\"')
vs = []
i = 0
n = len(value)
# until we've processed the whole string
while i < n:
# start with a full chunk size
c = min(self.CHUNK_SIZE, n - i)
# make sure that we don't break on escape chars
while value[i + c - 1] == '\\':
c -= 1
# we have our chunk now
vs.append(value[i : i + c])
# and can step over if
i += c
vs = '" "'.join(vs)
return self._value_type(f'"{vs}"')
@property
def chunked_values(self):
values = []
for v in self.values:
values.append(self.chunked_value(v))
return values
@property
def rr_values(self):
return self.chunked_values
[docs]
class _ChunkedValue(str):
VALIDATORS = [chunked_value_validator]
[docs]
@classmethod
def parse_rdata_text(cls, value):
try:
return value.replace(';', '\\;')
except AttributeError:
return value
[docs]
@classmethod
def _schema(cls):
return {'type': 'string'}
[docs]
@classmethod
def process(cls, values):
ret = []
for v in values:
if v and v[0] == '"':
v = v[1:-1]
ret.append(cls(v.replace('" "', '')))
return ret
@property
def rdata_text(self):
return self
[docs]
def template(self, params):
if '{' not in self:
return self
return self.__class__(self.format(**params))