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# -*- coding: utf-8 -*-
# utils.py
# Copyright (C) 2013 LEAP
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
Mail utilities.
"""
import json
import re
import traceback
CHARSET_PATTERN = r"""charset=([\w-]+)"""
CHARSET_RE = re.compile(CHARSET_PATTERN, re.IGNORECASE)
def first(things):
"""
Return the head of a collection.
"""
try:
return things[0]
except (IndexError, TypeError):
return None
def find_charset(thing, default=None):
"""
Looks into the object 'thing' for a charset specification.
It searchs into the object's `repr`.
:param thing: the object to look into.
:type thing: object
:param default: the dafault charset to return if no charset is found.
:type default: str
:returns: the charset or 'default'
:rtype: str or None
"""
charset = first(CHARSET_RE.findall(repr(thing)))
if charset is None:
charset = default
return charset
class CustomJsonScanner(object):
"""
This class is a context manager definition used to monkey patch the default
json string parsing behavior.
The emails can have more than one encoding, so the `str` objects have more
than one encoding and json does not support direct work with `str`
(only `unicode`).
"""
def _parse_string_str(self, s, idx, *args, **kwargs):
"""
Parses the string "s" starting at the point idx and returns an `str`
object. Which basically means it works exactly the same as the regular
JSON string parsing, except that it doesn't try to decode utf8.
We need this because mail raw strings might have bytes in multiple
encodings.
:param s: the string we want to parse
:type s: str
:param idx: the starting point for parsing
:type idx: int
:returns: the parsed string and the index where the
string ends.
:rtype: tuple (str, int)
"""
# NOTE: we just want to use this monkey patched version if we are
# calling the loads from our custom method. Otherwise, we use the
# json's default parser.
monkey_patched = False
for i in traceback.extract_stack():
# look for json_loads method in the call stack
if i[2] == json_loads.__name__:
monkey_patched = True
break
if not monkey_patched:
return self._orig_scanstring(s, idx, *args, **kwargs)
found = False
end = s.find("\"", idx)
while not found:
try:
if s[end-1] != "\\":
found = True
else:
end = s.find("\"", end+1)
except Exception:
found = True
return s[idx:end].decode("string-escape"), end+1
def __enter__(self):
"""
Replace the json methods with the needed ones.
Also make a backup to restore them later.
"""
# backup original values
self._orig_make_scanner = json.scanner.make_scanner
self._orig_scanstring = json.decoder.scanstring
# We need the make_scanner function to be the python one so we can
# monkey_patch the json string parsing
json.scanner.make_scanner = json.scanner.py_make_scanner
# And now we monkey patch the money method
json.decoder.scanstring = self._parse_string_str
def __exit__(self, exc_type, exc_value, traceback):
"""
Restores the backuped methods.
"""
# restore original values
json.scanner.make_scanner = self._orig_make_scanner
json.decoder.scanstring = self._orig_scanstring
def json_loads(data):
"""
It works as json.loads but supporting multiple encodings in the same
string and accepting an `str` parameter that won't be converted to unicode.
:param data: the string to load the objects from
:type data: str
:returns: the corresponding python object result of parsing 'data', this
behaves similarly as json.loads, with the exception of that
returns always `str` instead of `unicode`.
"""
obj = None
with CustomJsonScanner():
# We need to use the cls parameter in order to trigger the code
# that will let us control the string parsing method.
obj = json.loads(data, cls=json.JSONDecoder)
return obj
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