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authorIvan Alejandro <ivanalejandro0@gmail.com>2014-01-17 14:59:09 -0300
committerIvan Alejandro <ivanalejandro0@gmail.com>2014-01-17 15:43:24 -0300
commit7b558eb23208d6de0b115fa453334421cc941e44 (patch)
tree5d40ab5040170b28d7da47659a0803094e023fbb /src/leap/mail/utils.py
parent06eebf54ab572ebaf6730f2095a062cd9549f12e (diff)
Add custom json.loads method.
This allows us to support the use of an `str` parameter that won't be converted to unicode. So in the case of a string containing bytes with different encodings this won't break.
Diffstat (limited to 'src/leap/mail/utils.py')
-rw-r--r--src/leap/mail/utils.py101
1 files changed, 100 insertions, 1 deletions
diff --git a/src/leap/mail/utils.py b/src/leap/mail/utils.py
index 2480efc..93388d3 100644
--- a/src/leap/mail/utils.py
+++ b/src/leap/mail/utils.py
@@ -15,8 +15,10 @@
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
-Small utilities.
+Mail utilities.
"""
+import json
+import traceback
def first(things):
@@ -27,3 +29,100 @@ def first(things):
return things[0]
except (IndexError, TypeError):
return None
+
+
+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