diff --git a/synapse/types.py b/synapse/types.py
index 41afb27a74..d8cb64addb 100644
--- a/synapse/types.py
+++ b/synapse/types.py
@@ -12,6 +12,7 @@
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
+import re
import string
from collections import namedtuple
@@ -228,6 +229,71 @@ def contains_invalid_mxid_characters(localpart):
return any(c not in mxid_localpart_allowed_characters for c in localpart)
+UPPER_CASE_PATTERN = re.compile(b"[A-Z_]")
+
+# the following is a pattern which matches '=', and bytes which are not allowed in a mxid
+# localpart.
+#
+# It works by:
+# * building a string containing the allowed characters (excluding '=')
+# * escaping every special character with a backslash (to stop '-' being interpreted as a
+# range operator)
+# * wrapping it in a '[^...]' regex
+# * converting the whole lot to a 'bytes' sequence, so that we can use it to match
+# bytes rather than strings
+#
+NON_MXID_CHARACTER_PATTERN = re.compile(
+ ("[^%s]" % (
+ re.escape("".join(mxid_localpart_allowed_characters - {"="}),),
+ )).encode("ascii"),
+)
+
+
+def map_username_to_mxid_localpart(username, case_sensitive=False):
+ """Map a username onto a string suitable for a MXID
+
+ This follows the algorithm laid out at
+ https://matrix.org/docs/spec/appendices.html#mapping-from-other-character-sets.
+
+ Args:
+ username (unicode|bytes): username to be mapped
+ case_sensitive (bool): true if TEST and test should be mapped
+ onto different mxids
+
+ Returns:
+ unicode: string suitable for a mxid localpart
+ """
+ if not isinstance(username, bytes):
+ username = username.encode('utf-8')
+
+ # first we sort out upper-case characters
+ if case_sensitive:
+ def f1(m):
+ return b"_" + m.group().lower()
+
+ username = UPPER_CASE_PATTERN.sub(f1, username)
+ else:
+ username = username.lower()
+
+ # then we sort out non-ascii characters
+ def f2(m):
+ g = m.group()[0]
+ if isinstance(g, str):
+ # on python 2, we need to do a ord(). On python 3, the
+ # byte itself will do.
+ g = ord(g)
+ return b"=%02x" % (g,)
+
+ username = NON_MXID_CHARACTER_PATTERN.sub(f2, username)
+
+ # we also do the =-escaping to mxids starting with an underscore.
+ username = re.sub(b'^_', b'=5f', username)
+
+ # we should now only have ascii bytes left, so can decode back to a
+ # unicode.
+ return username.decode('ascii')
+
+
class StreamToken(
namedtuple("Token", (
"room_key",
|
