Avoid cyclic imports on older Python versions

telethon/helpers.py

@@ -1,5 +1,6 @@
 """Various helpers not related to the Telegram API itself"""
 import os
+import struct
 from hashlib import sha1, sha256
 
 
@@ -17,6 +18,20 @@ def ensure_parent_dir_exists(file_path):
     if parent:
         os.makedirs(parent, exist_ok=True)
 
+
+def add_surrogate(text):
+    return ''.join(
+        # SMP -> Surrogate Pairs (Telegram offsets are calculated with these).
+        # See https://en.wikipedia.org/wiki/Plane_(Unicode)#Overview for more.
+        ''.join(chr(y) for y in struct.unpack('<HH', x.encode('utf-16le')))
+        if (0x10000 <= ord(x) <= 0x10FFFF) else x for x in text
+    )
+
+
+def del_surrogate(text):
+    return text.encode('utf-16', 'surrogatepass').decode('utf-16')
+
+
 # endregion
 
 # region Cryptographic related utils