Set a known buffer size if possible on BinaryWriter()s

telethon/network/authenticator.py

@@ -19,7 +19,7 @@ def do_authentication(connection):
 
     # Step 1 sending: PQ Request
     nonce = os.urandom(16)
-    with BinaryWriter() as writer:
+    with BinaryWriter(known_length=20) as writer:
         writer.write_int(0x60469778, signed=False)  # Constructor number
         writer.write(nonce)
         sender.send(writer.get_bytes())

telethon/network/connection.py

@@ -151,8 +151,9 @@ class Connection:
     def _send_tcp_full(self, message):
         # https://core.telegram.org/mtproto#tcp-transport
         # total length, sequence number, packet and checksum (CRC32)
-        with BinaryWriter() as writer:
-            writer.write_int(len(message) + 12)
+        length = len(message) + 12
+        with BinaryWriter(known_length=length) as writer:
+            writer.write_int(length)
             writer.write_int(self._send_counter)
             writer.write(message)
             writer.write_int(crc32(writer.get_bytes()), signed=False)
@@ -160,13 +161,13 @@ class Connection:
             self.write(writer.get_bytes())
 
     def _send_intermediate(self, message):
-        with BinaryWriter() as writer:
+        with BinaryWriter(known_length=len(message) + 4) as writer:
             writer.write_int(len(message))
             writer.write(message)
             self.write(writer.get_bytes())
 
     def _send_abridged(self, message):
-        with BinaryWriter() as writer:
+        with BinaryWriter(known_length=len(message) + 4) as writer:
             length = len(message) >> 2
             if length < 127:
                 writer.write_byte(length)

telethon/network/mtproto_plain_sender.py

@@ -20,7 +20,7 @@ class MtProtoPlainSender:
 
     def send(self, data):
         """Sends a plain packet (auth_key_id = 0) containing the given message body (data)"""
-        with BinaryWriter() as writer:
+        with BinaryWriter(known_length=len(data) + 20) as writer:
             writer.write_long(0)
             writer.write_long(self._get_new_msg_id())
             writer.write_int(len(data))