From c667a00281d82c560bc25637fa57d67cacfd742d Mon Sep 17 00:00:00 2001
From: Lonami Exo <totufals@hotmail.com>
Date: Wed, 27 Sep 2017 21:23:59 +0200
Subject: [PATCH] Avoid using BinaryWriter where possible

---
 telethon/crypto/auth_key.py    | 12 ++++--------
 telethon/crypto/rsa.py         | 11 +++++------
 telethon/network/connection.py | 35 ++++++++++++++--------------------
 telethon/tl/gzip_packed.py     |  8 +++-----
 4 files changed, 26 insertions(+), 40 deletions(-)

diff --git a/telethon/crypto/auth_key.py b/telethon/crypto/auth_key.py
index 02774d58..710ebed8 100644
--- a/telethon/crypto/auth_key.py
+++ b/telethon/crypto/auth_key.py
@@ -1,7 +1,8 @@
+import struct
 from hashlib import sha1
 
 from .. import helpers as utils
-from ..extensions import BinaryReader, BinaryWriter
+from ..extensions import BinaryReader
 
 
 class AuthKey:
@@ -17,10 +18,5 @@ class AuthKey:
         """Calculates the new nonce hash based on
            the current class fields' values
         """
-        with BinaryWriter() as writer:
-            writer.write(new_nonce)
-            writer.write_byte(number)
-            writer.write_long(self.aux_hash, signed=False)
-
-            new_nonce_hash = utils.calc_msg_key(writer.get_bytes())
-            return new_nonce_hash
+        data = new_nonce + struct.pack('<BQ', number, self.aux_hash)
+        return utils.calc_msg_key(data)
diff --git a/telethon/crypto/rsa.py b/telethon/crypto/rsa.py
index 4e8d3384..858f4132 100644
--- a/telethon/crypto/rsa.py
+++ b/telethon/crypto/rsa.py
@@ -7,7 +7,7 @@ except ImportError:
     rsa = None
     raise ImportError('Missing module "rsa", please install via pip.')
 
-from ..extensions import BinaryWriter
+from ..tl import TLObject
 
 
 # {fingerprint: Crypto.PublicKey.RSA._RSAobj} dictionary
@@ -34,11 +34,10 @@ def _compute_fingerprint(key):
     """For a given Crypto.RSA key, computes its 8-bytes-long fingerprint
        in the same way that Telegram does.
     """
-    with BinaryWriter() as writer:
-        writer.tgwrite_bytes(get_byte_array(key.n))
-        writer.tgwrite_bytes(get_byte_array(key.e))
-        # Telegram uses the last 8 bytes as the fingerprint
-        return sha1(writer.get_bytes()).digest()[-8:]
+    n = TLObject.serialize_bytes(get_byte_array(key.n))
+    e = TLObject.serialize_bytes(get_byte_array(key.e))
+    # Telegram uses the last 8 bytes as the fingerprint
+    return sha1(n + e).digest()[-8:]
 
 
 def add_key(pub):
diff --git a/telethon/network/connection.py b/telethon/network/connection.py
index dbd76f68..d333b8ff 100644
--- a/telethon/network/connection.py
+++ b/telethon/network/connection.py
@@ -1,4 +1,5 @@
 import os
+import struct
 from datetime import timedelta
 from zlib import crc32
 from enum import Enum
@@ -6,7 +7,7 @@ from enum import Enum
 import errno
 
 from ..crypto import AESModeCTR
-from ..extensions import BinaryWriter, TcpClient
+from ..extensions import TcpClient
 from ..errors import InvalidChecksumError
 
 
@@ -175,30 +176,22 @@ class Connection:
         # https://core.telegram.org/mtproto#tcp-transport
         # total length, sequence number, packet and checksum (CRC32)
         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)
-            self._send_counter += 1
-            self.write(writer.get_bytes())
+        data = struct.pack('<ii', length, self._send_counter) + message
+        crc = struct.pack('<I', crc32(data))
+        self._send_counter += 1
+        self.write(data + crc)
 
     def _send_intermediate(self, message):
-        with BinaryWriter(known_length=len(message) + 4) as writer:
-            writer.write_int(len(message))
-            writer.write(message)
-            self.write(writer.get_bytes())
+        self.write(struct.pack('<i', len(message)) + message)
 
     def _send_abridged(self, message):
-        with BinaryWriter(known_length=len(message) + 4) as writer:
-            length = len(message) >> 2
-            if length < 127:
-                writer.write_byte(length)
-            else:
-                writer.write_byte(127)
-                writer.write(int.to_bytes(length, 3, 'little'))
-            writer.write(message)
-            self.write(writer.get_bytes())
+        length = len(message) >> 2
+        if length < 127:
+            length = struct.pack('B', length)
+        else:
+            length = b'\x7f' + int.to_bytes(length, 3, 'little')
+
+        self.write(length + message)
 
     # endregion
 
diff --git a/telethon/tl/gzip_packed.py b/telethon/tl/gzip_packed.py
index c2fe17c7..9a0d547a 100644
--- a/telethon/tl/gzip_packed.py
+++ b/telethon/tl/gzip_packed.py
@@ -1,7 +1,7 @@
 import gzip
+import struct
 
 from . import TLObject
-from ..extensions import BinaryWriter
 
 
 class GzipPacked(TLObject):
@@ -29,10 +29,8 @@ class GzipPacked(TLObject):
 
     def to_bytes(self):
         # TODO Maybe compress level could be an option
-        with BinaryWriter() as writer:
-            writer.write_int(GzipPacked.constructor_id, signed=False)
-            writer.tgwrite_bytes(gzip.compress(self.data))
-            return writer.get_bytes()
+        return struct.pack('<I', GzipPacked.constructor_id) + \
+               TLObject.serialize_bytes(gzip.compress(self.data))
 
     @staticmethod
     def read(reader):