gh-141968: Inline traditional ZIP key updates

Author: methane

Lib/zipfile/__init__.py

@@ -752,13 +752,21 @@ def update_keys(c):
 
     def decrypter(data):
         """Decrypt a bytes object."""
+        nonlocal key0, key1, key2
+        k0, k1, k2 = key0, key1, key2
         result = bytearray()
         append = result.append
+        crc_table = crctable
+        # Inline update_keys() to avoid a function call for every byte.
         for c in data:
-            k = key2 | 2
+            k = k2 | 2
             c ^= ((k * (k^1)) >> 8) & 0xFF
-            update_keys(c)
+            k0 = (k0 >> 8) ^ crc_table[(k0 ^ c) & 0xFF]
+            k1 = (k1 + (k0 & 0xFF)) & 0xFFFFFFFF
+            k1 = (k1 * 134775813 + 1) & 0xFFFFFFFF
+            k2 = (k2 >> 8) ^ crc_table[(k2 ^ (k1 >> 24)) & 0xFF]
             append(c)
+        key0, key1, key2 = k0, k1, k2
         return result.take_bytes()
 
     return decrypter