Cache parsing of the content-type (#10552)

Author: bdraco

CHANGES/10552.misc.rst

@@ -0,0 +1 @@
+Improved performance of parsing content types by adding a cache in the same manner currently done with mime types -- by :user:`bdraco`.

aiohttp/helpers.py

@@ -24,7 +24,7 @@
 from http.cookies import SimpleCookie
 from math import ceil
 from pathlib import Path
-from types import TracebackType
+from types import MappingProxyType, TracebackType
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -367,6 +367,20 @@ def parse_mimetype(mimetype: str) -> MimeType:
     )
 
 
+@functools.lru_cache(maxsize=56)
+def parse_content_type(raw: str) -> Tuple[str, MappingProxyType[str, str]]:
+    """Parse Content-Type header.
+
+    Returns a tuple of the parsed content type and a
+    MappingProxyType of parameters.
+    """
+    msg = HeaderParser().parsestr(f"Content-Type: {raw}")
+    content_type = msg.get_content_type()
+    params = msg.get_params(())
+    content_dict = dict(params[1:])  # First element is content type again
+    return content_type, MappingProxyType(content_dict)
+
+
 def guess_filename(obj: Any, default: Optional[str] = None) -> Optional[str]:
     name = getattr(obj, "name", None)
     if name and isinstance(name, str) and name[0] != "<" and name[-1] != ">":
@@ -733,10 +747,10 @@ def _parse_content_type(self, raw: Optional[str]) -> None:
             self._content_type = "application/octet-stream"
             self._content_dict = {}
         else:
-            msg = HeaderParser().parsestr("Content-Type: " + raw)
-            self._content_type = msg.get_content_type()
-            params = msg.get_params(())
-            self._content_dict = dict(params[1:])  # First element is content type again
+            content_type, content_mapping_proxy = parse_content_type(raw)
+            self._content_type = content_type
+            # _content_dict needs to be mutable so we can update it
+            self._content_dict = content_mapping_proxy.copy()
 
     @property
     def content_type(self) -> str: