HTTP1 header formatting moved to headers.format_headers and rewritten.

- New implementation is one line of code and twice faster than the old one.
- Whole header block encoded to UTF-8 in one pass.
- No longer supports custom encode method on header values.
- Cookie objects now have __str__ in addition to encode, to work with this.

sanic/cookies.py

@@ -130,6 +130,10 @@ class Cookie(dict):
         :return: Cookie encoded in a codec of choosing.
         :except: UnicodeEncodeError
         """
+        return str(self).encode(encoding)
+
+    def __str__(self):
+        """Format as a Set-Cookie header value."""
         output = ["%s=%s" % (self.key, _quote(self.value))]
         for key, value in self.items():
             if key == "max-age":
@@ -147,4 +151,4 @@ class Cookie(dict):
             else:
                 output.append("%s=%s" % (self._keys[key], value))
 
-        return "; ".join(output).encode(encoding)
+        return "; ".join(output)

sanic/headers.py

@@ -1,9 +1,9 @@
 import re
 
-from typing import Dict, Iterable, Optional, Tuple
+from typing import Any, Dict, Iterable, Optional, Tuple
 from urllib.parse import unquote
 
-
+HeaderIterable = Iterable[Tuple[str, Any]]  # Values convertible to str
 Options = Dict[str, str]  # key=value fields in various headers
 OptionsIterable = Iterable[Tuple[str, str]]  # May contain duplicate keys
 
@@ -165,3 +165,12 @@ def parse_host(host: str) -> Tuple[Optional[str], Optional[int]]:
         return None, None
     host, port = m.groups()
     return host.lower(), port and int(port)
+
+
+def format_http1(headers: HeaderIterable) -> bytes:
+    """Convert a headers iterable into HTTP/1 header format.
+
+    - Outputs UTF-8 bytes where each header line ends with \\r\\n.
+    - Values are converted into strings if necessary.
+    """
+    return "".join(f"{name}: {val}\r\n" for name, val in headers).encode()

sanic/response.py

@@ -7,6 +7,7 @@ from aiofiles import open as open_async
 
 from sanic.compat import Header
 from sanic.cookies import CookieJar
+from sanic.headers import format_http1
 from sanic.helpers import STATUS_CODES, has_message_body, remove_entity_headers
 
 
@@ -30,20 +31,7 @@ class BaseHTTPResponse:
             return str(data).encode()
 
     def _parse_headers(self):
-        headers = b""
+        return format_http1(self.headers.items())
-        for name, value in self.headers.items():
-            try:
-                headers += b"%b: %b\r\n" % (
-                    name.encode(),
-                    value.encode("utf-8"),
-                )
-            except AttributeError:
-                headers += b"%b: %b\r\n" % (
-                    str(name).encode(),
-                    str(value).encode("utf-8"),
-                )
-
-        return headers
 
     @property
     def cookies(self):