Add timeout for each ASGI http.response.body message

Ensures that if a client becomes idle the segment generator is exited
within a constant amount of time (probably more than this timeout
because of the ASGI server's write buffer and the OS's socket write
buffer, but still constant).

anonstream/__init__.py

@@ -6,10 +6,10 @@ import secrets
 import toml
 from collections import OrderedDict
 
-from quart import Quart
 from quart_compress import Compress
 from werkzeug.security import generate_password_hash
 
+from anonstream.quart import Quart
 from anonstream.utils.captcha import create_captcha_factory, create_captcha_signer
 from anonstream.utils.colour import color_to_colour
 from anonstream.utils.user import generate_token

anonstream/quart.py

@@ -0,0 +1,51 @@
+import asyncio
+
+from werkzeug.wrappers import Response as WerkzeugResponse
+from quart.app import Quart as Quart_
+from quart.asgi import ASGIHTTPConnection as ASGIHTTPConnection_
+from quart.utils import encode_headers
+
+
+RESPONSE_ITERATOR_TIMEOUT = 10
+
+
+class ASGIHTTPConnection(ASGIHTTPConnection_):
+    async def _send_response(self, send, response):
+        await send({
+            "type": "http.response.start",
+            "status": response.status_code,
+            "headers": encode_headers(response.headers),
+        })
+
+        if isinstance(response, WerkzeugResponse):
+            for data in response.response:
+                body = data.encode(response.charset) if isinstance(data, str) else data
+                await asyncio.wait_for(
+                    send({
+                        "type": "http.response.body",
+                        "body": body,
+                        "more_body": True,
+                    }),
+                    timeout=RESPONSE_ITERATOR_TIMEOUT,
+                )
+        else:
+            async with response.response as response_body:
+                async for data in response_body:
+                    body = data.encode(response.charset) if isinstance(data, str) else data
+                    await asyncio.wait_for(
+                        send({
+                            "type": "http.response.body",
+                            "body": body,
+                            "more_body": True,
+                        }),
+                        timeout=RESPONSE_ITERATOR_TIMEOUT,
+                    )
+        await send({
+            "type": "http.response.body",
+            "body": b"",
+            "more_body": False,
+        })
+
+
+class Quart(Quart_):
+    asgi_http_class = ASGIHTTPConnection