feat(dirty): update arbiter for binary protocol

Update arbiter tests to work with the binary protocol:
- Update MockStreamWriter to decode binary messages
- Import binary protocol constants from module level

tests/test_dirty_arbiter.py

@@ -14,7 +14,12 @@ import pytest
 from gunicorn.config import Config
 from gunicorn.dirty.arbiter import DirtyArbiter
 from gunicorn.dirty.errors import DirtyError
-from gunicorn.dirty.protocol import DirtyProtocol, make_request
+from gunicorn.dirty.protocol import (
+    DirtyProtocol,
+    BinaryProtocol,
+    make_request,
+    HEADER_SIZE,
+)
 
 
 class MockStreamWriter:
@@ -29,16 +34,22 @@ class MockStreamWriter:
         self._buffer += data
 
     async def drain(self):
-        while len(self._buffer) >= DirtyProtocol.HEADER_SIZE:
-            length = struct.unpack(
-                DirtyProtocol.HEADER_FORMAT,
-                self._buffer[:DirtyProtocol.HEADER_SIZE]
-            )[0]
-            total_size = DirtyProtocol.HEADER_SIZE + length
+        # Decode the buffer to extract messages using binary protocol
+        while len(self._buffer) >= HEADER_SIZE:
+            # Decode header to get payload length
+            _, _, length = BinaryProtocol.decode_header(
+                self._buffer[:HEADER_SIZE]
+            )
+            total_size = HEADER_SIZE + length
             if len(self._buffer) >= total_size:
-                msg_data = self._buffer[DirtyProtocol.HEADER_SIZE:total_size]
+                msg_data = self._buffer[:total_size]
                 self._buffer = self._buffer[total_size:]
-                self.messages.append(DirtyProtocol.decode(msg_data))
+                # decode_message returns (msg_type_str, request_id, payload_dict)
+                msg_type_str, request_id, payload_dict = BinaryProtocol.decode_message(msg_data)
+                # Reconstruct the dict format for backwards compatibility
+                result = {"type": msg_type_str, "id": request_id}
+                result.update(payload_dict)
+                self.messages.append(result)
             else:
                 break