feat: speed up unpacking TXT record data in ServiceInfo (#1318)

bdraco · web-flow · commit a20084281e66 · 2023-12-02T13:16:45.000-10:00
diff --git a/bench/txt_properties.py b/bench/txt_properties.py
@@ -0,0 +1,22 @@
+import timeit
+
+from zeroconf import ServiceInfo
+
+info = ServiceInfo(
+    "_test._tcp.local.",
+    "test._test._tcp.local.",
+    properties=(
+        b"\x19md=AlexanderHomeAssistant\x06pv=1.0\x14id=59:8A:0B:74:65:1D\x05"
+        b"c#=14\x04s#=1\x04ff=0\x04ci=2\x04sf=0\x0bsh=ccZLPA=="
+    ),
+)
+
+
+def process_properties() -> None:
+    info._properties = None
+    info.properties
+
+
+count = 100000
+time = timeit.Timer(process_properties).timeit(count)
+print(f"Processing {count} properties took {time} seconds")
diff --git a/src/zeroconf/_services/info.pxd b/src/zeroconf/_services/info.pxd
@@ -63,7 +63,8 @@ cdef class ServiceInfo(RecordUpdateListener):
     @cython.locals(cache=DNSCache)
     cpdef bint _load_from_cache(self, object zc, cython.float now)
 
-    cdef _unpack_text_into_properties(self)
+    @cython.locals(length="unsigned char", index="unsigned int", key_value=bytes, key_sep_value=tuple)
+    cdef void _unpack_text_into_properties(self)
 
     cdef _set_properties(self, cython.dict properties)
 
diff --git a/src/zeroconf/_services/info.py b/src/zeroconf/_services/info.py
@@ -388,27 +388,26 @@ def _set_text(self, text: bytes) -> None:
     def _unpack_text_into_properties(self) -> None:
         """Unpacks the text field into properties"""
         text = self.text
-        if not text:
+        end = len(text)
+        if end == 0:
             # Properties should be set atomically
             # in case another thread is reading them
             self._properties = {}
             return
 
         index = 0
-        pairs: List[bytes] = []
-        end = len(text)
+        properties: Dict[Union[str, bytes], Optional[Union[str, bytes]]] = {}
         while index < end:
             length = text[index]
             index += 1
-            pairs.append(text[index : index + length])
+            key_value = text[index : index + length]
+            key_sep_value = key_value.partition(b'=')
+            key = key_sep_value[0]
+            if key not in properties:
+                properties[key] = key_sep_value[2] or None
             index += length
 
-        # Reverse the list so that the first item in the list
-        # is the last item in the text field. This is important
-        # to preserve backwards compatibility where the first
-        # key always wins if the key is seen multiple times.
-        pairs.reverse()
-        self._properties = {key: value or None for key, _, value in (pair.partition(b'=') for pair in pairs)}
+        self._properties = properties
 
     def get_name(self) -> str:
         """Name accessor"""
