feat: speed up incoming packet processing with a memory view (#1290)

bdraco · web-flow · commit f1f0a2504afd · 2023-11-04T19:33:02.000-05:00
diff --git a/src/zeroconf/_protocol/incoming.pxd b/src/zeroconf/_protocol/incoming.pxd
@@ -50,6 +50,7 @@ cdef class DNSIncoming:
     cdef public unsigned int flags
     cdef cython.uint offset
     cdef public bytes data
+    cdef const unsigned char [:] view
     cdef unsigned int _data_len
     cdef public cython.dict name_cache
     cdef public cython.list questions
diff --git a/src/zeroconf/_protocol/incoming.py b/src/zeroconf/_protocol/incoming.py
@@ -78,6 +78,7 @@ class DNSIncoming:
         'flags',
         'offset',
         'data',
+        'view',
         '_data_len',
         'name_cache',
         'questions',
@@ -105,6 +106,7 @@ def __init__(
         self.flags = 0
         self.offset = 0
         self.data = data
+        self.view = data
         self._data_len = len(data)
         self.name_cache: Dict[int, List[str]] = {}
         self.questions: List[DNSQuestion] = []
@@ -228,7 +230,7 @@ def _read_questions(self) -> None:
 
     def _read_character_string(self) -> str:
         """Reads a character string from the packet"""
-        length = self.data[self.offset]
+        length = self.view[self.offset]
         self.offset += 1
         info = self.data[self.offset : self.offset + length].decode('utf-8', 'replace')
         self.offset += length
@@ -334,8 +336,8 @@ def _read_bitmap(self, end: _int) -> List[int]:
             offset = self.offset
             offset_plus_one = offset + 1
             offset_plus_two = offset + 2
-            window = self.data[offset]
-            bitmap_length = self.data[offset_plus_one]
+            window = self.view[offset]
+            bitmap_length = self.view[offset_plus_one]
             bitmap_end = offset_plus_two + bitmap_length
             for i, byte in enumerate(self.data[offset_plus_two:bitmap_end]):
                 for bit in range(0, 8):
@@ -361,7 +363,7 @@ def _read_name(self) -> str:
     def _decode_labels_at_offset(self, off: _int, labels: List[str], seen_pointers: Set[int]) -> int:
         # This is a tight loop that is called frequently, small optimizations can make a difference.
         while off < self._data_len:
-            length = self.data[off]
+            length = self.view[off]
             if length == 0:
                 return off + DNS_COMPRESSION_HEADER_LEN
 
@@ -377,7 +379,7 @@ def _decode_labels_at_offset(self, off: _int, labels: List[str], seen_pointers:
                 )
 
             # We have a DNS compression pointer
-            link_data = self.data[off + 1]
+            link_data = self.view[off + 1]
             link = (length & 0x3F) * 256 + link_data
             link_py_int = link
             if link > self._data_len:
