Tuned maybe_extract_next_line to search only \r\n

ref #115 (comment)

Author: cdeler

h11/_receivebuffer.py

@@ -86,14 +86,16 @@ def maybe_extract_next_line(self):
         Extract the first line, if it is completed in the buffer.
         """
         # Only search in buffer space that we've not already looked at.
-        partial_buffer = self._data[self._next_line_search :]
-        partial_idx = partial_buffer.find(b"\n")
+        search_start_index = max(0, self._next_line_search - 1)
+        partial_buffer = self._data[search_start_index:]
+        partial_idx = partial_buffer.find(b"\r\n")
         if partial_idx == -1:
             self._next_line_search = len(self._data)
             return None
 
         # Truncate the buffer and return it.
-        idx = self._next_line_search + partial_idx + 1
+        # + 2 is to compensate len(b"\r\n")
+        idx = search_start_index + partial_idx + 2
         out = self._data[:idx]
         self._data[:idx] = b""
         self._next_line_search = 0

h11/tests/test_receivebuffer.py

@@ -35,26 +35,28 @@ def test_receivebuffer():
     # maybe_extract_until_next
     ################################################################
 
-    b += b"12345\n6789\r\n"
+    b += b"123\n456\r\n789\r\n"
 
-    assert b.maybe_extract_next_line() == b"12345\n"
-    assert bytes(b) == b"6789\r\n"
+    assert b.maybe_extract_next_line() == b"123\n456\r\n"
+    assert bytes(b) == b"789\r\n"
 
-    assert b.maybe_extract_next_line() == b"6789\r\n"
+    assert b.maybe_extract_next_line() == b"789\r\n"
     assert bytes(b) == b""
 
     b += b"12\r"
     assert b.maybe_extract_next_line() is None
     assert bytes(b) == b"12\r"
 
-    # check repeated searches for the same needle, triggering the
-    # pickup-where-we-left-off logic
     b += b"345\n\r"
-    assert b.maybe_extract_next_line() == b"12\r345\n"
-    assert bytes(b) == b"\r"
+    assert b.maybe_extract_next_line() is None
+    assert bytes(b) == b"12\r345\n\r"
+
+    # here we stopped at the middle of b"\r\n" delimiter
 
-    b += b"6789aaa123\n"
-    assert b.maybe_extract_next_line() == b"\r6789aaa123\n"
+    b += b"\n6789aaa123\r\n"
+    assert b.maybe_extract_next_line() == b"12\r345\n\r\n"
+    assert b.maybe_extract_next_line() == b"6789aaa123\r\n"
+    assert b.maybe_extract_next_line() is None
     assert bytes(b) == b""
 
     ################################################################