faster cython loop

Author: deanlee

selfdrive/boardd/boardd_api_impl.pyx

@@ -1,5 +1,6 @@
 # distutils: language = c++
 # cython: language_level=3
+from cython.operator cimport dereference as deref, preincrement as preinc
 from libcpp.vector cimport vector
 from libcpp.string cimport string
 from libcpp cimport bool
@@ -45,7 +46,11 @@ def can_capnp_to_list(strings, sendcan=False):
   cdef vector[CanData] data
   can_capnp_to_can_list_cpp(strings, data, sendcan)
   result = []
-  for c in data:
-    frames = [[f.address, 0, f.dat, f.src] for f in c.frames]
-    result.append([c.nanos, frames])
+  cdef vector[CanData].iterator it = data.begin()
+  cdef CanData *d
+  while it != data.end():
+    d = &deref(it)
+    frames = [[f.address, 0, (<char *>&f.dat[0])[:f.dat.size()], f.src] for f in d.frames]
+    result.append([d.nanos, frames])
+    preinc(it)
   return result