breaking change: return None if find_first_sensor_time fails

Author: berndpfrommer

include/event_camera_py/decoder.h

@@ -23,9 +23,11 @@
 #include <event_camera_py/event_ext_trig.h>
 #include <pybind11/numpy.h>
 #include <pybind11/pybind11.h>
+#include <pybind11/stl.h>
 
 #include <string>
 #include <tuple>
+#include <variant>
 #include <vector>
 
 template <class A>
@@ -68,7 +70,7 @@ class Decoder
     return (std::tuple<bool, uint64_t>({reachedTimeLimit, nextTime}));
   }
 
-  std::tuple<bool, uint64_t> find_first_sensor_time(pybind11::object msg)
+  std::variant<uint64_t, pybind11::none> find_first_sensor_time(pybind11::object msg)
   {
     auto decoder = initialize_decoder(
       get_attr<std::string>(msg, "encoding"), get_attr<uint32_t>(msg, "width"),
@@ -79,11 +81,16 @@ class Decoder
     if (PyObject_GetBuffer(eventsObj.ptr(), &view, PyBUF_CONTIG_RO) != 0) {
       throw std::runtime_error("cannot convert events to byte buffer");
     }
+    decoder->setTimeBase(get_attr<uint64_t>(msg, "time_base"));
     uint64_t firstTime{0};
     const bool foundTime = decoder->findFirstSensorTime(
       reinterpret_cast<const uint8_t *>(view.buf), view.len, &firstTime);
     PyBuffer_Release(&view);
-    return (std::tuple<bool, uint64_t>({foundTime, firstTime}));
+    if (foundTime) {
+      return (firstTime);
+    } else {
+      return (pybind11::cast<pybind11::none>(Py_None));
+    }
   }
 
   void decode_bytes(

src/decoder.cpp

@@ -95,7 +95,7 @@ void declare_decoder(pybind11::module & m, std::string typestr)
         :rtype: tuple[boolean, uint64_t]
         )pbdoc")
     .def("find_first_sensor_time", &MyDecoder::find_first_sensor_time, R"pbdoc(
-        find_first_sensor_time(msg) -> tuple[Boolean, uint64_t]
+        find_first_sensor_time(msg) -> uint64|None
 
         Peeks into encoded message to find first event sensor time stamp. The
         boolean return flag indicates whether any time stamp was detected.
@@ -105,8 +105,8 @@ void declare_decoder(pybind11::module & m, std::string typestr)
 
         :param msg: event packet message to decode
         :type msg:  event_camera_msgs/msgs/EventPacket
-        :return: tuple with flag (true if event sensor time was found) and the sensor time
-        :rtype: tuple[boolean, uint64_t]
+        :return: sensor time
+        :rtype:  uint64_t or None if not found
         )pbdoc")
     .def("get_start_time", &MyDecoder::get_start_time, R"pbdoc(
         get_start_time() -> uint64

tests/test_1.py

@@ -188,8 +188,8 @@ def test_find_first_sensor_time(verbose=True):
         print('Testing find_first_time_stamp')
     decoder = Decoder()
     for _, msg, _ in bag.read_messages(topics=['/event_camera/events']):
-        found_ts, ts = decoder.find_first_sensor_time(msg)
-        assert found_ts
+        ts = decoder.find_first_sensor_time(msg)
+        assert ts is not None
         if verbose:
             print('first sensor time stamp: ', ts)
         assert ts == 7139840