Add type_caster for ntcore raw values

- std::vector<uint8_t> is only used in raw contexts, so the type caster
  intercepts and converts the value automatically to/from bytes
- Fixes #45
- There may be other places we could use this technique?

subprojects/pyntcore/gen/GenericEntry.yml

@@ -1,5 +1,8 @@
 ---
 
+extra_includes:
+- src/nt_type_caster.h
+
 classes:
   GenericSubscriber:
     methods:

subprojects/pyntcore/gen/RawTopic.yml

@@ -1,5 +1,8 @@
 ---
 
+extra_includes:
+- src/nt_type_caster.h
+
 classes:
   RawSubscriber:
     methods:

subprojects/pyntcore/gen/ntcore_cpp_types.yml

@@ -1,5 +1,8 @@
 ---
 
+extra_includes:
+- src/nt_type_caster.h
+
 defaults:
   ignore: true
   report_ignored_missing: false

subprojects/pyntcore/ntcore/src/nt_type_caster.h

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <pybind11/pybind11.h>
+
+namespace pybind11 {
+namespace detail {
+
+// ntcore uses std::vector<uint8_t> anytime there is a raw value, so
+// add this specialization to convert to/from bytes directly
+
+template<>
+struct type_caster<std::vector<uint8_t>> {
+    using vector_type = std::vector<uint8_t>;
+    PYBIND11_TYPE_CASTER(vector_type, const_name("bytes"));
+
+    bool load(handle src, bool convert) {
+        if (!isinstance<buffer>(src)) {
+            return false;
+        }
+        auto buf = reinterpret_borrow<buffer>(src);
+        auto req = buf.request();
+        if (req.ndim != 1) {
+            return false;
+        }
+
+        auto begin = (const uint8_t*)req.ptr;
+        auto end = begin + req.size*req.itemsize;
+
+        value = std::vector<uint8_t>(begin, end);
+        return true;
+    }
+
+    static handle cast(const std::vector<uint8_t> &src, return_value_policy policy, handle parent) {
+        return py::bytes((char*)src.data(), src.size()).release();
+    }
+};
+
+}
+}