Add Python bindings to access the underlying buffer of a MemoryStream

include/mitsuba/core/mstream.h

@@ -110,6 +110,9 @@ class MI_EXPORT_LIB MemoryStream : public Stream {
     /// Return whether or not the memory stream owns the underlying buffer
     bool owns_buffer() const { return m_owns_buffer; }
 
+    /// Return the underlying raw byte array
+    const uint8_t *raw_buffer() const { return m_data; }
+
     //! @}
     // =========================================================================
 

src/core/python/stream.cpp

@@ -94,7 +94,10 @@ MI_PY_EXPORT(MemoryStream) {
         .def(py::init<size_t>(), D(MemoryStream, MemoryStream),
             "capacity"_a = 512)
         .def_method(MemoryStream, capacity)
-        .def_method(MemoryStream, owns_buffer);
+        .def_method(MemoryStream, owns_buffer)
+        .def("raw_buffer", [](MemoryStream &s) -> py::bytes {
+            return py::bytes(reinterpret_cast<const char*>(s.raw_buffer()), s.size());
+        });
 }
 
 MI_PY_EXPORT(ZStream) {

src/core/tests/test_stream.py

@@ -213,9 +213,12 @@ def test07_memory_stream():
     assert s.can_write()
     assert s.can_read()
 
-    s.write_string('hello world')
+    string = 'hello world'
     s.set_byte_order(Stream.EBigEndian)
+    s.write_string(string)
 
+    reference = int(len(string)).to_bytes(4, 'big') + bytes(string, encoding='ascii')
+    assert s.raw_buffer() == reference
     assert str(s) == """MemoryStream[
   host_byte_order = little-endian,
   byte_order = big-endian,