Refactor texture.data to be handled using py::bytes

PiperOrigin-RevId: 843226742
Change-Id: I7ab920da3c387467b1fced27f557c6edd1af4bce

doc/python.rst

@@ -656,10 +656,8 @@ The :ref:`mjsMesh` object includes convenience methods for model creation with n
 
 Texture editing
 ^^^^^^^^^^^^^^^
-The :ref:`mjsTexture` buffer option stores the texture bytes in the ``data`` attribute. This attribute is stored as
+The :ref:`mjsTexture` buffer option stores the texture bytes in the ``data`` attribute. This attribute can be read and
-bytes but its elements can be read and modified as ``int``\s via index access and read as Python's built-in ``bytes`` or
+modified, for example:
-``bytearray`` objects.  See `specs_test.py
-<https://github.com/google-deepmind/mujoco/blob/main/python/mujoco/specs_test.py>`__.
 
 .. code-block:: python
 

python/mujoco/codegen/generate_spec_bindings.py

@@ -226,17 +226,17 @@ def _ptr_binding_code(
     return f"""\
   {classname}.def_property(
     "{varname}",
-    []({rawclassname}& self) -> MjTypeVec<std::byte> {{
+    []({rawclassname}& self) -> py::bytes {{
-        return MjTypeVec<std::byte>(self.{fullvarname}->data(),
+      return py::bytes(reinterpret_cast<const char*>(self.{fullvarname}->data()),
-                                    self.{fullvarname}->size());
+                                                     self.{fullvarname}->size());
-      }},
+    }},
-    []({rawclassname}& self, py::bytes& rhs) {{
+    []({rawclassname}& self, py::bytes rhs) {{
-        self.{fullvarname}->clear();
+      self.{fullvarname}->clear();
-        self.{fullvarname}->reserve(py::len(rhs));
+      std::string_view rhs_view = py::cast<std::string_view>(rhs);
-        std::string_view rhs_view = py::cast<std::string_view>(rhs);
+      self.{fullvarname}->reserve(rhs_view.length());
-        for (auto val : rhs_view) {{
+      for (char val : rhs_view) {{
-          self.{fullvarname}->push_back(static_cast<std::byte>(val));
+        self.{fullvarname}->push_back(static_cast<std::byte>(val));
-        }}
+      }}
     }}, py::return_value_policy::move);"""
   elif vartype == 'mjStringVec':
     return f"""\

python/mujoco/specs.cc

@@ -134,41 +134,6 @@ void DefineArray(py::module& m, const std::string& typestr) {
       }, py::keep_alive<0, 1>(), py::return_value_policy::reference_internal);
 };
 
-// Specialization for std::byte to convert to int for Python iteration
-template <>
-void DefineArray<std::byte>(py::module& m, const std::string& typestr) {
-  using Class = MjTypeVec<std::byte>;
-  py::class_<Class>(m, typestr.c_str())
-      .def(
-          py::init([](std::byte* data, int size) { return Class(data, size); }))
-      .def("__getitem__",
-           [](Class& v, int i) -> int {
-             if (i < 0 || i >= v.size) {
-               throw py::index_error("Index out of range.");
-             }
-             return static_cast<int>(v.ptr[i]);
-           })
-      .def("__setitem__",
-           [](Class& v, int i, int c) {
-             if (i < 0 || i >= v.size) {
-               throw py::index_error("Index out of range.");
-             }
-             if (c < 0 || c > 255) {
-               throw py::value_error("Value out of range [0, 255].");
-             }
-             v.ptr[i] = static_cast<std::byte>(c);
-           })
-      .def("__len__", [](Class& v) { return v.size; })
-      .def(
-          "__iter__",
-          [](Class& v) {
-            return py::make_iterator(
-                reinterpret_cast<unsigned char*>(v.ptr),
-                reinterpret_cast<unsigned char*>(v.ptr + v.size));
-          },
-          py::keep_alive<0, 1>(), py::return_value_policy::reference_internal);
-};
-
 py::list FindAllImpl(raw::MjsBody& body, mjtObj objtype, bool recursive) {
   py::list list;
   raw::MjsElement* el = mjs_firstChild(&body, objtype, recursive);

python/mujoco/specs_test.py

@@ -1040,7 +1040,7 @@ class SpecsTest(absltest.TestCase):
     spec = mujoco.MjSpec()
     texture = spec.add_texture(name='texture', height=1, width=2, nchannel=3)
     texture.data = bytes([1, 2, 3, 4, 5, 6])
-    read_bytes = bytes(texture.data)
+    read_bytes = texture.data
     self.assertEqual(read_bytes, bytes([1, 2, 3, 4, 5, 6]))
 
   def test_modify_texture(self):
@@ -1048,16 +1048,18 @@ class SpecsTest(absltest.TestCase):
     spec = mujoco.MjSpec()
     texture = spec.add_texture(name='texture', height=1, width=3, nchannel=3)
     texture.data = bytes([255, 0, 0, 0, 255, 0, 0, 0, 255])
-    texture.data[1] = 255
+    data_array = bytearray(texture.data)
+    data_array[1] = 255
+    texture.data = bytes(data_array)
     self.assertEqual(
-        bytes(texture.data), bytes([255, 255, 0, 0, 255, 0, 0, 0, 255])
+        texture.data, bytes([255, 255, 0, 0, 255, 0, 0, 0, 255])
     )
 
     # Assigning values outside the range [0, 255] should raise an error.
     with self.assertRaises(ValueError):
-      texture.data[3] = 256
+      data_array[0] = 256
     with self.assertRaises(ValueError):
-      texture.data[3] = -1
+      data_array[0] = -1
 
   def test_find_unnamed_asset(self):
     spec = mujoco.MjSpec()