py/objarray: Add MP_DEFINE_MEMORYVIEW_OBJ convenience macro.

This allows defining a `memoryview` instance, either statically or on the
C stack.

Signed-off-by: Damien George <[email protected]>

Author: dpgeorge

py/objarray.h

@@ -53,13 +53,18 @@ typedef struct _mp_obj_array_t {
 } mp_obj_array_t;
 
 #if MICROPY_PY_BUILTINS_MEMORYVIEW
+
+#define MP_DEFINE_MEMORYVIEW_OBJ(obj_name, typecode, offset, len, ptr) \
+    mp_obj_array_t obj_name = {{&mp_type_memoryview}, (typecode), (offset), (len), (ptr)}
+
 static inline void mp_obj_memoryview_init(mp_obj_array_t *self, size_t typecode, size_t offset, size_t len, void *items) {
     self->base.type = &mp_type_memoryview;
     self->typecode = typecode;
     self->free = offset;
     self->len = len;
     self->items = items;
 }
+
 #endif
 
 #if MICROPY_PY_ARRAY || MICROPY_PY_BUILTINS_BYTEARRAY