Add a SharedArray type

This is based on the SharedString code and will allow sharing ownership
of arrays between Rust and C++.

api/sixtyfps-cpp/include/sixtyfps_sharedarray.h

@@ -0,0 +1,42 @@
+#pragma once
+#include "sixtyfps_sharedarray_internal.h"
+
+namespace sixtyfps {
+
+template<typename T>
+struct SharedArray
+{
+    SharedArray()
+    {
+        internal::sixtyfps_shared_array_new_null(reinterpret_cast<SharedArray<uint8_t> *>(this));
+    }
+    explicit SharedArray(void *inner) : inner(inner) { }
+
+    SharedArray(const SharedArray &other)
+    {
+        internal::sixtyfps_shared_array_clone(
+                reinterpret_cast<SharedArray<uint8_t> *>(this),
+                reinterpret_cast<const SharedArray<uint8_t> *>(&other));
+    }
+    ~SharedArray()
+    {
+        internal::sixtyfps_shared_array_drop(reinterpret_cast<SharedArray<uint8_t> *>(this));
+    }
+    SharedArray &operator=(const SharedArray &other)
+    {
+        internal::sixtyfps_shared_array_drop(reinterpret_cast<SharedArray<uint8_t> *>(this));
+        internal::sixtyfps_shared_array_clone(
+                reinterpret_cast<SharedArray<uint8_t> *>(this),
+                reinterpret_cast<const SharedArray<uint8_t> *>(&other));
+        return *this;
+    }
+    SharedArray &operator=(SharedArray &&other)
+    {
+        std::swap(inner, other.inner);
+        return *this;
+    }
+
+private:
+    void *inner; // opaque
+};
+}