xo-object2: beginning of DString + utest

xo-object2/src/object2/DString.cpp

@@ -0,0 +1,37 @@
+/** @file DString.cpp
+ *
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#include "DString.hpp"
+
+namespace xo {
+    using xo::facet::typeseq;
+
+    namespace scm {
+        DString *
+        DString::empty(obj<AAllocator> mm,
+                       size_type cap)
+        {
+            assert(cap > 0);
+
+            DString * result = nullptr;
+
+            if (cap > 0) {
+                void * mem = mm.alloc(typeseq::id<DString>(),
+                                      sizeof(DString) + cap);
+
+                result = new (mem) DString();
+                result->capacity_ = cap;
+                result->size_ = 0;
+                if (cap > 0) {
+                    result->chars_[0] = '\0';
+                }
+            }
+
+            return result;
+        }
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end DString.cpp */