xo-expression2 stack: + mvp DGlobalSymtab impl

include/xo/object2/DArray.hpp

@@ -58,6 +58,13 @@ namespace xo {
             static DArray * empty(obj<AAllocator> mm,
                                   size_type cap);
 
+            /** create copy of @p src using memory from @p mm
+             *  with capacity for @p new_cap elements
+             **/
+            static DArray * copy(obj<AAllocator> mm,
+                                 DArray * src,
+                                 size_type new_cap);
+
             /** create array containing elements @p args, using memory from @p mm.
              *  Nullptr if space exhausted.
              *

src/object2/DArray.cpp

@@ -37,6 +37,23 @@ namespace xo {
             return result;
         }
 
+        DArray *
+        DArray::copy(obj<AAllocator> mm,
+                     DArray * src,
+                     size_type new_cap)
+        {
+            DArray * dest = empty(mm, new_cap);
+
+            /** could just memcpy here **/
+            for (size_type i = 0, n = src->size(); i < n; ++i) {
+                dest->elts_[i] = src->elts_[i];
+            }
+
+            dest->size_ = src->size();
+
+            return dest;
+        }
+
         obj<AGCObject>
         DArray::at(size_type ix) const
         {