xo-expression2: + StringTable + utest [WIP] [FAILING]

include/xo/expression2/StringTable.hpp

@@ -0,0 +1,56 @@
+/** @file StringTable.hpp
+ *
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#pragma once
+
+#include <xo/object2/DString.hpp>
+#include <xo/arena/DArenaHashMap.hpp>
+#include <xo/arena/DArena.hpp>
+#include <xo/arena/hashmap/verify_policy.hpp>
+
+namespace xo {
+    namespace scm {
+
+        /** @class StringTable
+         *  @brief table containing a set of interned strings
+         *
+         *  A table of strings referenced in schematika expressions
+         **/
+        class StringTable {
+        public:
+            using DArena = xo::mm::DArena;
+            using StringMap = xo::map::DArenaHashMap<std::string_view,
+                                                     DString*>;
+            using size_type = StringMap::size_type;
+
+        public:
+            StringTable(size_type hint_max_capacity,
+                        bool debug_flag = false);
+
+            /** lookup interned string; nullptr if not present **/
+            const DString * lookup(std::string_view key) const;
+
+            /** return unique string with contents @p key. Idempotent! **/
+            const DString * intern(std::string_view key);
+
+            /** verify StringTable invariants.
+             *  Act on failure according to policy @p p
+             **/
+            bool verify_ok(verify_policy p = verify_policy::throw_only()) const;
+
+        private:
+            /** allocate string storage in this arena; use DString to represent each string.
+             *  Can't use DArenaVector b/c DString has variable size
+             **/
+            DArena strings_;
+            /** map_[s] points to arena strings, i.e. members of @ref strings_ **/
+            StringMap map_;
+        };
+
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end StringTable.hpp */