xo-interpreter2: work on global symtab [WIP]

include/xo/interpreter2/DGlobalEnv.hpp

@@ -6,26 +6,43 @@
 #pragma once
 
 #include <xo/expression2/DGlobalSymtab.hpp>
-#include <xo/object2/DList.hpp>
 #include <xo/object2/DArray.hpp>
 
 namespace xo {
     namespace scm {
 
-
         /** @brief runtime bindings for global variabels
+         *
+         *  Implementation here uses a DArenaHashMap to hold <key,value> pairs.
+         *  The hash map has its own memory outside GC space.
+         *  Keys are DUniqueStrings, also outside GC space.
+         *  Values are regular gc-aware objects, generally will be in GC space.
+         *
+         *  We need collector to traverse all the values in a global env
+         *  on each cycle.  Arrange that by having DGlobalEnv itself
+         *  in GC space.
+         *
          **/
         class DGlobalEnv {
+        public:
+            using MemorySizeVisitor = xo::mm::MemorySizeVisitor;
+
         public:
             DGlobalEnv() = default;
 
+            /** visit env-owned memory pools; call visitor(info) for each **/
+            void visit_pools(const MemorySizeVisitor & visitor) const;
+
         protected: // temporary, to appease compiler
 
             // absurd O(n) implementation for now
             // replace with gc-aware hashtable, when available.
 
-            /** globals.  Slots in @ref global_v_ are numbered in DLocalSymtab **/
-            DArray * global_v_ = nullptr;
+            /** symbol table assigns a unique index for each symbol **/
+            DGlobalSymtab * symtab_;
+
+            /** value for a symbol S will be in values_[symtab->lookup_binding(S)] **/
+            DArray * values_ = nullptr;
         };
     }
 }