filterx: add scope generations to avoid having to clone the scope

Instead of having to clone variables at every transition between filterx
scopes, add a "generation" counter which indicates if a previously
stored value is considered part of the scope or not.

At every transition we bump the generation counter of the scope (and at clone
we set it to 0). If our lookup returns a variable from a previous
generation, it is considered unset, just as we would unset it if
we were to sync() or clone() the scope.

Signed-off-by: Balazs Scheidler <[email protected]>

lib/filterx/filterx-scope.c

@@ -24,6 +24,7 @@
 #include "scratch-buffers.h"
 
 #define FILTERX_HANDLE_FLOATING_BIT (1UL << 31)
+#define FILTERX_SCOPE_MAX_GENERATION ((1UL << 20) - 1)
 
 struct _FilterXVariable
 {
@@ -35,7 +36,8 @@ struct _FilterXVariable
    * declared -- this variable is declared (e.g. retained for the entire input pipeline)
    */
   guint32 assigned:1,
-          declared:1;
+          declared:1,
+          generation:20;
   FilterXObject *value;
 };
 
@@ -103,6 +105,7 @@ struct _FilterXScope
   GPtrArray *weak_refs;
   gboolean write_protected;
   gboolean dirty;
+  gint generation;
 };
 
 static gboolean
@@ -166,7 +169,12 @@ filterx_scope_lookup_variable(FilterXScope *self, FilterXVariableHandle handle)
   FilterXVariable *v;
 
   if (_lookup_variable(self, handle, &v))
-    return v;
+    {
+      if (filterx_variable_handle_is_floating(handle) &&
+          !v->declared && v->generation != self->generation)
+        return NULL;
+      return v;
+    }
   return NULL;
 }
 
@@ -180,6 +188,16 @@ filterx_scope_register_variable(FilterXScope *self,
   if (_lookup_variable(self, handle, &v_slot))
     {
       /* already present */
+      if (v_slot->generation != self->generation)
+        {
+          /* existing value is from a previous generation, override it as if
+           * it was a new value */
+
+          v_slot->generation = self->generation;
+          filterx_variable_set_value(v_slot, initial_value);
+          /* consider this to be unset just as an initial registration is */
+          v_slot->assigned = FALSE;
+        }
       return v_slot;
     }
   /* turn v_slot into an index */
@@ -190,6 +208,7 @@ filterx_scope_register_variable(FilterXScope *self,
   v.handle = handle;
   v.assigned = FALSE;
   v.value = filterx_object_ref(initial_value);
+  v.generation = self->generation;
   g_array_insert_val(self->variables, v_index, v);
 
   return &g_array_index(self->variables, FilterXVariable, v_index);
@@ -305,6 +324,7 @@ filterx_scope_clone(FilterXScope *other)
           g_array_append_val(self->variables, *v);
           FilterXVariable *v_clone = &g_array_index(self->variables, FilterXVariable, dst_index);
 
+          v_clone->generation = 0;
           v_clone->value = filterx_object_clone(v->value);
           dst_index++;
           msg_trace("Filterx scope, cloning scope variable",
@@ -341,6 +361,8 @@ filterx_scope_make_writable(FilterXScope **pself)
       filterx_scope_unref(*pself);
       *pself = new;
     }
+  (*pself)->generation++;
+  g_assert((*pself)->generation < FILTERX_SCOPE_MAX_GENERATION);
   return *pself;
 }