outitf.c, add flag 'save none' for shared ngspice. Output data will not be stored, but are available via callback function ng_data.

README.shared-xspice

@@ -0,0 +1,28 @@
+Enabling XSPICE data transfer over the shared ngspice api.
+
+This branch enhances shared ngspice capability to event driven XSPICE data transfer.
+
+The shared library (dll) exports three new function:
+ngSpice_Init_Evt() provides addresses for two new callback functions.
+  To be called upon initialization.
+ngGet_Evt_NodeInfo() provides info for a specific node.
+ngSpice_AllEvtNodes() provides a list of all event nodes.
+
+There are two new callback functions
+
+sendinitevt() sends info upon the event nodes: name, type an dcorresponding index
+and is calles once per event nodes upon initialization of the circuit.
+
+sendevt() is called each time, when for a given event node, that is determined
+by index, a time step has been accepted and its value has changed. This allows
+to immediately make use of that value in the calling process.
+
+For details on the definitions you may have a look at sharedspice.h.
+
+There is an example caller file (currently tested only under Windows,
+and compiled with Visual Studio) in directory ngspice\visualc\ng_shared_xspice_v.
+
+There is also a new feature: The 'save' command accepts the flag none of run in
+shared mode. Then there is no internal storage of analog output data, they are
+still available with the callback function ng_data. The above mentioned example
+file now includes a testrun2 to demonstrate this feature.

src/frontend/outitf.c

@@ -90,6 +90,8 @@ static bool shouldstop = FALSE; /* Tell simulator to stop next time it asks. */
 static bool interpolated = FALSE;
 static double *valueold, *valuenew;
 
+static bool savenone = FALSE;
+
 /* The two "begin plot" routines share all their internals... */
 
 int
@@ -207,6 +209,16 @@ beginPlot(JOB *analysisPtr, CKTcircuit *circuitPtr, char *cktName, char *analNam
                     saves[i].used = 1;
                     continue;
                 }
+#ifdef SHARED_MODULE
+                /* this may happen if shared ngspice*/
+                if (cieq(saves[i].name, "none")) {
+                    savenone = TRUE;
+                    saveall = TRUE;
+                    savesused[i] = TRUE;
+                    saves[i].used = 1;
+                    continue;
+                }
+#endif
             }
         }
 
@@ -1065,6 +1077,11 @@ plotAddRealValue(dataDesc *desc, double value)
 {
     struct dvec *v = desc->vec;
 
+#ifdef SHARED_MODULE
+    if(savenone)
+        v->v_length = 0;
+#endif
+
     if (v->v_length >= v->v_alloc_length)
         dvec_extend(v, v->v_length + vlength2delta(v->v_length));
 
@@ -1086,6 +1103,11 @@ plotAddComplexValue(dataDesc *desc, IFcomplex value)
 {
     struct dvec *v = desc->vec;
 
+#ifdef SHARED_MODULE
+    if (savenone)
+        v->v_length = 0;
+#endif
+
     if (v->v_length >= v->v_alloc_length)
         dvec_extend(v, v->v_length + vlength2delta(v->v_length));