@2336839 Handle std::forward_list data type conversion. Currently SWI…

…G doesn't provide std_forward_list.i for data type conversion between Python and C++.

SwigUtils.i

@@ -1,6 +1,8 @@
 // Copyright (c) 2014 Arista Networks, Inc.  All rights reserved.
 // Arista Networks, Inc. Confidential and Proprietary.
 
+%include exception.i
+
 // Based on http://www.swig.org/Doc2.0/SWIGDocumentation.html#Python_nn60
 %typemap(in) (int argc, char **argv) {
    if (!PyList_Check($input)) {
@@ -52,3 +54,58 @@ namespace std {
       size_t size() const;
    };
 }
+
+%define STD_FORWARD_LIST(data_type)
+
+// Python --> C
+%typemap(in) std::forward_list<eos::##data_type> const & {
+   PyObject *t = $input;
+   if (PyTuple_Check(t) != true) {
+      PyErr_SetString(PyExc_TypeError, "argument must be a tuple");
+      return NULL;
+   }
+
+   std::forward_list<eos::##data_type> *a = new std::forward_list<eos::##data_type>();
+   auto it = a->before_begin();
+   for (int i=0; i<PyTuple_Size(t); i++) {
+      PyObject *fv = PyTuple_GetItem(t, i);
+      eos::##data_type *fv_c;
+      if (SWIG_ConvertPtr(fv, (void **)&fv_c,
+               SWIGTYPE_p_eos__##data_type,
+               SWIG_POINTER_EXCEPTION) == -1) {
+         char buf[256];
+         delete a;
+         snprintf(buf, 256, "expected data type is eos::%s.", #data_type);
+         SWIG_exception(SWIG_TypeError, buf);
+         return NULL;
+      } else {
+         it = a->insert_after(it, *fv_c);
+      }
+   }
+
+   $1 = a;
+}
+
+// C --> Python
+%typemap(out) std::forward_list<eos::##data_type> const & {
+   std::forward_list<eos::##data_type> *a = $1;
+   std::forward_list<eos::##data_type>::const_iterator it;
+   int count = 0;
+   for (it=a->cbegin(); it!=a->cend(); ++it) {
+      count += 1;
+   }
+   PyObject *t = PyTuple_New(count);
+   int i = 0;
+   for (it=a->cbegin(); it!=a->cend(); ++it) {
+      PyObject *fv = SWIG_NewPointerObj((void *)&(*it),
+                                        SWIGTYPE_p_eos__##data_type,
+                                        0);
+      PyTuple_SetItem(t, i, fv);
+      i++;
+   }
+   $result = t;
+}
+%enddef
+
+STD_FORWARD_LIST(fib_via_t)
+STD_FORWARD_LIST(mpls_label_t)