Add longest inheritance path interface

Author: aaronj0

clingwrapper/src/clingwrapper.cxx

@@ -1211,6 +1211,57 @@ Cppyy::TCppIndex_t Cppyy::GetNumBases(TCppScope_t klass)
     return Cpp::GetNumBases(klass);
 }
 
+////////////////////////////////////////////////////////////////////////////////
+/// \fn Cppyy::TCppIndex_t Cppyy::GetNumBasesLongestBranch(TCppScope_t klass)
+/// \brief Retrieve number of base classes in the longest branch of the
+///        inheritance tree of the input class.
+/// \param[in] klass The class to start the retrieval process from.
+///
+/// This is a helper function for Cppyy::GetNumBasesLongestBranch.
+/// Given an inheritance tree, the function assigns weight 1 to each class that
+/// has at least one base. Starting from the input class, the function is
+/// called recursively on all the bases. For each base the return value is one
+/// (the weight of the base itself) plus the maximum value retrieved for their
+/// bases in turn. For example, given the following inheritance tree:
+///
+/// ~~~{.cpp}
+/// class A {}; class B: public A {};
+/// class X {}; class Y: public X {}; class Z: public Y {};
+/// class C: public B, Z {};
+/// ~~~
+///
+/// calling this function on an instance of `C` will return 3, the steps
+/// required to go from C to X.
+Cppyy::TCppIndex_t Cppyy::GetNumBasesLongestBranch(TCppScope_t klass) {
+    std::vector<TCppScope_t> directbases;
+    for (TCppIndex_t ibase = 0; ibase < GetNumBases(klass); ++ibase)
+        directbases.push_back(GetScope(GetBaseName(klass, ibase)));
+    return directbases.size();
+//    if (directbases.empty()) {
+//       // This is a leaf with no bases
+//       return 0;
+//    }
+
+//  else {
+//       // If there is at least one direct base
+//       std::vector<Cppyy::TCppIndex_t> nbases_branches;
+//       nbases_branches.reserve(ndirectbases);
+//       // Traverse all direct bases of the current class and call the function
+//       // recursively
+//       for (auto baseclass : TRangeDynCast<TBaseClass>(directbases)) {
+//          if (!baseclass)
+//             continue;
+//          if (auto baseclass_tclass = baseclass->GetClassPointer()) {
+//             nbases_branches.emplace_back(GetLongestInheritancePath(baseclass_tclass));
+//          }
+//       }
+//       // Get longest path among the direct bases of the current class
+//       auto longestbranch = std::max_element(std::begin(nbases_branches), std::end(nbases_branches));
+//       // Add 1 to include the current class in the count
+//       return 1 + *longestbranch;
+//    }
+}
+
 std::string Cppyy::GetBaseName(TCppType_t klass, TCppIndex_t ibase)
 {
     return Cpp::GetName(Cpp::GetBaseClass(klass, ibase));

clingwrapper/src/cpp_cppyy.h

@@ -232,6 +232,8 @@ namespace Cppyy {
     RPY_EXPORTED
     TCppIndex_t GetNumBases(TCppScope_t klass);
     RPY_EXPORTED
+    TCppIndex_t GetNumBasesLongestBranch(TCppScope_t klass);
+    RPY_EXPORTED
     std::string GetBaseName(TCppScope_t klass, TCppIndex_t ibase);
     RPY_EXPORTED
     TCppScope_t GetBaseScope(TCppScope_t klass, TCppIndex_t ibase);