From 882422d4bcb5b369f2f142508e8319ec461374f2 Mon Sep 17 00:00:00 2001
From: Erik Zenker <erikzenker@posteo.de>
Date: Sun, 4 Jul 2021 22:08:34 +0200
Subject: [PATCH] feat: Improve index of compile time (#165)

---
 benchmark/components/index_of_benchmark.cpp | 107 +++++++++++++++++++-
 include/hsm/details/fill_dispatch_table.h   |   2 +
 include/hsm/details/index_map.h             |  34 +++++--
 test/unit/stateidx_tests.cpp                |   2 +
 4 files changed, 135 insertions(+), 10 deletions(-)

diff --git a/benchmark/components/index_of_benchmark.cpp b/benchmark/components/index_of_benchmark.cpp
index d2fe44c..3cba31e 100644
--- a/benchmark/components/index_of_benchmark.cpp
+++ b/benchmark/components/index_of_benchmark.cpp
@@ -1,10 +1,111 @@
-#include <iostream>
-
-#include "ComplexStateMachine.h"
 #include "hsm/details/index_map.h"
 
 using namespace hsm;
 
+namespace {
+class s1 {
+};
+class s2 {
+};
+class s3 {
+};
+class s4 {
+};
+class s5 {
+};
+class s6 {
+};
+class s7 {
+};
+class s8 {
+};
+class s9 {
+};
+class s10 {
+};
+class s11 {
+};
+class s12 {
+};
+class s13 {
+};
+class s14 {
+};
+class s15 {
+};
+class s16 {
+};
+class s17 {
+};
+class s18 {
+};
+class s19 {
+};
+class s20 {
+};
+class s21 {
+};
+class s22 {
+};
+class s23 {
+};
+class s24 {
+};
+class s25 {
+};
+class s26 {
+};
+class s27 {
+};
+class s28 {
+};
+class s29 {
+};
+class s30 {
+};
+class s31 {
+};
+class s32 {
+};
+class s33 {
+};
+class s34 {
+};
+class s35 {
+};
+class s36 {
+};
+class s37 {
+};
+class s38 {
+};
+class s39 {
+};
+class s40 {
+};
+class s41 {
+};
+class s42 {
+};
+class s43 {
+};
+class s44 {
+};
+class s45 {
+};
+class s46 {
+};
+class s47 {
+};
+class s48 {
+};
+class s49 {
+};
+class s50 {
+};
+
+}
+
 int main()
 {
     using namespace boost::hana;
diff --git a/include/hsm/details/fill_dispatch_table.h b/include/hsm/details/fill_dispatch_table.h
index 6e67e5e..2731534 100644
--- a/include/hsm/details/fill_dispatch_table.h
+++ b/include/hsm/details/fill_dispatch_table.h
@@ -75,6 +75,8 @@ constexpr auto addDispatchTableEntry(
                         [=](auto& dispatchTable, auto&& transition2, bool internal) -> void {
                             const auto defer = false;
                             const auto valid = true;
+
+                            // NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-constant-array-index)
                             dispatchTable[fromIdx].push_front(
                                 { toIdx, history, defer, valid, internal, std::move(transition2) });
                         },
diff --git a/include/hsm/details/index_map.h b/include/hsm/details/index_map.h
index 9c83843..ac28212 100644
--- a/include/hsm/details/index_map.h
+++ b/include/hsm/details/index_map.h
@@ -11,7 +11,31 @@
 #include <boost/hana/basic_tuple.hpp>
 #include <boost/hana/zip.hpp>
 
-//#include <boost/mp11.hpp>
+namespace {
+template <class X, class Tuple> class GetIdx;
+
+template <class X, class... T> class GetIdx<X, boost::hana::tuple<T...>> {
+    template <std::size_t... idx>
+    static constexpr auto find_idx(std::index_sequence<idx...> seq) -> std::size_t
+    {
+        return seq.size() + ((std::is_same<X, T>::value ? idx - seq.size() : 0) + ...);
+    }
+
+  public:
+    static constexpr std::size_t value = find_idx(std::index_sequence_for<T...> {});
+};
+
+template <class X, class... T> class GetIdx<X, boost::hana::basic_tuple<T...>> {
+    template <std::size_t... idx>
+    static constexpr auto find_idx(std::index_sequence<idx...> seq) -> std::size_t
+    {
+        return seq.size() + ((std::is_same<X, T>::value ? idx - seq.size() : 0) + ...);
+    }
+
+  public:
+    static constexpr std::size_t value = find_idx(std::index_sequence_for<T...> {});
+};
+}
 
 namespace hsm {
 
@@ -19,13 +43,9 @@ namespace bh {
 using namespace boost::hana;
 }
 
-template <class Iterable, class Element>
-constexpr auto index_of(Iterable const& iterable, Element const& element)
+template <class Iterable, class Element> constexpr auto index_of(Iterable const&, Element const&)
 {
-    return bh::apply(
-        [](auto size, auto dropped) { return size - dropped; },
-        bh::size(iterable),
-        bh::size(bh::drop_while(iterable, bh::not_equal.to(element))));
+    return GetIdx<Element, Iterable>::value;
 }
 
 template <class Typeids> constexpr auto make_index_map(Typeids typeids)
diff --git a/test/unit/stateidx_tests.cpp b/test/unit/stateidx_tests.cpp
index d90ec45..614d089 100644
--- a/test/unit/stateidx_tests.cpp
+++ b/test/unit/stateidx_tests.cpp
@@ -1,6 +1,8 @@
 #include "hsm/details/fill_dispatch_table.h"
+#include "hsm/details/index_map.h"
 #include "hsm/details/state.h"
 #include "hsm/details/transition_table.h"
+
 #include "hsm/front/transition_tuple.h"
 
 #include <gtest/gtest.h>