commit e153d90: [Minor] Add enumerate helper

[Vsevolod Stakhov]

Author: Vsevolod Stakhov
Date: 2022-05-04 21:24:06 +0100
URL: https://github.com/rspamd/rspamd/commit/e153d90011395d349b91cd60758c2887615ab6fc

[Minor] Add enumerate helper

---
 src/libutil/cxx/util.hxx | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/src/libutil/cxx/util.hxx b/src/libutil/cxx/util.hxx
index 8011f67a1..0df3349a3 100644
--- a/src/libutil/cxx/util.hxx
+++ b/src/libutil/cxx/util.hxx
@@ -22,6 +22,7 @@
 #include <array>
 #include <string_view>
 #include <optional>
+#include <tuple>
 
 /*
  * Common C++ utilities
@@ -103,6 +104,31 @@ inline constexpr auto make_string_view_from_it(_It begin, _It end)
 	};
 }
 
+/**
+ * Enumerate for range loop
+ */
+template <typename T,
+		typename TIter = decltype(std::begin(std::declval<T>())),
+		typename = decltype(std::end(std::declval<T>()))>
+constexpr auto enumerate(T && iterable)
+{
+	struct iterator
+	{
+		size_t i;
+		TIter iter;
+		bool operator != (const iterator & other) const { return iter != other.iter; }
+		void operator ++ () { ++i; ++iter; }
+		auto operator * () const { return std::tie(i, *iter); }
+	};
+	struct iterable_wrapper
+	{
+		T iterable;
+		auto begin() { return iterator{ 0, std::begin(iterable) }; }
+		auto end() { return iterator{ 0, std::end(iterable) }; }
+	};
+	return iterable_wrapper{ std::forward<T>(iterable) };
+}
+
 }
 
 #endif //RSPAMD_UTIL_HXX