From 3d5a45b283d2a59211f9e24f100b95169375213d Mon Sep 17 00:00:00 2001
From: Steven Le Rouzic <steven.lerouzic@gmail.com>
Date: Tue, 4 Feb 2025 00:37:08 +0100
Subject: Add deref utilities & use them for log writer

---
 asl/meta.hpp | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

(limited to 'asl/meta.hpp')

diff --git a/asl/meta.hpp b/asl/meta.hpp
index 9909be6..a464e36 100644
--- a/asl/meta.hpp
+++ b/asl/meta.hpp
@@ -117,6 +117,8 @@ template<typename T> struct _is_ref_helper<T&>  { static constexpr bool l = true
 template<typename T> struct _is_ref_helper<T&&> { static constexpr bool l = false; static constexpr bool r = true;  };
 
 template<typename T> concept is_ref = _is_ref_helper<T>::l || _is_ref_helper<T>::r;
+template<typename T> concept is_rref = _is_ref_helper<T>::r;
+template<typename T> concept is_lref = _is_ref_helper<T>::l;
 
 template<typename T> struct _is_ptr_helper     : false_type {};
 template<typename T> struct _is_ptr_helper<T*> : true_type {};
@@ -218,4 +220,29 @@ concept has_niche = constructible_from<T, niche_t> && equality_comparable_with<T
 template<typename T>
 concept is_niche = same_as<un_cvref_t<T>, niche_t>;
 
+template<typename T, typename U>
+concept _derefs_with_indirection_as = requires(T& t)
+{
+    *t;
+    requires convertible_from<U&, decltype(*t)>;
+};
+
+template<typename T, typename U>
+concept _derefs_reference_as = is_ref<T> && convertible_from<U&, T>;
+
+template<typename T, typename U>
+concept _derefs_value_as = !is_ref<T> && convertible_from<U&, T&>;
+
+template<typename U, _derefs_with_indirection_as<U> T>
+constexpr U& deref(T&& t) { return static_cast<U&>(*t); }
+
+template<typename U, _derefs_reference_as<U> T>
+constexpr U& deref(T&& t) { return static_cast<U&>(t); }
+
+template<typename U, _derefs_value_as<U> T>
+constexpr U& deref(T&& t) { return static_cast<U&>(t); }
+
+template<typename T, typename U>
+concept derefs_as = _derefs_with_indirection_as<T, U> || _derefs_reference_as<T, U> || _derefs_value_as<T, U>;
+
 } // namespace asl
-- 
cgit