From 3c1fec6058de8c34e3e5e0471ed3ef03b7cf1b81 Mon Sep 17 00:00:00 2001
From: mutouyun <orz@orzz.org>
Date: Sat, 27 May 2023 16:18:18 +0800
Subject: [PATCH] upd: [imp] span

---
 include/libconcur/queue.h  |  2 +-
 include/libimp/span.h      | 15 +++++++++++++++
 test/imp/test_imp_span.cpp | 12 ++++++++++++
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/include/libconcur/queue.h b/include/libconcur/queue.h
index 25cc1ec..32bc9b8 100644
--- a/include/libconcur/queue.h
+++ b/include/libconcur/queue.h
@@ -43,7 +43,7 @@ private:
     data(U &&model) noexcept
       : header_(std::forward<U>(model)) {
       auto elements = this->elements();
-      decltype(elements)::size_type i = 0;
+      typename decltype(elements)::size_type i = 0;
       LIBIMP_TRY {
         for (; i < elements.size(); ++i) {
           (void)::LIBIMP::construct<element<value_type>>(&elements[i]);
diff --git a/include/libimp/span.h b/include/libimp/span.h
index 814b584..c05f79b 100644
--- a/include/libimp/span.h
+++ b/include/libimp/span.h
@@ -19,6 +19,8 @@
 
 #include "libimp/def.h"
 #include "libimp/detect_plat.h"
+#include "libimp/countof.h"
+#include "libimp/dataof.h"
 
 #if defined(LIBIMP_CPP_20) && defined(__cpp_lib_span)
 #include <span>
@@ -56,6 +58,10 @@ using is_sized_sentinel_for =
   typename std::enable_if<std::is_convertible<decltype(std::declval<S>() - std::declval<I>()), 
                           std::ptrdiff_t>::value>::type;
 
+template <typename T>
+using is_continuous_container =
+  decltype(dataof(std::declval<T>()), countof(std::declval<T>()));
+
 /// \brief Obtain the address represented by p 
 ///        without forming a reference to the object pointed to by p.
 /// \see https://en.cppreference.com/w/cpp/memory/to_address
@@ -119,6 +125,15 @@ public:
     : ptr_   (detail::to_address(first))
     , extent_(static_cast<size_type>(last - first)) {}
 
+  template <typename U,
+            typename = detail::is_continuous_container<U>,
+            typename = detail::is_array_convertible<std::remove_pointer_t<
+              decltype(dataof(std::declval<U>()))>, element_type>>
+  constexpr span(U &&u) noexcept(noexcept(dataof (std::forward<U>(u)), 
+                                          countof(std::forward<U>(u))))
+    : ptr_   (dataof (std::forward<U>(u)))
+    , extent_(countof(std::forward<U>(u))) {}
+
   template <typename U, std::size_t E,
             typename = detail::is_array_convertible<U, element_type>>
   constexpr span(U (&arr)[E]) noexcept
diff --git a/test/imp/test_imp_span.cpp b/test/imp/test_imp_span.cpp
index 0304f7e..dd1f717 100644
--- a/test/imp/test_imp_span.cpp
+++ b/test/imp/test_imp_span.cpp
@@ -60,4 +60,16 @@ TEST(span, span) {
 TEST(span, fmt) {
   EXPECT_EQ(imp::fmt(imp::span<int>{}), "");
   EXPECT_EQ(imp::fmt(imp::make_span({1, 3, 2, 4, 5, 6, 7})), "1 3 2 4 5 6 7");
+}
+
+TEST(span, construct) {
+  struct test_imp_span_construct {
+    /* data */
+    int  size() const noexcept { return sizeof(this); }
+    auto Data() const noexcept { return this; }
+  } d1;
+  imp::span<test_imp_span_construct const> sp {d1};
+  // imp::span<int const> spp {d1};
+  EXPECT_EQ(sp.size(), d1.size());
+  EXPECT_EQ(sp.data(), d1.Data());
 }
\ No newline at end of file