From 8def2618cba3c471f22d6b1bdd40c5e26484c478 Mon Sep 17 00:00:00 2001
From: MikeGitb <MikeGitb@users.noreply.github.com>
Date: Sat, 19 Nov 2016 03:15:37 +0100
Subject: [PATCH] Add overload for as_bytes taking a single object

---
 gsl/span             | 13 +++++++++++++
 tests/span_tests.cpp | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/gsl/span b/gsl/span
index aec826a..0651329 100644
--- a/gsl/span
+++ b/gsl/span
@@ -670,6 +670,19 @@ span<typename Ptr::element_type>
 make_span(Ptr& cont)
 { return span<typename Ptr::element_type>(cont); }
 
+template <class T, class = std::enable_if_t<std::is_pod<T>::value>>
+span<const byte, sizeof(T)>
+as_bytes(const T& e) noexcept
+{
+    return{ reinterpret_cast<const byte*>(&e),sizeof(T) };
+}
+
+template <class T, class = std::enable_if_t<std::is_trivially_copyable<T>::value>>
+span<byte, sizeof(T)>
+as_writeable_bytes(T& e) noexcept
+{
+    return{ reinterpret_cast<byte*>(&e),sizeof(T) };
+}
 
 // Specialization of gsl::at for span
 template <class ElementType, std::ptrdiff_t Extent>
diff --git a/tests/span_tests.cpp b/tests/span_tests.cpp
index 9669464..d622eb7 100644
--- a/tests/span_tests.cpp
+++ b/tests/span_tests.cpp
@@ -1444,6 +1444,47 @@ SUITE(span_tests)
         }
     }
 
+    struct MyTriviallyCopyableType {
+        MyTriviallyCopyableType(int i) :a(i), b(static_cast<char>(i)), c(i) {}
+        int a;
+        char b;
+        double c;
+        friend bool operator==(MyTriviallyCopyableType& l, MyTriviallyCopyableType& r) { return l.a == r.a && l.b == r.b && l.c == r.c; }
+    };
+
+    TEST(pod_as_bytes)
+    {
+        {
+            double src{ 10.5 };
+            double dst{};
+            auto src_b = as_bytes(src);
+            auto dst_b = as_writeable_bytes(dst);
+            std::copy(src_b.begin(), src_b.end(), dst_b.begin());
+            CHECK(std::equal(src_b.begin(), src_b.end(), dst_b.begin()));
+            CHECK(src == dst);
+        }
+        {
+            std::array<int, 10> src{ 1,2,3,4,5,6,7,8,9,10 };
+            std::array<int, 10> dst{};
+            auto src_b = as_bytes(src);
+            auto dst_b = as_writeable_bytes(dst);
+            std::copy(src_b.begin(), src_b.end(), dst_b.begin());
+            CHECK(std::equal(src_b.begin(), src_b.end(), dst_b.begin()));
+            CHECK(src == dst);
+        }
+#ifdef CONFIRM_COMPILATION_ERRORS
+        {
+            MyTC_t src{ 5 };
+            MyTC_t dst{ 1 };
+            auto src_b = as_bytes(src);
+            auto dst_b = as_writeable_bytes(dst);
+            std::copy(src_b.begin(), src_b.end(), dst_b.begin());
+            CHECK(std::equal(src_b.begin(), src_b.end(), dst_b.begin()));
+            CHECK(src == dst);
+        }
+#endif
+    }
+
     TEST(fixed_size_conversions)
     {
         int arr[] = {1, 2, 3, 4};