parallel/stack: add view accessor for underlying data

parallel/stack.hpp

@@ -11,6 +11,7 @@
 #include "../thread/primitive.hpp"
 #include "../debug/assert.hpp"
 #include "../thread/spinlock.hpp"
+#include "../view.hpp"
 
 #include <atomic>
 #include <vector>
@@ -84,6 +85,24 @@ namespace cruft::parallel {
             return true;
         }
 
+        // DO NOT make this enum easier to use. It's supposed to be annoying
+        // so that people don't use it.
+        enum class contract { I_HAVE_LOCKED_THIS_STRUCTURE };
+
+        /// Returns the currently available data.
+        ///
+        /// Data is laid out bottom-to-top of the stack.
+        ///
+        /// DO NOT call this if there are any other potential clients
+        /// accessing the structure as it will not be protected by locks.
+        cruft::view<ValueT*> store (contract)
+        {
+            auto begin = reinterpret_cast<ValueT*> (m_store.data ());
+            auto end   = begin + m_cursor.load ();
+
+            return cruft::view<ValueT*> { begin, end };
+        }
+
     private:
         using index_type = std::size_t;
         using raw_type = std::aligned_storage_t<sizeof(ValueT), alignof(ValueT)>;