diff --git a/device_memory.cpp b/device_memory.cpp
index 7ad0741..26dd871 100644
--- a/device_memory.cpp
+++ b/device_memory.cpp
@@ -23,29 +23,86 @@ using cruft::vk::device_memory;
 
 
 ///////////////////////////////////////////////////////////////////////////////
-void*
-device_memory::map (const device &dev,
-                    VkDeviceSize offset,
-                    VkDeviceSize size,
-                    VkMemoryMapFlags flags)
+cruft::vk::map_t::~map_t ()
 {
-    void *res;
-
-    auto err = vkMapMemory (dev.native (), native (), offset, size, flags, &res);
-    error::try_code (err);
-
-    return res;
+    CHECK_ZERO (cbegin ());
+    CHECK_ZERO (cend   ());
 }
 
 
 //-----------------------------------------------------------------------------
 void
-device_memory::unmap (const device &dev)
+cruft::vk::map_t::destroy (device &_device, device_memory &_memory)
 {
-    vkUnmapMemory (dev.native (), native ());
+    CHECK_NEZ (cbegin ());
+    CHECK_NEZ (cend   ());
+
+    vkUnmapMemory (_device.native (), _memory.native ());
+
+    *this = {nullptr, nullptr};
 }
 
 
+
+///////////////////////////////////////////////////////////////////////////////
+cruft::vk::map_t
+cruft::vk::map (device &_device, device_memory &_memory, int len)
+{
+    void *ptr = nullptr;
+    auto err = vkMapMemory (_device.native (), _memory.native (), 0, len, 0, &ptr);
+    error::try_code (err);
+
+    return {
+        reinterpret_cast<std::byte*> (ptr),
+        reinterpret_cast<std::byte*> (ptr) + len
+    };
+}
+
+
+
+///////////////////////////////////////////////////////////////////////////////
+cruft::vk::owned_map_t::owned_map_t (owned_ptr<device_memory> &_memory,
+                                     std::byte *first,
+                                     std::byte *last):
+    map_t (first, last),
+    m_memory (_memory)
+{ ; }
+
+
+//-----------------------------------------------------------------------------
+cruft::vk::owned_map_t::~owned_map_t ()
+{
+    destroy ();
+}
+
+
+//-----------------------------------------------------------------------------
+void
+cruft::vk::owned_map_t::destroy ()
+{
+    if (cbegin ())
+        map_t::destroy (m_memory.owner (), *m_memory);
+}
+
+
+
+///////////////////////////////////////////////////////////////////////////////
+cruft::vk::owned_map_t
+cruft::vk::map (owned_ptr<device_memory> &_memory, int len)
+{
+    void *ptr = nullptr;
+    auto err = vkMapMemory (_memory.owner ().native (), _memory->native (), 0, len, 0, &ptr);
+    error::try_code (err);
+
+    return owned_map_t {
+        _memory,
+        reinterpret_cast<std::byte*> (ptr),
+        reinterpret_cast<std::byte*> (ptr) + len
+    };
+};
+
+
+
 ///////////////////////////////////////////////////////////////////////////////
 VkDeviceSize
 device_memory::commitment (const device &dev) const
diff --git a/device_memory.hpp b/device_memory.hpp
index 0e29f35..90ade3d 100644
--- a/device_memory.hpp
+++ b/device_memory.hpp
@@ -21,15 +21,46 @@
 #include "./object.hpp"
 #include "./fwd.hpp"
 
+#include <cruft/util/view.hpp>
+
+#include <cstddef>
+
+
 namespace cruft::vk {
+    ///////////////////////////////////////////////////////////////////////////
+    struct map_t : public util::view<std::byte*> {
+    public:
+        using view::view;
+
+        ~map_t ();
+
+        void destroy (device&, device_memory&);
+    };
+
+
+    //-------------------------------------------------------------------------
+    map_t map (device&, device_memory&, int len);
+
+
+    //////////////////////////////////////////////////////////////////////////
+    struct owned_map_t : public map_t {
+        owned_map_t (owned_ptr<device_memory>&, std::byte *first, std::byte *last);
+        ~owned_map_t ();
+
+        void destroy (void);
+
+    private:
+        owned_ptr<device_memory> &m_memory;
+    };
+
+
+    owned_map_t map (owned_ptr<device_memory>&, int len);
+
+
+    ///////////////////////////////////////////////////////////////////////////
     struct device_memory : public owned<device_memory,device> {
         using owned::owned;
 
-        void* map (const device&,
-                   VkDeviceSize offset,
-                   VkDeviceSize size,
-                   VkMemoryMapFlags flags);
-
         void unmap (const device&);
 
         VkDeviceSize commitment (const device&) const;
diff --git a/object.hpp b/object.hpp
index 805c27d..07e948b 100644
--- a/object.hpp
+++ b/object.hpp
@@ -187,13 +187,21 @@ namespace cruft::vk {
         const SelfT& get (void) const& { return m_self; }
         SelfT& get (void)& { return m_self; }
 
-        SelfT& operator* ()&
+        SelfT& operator* ()& noexcept
         { return m_self; }
 
         SelfT*
-        operator-> ()&
+        operator-> ()& noexcept
         { return &m_self; }
 
+        auto&
+        owner (void)& noexcept
+        { return m_owner; }
+
+        const auto&
+        owner (void) const& noexcept
+        { return m_owner; }
+
     private:
         SelfT m_self;
         owner_t<SelfT> &m_owner;
diff --git a/tools/hello.cpp b/tools/hello.cpp
index 622b822..f5fcbb2 100644
--- a/tools/hello.cpp
+++ b/tools/hello.cpp
@@ -96,6 +96,7 @@ main (void)
        "VK_LAYER_LUNARG_standard_validation"
     };
 
+    //-------------------------------------------------------------------------
     cruft::vk::instance instance (
         util::make_view (layers),
         util::make_view (extensions.data (), extensions.data () + extensions.size ())
@@ -103,23 +104,30 @@ main (void)
 
     load_traits (instance);
 
-    auto callback = [&instance] () {
-        VkDebugReportCallbackCreateInfoEXT debug_info {};
-        debug_info.sType = cruft::vk::structure_type_v<VkDebugReportCallbackCreateInfoEXT>;
-        debug_info.flags = //VK_DEBUG_REPORT_INFORMATION_BIT_EXT |
-                           VK_DEBUG_REPORT_WARNING_BIT_EXT |
-                           VK_DEBUG_REPORT_PERFORMANCE_WARNING_BIT_EXT |
-                           VK_DEBUG_REPORT_ERROR_BIT_EXT
-                           //VK_DEBUG_REPORT_DEBUG_BIT_EXT |
-                           ;
-        debug_info.pfnCallback = vk_debug_callback;
 
-        return cruft::vk::make_owned<cruft::vk::debug_report> (instance, &debug_info, nullptr);
-    } ();
+    //-------------------------------------------------------------------------
+    VkDebugReportCallbackCreateInfoEXT debug_info {};
+    debug_info.sType = cruft::vk::structure_type_v<VkDebugReportCallbackCreateInfoEXT>;
+    debug_info.flags =
+        //VK_DEBUG_REPORT_INFORMATION_BIT_EXT |
+        VK_DEBUG_REPORT_WARNING_BIT_EXT |
+        VK_DEBUG_REPORT_PERFORMANCE_WARNING_BIT_EXT |
+        VK_DEBUG_REPORT_ERROR_BIT_EXT
+        //VK_DEBUG_REPORT_DEBUG_BIT_EXT |
+        ;
 
+    debug_info.pfnCallback = vk_debug_callback;
+    auto debug_callback = cruft::vk::make_owned<cruft::vk::debug_report> (
+        instance, &debug_info, nullptr
+    );
+
+
+    //-------------------------------------------------------------------------
     auto pdevices = cruft::vk::physical_device::find (instance);
     auto &pdevice = pdevices[0];
 
+
+    //-------------------------------------------------------------------------
     auto surface = cruft::vk::make_owned<cruft::vk::surface> (
         cruft::vk::error::try_query (
             glfwCreateWindowSurface, instance.native (), window, nullptr
@@ -192,6 +200,8 @@ main (void)
 
     cruft::vk::device ldevice (pdevice, device_info);
 
+
+    //-------------------------------------------------------------------------
 #if 0
     VkSurfaceFormatKHR surface_format =
         (surface_formats.size () == 1 && surface_formats[0].format == VK_FORMAT_UNDEFINED)
@@ -238,17 +248,13 @@ main (void)
 
     auto swapchain = cruft::vk::make_owned<cruft::vk::swapchain> (ldevice, &swap_create_info, nullptr);
 
-    uint32_t swap_image_count = 0;
-    cruft::vk::error::try_code (
-        vkGetSwapchainImagesKHR (ldevice.native (), swapchain->native (), &swap_image_count, nullptr)
-    );
     std::vector<VkImage> swap_images = cruft::vk::error::try_values (
         vkGetSwapchainImagesKHR, ldevice.native (), swapchain->native ()
     );
 
     using image_view_ptr = cruft::vk::owned_ptr<cruft::vk::image_view>;
     std::vector<image_view_ptr> swap_image_views;
-    swap_image_views.reserve (swap_image_count);
+    swap_image_views.reserve (std::size (swap_images));
     std::transform (
         std::cbegin (swap_images), std::cend (swap_images),
         std::back_inserter (swap_image_views),
@@ -317,11 +323,10 @@ main (void)
         vkBindBufferMemory (ldevice.native (), vertex_buffer->native (), vertex_memory->native (), 0)
     );
 
-    auto data = cruft::vk::error::try_query (
-        vkMapMemory, ldevice.native (), vertex_memory->native (), 0, buffer_info.size, 0
-    );
-    memcpy (data, std::data (VERTICES), sizeof (VERTICES));
-    vkUnmapMemory (ldevice.native (), vertex_memory->native ());
+    {
+        auto data = map (vertex_memory, sizeof (VERTICES));
+        memcpy (std::data (data), std::data (VERTICES), sizeof (VERTICES));
+    }
 
     VkPipelineShaderStageCreateInfo vert_stage_info {};
     vert_stage_info.sType = cruft::vk::structure_type_v<VkPipelineShaderStageCreateInfo>;