alloc: add base and offset methods

alloc/dynamic.hpp

@@ -64,6 +64,16 @@ namespace util { namespace alloc {
             return m_child->deallocate (ptr, bytes, alignment);
         }
 
+        void*
+        base (void)
+        {
+            return m_child->base ();
+        }
+
+        size_t
+        offset (const void *ptr) const
+        { return m_child->offset (ptr); }
+
         void reset (void) { m_child->reset (); }
 
         // capacity queries
@@ -74,15 +84,15 @@ namespace util { namespace alloc {
     private:
         // Internal base for arbitrary allocator types. Necessary for
         // type ellision in super-client classes.
-        class base {
+        class interface {
         public:
-            base () = default;
-            base (const base&) = delete;
-            base (base&&) = delete;
-            base& operator= (const base&) = delete;
-            base& operator= (base&&) = delete;
+            interface () = default;
+            interface (const interface&) = delete;
+            interface (interface&&) = delete;
+            interface& operator= (const interface&) = delete;
+            interface& operator= (interface&&) = delete;
 
-            virtual ~base () { ; }
+            virtual ~interface () { ; }
 
             // allocation management
             virtual void*
@@ -94,6 +104,9 @@ namespace util { namespace alloc {
                         size_t bytes,
                         size_t alignment = DEFAULT_ALIGNMENT) = 0;
 
+            virtual void* base (void) = 0;
+            virtual size_t offset (const void*) const = 0;
+
             virtual void reset (void) = 0;
 
             // capacity queries
@@ -104,11 +117,11 @@ namespace util { namespace alloc {
 
 
         template <typename T>
-        class child final : public base {
+        class child final : public interface {
         public:
             template <typename ...Args>
             child (Args &&...args):
-                base (),
+                interface (),
                 m_target (std::forward<Args> (args)...)
             { ; }
 
@@ -128,6 +141,18 @@ namespace util { namespace alloc {
                 m_target.deallocate (ptr, bytes, alignment);
             }
 
+            void *
+            base (void)
+            {
+                return m_target.base ();
+            }
+
+            size_t
+            offset (const void *ptr) const
+            {
+                return m_target.offset (ptr);
+            }
+
             void reset (void) override
             { m_target.reset (); }
 
@@ -141,11 +166,11 @@ namespace util { namespace alloc {
         };
 
 
-        dynamic (std::unique_ptr<base> _child):
+        dynamic (std::unique_ptr<interface> _child):
             m_child (std::move (_child))
         { ; }
 
-        std::unique_ptr<base> m_child;
+        std::unique_ptr<interface> m_child;
     };
 } }
 

alloc/linear.cpp

@@ -60,6 +60,25 @@ linear::deallocate (void *ptr, size_t bytes, size_t alignment)
 }
 
 
+//-----------------------------------------------------------------------------
+void*
+linear::base (void)
+{
+    return m_begin;
+}
+
+
+//-----------------------------------------------------------------------------
+size_t
+linear::offset (const void *_ptr) const
+{
+    auto ptr = reinterpret_cast<const char*> (_ptr);
+
+    CHECK_GE (ptr, m_begin);
+    return ptr - m_begin;
+}
+
+
 ///////////////////////////////////////////////////////////////////////////////
 void
 linear::reset (void)

alloc/linear.hpp

@@ -33,6 +33,8 @@ namespace util { namespace alloc {
 
         void* allocate (size_t bytes, size_t alignment = alignof (std::max_align_t));
         void  deallocate (void *ptr, size_t bytes, size_t alignment = alignof (std::max_align_t));
+        void* base (void);
+        size_t offset (const void*) const;
 
         void reset (void);
 

alloc/null.hpp

@@ -29,6 +29,9 @@ namespace util { namespace alloc {
         void* allocate (size_t bytes, size_t align = alignof (std::max_align_t));
         void deallocate (void *ptr, size_t bytes, size_t align = alignof (std::max_align_t));
 
+        constexpr void* base (void) { return nullptr; }
+        constexpr size_t offset (const void*) const { return 0; }
+
         void reset (void) { ; }
 
         constexpr size_t capacity (void) const { return 0u; }

alloc/stack.cpp

@@ -94,6 +94,25 @@ stack::deallocate (void *_ptr, size_t bytes, size_t alignment)
 }
 
 
+//-----------------------------------------------------------------------------
+void*
+stack::base (void)
+{
+    return m_begin;
+}
+
+
+//-----------------------------------------------------------------------------
+size_t
+stack::offset (const void *_ptr) const
+{
+    auto ptr = reinterpret_cast<const char*> (_ptr);
+
+    CHECK_GE (ptr, m_begin);
+    return ptr - m_begin;
+}
+
+
 //-----------------------------------------------------------------------------
 void
 stack::reset (void)

alloc/stack.hpp

@@ -36,6 +36,8 @@ namespace util { namespace alloc {
         //[[gnu::alloc_align (2), gnu::alloc_size (1), gnu::returns_nonnull, gnu::warn_unused_result]
         void *allocate  (size_t bytes, size_t alignment = alignof (std::max_align_t));
         void deallocate (void *ptr, size_t bytes, size_t alignment = alignof (std::max_align_t));
+        void* base (void);
+        size_t offset (const void*) const;
 
         void reset (void);
 

test/alloc/linear.cpp

@@ -12,6 +12,8 @@ main (void)
     alignas (std::max_align_t) char memory[BUFFER_SIZE];
     util::alloc::linear store (std::begin (memory), std::end (memory));
 
+    tap.expect_eq (store.base (), std::begin (memory), "base pointers match");
+    tap.expect_eq (store.offset (std::begin (memory)), 0u, "base offset is 0");
     tap.expect_eq (store.capacity (), BUFFER_SIZE, "bytes capacity matches");
 
     tap.expect_throw<std::bad_alloc> (

test/alloc/stack.cpp

@@ -34,6 +34,8 @@ main (void)
 
     util::alloc::stack store (memory, memory + BUFFER_AVAILABLE);
 
+    tap.expect_eq (store.base (), std::begin (memory), "base pointers match");
+    tap.expect_eq (store.offset (std::begin (memory)), 0u, "base offset is 0");
     tap.expect_eq (store.capacity (), BUFFER_AVAILABLE, "bytes capacity matches");
 
     // larger than total allocations should throw