From 6f0d40508286afc8cdd72a0b5f807d5c2a589cfc Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Fri, 4 Jun 2010 16:33:08 +0200
Subject: Initial implementation

---
 odb/shared-ptr/base.txx | 183 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 183 insertions(+)
 create mode 100644 odb/shared-ptr/base.txx

(limited to 'odb/shared-ptr/base.txx')

diff --git a/odb/shared-ptr/base.txx b/odb/shared-ptr/base.txx
new file mode 100644
index 0000000..a8d5f26
--- /dev/null
+++ b/odb/shared-ptr/base.txx
@@ -0,0 +1,183 @@
+// file      : odb/shared-ptr/base.txx
+// author    : Boris Kolpackov <boris@codesynthesis.com>
+// copyright : Copyright (c) 2009-2010 Code Synthesis Tools CC
+// license   : GNU GPL v2; see accompanying LICENSE file
+
+#include <odb/meta/answer.hxx>
+#include <odb/meta/polymorphic-p.hxx>
+
+namespace odb
+{
+  namespace bits
+  {
+    // Support for locating the counter in the memory block.
+    //
+    template <typename X, bool poly = meta::polymorphic_p<X>::r>
+    struct locator;
+
+    template <typename X>
+    struct locator<X, false>
+    {
+      static std::size_t*
+      counter (X* x)
+      {
+        std::size_t* p (reinterpret_cast<std::size_t*> (x));
+
+        if (*(--p) != 0xDEADBEEF)
+          throw not_shared ();
+
+        return --p;
+      }
+    };
+
+    template <typename X>
+    struct locator<X, true>
+    {
+      static std::size_t*
+      counter (X* x)
+      {
+        std::size_t* p (
+          static_cast<std::size_t*> (
+            dynamic_cast<void*> (x)));
+
+        if (*(--p) != 0xDEADBEEF)
+          throw not_shared ();
+
+        return --p;
+      }
+    };
+
+    template <typename X>
+    std::size_t*
+    counter (X const* p)
+    {
+      return bits::locator<X>::counter (const_cast<X*> (p));
+    }
+
+    // Counter type and operations.
+    //
+    meta::no test (...);
+    meta::yes test (shared_base*);
+
+    template <typename X,
+              std::size_t A = sizeof (bits::test (reinterpret_cast<X*> (0)))>
+    struct counter_type;
+
+    template <typename X>
+    struct counter_type<X, sizeof (meta::no)>
+    {
+      typedef X r;
+    };
+
+    template <typename X>
+    struct counter_type<X, sizeof (meta::yes)>
+    {
+      typedef shared_base r;
+    };
+
+    template <typename X, typename Y>
+    struct counter_ops;
+
+    template <typename X>
+    struct counter_ops<X, X>
+    {
+      counter_ops (X const* p) : counter_ (p ? bits::counter (p) : 0) {}
+      counter_ops (counter_ops const& x) : counter_ (x.counter_) {}
+
+      template <typename Y>
+      counter_ops (counter_ops<Y, Y> const& x) : counter_ (x.counter_) {}
+
+      counter_ops&
+      operator= (counter_ops const& x)
+      {
+        counter_ = x.counter_;
+        return *this;
+      }
+
+      template <typename Y>
+      counter_ops&
+      operator= (counter_ops<Y, Y> const& x)
+      {
+        counter_ = x.counter_;
+        return *this;
+      }
+
+      void
+      reset (X const* p)
+      {
+        counter_ = p ? bits::counter (p) : 0;
+      }
+
+      void
+      inc (X*)
+      {
+        (*counter_)++;
+      }
+
+      void
+      dec (X* p)
+      {
+        if (--(*counter_) == 0)
+        {
+          p->~X ();
+          operator delete (counter_); // Counter is the top of the memory block.
+        }
+      }
+
+      std::size_t
+      count (X const*) const
+      {
+        return *counter_;
+      }
+
+      std::size_t* counter_;
+    };
+
+    template <typename Y>
+    struct counter_ops<shared_base, Y>
+    {
+      counter_ops (Y const*) {}
+
+      void
+      reset (Y const*) {}
+
+      void
+      inc (shared_base* p) {p->_inc_ref ();}
+
+      void
+      dec (Y* p)
+      {
+        if (static_cast<shared_base*> (p)->_dec_ref ())
+          delete p;
+      }
+
+      std::size_t
+      count (shared_base const* p) const {return p->_ref_count ();}
+    };
+  }
+
+  template <typename X>
+  inline X*
+  inc_ref (X* p)
+  {
+    bits::counter_ops<typename bits::counter_type<X>::r, X> c (p);
+    c.inc (p);
+    return p;
+  }
+
+  template <typename X>
+  inline void
+  dec_ref (X* p)
+  {
+    bits::counter_ops<typename bits::counter_type<X>::r, X> c (p);
+    c.dec (p);
+  }
+
+  template <typename X>
+  inline std::size_t
+  ref_count (X const* p)
+  {
+    bits::counter_ops<typename bits::counter_type<X>::r, X> c (p);
+    return c.count (p);
+  }
+}
-- 
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