From bee78ab4c63bcc1eca1603e5a3dbb9fd06dfd41d Mon Sep 17 00:00:00 2001
From: jwellbelove <john.wellbelove@raymarine.com>
Date: Fri, 30 Sep 2016 14:38:40 +0100
Subject: [PATCH] Initial implementation of intrusive stack. Uncompiled &
 untested.

---
 src/intrusive_stack.h | 138 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 138 insertions(+)
 create mode 100644 src/intrusive_stack.h

diff --git a/src/intrusive_stack.h b/src/intrusive_stack.h
new file mode 100644
index 00000000..025dac89
--- /dev/null
+++ b/src/intrusive_stack.h
@@ -0,0 +1,138 @@
+///\file
+
+/******************************************************************************
+The MIT License(MIT)
+
+Embedded Template Library.
+https://github.com/ETLCPP/etl
+http://www.etlcpp.com
+
+Copyright(c) 2016 jwellbelove
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files(the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions :
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+******************************************************************************/
+
+#ifndef __ETL_INTRUSIVE_STACK__
+#define __ETL_INTRUSIVE_STACK__
+
+#include <stddef.h>
+
+#include "type_traits.h"
+#include "parameter_type.h"
+#include "error_handler.h"
+
+namespace etl
+{
+  //***************************************************************************
+  ///\ingroup stack
+  /// An intrusive stack. Stores elements derived from etl::forward_link
+  /// \warning This stack cannot be used for concurrent access from multiple threads.
+  /// \tparam TValue The type of value that the stack holds.
+  /// \tparam TLink  The link type that the value is derived from.
+  //***************************************************************************
+  template <typename TValue, typename TLink = etl::bidirectional_link<0> >
+  class intrusive_stack
+  {
+  public:
+
+    // Node typedef.
+    typedef TLink             link_type;
+
+    // STL style typedefs.
+    typedef TValue            value_type;
+    typedef value_type*       pointer;
+    typedef const value_type* const_pointer;
+    typedef value_type&       reference;
+    typedef const value_type& const_reference;
+    typedef size_t            size_type;
+
+  public:
+
+    //*************************************************************************
+    /// Constructor
+    //*************************************************************************
+    intrusive_stack()
+    : p_top(&base)
+    {
+
+    }
+
+    //*************************************************************************
+    /// Gets a reference to the value at the top of the stack.
+    /// Undefined behaviour if the stack is empty.
+    /// \return A reference to the value at the top of the stack.
+    //*************************************************************************
+    reference top()
+    {
+      return *p_top;
+    }
+
+    //*************************************************************************
+    /// Adds a value to the stack.
+    ///\param value The value to push to the stack.
+    //*************************************************************************
+    void push(link_type& value)
+    {
+      etl::link(p_top, value);
+      p_top = &value;
+    }
+
+    //*************************************************************************
+    /// Gets a const reference to the value at the top of the stack.<br>
+    /// \return A const reference to the value at the top of the stack.
+    //*************************************************************************
+    const_reference top() const
+    {
+      return *p_top;
+    }
+
+    //*************************************************************************
+    /// Clears the stack to the empty state.
+    //*************************************************************************
+    void clear()
+    {
+        unlink(base, *p_top);
+    }
+
+    //*************************************************************************
+    /// Removes the oldest item from the top of the stack.
+    /// Does nothing if the stack is already empty.
+    //*************************************************************************
+    void pop()
+    {
+#if defined(ETL_CHECK_PUSH_POP)
+      ETL_ASSERT(p_top != &base, ETL_ERROR(intrusive_stack_empty));
+#endif
+      link_type* p_previous = p_top->etl_previous;
+      unlink(p_top);
+      p_top = p_previous;
+    }
+
+  private:
+
+    // Disable copy construction and assignment.
+    intrusive_stack(const intrusive_stack&);
+    intrusive_stack& operator = (const intrusive_stack& rhs)
+
+    link_type  base;  // The base of the stack.
+    link_type* p_top; // The current top of the stack.
+  };
+}
+
+#endif