From 13380aa85d12c1d9d29f557506ec7b6fcd6035e6 Mon Sep 17 00:00:00 2001
From: Mathew Sutcliffe <oktal3700@gmail.com>
Date: Tue, 25 Oct 2016 22:40:22 +0100
Subject: [PATCH] refs #784 Added CMemoTable, a data structure for performing
 memoization.

---
 src/blackmisc/memotable.h | 51 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 src/blackmisc/memotable.h

diff --git a/src/blackmisc/memotable.h b/src/blackmisc/memotable.h
new file mode 100644
index 000000000..d976cc919
--- /dev/null
+++ b/src/blackmisc/memotable.h
@@ -0,0 +1,51 @@
+/* Copyright (C) 2016
+ * swift project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+//! \file
+
+#ifndef BLACKMISC_MEMOTABLE_H
+#define BLACKMISC_MEMOTABLE_H
+
+#include "blackmisc/dictionary.h"
+#include "blackmisc/sequence.h"
+
+namespace BlackMisc
+{
+    /*!
+     * A data memoization pattern useful for compressing JSON representations of containers.
+     */
+    template <typename T>
+    class CMemoTable
+    {
+    public:
+        //! Return the index of a value, inserting it if it is not already in the table.
+        int getIndex(const T &value)
+        {
+            int &index = m_dict[value];
+            if (! index)
+            {
+                m_list.push_back(value);
+                index = m_list.size();
+            }
+            return index - 1;
+        }
+
+        //! Return the values in the table as a flat list.
+        const CSequence<T> &getTable() const
+        {
+            return m_list;
+        }
+
+    private:
+        CSequence<T> m_list;
+        CDictionary<T, int, QMap> m_dict;
+    };
+}
+
+#endif