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diff --git a/src/utils/string-pool.H b/src/utils/string-pool.H
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+// Copyright (C) 2010, Gabriel Dos Reis.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     - Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//
+//     - Redistributions in binary form must reproduce the above copyright
+//       notice, this list of conditions and the following disclaimer in
+//       the documentation and/or other materials provided with the
+//       distribution.
+//
+//     - Neither the name of The Numerical Algorithms Group Ltd. nor the
+//       names of its contributors may be used to endorse or promote products
+//       derived from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
+// OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef OPENAXIOM_STRING_POOL_INCLUDED
+#define OPENAXIOM_STRING_POOL_INCLUDED
+
+#include <string.h>
+#include "hash-table.H"
+
+// --% Author: Gabriel Dos Reis.
+// --% Description:
+// --%   Basic persistent string facility.
+// --%   A stringpool for allocating long-living string objects.
+
+namespace OpenAxiom {
+   struct StringPool;
+
+   // ----------------
+   // -- StringItem --
+   // ----------------
+   // String data allocated from a stringpool.
+   struct StringItem {
+      const char* begin() const { return text; }
+      const char* end() const { return text + length; }
+      size_t size() const { return length; }
+      bool equal(const char*, size_t) const;
+   protected:
+      const char* text;         // pointer to the byte sequence
+      size_t length;            // number of bytes in this string
+      friend class StringPool;
+      StringItem() : text(), length() { }
+   };
+
+   // ----------------
+   // -- StringPool --
+   // ----------------
+   // A stringpool object is a repository of long-living string objects.
+   // It contains no duplicates, therefore allowing fast string
+   // object comparison for equality.
+   struct StringPool : private BasicHashTable<StringItem> {
+      using BasicHashTable<StringItem>::EntryType;
+
+      StringPool();
+      // Intern a NUL-terminated sequence of characters.
+      EntryType* intern(const char* s) {
+         return intern(s, strlen(s));
+      }
+
+      // Intern a sequence of characters given by its start and length.
+      EntryType* intern(const char*, size_t);
+   private:
+      Memory::Arena<char> strings; // character blub
+      // Allocate a string from the internal arena.
+      const char* make_copy(const char*, size_t);
+   };
+
+   typedef const StringPool::EntryType* BasicString;
+}
+
+#endif  // OPENAXIOM_STRING_POOL_INCLUDED