STL advance / distance.

Change-Id: I9cdf9459f2970def812b1681897fe7d0cdda37ac
Reviewed-on: http://gfw160.austin.ibm.com:8080/gerrit/669
Tested-by: Jenkins Server
Reviewed-by: Douglas R. Gilbert <dgilbert@us.ibm.com>
Reviewed-by: Terry J. Opie <opiet@us.ibm.com>
Reviewed-by: MIKE J. JONES <mjjones@us.ibm.com>
Reviewed-by: A. Patrick Williams III <iawillia@us.ibm.com>

1 files changed, 147 insertions, 0 deletions

diff --git a/src/include/util/impl/iterator.h b/src/include/util/impl/iterator.h
new file mode 100644
index 000000000..de6b445aa
--- /dev/null
+++ b/src/include/util/impl/iterator.h
@@ -0,0 +1,147 @@
+//  IBM_PROLOG_BEGIN_TAG
+//  This is an automatically generated prolog.
+//
+//  $Source: src/include/util/impl/iterator.h $
+//
+//  IBM CONFIDENTIAL
+//
+//  COPYRIGHT International Business Machines Corp. 2012
+//
+//  p1
+//
+//  Object Code Only (OCO) source materials
+//  Licensed Internal Code Source Materials
+//  IBM HostBoot Licensed Internal Code
+//
+//  The source code for this program is not published or other-
+//  wise divested of its trade secrets, irrespective of what has
+//  been deposited with the U.S. Copyright Office.
+//
+//  Origin: 30
+//
+//  IBM_PROLOG_END
+
+#ifndef __UTIL_IMPL_ITERATOR_H
+#define __UTIL_IMPL_ITERATOR_H
+
+/** @file iterator.h
+ *
+ *  Contains the internal implementation details of the stl <iterator> header.
+ */
+
+#include <util/traits/has_plusequals.H>
+#include <util/traits/has_minus.H>
+
+namespace Util
+{
+    namespace __Util_Iterator_Impl
+    {
+
+        /**
+         *  Template definition of an iterator advance functor.
+         */
+        template <typename InputIterator, typename Distance,
+                  bool HasPlusEquals> struct AdvanceImpl;
+
+        /**
+         *  Template specialization of the advance functor for iterators
+         *  which do not support random access.
+         */
+        template <typename InputIterator, typename Distance>
+        struct AdvanceImpl<InputIterator, Distance, false>
+        {
+            static void advance(InputIterator& i, Distance n)
+            {
+                while(n--)
+                    ++i;
+            }
+        };
+
+        /**
+         *  Template specialization of the advance functor for iterators
+         *  which do support random access.
+         */
+        template <typename RandomIterator, typename Distance>
+        struct AdvanceImpl<RandomIterator, Distance, true>
+        {
+            static void advance(RandomIterator& i, Distance n)
+            {
+                i += n;
+            }
+        };
+
+        /**
+         *  Template wrapper function for the iterator advance.
+         *
+         *  Uses the existance of a += operator on the iterator to determine
+         *  if the random-access or non-random-access version should be used.
+         */
+        template <typename InputIterator, typename Distance>
+        void advance(InputIterator& i, Distance n)
+        {
+            AdvanceImpl<InputIterator, Distance,
+                    Util::Traits::has_plusequals<InputIterator,Distance,
+                                                 InputIterator>::value
+                >::advance(i,n);
+        }
+
+        /**
+         *  Template definition of an iterator distance functor.
+         */
+        template <typename InputIterator, typename Distance,
+                  bool HasMinus> struct DistanceImpl;
+
+        /**
+         *  Template specialization of the distance functor for iterators
+         *  which do not support random access.
+         */
+        template <typename InputIterator, typename Distance>
+        struct DistanceImpl<InputIterator, Distance, false>
+        {
+            static Distance distance(InputIterator& first,
+                                     InputIterator& last)
+            {
+                Distance i = 0;
+                while (first != last)
+                {
+                    ++i;
+                    ++first;
+                }
+                return i;
+            }
+        };
+
+        /**
+         *  Template specialization of the distance functor for iterators
+         *  which do support random access.
+         */
+        template <typename RandomIterator, typename Distance>
+        struct DistanceImpl<RandomIterator, Distance, true>
+        {
+            static Distance distance(RandomIterator& first,
+                                     RandomIterator& last)
+            {
+                return last - first;
+            }
+        };
+
+        /**
+         *  Template wrapper function for the iterator distance.
+         *
+         *  Uses the existance of a - operator on the iterator to determine
+         *  if the random-access or non-random-access version should be used.
+         */
+        template <typename InputIterator, typename Distance>
+        Distance distance(InputIterator& first,
+                          InputIterator& last)
+        {
+            return DistanceImpl<InputIterator, Distance,
+                        Util::Traits::has_minus<InputIterator, InputIterator,
+                                                Distance>::value
+                    >::distance(first,last);
+        }
+
+    };
+};
+
+#endif