Implement boost::hash_unordered_range

include/boost/container_hash/hash.hpp

@@ -637,22 +637,54 @@ namespace boost
     //
 
     template <class It>
-    inline std::size_t hash_range(It first, It last)
+    inline void hash_range( std::size_t& seed, It first, It last )
+    {
+        for( ; first != last; ++first )
+        {
+            hash_combine<typename std::iterator_traits<It>::value_type>( seed, *first );
+        }
+    }
+
+    template <class It>
+    inline std::size_t hash_range( It first, It last )
     {
         std::size_t seed = 0;
 
-        hash_range(seed, first, last);
+        hash_range( seed, first, last );
 
         return seed;
     }
 
+    //
+    // boost::hash_unordered_range
+    //
+
     template <class It>
-    inline void hash_range(std::size_t& seed, It first, It last)
+    inline void hash_unordered_range( std::size_t& seed, It first, It last )
     {
-        for(; first != last; ++first)
+        std::size_t r = 0;
+        std::size_t const s2( seed );
+
+        for( ; first != last; ++first )
         {
-            hash_combine<typename std::iterator_traits<It>::value_type>(seed, *first);
+            std::size_t s3( s2 );
+
+            hash_combine<typename std::iterator_traits<It>::value_type>( s3, *first );
+
+            r += s3;
         }
+
+        seed += r;
+    }
+
+    template <class It>
+    inline std::size_t hash_unordered_range( It first, It last )
+    {
+        std::size_t seed = 0;
+
+        hash_unordered_range( seed, first, last );
+
+        return seed;
     }
 
     //

include/boost/container_hash/hash_fwd.hpp

@@ -24,11 +24,11 @@ template<class T> struct hash;
 
 template<class T> void hash_combine( std::size_t& seed, T const& v );
 
-template<class It> std::size_t hash_range( It, It );
 template<class It> void hash_range( std::size_t&, It, It );
+template<class It> std::size_t hash_range( It, It );
 
-template<class It> std::size_t hash_unordered_range( It, It );
 template<class It> void hash_unordered_range( std::size_t&, It, It );
+template<class It> std::size_t hash_unordered_range( It, It );
 
 } // namespace boost
 

test/Jamfile.v2

@@ -89,3 +89,5 @@ run hash_string_test4.cpp ;
 
 run hash_multiset_test.cpp ;
 run hash_multimap_test.cpp ;
+
+run hash_unordered_range_test.cpp ;

test/hash_unordered_range_test.cpp

@@ -0,0 +1,33 @@
+// Copyright 2021, 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/container_hash/hash.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <algorithm>
+#include <vector>
+
+int main()
+{
+    int const N = 16;
+
+    std::vector<int> v;
+
+    for( int i = 0; i < N; ++i )
+    {
+        v.push_back( i );
+    }
+
+    std::size_t h0 = boost::hash_unordered_range( v.begin(), v.end() );
+
+    int const M = 256;
+
+    for( int i = 0; i < M; ++i )
+    {
+        std::next_permutation( v.begin(), v.end() );
+        std::size_t h1 = boost::hash_unordered_range( v.begin(), v.end() );
+        BOOST_TEST_EQ( h0, h1 );
+    }
+
+    return boost::report_errors();
+}