From b286131642a1ae75045be2895c8c3241ebabe85b Mon Sep 17 00:00:00 2001
From: Daniel James <daniel@calamity.org.uk>
Date: Wed, 22 Aug 2012 11:40:27 +0000
Subject: [PATCH] Hash: Quick attempt at supporting enums.
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Thanks to Filip Konvička.


[SVN r80139]
---
 hash/test/Jamfile.v2                   |  1 +
 hash/test/hash_enum_test.cpp           | 59 ++++++++++++++++++++++++++
 include/boost/functional/hash/hash.hpp | 13 ++++++
 3 files changed, 73 insertions(+)
 create mode 100644 hash/test/hash_enum_test.cpp

diff --git a/hash/test/Jamfile.v2 b/hash/test/Jamfile.v2
index 07df1a0..0f41d3e 100644
--- a/hash/test/Jamfile.v2
+++ b/hash/test/Jamfile.v2
@@ -22,6 +22,7 @@ test-suite functional/hash
         [ run hash_fwd_test_1.cpp ]
         [ run hash_fwd_test_2.cpp ]
         [ run hash_number_test.cpp ]
+        [ run hash_enum_test.cpp ]
         [ run hash_pointer_test.cpp ]
         [ run hash_function_pointer_test.cpp ]
         [ run hash_float_test.cpp ]
diff --git a/hash/test/hash_enum_test.cpp b/hash/test/hash_enum_test.cpp
new file mode 100644
index 0000000..d17b608
--- /dev/null
+++ b/hash/test/hash_enum_test.cpp
@@ -0,0 +1,59 @@
+
+// Copyright 2012 Daniel James.
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include "./config.hpp"
+
+#ifdef TEST_STD_INCLUDES
+#  include <functional>
+#else
+#  include <boost/functional/hash.hpp>
+#endif
+
+#include <boost/detail/lightweight_test.hpp>
+
+#include <boost/mpl/assert.hpp>
+#include <boost/type_traits/is_base_and_derived.hpp>
+
+namespace test {
+	enum enum_override { enum_override1, enum_override2 };
+	std::size_t hash_value(enum_override x) { return -896532; }
+
+	enum enum1 { enum1a };
+	enum enum2 { enum2a, enum2b };
+	enum enum3 { enum3a = 574, enum3b };
+	enum enum4 { enum4a = -12574, enum4b };
+}
+
+int main() {
+	boost::hash<test::enum1> hash1;
+	boost::hash<test::enum2> hash2;
+	boost::hash<test::enum3> hash3;
+	boost::hash<test::enum4> hash4;
+	
+	BOOST_TEST(hash1(test::enum1a) == hash1(test::enum1a));
+
+	BOOST_TEST(hash2(test::enum2a) == hash2(test::enum2a));
+	BOOST_TEST(hash2(test::enum2a) != hash2(test::enum2b));
+	BOOST_TEST(hash2(test::enum2b) == hash2(test::enum2b));
+
+	BOOST_TEST(hash3(test::enum3a) == hash3(test::enum3a));
+	BOOST_TEST(hash3(test::enum3a) != hash3(test::enum3b));
+	BOOST_TEST(hash3(test::enum3b) == hash3(test::enum3b));
+
+	BOOST_TEST(hash4(test::enum4a) == hash4(test::enum4a));
+	BOOST_TEST(hash4(test::enum4a) != hash4(test::enum4b));
+	BOOST_TEST(hash4(test::enum4b) == hash4(test::enum4b));
+
+	boost::hash<test::enum_override> hash_override;
+
+	BOOST_TEST(hash_override(test::enum_override1) ==
+		hash_override(test::enum_override1));
+	BOOST_TEST(hash_override(test::enum_override1) ==
+		hash_override(test::enum_override2));
+	BOOST_TEST(hash_override(test::enum_override1) ==
+		hash_override(test::enum_override1));
+
+	return boost::report_errors();
+}
diff --git a/include/boost/functional/hash/hash.hpp b/include/boost/functional/hash/hash.hpp
index c179fab..647fd68 100644
--- a/include/boost/functional/hash/hash.hpp
+++ b/include/boost/functional/hash/hash.hpp
@@ -15,6 +15,8 @@
 #include <boost/functional/hash/detail/hash_float.hpp>
 #include <string>
 #include <boost/limits.hpp>
+#include <boost/type_traits/is_enum.hpp>
+#include <boost/utility/enable_if.hpp>
 
 #if defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
 #include <boost/type_traits/is_pointer.hpp>
@@ -90,6 +92,10 @@ namespace boost
     template <typename T>
     typename boost::hash_detail::ulong_numbers<T>::type hash_value(T);
 
+    template <typename T>
+    typename boost::enable_if<boost::is_enum<T>, std::size_t>::type
+    	hash_value(T);
+
 #if !BOOST_WORKAROUND(__DMC__, <= 0x848)
     template <class T> std::size_t hash_value(T* const&);
 #else
@@ -179,6 +185,13 @@ namespace boost
         return hash_detail::hash_value_unsigned(v);
     }
 
+    template <typename T>
+    typename boost::enable_if<boost::is_enum<T>, std::size_t>::type
+    	hash_value(T v)
+    {
+    	return static_cast<std::size_t>(v);
+    }
+
     // Implementation by Alberto Barbati and Dave Harris.
 #if !BOOST_WORKAROUND(__DMC__, <= 0x848)
     template <class T> std::size_t hash_value(T* const& v)