Add yk::hash_combine

yaito3014 · Aug 22, 2024 · d08bec4 · d08bec4
1 parent 7d1c750
commit d08bec4
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Showing 3 changed files with 40 additions and 3 deletions.
diff --git a/include/yk/util/hash/hash.hpp b/include/yk/util/hash/hash.hpp
@@ -1,6 +1,8 @@
 #ifndef YK_UTIL_HASH_HASH_HPP
 #define YK_UTIL_HASH_HASH_HPP
 
+#define YK_PP_REQUIRE_SEMICOLON static_assert(true)
+
 #define YK_ADAPT_HASH(ns, type, param, hash_stmt)                                               \
   namespace std {                                                                               \
   template <>                                                                                   \
@@ -15,7 +17,8 @@
   {                                                                                             \
     return ::yk::hash_value_for(value);                                                         \
   }                                                                                             \
-  } /* ns */
+  } /* ns */                                                                                    \
+  YK_PP_REQUIRE_SEMICOLON
 
 #define YK_PP_EXPAND(...) __VA_ARGS__
 #define YK_PP_REMOVE_PAREN(expr) YK_PP_EXPAND expr
@@ -35,6 +38,7 @@
   {                                                                                                                               \
     return ::yk::hash_value_for(value);                                                                                           \
   }                                                                                                                               \
-  } /* ns */
+  } /* ns */                                                                                                                      \
+  YK_PP_REQUIRE_SEMICOLON
 
 #endif  // YK_UTIL_HASH_HASH_HPP
diff --git a/include/yk/util/hash/hash_combine.hpp b/include/yk/util/hash/hash_combine.hpp
@@ -0,0 +1,20 @@
+#ifndef YK_UTIL_HASH_HASH_COMBINE_HPP
+#define YK_UTIL_HASH_HASH_COMBINE_HPP
+
+#include <boost/container_hash/hash.hpp>
+
+#include <cstddef>
+
+namespace yk {
+
+template <class T, class... Rest>
+[[nodiscard]] constexpr std::size_t hash_combine(T const& first_arg, Rest const&... rest) noexcept /* strengthened */
+{
+  std::size_t seed = hash_value(first_arg);
+  (boost::hash_combine(seed, hash_value(rest)), ...);
+  return seed;
+}
+
+}  // namespace yk
+
+#endif  // YK_HASH_HASH_COMBINE_HPP
diff --git a/test/test.cpp b/test/test.cpp
@@ -5,6 +5,7 @@
 #include "yk/util/forward_like.hpp"
 #include "yk/util/hash.hpp"
 #include "yk/util/hash/boost.hpp"
+#include "yk/util/hash/hash_combine.hpp"
 #include "yk/util/pack_indexing.hpp"
 #include "yk/util/reverse.hpp"
 #include "yk/util/specialization_of.hpp"
@@ -46,9 +47,14 @@ struct S {
   int val;
 };
 
+struct MultiS {
+  int a, b;
+};
+
 }  // namespace hash_test
 
-YK_ADAPT_HASH_TEMPLATE(hash_test, (S<T, Ts...>), val, { return val.val; }, class T, class... Ts)
+YK_ADAPT_HASH_TEMPLATE(hash_test, (S<T, Ts...>), val, { return val.val; }, class T, class... Ts);
+YK_ADAPT_HASH(hash_test, MultiS, val, { return yk::hash_combine(val.a, val.b); });
 
 BOOST_AUTO_TEST_SUITE(yk_util)
 
@@ -238,6 +244,13 @@ BOOST_AUTO_TEST_CASE(Hash) {
   hash_test::S<int, double> s{42};
   BOOST_TEST(yk::hash_value_for(s) == yk::hash_value_for(42));
   BOOST_TEST(hash_value(s) == yk::hash_value_for(42));  // call hash_value by ADL
+
+  {
+    hash_test::MultiS s{334, 314151765};
+    std::size_t seed = yk::hash_value_for(s.a);
+    boost::hash_combine(seed, yk::hash_value_for(s.b));
+    BOOST_TEST(hash_value(s) == seed);
+  }
 }
 
 BOOST_AUTO_TEST_SUITE_END()  // yk_util