Rework hashing, use a more extensible framework similar to n3876 proposal

std::hash specialization is a pain to work with, stop using that, and
just specialize a 'size_t hash_value(const T&)' free function.

1 files changed, 57 insertions, 0 deletions

diff --git a/src/hash.hh b/src/hash.hh
new file mode 100644
index 00000000..838fdffa
--- /dev/null
+++ b/src/hash.hh
@@ -0,0 +1,57 @@
+#ifndef hash_hh_INCLUDED
+#define hash_hh_INCLUDED
+
+#include <type_traits>
+#include <functional>
+
+namespace Kakoune
+{
+
+size_t hash_data(const char* data, size_t len);
+
+template<typename Type>
+typename std::enable_if<not std::is_enum<Type>::value, size_t>::type
+hash_value(const Type& val)
+{
+    return std::hash<Type>()(val);
+}
+
+template<typename Type>
+typename std::enable_if<std::is_enum<Type>::value, size_t>::type
+hash_value(const Type& val)
+{
+    return hash_value((typename std::underlying_type<Type>::type)val);
+}
+
+template<typename Type>
+size_t hash_values(Type&& t)
+{
+    return hash_value(std::forward<Type>(t));
+}
+
+template<typename Type, typename... RemainingTypes>
+size_t hash_values(Type&& t, RemainingTypes&&... rt)
+{
+    size_t seed = hash_values(std::forward<RemainingTypes>(rt)...);
+    return seed ^ (hash_value(std::forward<Type>(t)) + 0x9e3779b9 +
+                   (seed << 6) + (seed >> 2));
+}
+
+template<typename T1, typename T2>
+size_t hash_value(const std::pair<T1, T2>& val)
+{
+    return hash_values(val.first, val.second);
+}
+
+template<typename Type>
+struct Hash
+{
+    size_t operator()(const Type& val) const
+    {
+        return hash_value(val);
+    }
+};
+
+}
+
+#endif // hash_hh_INCLUDED