From d486ea84e57bdabec07fe38a0bb4fb5bdf21848f Mon Sep 17 00:00:00 2001
From: Maxime Coste <mawww@kakoune.org>
Date: Tue, 17 Oct 2017 22:45:17 +0800
Subject: [PATCH] Constexprify various hash functions

---
 src/color.hh  |  2 +-
 src/coord.hh  |  4 ++--
 src/hash.hh   | 21 ++++++++++++++-------
 src/keys.hh   |  2 +-
 src/string.hh |  2 +-
 src/units.hh  |  4 ++--
 6 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/src/color.hh b/src/color.hh
index d8a2fcce..e4ef24cb 100644
--- a/src/color.hh
+++ b/src/color.hh
@@ -55,7 +55,7 @@ void option_from_string(StringView str, Color& color);
 
 bool is_color_name(StringView color);
 
-inline size_t hash_value(const Color& val)
+constexpr size_t hash_value(const Color& val)
 {
     return val.color == Color::RGB ?
         hash_values(val.color, val.r, val.g, val.b)
diff --git a/src/coord.hh b/src/coord.hh
index 06c1032d..6109bf14 100644
--- a/src/coord.hh
+++ b/src/coord.hh
@@ -81,7 +81,7 @@ struct LineAndColumn
         return line != other.line or column != other.column;
     }
 
-    friend size_t hash_value(const EffectiveType& val)
+    friend constexpr size_t hash_value(const EffectiveType& val)
     {
         return hash_values(val.line, val.column);
     }
@@ -116,7 +116,7 @@ struct BufferCoordAndTarget : BufferCoord
     ColumnCount target;
 };
 
-inline size_t hash_value(const BufferCoordAndTarget& val)
+constexpr size_t hash_value(const BufferCoordAndTarget& val)
 {
     return hash_values(val.line, val.column, val.target);
 }
diff --git a/src/hash.hh b/src/hash.hh
index 35e89e84..e90232d8 100644
--- a/src/hash.hh
+++ b/src/hash.hh
@@ -12,39 +12,46 @@ namespace Kakoune
 size_t hash_data(const char* data, size_t len);
 
 template<typename... Type>
-size_t hash_value(const Type&... val)
+constexpr size_t hash_value(const Type&... val)
 {
     static_assert(sizeof...(Type) == 1, "");
     return std::hash<Type...>()(val...);
 }
 
+template<typename Type>
+std::enable_if_t<std::is_integral<Type>::value, size_t>
+constexpr hash_value(const Type& val)
+{
+    return (size_t)val;
+}
+
 template<typename Type>
 std::enable_if_t<std::is_enum<Type>::value, size_t>
-hash_value(const Type& val)
+constexpr hash_value(const Type& val)
 {
     return hash_value((std::underlying_type_t<Type>)val);
 }
 
 template<typename Type>
-size_t hash_values(Type&& t)
+constexpr size_t hash_values(Type&& t)
 {
     return hash_value(std::forward<Type>(t));
 }
 
-inline size_t combine_hash(size_t lhs, size_t rhs)
+constexpr size_t combine_hash(size_t lhs, size_t rhs)
 {
     return lhs ^ (rhs + 0x9e3779b9 + (lhs << 6) + (lhs >> 2));
 }
 
 template<typename Type, typename... RemainingTypes>
-size_t hash_values(Type&& t, RemainingTypes&&... rt)
+constexpr size_t hash_values(Type&& t, RemainingTypes&&... rt)
 {
     size_t seed = hash_values(std::forward<RemainingTypes>(rt)...);
     return combine_hash(seed, hash_value(std::forward<Type>(t)));
 }
 
 template<typename T1, typename T2>
-size_t hash_value(const std::pair<T1, T2>& val)
+constexpr size_t hash_value(const std::pair<T1, T2>& val)
 {
     return hash_values(val.first, val.second);
 }
@@ -52,7 +59,7 @@ size_t hash_value(const std::pair<T1, T2>& val)
 template<typename Type>
 struct Hash
 {
-    size_t operator()(const Type& val) const
+    constexpr size_t operator()(const Type& val) const
     {
         return hash_value(val);
     }
diff --git a/src/keys.hh b/src/keys.hh
index 3d023453..b1219fc2 100644
--- a/src/keys.hh
+++ b/src/keys.hh
@@ -112,7 +112,7 @@ constexpr Codepoint encode_coord(DisplayCoord coord) { return (Codepoint)(((int)
 
 constexpr Key resize(DisplayCoord dim) { return { Key::Modifiers::Resize, encode_coord(dim) }; }
 
-inline size_t hash_value(const Key& key) { return hash_values(key.modifiers, key.key); }
+constexpr size_t hash_value(const Key& key) { return hash_values(key.modifiers, key.key); }
 
 }
 
diff --git a/src/string.hh b/src/string.hh
index a4d62804..ddb5be8d 100644
--- a/src/string.hh
+++ b/src/string.hh
@@ -19,7 +19,7 @@ class StringOps
 public:
     using value_type = CharType;
 
-    friend inline size_t hash_value(const Type& str)
+    friend constexpr size_t hash_value(const Type& str)
     {
         return hash_data(str.data(), (int)str.length());
     }
diff --git a/src/units.hh b/src/units.hh
index 0218055f..1c10c3af 100644
--- a/src/units.hh
+++ b/src/units.hh
@@ -115,8 +115,8 @@ public:
     [[gnu::always_inline]]
     explicit constexpr operator bool() const { return m_value; }
 
-    friend size_t hash_value(RealType val) { return hash_value(val.m_value); }
-    friend size_t abs(RealType val) { return val.m_value < ValueType(0) ? -val.m_value : val.m_value; }
+    friend constexpr size_t hash_value(RealType val) { return hash_value(val.m_value); }
+    friend constexpr size_t abs(RealType val) { return val.m_value < ValueType(0) ? -val.m_value : val.m_value; }
 
     explicit operator size_t() { kak_assert(m_value >= 0); return (size_t)m_value; }