Create EnumMap

6 files changed, 122 insertions, 8 deletions

diff --git a/Source/Core/Common/CMakeLists.txt b/Source/Core/Common/CMakeLists.txt
index 1b806129fd..b1e25af45b 100644
--- a/Source/Core/Common/CMakeLists.txt
+++ b/Source/Core/Common/CMakeLists.txt
@@ -42,6 +42,7 @@ add_library(common
   ENetUtil.cpp
   ENetUtil.h
   EnumFormatter.h
+  EnumMap.h
   Event.h
   FileSearch.cpp
   FileSearch.h
diff --git a/Source/Core/Common/ChunkFile.h b/Source/Core/Common/ChunkFile.h
index 85507354af..8b84a4cf1c 100644
--- a/Source/Core/Common/ChunkFile.h
+++ b/Source/Core/Common/ChunkFile.h
@@ -27,6 +27,7 @@
 
 #include "Common/Assert.h"
 #include "Common/CommonTypes.h"
+#include "Common/EnumMap.h"
 #include "Common/Flag.h"
 #include "Common/Inline.h"
 #include "Common/Logging/Log.h"
@@ -175,6 +176,12 @@ public:
     DoArray(x.data(), static_cast<u32>(x.size()));
   }
 
+  template <typename V, auto last_member, typename = decltype(last_member)>
+  void DoArray(Common::EnumMap<V, last_member>& x)
+  {
+    DoArray(x.data(), static_cast<u32>(x.size()));
+  }
+
   template <typename T, typename std::enable_if_t<std::is_trivially_copyable_v<T>, int> = 0>
   void DoArray(T* x, u32 count)
   {
diff --git a/Source/Core/Common/EnumFormatter.h b/Source/Core/Common/EnumFormatter.h
index f590e761d4..1ab6bbeadd 100644
--- a/Source/Core/Common/EnumFormatter.h
+++ b/Source/Core/Common/EnumFormatter.h
@@ -3,7 +3,8 @@
 
 #pragma once
 
-#include <array>
+#include "Common/EnumMap.h"
+
 #include <fmt/format.h>
 #include <type_traits>
 
@@ -41,11 +42,15 @@
  *   formatter() : EnumFormatter(names) {}
  * };
  */
-template <auto last_member, typename T = decltype(last_member),
-          size_t size = static_cast<size_t>(last_member) + 1,
-          std::enable_if_t<std::is_enum_v<T>, bool> = true>
+template <auto last_member, typename = decltype(last_member)>
 class EnumFormatter
 {
+  // The second template argument is needed to avoid compile errors from ambiguity with multiple
+  // enums with the same number of members in GCC prior to 8.  See https://godbolt.org/z/xcKaW1seW
+  // and https://godbolt.org/z/hz7Yqq1P5
+  using T = decltype(last_member);
+  static_assert(std::is_enum_v<T>);
+
 public:
   constexpr auto parse(fmt::format_parse_context& ctx)
   {
@@ -61,19 +66,19 @@ public:
   {
     const auto value_s = static_cast<std::underlying_type_t<T>>(e);      // Possibly signed
     const auto value_u = static_cast<std::make_unsigned_t<T>>(value_s);  // Always unsigned
-    const bool has_name = value_s >= 0 && value_u < size && m_names[value_u] != nullptr;
+    const bool has_name = m_names.InBounds(e) && m_names[e] != nullptr;
 
     if (!formatting_for_shader)
     {
       if (has_name)
-        return fmt::format_to(ctx.out(), "{} ({})", m_names[value_u], value_s);
+        return fmt::format_to(ctx.out(), "{} ({})", m_names[e], value_s);
       else
         return fmt::format_to(ctx.out(), "Invalid ({})", value_s);
     }
     else
     {
       if (has_name)
-        return fmt::format_to(ctx.out(), "{:#x}u /* {} */", value_u, m_names[value_u]);
+        return fmt::format_to(ctx.out(), "{:#x}u /* {} */", value_u, m_names[e]);
       else
         return fmt::format_to(ctx.out(), "{:#x}u /* Invalid */", value_u);
     }
@@ -81,7 +86,7 @@ public:
 
 protected:
   // This is needed because std::array deduces incorrectly if nullptr is included in the list
-  using array_type = std::array<const char*, size>;
+  using array_type = Common::EnumMap<const char*, last_member>;
 
   constexpr explicit EnumFormatter(const array_type names) : m_names(std::move(names)) {}
 
diff --git a/Source/Core/Common/EnumMap.h b/Source/Core/Common/EnumMap.h
new file mode 100644
index 0000000000..478ff42ec7
--- /dev/null
+++ b/Source/Core/Common/EnumMap.h
@@ -0,0 +1,83 @@
+// Copyright 2021 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+#include <type_traits>
+
+#include "Common/TypeUtils.h"
+
+template <std::size_t position, std::size_t bits, typename T, typename StorageType>
+struct BitField;
+
+namespace Common
+{
+// A type that allows lookup of values associated with an enum as the key.
+// Designed for enums whose numeric values start at 0 and increment continuously with few gaps.
+template <typename V, auto last_member, typename = decltype(last_member)>
+class EnumMap final
+{
+  // The third template argument is needed to avoid compile errors from ambiguity with multiple
+  // enums with the same number of members in GCC prior to 8.  See https://godbolt.org/z/xcKaW1seW
+  // and https://godbolt.org/z/hz7Yqq1P5
+  using T = decltype(last_member);
+  static_assert(std::is_enum_v<T>);
+  static constexpr size_t s_size = static_cast<size_t>(last_member) + 1;
+
+  using array_type = std::array<V, s_size>;
+  using iterator = typename array_type::iterator;
+  using const_iterator = typename array_type::const_iterator;
+
+public:
+  constexpr EnumMap() = default;
+  constexpr EnumMap(const EnumMap& other) = default;
+  constexpr EnumMap& operator=(const EnumMap& other) = default;
+  constexpr EnumMap(EnumMap&& other) = default;
+  constexpr EnumMap& operator=(EnumMap&& other) = default;
+
+  // Constructor that accepts exactly size Vs (enforcing that all must be specified).
+  template <typename... T, typename = std::enable_if_t<Common::IsNOf<V, s_size, T...>::value>>
+  constexpr EnumMap(T... values) : m_array{static_cast<V>(values)...}
+  {
+  }
+
+  constexpr const V& operator[](T key) const { return m_array[static_cast<std::size_t>(key)]; }
+  constexpr V& operator[](T key) { return m_array[static_cast<std::size_t>(key)]; }
+
+  // These only exist to perform the safety check; without them, BitField's implicit conversion
+  // would work (but since BitField is used for game-generated data, we need to be careful about
+  // bounds-checking)
+  template <std::size_t position, std::size_t bits, typename StorageType>
+  constexpr const V& operator[](BitField<position, bits, T, StorageType> key) const
+  {
+    static_assert(1 << bits == s_size, "Unsafe indexing into EnumMap (may go out of bounds)");
+    return m_array[static_cast<std::size_t>(key.Value())];
+  }
+  template <std::size_t position, std::size_t bits, typename StorageType>
+  constexpr V& operator[](BitField<position, bits, T, StorageType> key)
+  {
+    static_assert(1 << bits == s_size, "Unsafe indexing into EnumMap (may go out of bounds)");
+    return m_array[static_cast<std::size_t>(key.value())];
+  }
+
+  constexpr bool InBounds(T key) const { return static_cast<std::size_t>(key) < s_size; }
+
+  constexpr size_t size() const noexcept { return s_size; }
+
+  constexpr V* data() { return m_array.data(); }
+  constexpr const V* data() const { return m_array.data(); }
+
+  constexpr iterator begin() { return m_array.begin(); }
+  constexpr iterator end() { return m_array.end(); }
+  constexpr const_iterator begin() const { return m_array.begin(); }
+  constexpr const_iterator end() const { return m_array.end(); }
+  constexpr const_iterator cbegin() const { return m_array.cbegin(); }
+  constexpr const_iterator cend() const { return m_array.cend(); }
+
+  constexpr void fill(const V& v) { m_array.fill(v); }
+
+private:
+  array_type m_array{};
+};
+}  // namespace Common
diff --git a/Source/Core/Common/TypeUtils.h b/Source/Core/Common/TypeUtils.h
index c6875948c7..47077e11fb 100644
--- a/Source/Core/Common/TypeUtils.h
+++ b/Source/Core/Common/TypeUtils.h
@@ -3,6 +3,7 @@
 
 #pragma once
 
+#include <cstddef>
 #include <type_traits>
 
 namespace Common
@@ -66,4 +67,20 @@ static_assert(std::is_same_v<ObjectType<&Bar::d>, Bar>);
 static_assert(std::is_same_v<ObjectType<&Bar::c>, Foo>);
 static_assert(!std::is_same_v<ObjectType<&Bar::c>, Bar>);
 }  // namespace detail
+
+// Template for checking if Types is count occurrences of T.
+template <typename T, size_t count, typename... Ts>
+struct IsNOf : std::integral_constant<bool, std::conjunction_v<std::is_convertible<Ts, T>...> &&
+                                                sizeof...(Ts) == count>
+{
+};
+
+static_assert(IsNOf<int, 0>::value);
+static_assert(!IsNOf<int, 0, int>::value);
+static_assert(IsNOf<int, 1, int>::value);
+static_assert(!IsNOf<int, 1>::value);
+static_assert(!IsNOf<int, 1, int, int>::value);
+static_assert(IsNOf<int, 2, int, int>::value);
+static_assert(IsNOf<int, 2, int, short>::value);  // Type conversions ARE allowed
+static_assert(!IsNOf<int, 2, int, char*>::value);
 }  // namespace Common
diff --git a/Source/Core/DolphinLib.props b/Source/Core/DolphinLib.props
index b7e9bf3b32..fc429c0ab4 100644
--- a/Source/Core/DolphinLib.props
+++ b/Source/Core/DolphinLib.props
@@ -43,6 +43,7 @@
     <ClInclude Include="Common\DynamicLibrary.h" />
     <ClInclude Include="Common\ENetUtil.h" />
     <ClInclude Include="Common\EnumFormatter.h" />
+    <ClInclude Include="Common\EnumMap.h" />
     <ClInclude Include="Common\Event.h" />
     <ClInclude Include="Common\FileSearch.h" />
     <ClInclude Include="Common\FileUtil.h" />