From ff27dce24c2fb123194f2673026bb25e9edb7a75 Mon Sep 17 00:00:00 2001
From: PixelyIon <pixelyion@protonmail.com>
Date: Mon, 27 Dec 2021 00:13:42 +0530
Subject: [PATCH] Implement `ObjectHash` for hashing trivial objects in maps

`std::hash` doesn't have a generic template where it can be utilized for arbitrary trivial objects and implementing this might result in conflicts with other types. To fix this a generic templated hash is now provided as a utility structure, that can be utilized directly in hash-based containers such as `unordered_map`.
---
 app/src/main/cpp/skyline/common/utils.h | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/app/src/main/cpp/skyline/common/utils.h b/app/src/main/cpp/skyline/common/utils.h
index 1e9c62e7..d6bbe9d1 100644
--- a/app/src/main/cpp/skyline/common/utils.h
+++ b/app/src/main/cpp/skyline/common/utils.h
@@ -7,6 +7,7 @@
 #include <span>
 #include <frozen/unordered_map.h>
 #include <frozen/string.h>
+#include <xxhash.h>
 #include "base.h"
 
 namespace skyline::util {
@@ -190,6 +191,16 @@ namespace skyline::util {
         return frozen::elsa<frozen::string>{}(frozen::string(view.data(), view.size()), 0);
     }
 
+    /**
+     * @brief A fast hash for any trivial object that is designed to be utilized with hash-based containers
+     */
+    template<typename T> requires std::is_trivial_v<T>
+    struct ObjectHash {
+        size_t operator()(const T &object) const noexcept {
+            return XXH64(&object, sizeof(object), 0);
+        }
+    };
+
     /**
      * @brief Selects the largest possible integer type for representing an object alongside providing the size of the object in terms of the underlying type
      */
@@ -263,8 +274,7 @@ namespace skyline::util {
     };
 
     template<typename T, typename... TArgs, size_t... Is>
-    std::array<T, sizeof...(Is)> MakeFilledArray(std::index_sequence<Is...>, TArgs &&... args)
-    {
+    std::array<T, sizeof...(Is)> MakeFilledArray(std::index_sequence<Is...>, TArgs &&... args) {
         return {(void(Is), T(args...))...};
     }
 
@@ -272,4 +282,4 @@ namespace skyline::util {
     std::array<T, Size> MakeFilledArray(TArgs &&... args) {
         return MakeFilledArray<T>(std::make_index_sequence<Size>(), std::forward<TArgs>(args)...);
     }
-}
\ No newline at end of file
+}