Move all std related headers to "include_std"

include_std/std/functional.hpp

@@ -0,0 +1,50 @@
+/*
+   This file is part of Fennix Kernel.
+
+   Fennix Kernel is free software: you can redistribute it and/or
+   modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation, either version 3 of
+   the License, or (at your option) any later version.
+
+   Fennix Kernel is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with Fennix Kernel. If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#ifndef __FENNIX_KERNEL_STD_FUNCTIONAL_H__
+#define __FENNIX_KERNEL_STD_FUNCTIONAL_H__
+
+#include <types.h>
+#include <assert.h>
+
+namespace std
+{
+    template <typename Key>
+    struct hash
+    {
+        size_t operator()(const Key &key) const
+        {
+            static_assert(sizeof(size_t) == sizeof(uint64_t)); // size_t and uint64_t must have the same size
+            const uint64_t fnv_offset_basis = 14695981039346656037ull;
+            const uint64_t fnv_prime = 1099511628211ull;
+
+            const uint8_t *data = reinterpret_cast<const uint8_t *>(&key);
+            const size_t size = sizeof(Key);
+            uint64_t ret = fnv_offset_basis;
+
+            for (size_t i = 0; i < size; ++i)
+            {
+                ret ^= static_cast<uint64_t>(data[i]);
+                ret *= fnv_prime;
+            }
+
+            return static_cast<size_t>(ret);
+        }
+    };
+}
+
+#endif // !__FENNIX_KERNEL_STD_FUNCTIONAL_H__