From 48c126cf9c8cbb76b6fe1bb54158d1e7b4635fce Mon Sep 17 00:00:00 2001
From: Teebonne <80053070+Teebonne@users.noreply.github.com>
Date: Sat, 10 Sep 2022 21:35:48 +0100
Subject: [PATCH] Improving the hash function

Using Szudzik's pairing function (more efficient than the previous approach or Cantor's)
---
 include/xlnt/cell/cell_reference.hpp | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/xlnt/cell/cell_reference.hpp b/include/xlnt/cell/cell_reference.hpp
index c8efcb4b3..d551b6ab3 100644
--- a/include/xlnt/cell/cell_reference.hpp
+++ b/include/xlnt/cell/cell_reference.hpp
@@ -262,11 +262,13 @@ namespace std {
 template <>
 struct hash<xlnt::cell_reference>
 {
-    size_t operator()(const xlnt::cell_reference &x) const
+    size_t operator()(const xlnt::cell_reference &x) const // using Szudzik's pairing function
     {
-        static_assert(std::is_same<decltype(x.row()), std::uint32_t>::value, "this hash function expects both row and column to be 32-bit numbers");
-        static_assert(std::is_same<decltype(x.column_index()), std::uint32_t>::value, "this hash function expects both row and column to be 32-bit numbers");
-        return hash<std::uint64_t>{}(x.row() | static_cast<std::uint64_t>(x.column_index()) << 32);
+		if (x.column_index() >= x.row()) {
+			return hash<size_t>{}(x.column_index() * x.column_index() + x.column_index() + x.row());
+		} else {
+			return hash<size_t>{}(x.column_index() + x.row() * x.row());
+		};
     }
 };
 } // namespace std