From fac01888d17423d6c23a9ce15d98fc88fb34e3cc Mon Sep 17 00:00:00 2001
From: MarcoFalke <falke.marco@gmail.com>
Date: Tue, 2 Nov 2021 09:48:10 +0100
Subject: Move AdditionOverflow to util, Add CheckedAdd with unit tests

---
 src/util/overflow.h | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 src/util/overflow.h

(limited to 'src/util')

diff --git a/src/util/overflow.h b/src/util/overflow.h
new file mode 100644
index 0000000000..5982af8d04
--- /dev/null
+++ b/src/util/overflow.h
@@ -0,0 +1,31 @@
+// Copyright (c) 2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_OVERFLOW_H
+#define BITCOIN_UTIL_OVERFLOW_H
+
+#include <limits>
+#include <type_traits>
+
+template <class T>
+[[nodiscard]] bool AdditionOverflow(const T i, const T j) noexcept
+{
+    static_assert(std::is_integral<T>::value, "Integral required.");
+    if (std::numeric_limits<T>::is_signed) {
+        return (i > 0 && j > std::numeric_limits<T>::max() - i) ||
+               (i < 0 && j < std::numeric_limits<T>::min() - i);
+    }
+    return std::numeric_limits<T>::max() - i < j;
+}
+
+template <class T>
+[[nodiscard]] std::optional<T> CheckedAdd(const T i, const T j) noexcept
+{
+    if (AdditionOverflow(i, j)) {
+        return std::nullopt;
+    }
+    return i + j;
+}
+
+#endif // BITCOIN_UTIL_OVERFLOW_H
-- 
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