From e91c04b1d110bb1739afefb4e5f9bd25db47934f Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Tue, 6 Dec 2022 15:40:18 +0100
Subject: [PATCH] luna: Introduce safe arithmetic operations, which return an
 error if an operation would overflow

---
 luna/include/luna/SafeArithmetic.h | 38 ++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 luna/include/luna/SafeArithmetic.h

diff --git a/luna/include/luna/SafeArithmetic.h b/luna/include/luna/SafeArithmetic.h
new file mode 100644
index 00000000..b0336d6d
--- /dev/null
+++ b/luna/include/luna/SafeArithmetic.h
@@ -0,0 +1,38 @@
+#pragma once
+#include <luna/Result.h>
+
+template <typename T> constexpr bool add_will_overflow(T a, T b)
+{
+    return __builtin_add_overflow_p(a, b, (T)0);
+}
+
+template <typename T> constexpr bool sub_will_overflow(T a, T b)
+{
+    return __builtin_sub_overflow_p(a, b, (T)0);
+}
+
+template <typename T> constexpr bool mul_will_overflow(T a, T b)
+{
+    return __builtin_mul_overflow_p(a, b, (T)0);
+}
+
+template <typename T> Result<T> safe_add(T a, T b)
+{
+    if (add_will_overflow(a, b)) return err(EOVERFLOW);
+
+    return a + b;
+}
+
+template <typename T> Result<T> safe_sub(T a, T b)
+{
+    if (sub_will_overflow(a, b)) return err(EOVERFLOW);
+
+    return a - b;
+}
+
+template <typename T> Result<T> safe_mul(T a, T b)
+{
+    if (mul_will_overflow(a, b)) return err(EOVERFLOW);
+
+    return a * b;
+}
\ No newline at end of file