add math utils; integrate checked expression macros

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/utils/math.rs

@@ -0,0 +1,26 @@
+use std::{cmp, time::Duration};
+
+pub use checked_ops::checked_ops;
+
+/// Checked arithmetic expression. Returns a Result<R, Error::Arithmetic>
+#[macro_export]
+macro_rules! checked {
+	($($input:tt)*) => {
+		$crate::utils::math::checked_ops!($($input)*)
+			.ok_or_else(|| $crate::Error::Arithmetic("operation overflowed or result invalid"))
+	}
+}
+
+/// in release-mode. Use for performance when the expression is obviously safe.
+/// The check remains in debug-mode for regression analysis.
+#[cfg(not(debug_assertions))]
+#[macro_export]
+macro_rules! validated {
+	($($input:tt)*) => { Ok($($input)*) }
+}
+
+#[cfg(debug_assertions)]
+#[macro_export]
+macro_rules! validated {
+	($($input:tt)*) => { $crate::checked!($($input)*) }
+}