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)*) }
+}

src/core/utils/mod.rs

@@ -5,6 +5,7 @@ pub mod defer;
 pub mod hash;
 pub mod html;
 pub mod json;
+pub mod math;
 pub mod mutex_map;
 pub mod rand;
 pub mod string;

src/core/utils/tests.rs

@@ -62,3 +62,22 @@ fn common_prefix_none() {
 	let output = string::common_prefix(&input);
 	assert_eq!(output, "");
 }
+
+#[test]
+fn checked_add() {
+	use utils::math::checked;
+
+	let a = 1234;
+	let res = checked!(a + 1).unwrap();
+	assert_eq!(res, 1235);
+}
+
+#[test]
+#[should_panic(expected = "overflow")]
+fn checked_add_overflow() {
+	use utils::math::checked;
+
+	let a: u64 = u64::MAX;
+	let res = checked!(a + 1).expect("overflow");
+	assert_eq!(res, 0);
+}