optimize increment

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

src/core/utils/tests.rs

@@ -0,0 +1,37 @@
+#![cfg(test)]
+
+use crate::utils;
+
+#[test]
+fn increment_none() {
+	let bytes: [u8; 8] = utils::increment(None);
+	let res = u64::from_be_bytes(bytes);
+	assert_eq!(res, 1);
+}
+
+#[test]
+fn increment_fault() {
+	let start: u8 = 127;
+	let bytes: [u8; 1] = start.to_be_bytes();
+	let bytes: [u8; 8] = utils::increment(Some(&bytes));
+	let res = u64::from_be_bytes(bytes);
+	assert_eq!(res, 1);
+}
+
+#[test]
+fn increment_norm() {
+	let start: u64 = 1_234_567;
+	let bytes: [u8; 8] = start.to_be_bytes();
+	let bytes: [u8; 8] = utils::increment(Some(&bytes));
+	let res = u64::from_be_bytes(bytes);
+	assert_eq!(res, 1_234_568);
+}
+
+#[test]
+fn increment_wrap() {
+	let start = u64::MAX;
+	let bytes: [u8; 8] = start.to_be_bytes();
+	let bytes: [u8; 8] = utils::increment(Some(&bytes));
+	let res = u64::from_be_bytes(bytes);
+	assert_eq!(res, 0);
+}