optimize increment

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

src/core/utils/mod.rs

@@ -6,6 +6,7 @@
 pub mod json;
 pub mod mutex_map;
 pub mod sys;
+mod tests;
 
 use std::{
 	cmp::{self, Ordering},
@@ -34,16 +35,14 @@ pub fn millis_since_unix_epoch() -> u64 {
 		.as_millis() as u64
 }
 
-pub fn increment(old: Option<&[u8]>) -> Vec<u8> {
-	let number = match old.map(TryInto::try_into) {
-		Some(Ok(bytes)) => {
-			let number = u64::from_be_bytes(bytes);
-			number + 1
-		},
-		_ => 1, // Start at one. since 0 should return the first event in the db
-	};
-
-	number.to_be_bytes().to_vec()
+#[inline]
+#[must_use]
+pub fn increment(old: Option<&[u8]>) -> [u8; 8] {
+	const ZERO: u64 = 0;
+	old.map(TryInto::try_into)
+		.map_or(ZERO, |val| val.map_or(ZERO, u64::from_be_bytes))
+		.wrapping_add(1)
+		.to_be_bytes()
 }
 
 #[must_use]

src/core/utils/tests.rs

+#![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);
+}

src/database/rocksdb/kvtree.rs

@@ -155,13 +155,13 @@ fn increment(&self, key: &[u8]) -> Result<Vec<u8>> {
 		let new = utils::increment(old.as_deref());
 		self.db
 			.rocks
-			.put_cf_opt(&self.cf(), key, &new, &writeoptions)?;
+			.put_cf_opt(&self.cf(), key, new, &writeoptions)?;
 
 		if !self.db.corked() {
 			self.db.flush()?;
 		}
 
-		Ok(new)
+		Ok(new.to_vec())
 	}
 
 	fn increment_batch(&self, iter: &mut dyn Iterator<Item = Vec<u8>>) -> Result<()> {