Merge pull request #7 from Racum/number-overflow

Fix u64 overflow when decoding

Author: 4kimov

CHANGELOG.md

@@ -1,5 +1,8 @@
 # CHANGELOG
 
+**v0.4.2:**
+- Fix u64 overflow
+
 **v0.4.1:**
 - Derive `Clone` trait [[PR #6](https://github.com/sqids/sqids-rust/pull/6)]
 - Cargo update

Cargo.toml

@@ -4,7 +4,7 @@ description = "Generate short unique ids from numbers."
 repository = "https://github.com/sqids/sqids-rust"
 documentation = "https://docs.rs/sqids"
 homepage = "https://sqids.org/rust"
-version = "0.4.1"
+version = "0.4.2"
 license = "MIT"
 edition = "2021"
 readme = "README.md"

src/lib.rs

@@ -251,7 +251,9 @@ impl Sqids {
 
 				let alphabet_without_separator: Vec<char> =
 					alphabet.iter().copied().skip(1).collect();
-				ret.push(self.to_number(chunks[0], &alphabet_without_separator));
+				if let Some(value) = self.to_number(chunks[0], &alphabet_without_separator) {
+					ret.push(value)
+				}
 
 				if chunks.len() > 1 {
 					alphabet = Self::shuffle(&alphabet);
@@ -332,15 +334,19 @@ impl Sqids {
 		id.into_iter().collect()
 	}
 
-	fn to_number(&self, id: &str, alphabet: &[char]) -> u64 {
+	fn to_number(&self, id: &str, alphabet: &[char]) -> Option<u64> {
 		let mut result = 0;
 
 		for c in id.chars() {
 			let idx = alphabet.iter().position(|&x| x == c).unwrap();
-			result = result * alphabet.len() as u64 + idx as u64;
+			result = result * alphabet.len() as u128 + idx as u128;
 		}
 
-		result
+		if result <= u64::MAX.into() {
+			Some(result.try_into().unwrap())
+		} else {
+			None
+		}
 	}
 
 	fn shuffle(alphabet: &[char]) -> Vec<char> {

tests/decoding.rs

@@ -0,0 +1,15 @@
+use sqids::*;
+
+#[test]
+fn decode_number_maximum_value() {
+	let sqids = Sqids::default();
+	let numbers = sqids.decode("ABARpJzdz9");
+	assert_eq!(numbers, [9_007_199_254_740_991]); // 2 ^ 53
+}
+
+#[test]
+fn decode_number_overflows() {
+	let sqids = Sqids::default();
+	let numbers = sqids.decode("0J4AEXRN106Z0");
+	assert_eq!(numbers, Vec::<u64>::new());
+}