From 3c4f1946101c68d60d6538bb11e80a9a71c15e0c Mon Sep 17 00:00:00 2001
From: Tobie Morgan Hitchcock <tobie@abcum.com>
Date: Sat, 3 Dec 2022 23:30:38 +0000
Subject: [PATCH] Ensure string::slice does not panic with usize overflow

---
 lib/src/fnc/string.rs | 8 ++++++--
 lib/tests/function.rs | 7 ++++++-
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/lib/src/fnc/string.rs b/lib/src/fnc/string.rs
index e2d8969f..746f73f5 100644
--- a/lib/src/fnc/string.rs
+++ b/lib/src/fnc/string.rs
@@ -53,12 +53,16 @@ pub fn reverse((string,): (String,)) -> Result<Value, Error> {
 
 pub fn slice((val, beg, lim): (String, Option<isize>, Option<isize>)) -> Result<Value, Error> {
 	let val = match beg {
-		Some(v) if v < 0 => val.chars().skip(val.len() - v.unsigned_abs()).collect::<String>(),
+		Some(v) if v < 0 => {
+			val.chars().skip(val.len().saturating_sub(v.unsigned_abs())).collect::<String>()
+		}
 		Some(v) => val.chars().skip(v as usize).collect::<String>(),
 		None => val,
 	};
 	let val = match lim {
-		Some(v) if v < 0 => val.chars().take(val.len() - v.unsigned_abs()).collect::<String>(),
+		Some(v) if v < 0 => {
+			val.chars().take(val.len().saturating_sub(v.unsigned_abs())).collect::<String>()
+		}
 		Some(v) => val.chars().take(v as usize).collect::<String>(),
 		None => val,
 	};
diff --git a/lib/tests/function.rs b/lib/tests/function.rs
index cf15ae49..35f3bf28 100644
--- a/lib/tests/function.rs
+++ b/lib/tests/function.rs
@@ -235,11 +235,12 @@ async fn function_string_slice() -> Result<(), Error> {
 		RETURN string::slice("the quick brown fox jumps over the lazy dog.", 0, -1);
 		RETURN string::slice("the quick brown fox jumps over the lazy dog.", 16, -1);
 		RETURN string::slice("the quick brown fox jumps over the lazy dog.", -9, -1);
+		RETURN string::slice("the quick brown fox jumps over the lazy dog.", -100, -100);
 	"#;
 	let dbs = Datastore::new("memory").await?;
 	let ses = Session::for_kv().with_ns("test").with_db("test");
 	let res = &mut dbs.execute(&sql, &ses, None, false).await?;
-	assert_eq!(res.len(), 6);
+	assert_eq!(res.len(), 7);
 	//
 	let tmp = res.remove(0).result?;
 	let val = Value::parse("'the quick brown fox jumps over the lazy dog.'");
@@ -265,5 +266,9 @@ async fn function_string_slice() -> Result<(), Error> {
 	let val = Value::parse("'lazy dog'");
 	assert_eq!(tmp, val);
 	//
+	let tmp = res.remove(0).result?;
+	let val = Value::parse("''");
+	assert_eq!(tmp, val);
+	//
 	Ok(())
 }