From 52cc9a023c66f41eae268582ad66b53869af7183 Mon Sep 17 00:00:00 2001
From: Ron Kuris <ron.kuris@avalabs.org>
Date: Tue, 28 Nov 2023 12:51:12 -0800
Subject: [PATCH] Expose NibblesIterator::is_empty (#389)

---
 firewood/src/nibbles.rs | 37 ++++++++++++++++++++++++++++++++++++-
 firewood/src/proof.rs   |  4 ++--
 2 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/firewood/src/nibbles.rs b/firewood/src/nibbles.rs
index 8de0865eb..0f6152b06 100644
--- a/firewood/src/nibbles.rs
+++ b/firewood/src/nibbles.rs
@@ -120,7 +120,7 @@ impl<'a, const LEADING_ZEROES: usize> Iterator for NibblesIterator<'a, LEADING_Z
 
 impl<'a, const LEADING_ZEROES: usize> NibblesIterator<'a, LEADING_ZEROES> {
     #[inline(always)]
-    fn is_empty(&self) -> bool {
+    pub fn is_empty(&self) -> bool {
         self.head == self.tail
     }
 }
@@ -215,4 +215,39 @@ mod test {
 
         assert!(nib_iter.eq(expected));
     }
+
+    #[test]
+    fn empty() {
+        let nib = Nibbles::<0>(&[]);
+        assert!(nib.is_empty());
+        let it = nib.into_iter();
+        assert!(it.is_empty());
+        assert_eq!(it.size_hint().0, 0);
+    }
+
+    #[test]
+    fn not_empty_because_of_leading_nibble() {
+        let nib = Nibbles::<1>(&[]);
+        assert!(!nib.is_empty());
+        let mut it = nib.into_iter();
+        assert!(!it.is_empty());
+        assert_eq!(it.size_hint(), (1, Some(1)));
+        assert_eq!(it.next(), Some(0));
+        assert!(it.is_empty());
+        assert_eq!(it.size_hint(), (0, Some(0)));
+    }
+    #[test]
+    fn not_empty_because_of_data() {
+        let nib = Nibbles::<0>(&[1]);
+        assert!(!nib.is_empty());
+        let mut it = nib.into_iter();
+        assert!(!it.is_empty());
+        assert_eq!(it.size_hint(), (2, Some(2)));
+        assert_eq!(it.next(), Some(0));
+        assert!(!it.is_empty());
+        assert_eq!(it.size_hint(), (1, Some(1)));
+        assert_eq!(it.next(), Some(1));
+        assert!(it.is_empty());
+        assert_eq!(it.size_hint(), (0, Some(0)));
+    }
 }
diff --git a/firewood/src/proof.rs b/firewood/src/proof.rs
index fa50404a6..b5b571c69 100644
--- a/firewood/src/proof.rs
+++ b/firewood/src/proof.rs
@@ -126,7 +126,7 @@ impl<N: AsRef<[u8]> + Send> Proof<N> {
 
             cur_hash = match sub_proof {
                 // Return when reaching the end of the key.
-                Some(p) if key_nibbles.size_hint().0 == 0 => break p.encoded,
+                Some(p) if key_nibbles.is_empty() => break p.encoded,
                 // The trie doesn't contain the key.
                 Some(SubProof {
                     hash: Some(hash), ..
@@ -542,7 +542,7 @@ fn locate_subproof(
 
             Ok((sub_proof.into(), key_nibbles))
         }
-        NodeType::Branch(_) if key_nibbles.size_hint().0 == 0 => Err(ProofError::NoSuchNode),
+        NodeType::Branch(_) if key_nibbles.is_empty() => Err(ProofError::NoSuchNode),
         NodeType::Branch(n) => {
             let index = key_nibbles.next().unwrap() as usize;
             // consume items returning the item at index