From 956a2d5f837186e1a8b642acd34ca76ea74e5e57 Mon Sep 17 00:00:00 2001
From: Yuya Nishihara <yuya@tcha.org>
Date: Thu, 26 Jan 2023 15:29:36 +0900
Subject: [PATCH] index: remove redundant prefix tests from resolve_prefix
 functions

The "min" prefix guarantees that the first entry matches the hex prefix
if any. Spotted by @ilyagr.
---
 lib/src/index.rs | 14 ++++++--------
 lib/src/repo.rs  |  5 ++---
 2 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/lib/src/index.rs b/lib/src/index.rs
index cc0180514..b3061222d 100644
--- a/lib/src/index.rs
+++ b/lib/src/index.rs
@@ -1333,7 +1333,7 @@ impl IndexSegment for ReadonlyIndex {
     }
 
     fn segment_resolve_prefix(&self, prefix: &HexPrefix) -> PrefixResolution<CommitId> {
-        let (bytes_prefix, min_bytes_prefix) = prefix.bytes_prefixes();
+        let (_, min_bytes_prefix) = prefix.bytes_prefixes();
         let lookup_pos = self
             .commit_id_byte_prefix_to_lookup_pos(&min_bytes_prefix)
             .unwrap_or(self.num_local_commits);
@@ -1341,14 +1341,13 @@ impl IndexSegment for ReadonlyIndex {
         for i in lookup_pos..self.num_local_commits {
             let entry = self.lookup_entry(i);
             let id = entry.commit_id();
-            if !id.as_bytes().starts_with(bytes_prefix.as_bytes()) {
-                break;
-            }
             if prefix.matches(&id) {
                 if first_match.is_some() {
                     return PrefixResolution::AmbiguousMatch;
                 }
                 first_match = Some(id)
+            } else {
+                break;
             }
         }
         match first_match {
@@ -1437,20 +1436,19 @@ impl IndexSegment for MutableIndex {
     }
 
     fn segment_resolve_prefix(&self, prefix: &HexPrefix) -> PrefixResolution<CommitId> {
-        let (bytes_prefix, min_bytes_prefix) = prefix.bytes_prefixes();
+        let (_, min_bytes_prefix) = prefix.bytes_prefixes();
         let potential_range = self
             .lookup
             .range((Bound::Included(&min_bytes_prefix), Bound::Unbounded));
         let mut first_match = None;
         for (id, _pos) in potential_range {
-            if !id.as_bytes().starts_with(bytes_prefix.as_bytes()) {
-                break;
-            }
             if prefix.matches(id) {
                 if first_match.is_some() {
                     return PrefixResolution::AmbiguousMatch;
                 }
                 first_match = Some(id)
+            } else {
+                break;
             }
         }
         match first_match {
diff --git a/lib/src/repo.rs b/lib/src/repo.rs
index 4cb83353b..23e2b2dd4 100644
--- a/lib/src/repo.rs
+++ b/lib/src/repo.rs
@@ -1306,12 +1306,11 @@ where
         &'a self,
         prefix: &'b HexPrefix,
     ) -> impl Iterator<Item = (&'a K, &'a V)> + 'b {
-        let (bytes_prefix, min_bytes_prefix) = prefix.bytes_prefixes::<K>();
+        let (_, min_bytes_prefix) = prefix.bytes_prefixes::<K>();
         let pos = self.0.partition_point(|(k, _)| k < &min_bytes_prefix);
         self.0[pos..]
             .iter()
-            .take_while(move |(k, _)| k.as_bytes().starts_with(bytes_prefix.as_bytes()))
-            .filter(|(k, _)| prefix.matches(k))
+            .take_while(|(k, _)| prefix.matches(k))
             .map(|(k, v)| (k, v))
     }