From 71c54198fa733efd6bfc99a73cbc024fe9bdc901 Mon Sep 17 00:00:00 2001
From: Idan Horowitz <idan.horowitz@gmail.com>
Date: Tue, 8 Jun 2021 23:42:07 +0300
Subject: [PATCH] AK: Allow changing the HashTable behaviour for sets on
 existing entries

Specifically, replacing the existing entry or just keeping it and
canceling the set.
---
 AK/HashTable.h | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/AK/HashTable.h b/AK/HashTable.h
index 5d55c4f9cf..9c4c2f6227 100644
--- a/AK/HashTable.h
+++ b/AK/HashTable.h
@@ -15,7 +15,13 @@ namespace AK {
 
 enum class HashSetResult {
     InsertedNewEntry,
-    ReplacedExistingEntry
+    ReplacedExistingEntry,
+    KeptExistingEntry
+};
+
+enum class HashSetExistingEntryBehavior {
+    Keep,
+    Replace
 };
 
 template<typename HashTableType, typename T, typename BucketType>
@@ -184,10 +190,12 @@ public:
     }
 
     template<typename U = T>
-    HashSetResult set(U&& value)
+    HashSetResult set(U&& value, HashSetExistingEntryBehavior existing_entry_behaviour = HashSetExistingEntryBehavior::Replace)
     {
         auto& bucket = lookup_for_writing(value);
         if (bucket.used) {
+            if (existing_entry_behaviour == HashSetExistingEntryBehavior::Keep)
+                return HashSetResult::KeptExistingEntry;
             (*bucket.slot()) = forward<U>(value);
             return HashSetResult::ReplacedExistingEntry;
         }