From 9fb7d90449ce798bbc014ac6d17261a9df5ee3f2 Mon Sep 17 00:00:00 2001
From: Maxime Coste <mawww@kakoune.org>
Date: Fri, 5 Aug 2022 19:20:00 +1000
Subject: [PATCH] Change HashMap not to support multiple identical keys by
 default

We do not seem to have any uses for this remaining, and this is
better opt-in with MultiHashMap
---
 src/hash_map.cc | 13 ++++++++++++-
 src/hash_map.hh | 20 ++++++++++++++++++--
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/src/hash_map.cc b/src/hash_map.cc
index 4e45ab26..6972f34b 100644
--- a/src/hash_map.cc
+++ b/src/hash_map.cc
@@ -30,12 +30,23 @@ UnitTest test_hash_map{[] {
         kak_assert(map.size() == 2);
     }
 
-    // Multiple entries with the same key
+    // Replace Multiple entries with the same key
     {
         HashMap<int, int> map;
         map.insert({10, 1});
         map.insert({10, 2});
         kak_assert(map.find_index(10) == 0);
+        kak_assert(map[10] == 2);
+        map.remove(10);
+        kak_assert(map.find_index(10) == -1);
+    }
+
+    // Multiple entries with the same key
+    {
+        MultiHashMap<int, int> map;
+        map.insert({10, 1});
+        map.insert({10, 2});
+        kak_assert(map.find_index(10) == 0);
         map.remove(10);
         kak_assert(map.find_index(10) == 0);
         map.remove(10);
diff --git a/src/hash_map.hh b/src/hash_map.hh
index b7ae4494..759cdbe7 100644
--- a/src/hash_map.hh
+++ b/src/hash_map.hh
@@ -160,7 +160,8 @@ struct HashItem
 
 template<typename Key, typename Value,
          MemoryDomain domain = MemoryDomain::Undefined,
-         template<typename, MemoryDomain> class Container = Vector>
+         template<typename, MemoryDomain> class Container = Vector,
+         bool multi_key = false>
 struct HashMap
 {
     using Item = HashItem<Key, Value>;
@@ -176,8 +177,18 @@ struct HashMap
 
     constexpr Value& insert(Item item)
     {
+        const auto hash = hash_value(item.key);
+        if constexpr (not multi_key)
+        {
+            if (auto index = find_index(item.key, hash); index >= 0)
+            {
+                m_items[index] = std::move(item);
+                return m_items[index].value;
+            }
+        }
+
         m_index.reserve(m_items.size()+1);
-        m_index.add(hash_value(item.key), (int)m_items.size());
+        m_index.add(hash, (int)m_items.size());
         m_items.push_back(std::move(item));
         return m_items.back().value;
     }
@@ -315,6 +326,11 @@ private:
     HashIndex<domain, Container> m_index;
 };
 
+template<typename Key, typename Value,
+         MemoryDomain domain = MemoryDomain::Undefined,
+         template<typename, MemoryDomain> class Container = Vector>
+ using MultiHashMap = HashMap<Key, Value, domain, Container, true>;
+
 void profile_hash_maps();
 
 }