From 376e5ef9125fcc7c17c2b96f14cb4b64b28e191a Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Wed, 5 Jan 2022 16:53:24 +0100
Subject: [PATCH] AK: Add HashMap::remove_all_matching(predicate)

This removes all matching entries from a hash map in a single pass.
---
 AK/HashMap.h             | 15 +++++++++++++--
 Tests/AK/TestHashMap.cpp | 24 ++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/AK/HashMap.h b/AK/HashMap.h
index 33251fde72..8a7d2f3160 100644
--- a/AK/HashMap.h
+++ b/AK/HashMap.h
@@ -74,6 +74,17 @@ public:
         return false;
     }
 
+    template<typename TUnaryPredicate>
+    void remove_all_matching(TUnaryPredicate predicate)
+    {
+        for (auto it = begin(); it != end();) {
+            if (predicate(it->key, it->value))
+                it = remove(it);
+            else
+                ++it;
+        }
+    }
+
     using HashTableType = HashTable<Entry, EntryTraits, IsOrdered>;
     using IteratorType = typename HashTableType::Iterator;
     using ConstIteratorType = typename HashTableType::ConstIterator;
@@ -180,9 +191,9 @@ public:
         return find(value) != end();
     }
 
-    void remove(IteratorType it)
+    IteratorType remove(IteratorType it)
     {
-        m_table.remove(it);
+        return m_table.remove(it);
     }
 
     V& ensure(const K& key)
diff --git a/Tests/AK/TestHashMap.cpp b/Tests/AK/TestHashMap.cpp
index 86fc4e98d9..9fef97d8e9 100644
--- a/Tests/AK/TestHashMap.cpp
+++ b/Tests/AK/TestHashMap.cpp
@@ -71,6 +71,30 @@ TEST_CASE(map_remove)
     EXPECT(number_to_string.find(2) != number_to_string.end());
 }
 
+TEST_CASE(remove_all_matching)
+{
+    HashMap<int, String> map;
+
+    map.set(1, "One");
+    map.set(2, "Two");
+    map.set(3, "Three");
+    map.set(4, "Four");
+
+    EXPECT_EQ(map.size(), 4u);
+
+    map.remove_all_matching([&](int key, String const& value) {
+        return key == 1 || value == "Two";
+    });
+
+    EXPECT_EQ(map.size(), 2u);
+    EXPECT(map.contains(3));
+    EXPECT(map.contains(4));
+
+    map.remove_all_matching([&](int, String const&) { return true; });
+
+    EXPECT(map.is_empty());
+}
+
 TEST_CASE(case_insensitive)
 {
     HashMap<String, int, CaseInsensitiveStringTraits> casemap;