From e8e85f5457a225f6387efdf1f4d9f36f93fce3fb Mon Sep 17 00:00:00 2001
From: Andreas Kling <awesomekling@gmail.com>
Date: Wed, 7 Aug 2019 15:05:10 +0200
Subject: [PATCH] Vector: Use memcmp for comparing two vectors with trivial
 elements

---
 AK/Tests/TestVector.cpp | 25 +++++++++++++++++++++++++
 AK/Traits.h             |  2 +-
 AK/Vector.h             | 20 +++++++++++++-------
 3 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/AK/Tests/TestVector.cpp b/AK/Tests/TestVector.cpp
index 1405ccfb4af..88a53ba9fe8 100644
--- a/AK/Tests/TestVector.cpp
+++ b/AK/Tests/TestVector.cpp
@@ -142,4 +142,29 @@ TEST_CASE(prepend_vector_object)
     EXPECT_EQ(objects[5].subobject->value, 3);
 }
 
+TEST_CASE(vector_compare)
+{
+    Vector<int> ints;
+    Vector<int> same_ints;
+
+    for (int i = 0; i < 1000; ++i) {
+        ints.append(i);
+        same_ints.append(i);
+    }
+
+    EXPECT_EQ(ints.size(), 1000);
+    EXPECT_EQ(ints, same_ints);
+
+    Vector<String> strings;
+    Vector<String> same_strings;
+
+    for (int i = 0; i < 1000; ++i) {
+        strings.append(String::number(i));
+        same_strings.append(String::number(i));
+    }
+
+    EXPECT_EQ(strings.size(), 1000);
+    EXPECT_EQ(strings, same_strings);
+}
+
 TEST_MAIN(Vector)
diff --git a/AK/Traits.h b/AK/Traits.h
index 0eaf5d3e869..fb5ce773d36 100644
--- a/AK/Traits.h
+++ b/AK/Traits.h
@@ -7,12 +7,12 @@ namespace AK {
 
 template<typename T>
 struct GenericTraits {
+    static constexpr bool is_trivial() { return false; }
     static bool equals(const T& a, const T& b) { return a == b; }
 };
 
 template<typename T>
 struct Traits : public GenericTraits<T> {
-    static constexpr bool is_trivial() { return false; }
 };
 
 template<>
diff --git a/AK/Vector.h b/AK/Vector.h
index 21e3aa1b916..631efdb0649 100644
--- a/AK/Vector.h
+++ b/AK/Vector.h
@@ -85,6 +85,18 @@ public:
         for (size_t i = 0; i < count; ++i)
             new (&destination[i]) T(source[i]);
     }
+
+    static bool compare(const T* a, const T* b, size_t count)
+    {
+        if constexpr (Traits<T>::is_trivial())
+            return !memcmp(a, b, count * sizeof(T));
+
+        for (size_t i = 0; i < count; ++i) {
+            if (a[i] != b[i])
+                return false;
+        }
+        return true;
+    }
 };
 
 template<typename T, int inline_capacity = 0>
@@ -178,13 +190,7 @@ public:
     {
         if (m_size != other.m_size)
             return false;
-
-        for (int i = 0; i < m_size; ++i) {
-            if (at(i) != other.at(i))
-                return false;
-        }
-
-        return true;
+        return TypedTransfer<T>::compare(data(), other.data(), size());
     }
 
     bool operator!=(const Vector& other) const