From d54d84a213041f9b84bc3061019f1d089ab74019 Mon Sep 17 00:00:00 2001
From: Ivan Komissarov <abbapoh@gmail.com>
Date: Wed, 21 Apr 2021 14:03:58 +0200
Subject: Use binary search in Set::find()

Change-Id: I5ed154633233dfeedf6b69b52fc5339fef3a956a
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
---
 src/lib/corelib/tools/set.h      |  4 ++--
 src/lib/corelib/tools/stlutils.h | 15 +++++++++++++++
 tests/auto/tools/tst_tools.cpp   | 24 ++++++++++++++++++++++++
 tests/auto/tools/tst_tools.h     |  1 +
 4 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/src/lib/corelib/tools/set.h b/src/lib/corelib/tools/set.h
index 75db0528b..463d3beb6 100644
--- a/src/lib/corelib/tools/set.h
+++ b/src/lib/corelib/tools/set.h
@@ -112,8 +112,8 @@ public:
     Set &operator&=(const Set &other) { return intersect(other); }
     Set &operator&=(const T &v) { return intersect(Set{ v }); }
 
-    iterator find(const T &v) { return std::find(m_data.begin(), m_data.end(), v); }
-    const_iterator find(const T &v) const { return std::find(m_data.cbegin(), m_data.cend(), v); }
+    iterator find(const T &v) { return binaryFind(m_data.begin(), m_data.end(), v); }
+    const_iterator find(const T &v) const { return binaryFind(m_data.cbegin(), m_data.cend(), v); }
     std::pair<iterator, bool> insert(const T &v);
     Set &operator+=(const T &v) { insert(v); return *this; }
     Set &operator|=(const T &v) { return operator+=(v); }
diff --git a/src/lib/corelib/tools/stlutils.h b/src/lib/corelib/tools/stlutils.h
index 1b6d7278f..d4c569a95 100644
--- a/src/lib/corelib/tools/stlutils.h
+++ b/src/lib/corelib/tools/stlutils.h
@@ -123,6 +123,21 @@ bool none_of(const Container &container, const UnaryPredicate &predicate)
     return std::none_of(std::begin(container), std::end(container), predicate);
 }
 
+template <class It, class T, class Compare>
+It binaryFind(It begin, It end, const T &value, Compare comp)
+{
+    const auto it = std::lower_bound(begin, end, value, comp);
+    if (it == end || comp(value, *it))
+        return end;
+    return it;
+}
+
+template <class It, class T>
+It binaryFind(It begin, It end, const T &value)
+{
+    return binaryFind(begin, end, value, std::less<T>());
+}
+
 template <class C>
 C &operator<<(C &container, const typename C::value_type &v)
 {
diff --git a/tests/auto/tools/tst_tools.cpp b/tests/auto/tools/tst_tools.cpp
index edf5a1308..92e0978b5 100644
--- a/tests/auto/tools/tst_tools.cpp
+++ b/tests/auto/tools/tst_tools.cpp
@@ -673,6 +673,30 @@ void TestTools::set_containsSet()
     QVERIFY(set3.contains(set4));
 }
 
+void TestTools::set_find()
+{
+    Set<QString> set1;
+
+    for (int i = 0; i < 500; ++i) {
+        QVERIFY(set1.find(QString::number(i)) == set1.end());
+        set1.insert(QString::number(i));
+        const auto it = set1.find(QString::number(i));
+        QVERIFY(it != set1.end());
+        QVERIFY(*it == QString::number(i));
+    }
+
+    QCOMPARE(set1.size(), size_t { 500 });
+
+    for (int j = 0; j < 500; ++j) {
+        int i = (j * 17) % 500;
+        const auto it = set1.find(QString::number(i));
+        QVERIFY(it != set1.end());
+        QVERIFY(*it == QString::number(i));
+        set1.remove(QString::number(i));
+        QVERIFY(set1.find(QString::number(i)) == set1.end());
+    }
+}
+
 void TestTools::set_begin()
 {
     Set<int> set1;
diff --git a/tests/auto/tools/tst_tools.h b/tests/auto/tools/tst_tools.h
index bd8538be2..d1ba0a57b 100644
--- a/tests/auto/tools/tst_tools.h
+++ b/tests/auto/tools/tst_tools.h
@@ -79,6 +79,7 @@ private slots:
     void set_remove();
     void set_contains();
     void set_containsSet();
+    void set_find();
     void set_begin();
     void set_end();
     void set_insert();
-- 
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