1/****************************************************************************
2**
3** Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com>
4** Contact: http://www.qt.io/licensing/
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38****************************************************************************/
39#ifndef QDUPLICATETRACKER_P_H
40#define QDUPLICATETRACKER_P_H
41
42//
43// W A R N I N G
44// -------------
45//
46// This file is not part of the Qt API. It exists purely as an
47// implementation detail. This header file may change from version to
48// version without notice, or even be removed.
49//
50// We mean it.
51//
52
53#include <qglobal.h>
54
55#if QT_HAS_INCLUDE(<memory_resource>) && __cplusplus > 201402L
56# include <unordered_set>
57# include <memory_resource>
58# include <qhash.h> // for the hashing helpers
59#else
60# include <qset.h>
61#endif
62
63QT_BEGIN_NAMESPACE
64
65template <typename T, size_t Prealloc = 32>
66class QDuplicateTracker {
67#ifdef __cpp_lib_memory_resource
68 template <typename HT>
69 struct QHasher {
70 size_t storedSeed = qGlobalQHashSeed();
71 size_t operator()(const HT &t) const {
72 return QHashPrivate::calculateHash(t, storedSeed);
73 }
74 };
75
76 char buffer[Prealloc * sizeof(T)];
77 std::pmr::monotonic_buffer_resource res{buffer, sizeof buffer};
78 std::pmr::unordered_set<T, QHasher<T>> set{&res};
79#else
80 QSet<T> set;
81 int setSize = 0;
82#endif
83 Q_DISABLE_COPY_MOVE(QDuplicateTracker);
84public:
85 QDuplicateTracker() = default;
86 void reserve(int n) { set.reserve(n); }
87 [[nodiscard]] bool hasSeen(const T &s)
88 {
89 bool inserted;
90#ifdef __cpp_lib_memory_resource
91 inserted = set.insert(s).second;
92#else
93 set.insert(s);
94 const int n = set.size();
95 inserted = qExchange(setSize, n) != n;
96#endif
97 return !inserted;
98 }
99 [[nodiscard]] bool hasSeen(T &&s)
100 {
101 bool inserted;
102#ifdef __cpp_lib_memory_resource
103 inserted = set.insert(std::move(s)).second;
104#else
105 set.insert(std::move(s));
106 const int n = set.size();
107 inserted = qExchange(setSize, n) != n;
108#endif
109 return !inserted;
110 }
111
112 template <typename C>
113 void appendTo(C &c) const
114 {
115 for (const auto &e : set)
116 c.push_back(e);
117 }
118};
119
120QT_END_NAMESPACE
121
122#endif /* QDUPLICATETRACKER_P_H */
123