1 | /**************************************************************************** |
2 | ** |
3 | ** Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com> |
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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 | #else |
59 | # include <qset.h> |
60 | #endif |
61 | |
62 | QT_BEGIN_NAMESPACE |
63 | |
64 | template <typename T, size_t Prealloc = 32> |
65 | class QDuplicateTracker { |
66 | #ifdef __cpp_lib_memory_resource |
67 | struct node_guesstimate { void *next; size_t hash; T value; }; |
68 | static constexpr size_t bufferSize(size_t N) { |
69 | return N * sizeof(void*) // bucket list |
70 | + N * sizeof(node_guesstimate); // nodes |
71 | } |
72 | |
73 | char buffer[bufferSize(N: Prealloc)]; |
74 | std::pmr::monotonic_buffer_resource res{buffer, sizeof buffer}; |
75 | std::pmr::unordered_set<T> set{Prealloc, &res}; |
76 | #else |
77 | static QSet<T> makeQSet() { QSet<T> r; r.reserve(Prealloc); return r; } |
78 | QSet<T> set = makeQSet(); |
79 | int setSize = 0; |
80 | #endif |
81 | Q_DISABLE_COPY_MOVE(QDuplicateTracker); |
82 | public: |
83 | QDuplicateTracker() = default; |
84 | void reserve(int n) { set.reserve(n); } |
85 | Q_REQUIRED_RESULT bool hasSeen(const T &s) |
86 | { |
87 | bool inserted; |
88 | #ifdef __cpp_lib_memory_resource |
89 | inserted = set.insert(s).second; |
90 | #else |
91 | set.insert(s); |
92 | const int n = set.size(); |
93 | inserted = qExchange(setSize, n) != n; |
94 | #endif |
95 | return !inserted; |
96 | } |
97 | }; |
98 | |
99 | QT_END_NAMESPACE |
100 | |
101 | #endif /* QDUPLICATETRACKER_P_H */ |
102 | |