From 8c49ae522d184deb5a9118ba2368629709ff6e85 Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@kdab.com>
Date: Mon, 12 Jul 2021 10:10:38 +0200
Subject: QDuplicateTracker: bring back appendTo() &&
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This reverts commit c19695ab953c979f15bbc72c4f4a453e9a114cf6.

Just because QSet has limited API doesn't mean we can't provide this
in an efficient way for std::unordered_set :P

Added tests.

Pick-to: 6.2
Change-Id: I4f8f0e60c810acdc666cf34f929845227ed87f3b
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
---
 src/corelib/tools/qduplicatetracker_p.h | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

(limited to 'src/corelib/tools')

diff --git a/src/corelib/tools/qduplicatetracker_p.h b/src/corelib/tools/qduplicatetracker_p.h
index 565d592ac2..8d64ee5371 100644
--- a/src/corelib/tools/qduplicatetracker_p.h
+++ b/src/corelib/tools/qduplicatetracker_p.h
@@ -105,6 +105,13 @@ class QDuplicateTracker {
 #endif
     Q_DISABLE_COPY_MOVE(QDuplicateTracker);
 public:
+    static constexpr inline bool uses_pmr =
+        #ifdef __cpp_lib_memory_resource
+            true
+        #else
+            false
+        #endif
+            ;
     QDuplicateTracker() = default;
     explicit QDuplicateTracker(qsizetype n)
 #ifdef __cpp_lib_memory_resource
@@ -125,11 +132,22 @@ public:
     }
 
     template <typename C>
-    void appendTo(C &c) const
+    void appendTo(C &c) const &
     {
         for (const auto &e : set)
             c.push_back(e);
     }
+
+    template <typename C>
+    void appendTo(C &c) &&
+    {
+        if constexpr (uses_pmr) {
+            while (!set.empty())
+                c.push_back(std::move(set.extract(set.begin()).value()));
+        } else {
+            return appendTo(c); // lvalue version
+        }
+    }
 };
 
 QT_END_NAMESPACE
-- 
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