From 6cd37869ca724b0207dd4d784c0a7ac559220f08 Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Thu, 16 Feb 2023 09:04:11 +0100
Subject: [PATCH] QVarLengthArray: Extract Method QtPrivate::q_rotate()
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It seems like we'll need this in lots of other places, too.

Change-Id: I767495c2eb02a2fc85b6f835ad9003fa89315c7f
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
(cherry picked from commit 147dd6e82f41778060bdadf9b2a792bd11e1bc1e)
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
---
 src/corelib/tools/qcontainertools_impl.h | 20 ++++++++++++++++++++
 src/corelib/tools/qvarlengtharray.h      |  7 +------
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/src/corelib/tools/qcontainertools_impl.h b/src/corelib/tools/qcontainertools_impl.h
index adaa254a04a..d380421170c 100644
--- a/src/corelib/tools/qcontainertools_impl.h
+++ b/src/corelib/tools/qcontainertools_impl.h
@@ -86,6 +86,26 @@ void q_uninitialized_relocate_n(T* first, N n, T* out)
 
 QT_WARNING_POP
 
+/*!
+    \internal
+
+    A wrapper around std::rotate(), with an optimization for
+    Q_RELOCATABLE_TYPEs. We omit the return value, as it would be more work to
+    compute in the Q_RELOCATABLE_TYPE case and, unlike std::rotate on
+    ForwardIterators, callers can compute the result in constant time
+    themselves.
+*/
+template <typename T>
+void q_rotate(T *first, T *mid, T *last)
+{
+    if constexpr (QTypeInfo<T>::isRelocatable) {
+        const auto cast = [](T *p) { return reinterpret_cast<uchar*>(p); };
+        std::rotate(cast(first), cast(mid), cast(last));
+    } else {
+        std::rotate(first, mid, last);
+    }
+}
+
 template<typename iterator, typename N>
 void q_relocate_overlap_n_left_move(iterator first, N n, iterator d_first)
 {
diff --git a/src/corelib/tools/qvarlengtharray.h b/src/corelib/tools/qvarlengtharray.h
index 618e04b41cf..6428c359c0e 100644
--- a/src/corelib/tools/qvarlengtharray.h
+++ b/src/corelib/tools/qvarlengtharray.h
@@ -853,12 +853,7 @@ Q_OUTOFLINE_TEMPLATE auto QVLABase<T>::emplace_impl(qsizetype prealloc, void *ar
     emplace_back_impl(prealloc, array, std::forward<Args>(args)...);
     const auto b = begin() + offset;
     const auto e = end();
-    if constexpr (QTypeInfo<T>::isRelocatable) {
-        auto cast = [](T *p) { return reinterpret_cast<uchar*>(p); };
-        std::rotate(cast(b), cast(e - 1), cast(e));
-    } else {
-        std::rotate(b, e - 1, e);
-    }
+    QtPrivate::q_rotate(b, e - 1, e);
     return b;
 }