From 39efc7c3e3a08580f00a19678d2975608d41aa17 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C4=99drzej=20Nowacki?= <jedrzej.nowacki@digia.com>
Date: Wed, 19 Feb 2014 11:27:50 +0100
Subject: Optimize QVector::mid

Change-Id: Iff7d9ec85a095c6712e6045e7708bb88eac629e1
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
---
 src/corelib/tools/qvector.h                      | 12 +++++++-----
 tests/auto/corelib/tools/qvector/tst_qvector.cpp |  2 ++
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/corelib/tools/qvector.h b/src/corelib/tools/qvector.h
index 9692477e18..c547cec7be 100644
--- a/src/corelib/tools/qvector.h
+++ b/src/corelib/tools/qvector.h
@@ -833,11 +833,13 @@ Q_OUTOFLINE_TEMPLATE QVector<T> QVector<T>::mid(int pos, int len) const
         break;
     }
 
-    QVector<T> copy;
-    copy.reserve(len);
-    for (int i = pos; i < pos + len; ++i)
-        copy += at(i);
-    return copy;
+    QVector<T> midResult;
+    midResult.reallocData(0, len);
+    T *srcFrom = d->begin() + pos;
+    T *srcTo = d->begin() + pos + len;
+    midResult.copyConstruct(srcFrom, srcTo, midResult.data());
+    midResult.d->size = len;
+    return midResult;
 }
 
 template <typename T>
diff --git a/tests/auto/corelib/tools/qvector/tst_qvector.cpp b/tests/auto/corelib/tools/qvector/tst_qvector.cpp
index 776251fa52..97f370f146 100644
--- a/tests/auto/corelib/tools/qvector/tst_qvector.cpp
+++ b/tests/auto/corelib/tools/qvector/tst_qvector.cpp
@@ -1379,6 +1379,8 @@ void tst_QVector::mid() const
     list << "foo" << "bar" << "baz" << "bak" << "buck" << "hello" << "kitty";
 
     QCOMPARE(list.mid(3, 3), QVector<QString>() << "bak" << "buck" << "hello");
+    QCOMPARE(list.mid(6, 10), QVector<QString>() << "kitty");
+    QCOMPARE(list.mid(-1, 20), list);
     QCOMPARE(list.mid(4), QVector<QString>() << "buck" << "hello" << "kitty");
 }
 
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