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Add move constructor to QDateTime 

The move constructor is slightly more interesting than the copy
constructor because we can reset other to a short data state on 64-bit
systems. The assembly of that function is simply:

       mov    (%rsi),%rax
       mov    %rax,(%rdi)
       movq   $0x1,(%rsi)
       retq

The move-assignment operator for QDateTime was already there. There's no
need for one for QDateTime::Data since it's never called.

Change-Id: I06bae9392f534e45b3f1ffff144dffdd7f23b170
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
bb10
Thiago Macieira 2016-05-12 19:33:00 -07:00
parent 72393ac3b6
commit cbe62a0e6d
2 changed files with 26 additions and 2 deletions
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25
src/corelib/tools/qdatetime.cpp
View File

@ -2763,6 +2763,20 @@ inline QDateTime::Data::Data(const Data &other)
}
}
inline QDateTime::Data::Data(Data &&other)
: d(other.d)
{
// reset the other to a short state, if we can
if (CanBeSmall) {
Data dummy(Qt::LocalTime);
Q_ASSERT(dummy.isShort());
other.d = dummy.d;
} else if (!isShort()) {
// can't be small, so do implicit sharing
d->ref.ref();
}
}
inline QDateTime::Data &QDateTime::Data::operator=(const Data &other)
{
if (d == other.d)
@ -3095,12 +3109,21 @@ QDateTime::QDateTime(const QDate &date, const QTime &time, const QTimeZone &time
/*!
Constructs a copy of the \a other datetime.
*/
QDateTime::QDateTime(const QDateTime &other) Q_DECL_NOTHROW
: d(other.d)
{
}
/*!
\since 5.8
Moves the content of the temporary \a other datetime to this object and
leaves \a other in an unspecified (but proper) state.
*/
QDateTime::QDateTime(QDateTime &&other) Q_DECL_NOTHROW
: d(std::move(other.d))
{
}
/*!
Destroys the datetime.
*/

3
src/corelib/tools/qdatetime.h
View File

@ -232,8 +232,8 @@ class Q_CORE_EXPORT QDateTime
Data(Qt::TimeSpec);
Data(const Data &other);
Data(Data &&other);
Data &operator=(const Data &other);
// no move semantics (would be the same as copy)
~Data();
bool isShort() const;
@ -256,6 +256,7 @@ public:
QDateTime(const QDate &date, const QTime &time, const QTimeZone &timeZone);
#endif // QT_BOOTSTRAPPED
QDateTime(const QDateTime &other) Q_DECL_NOTHROW;
QDateTime(QDateTime &&other) Q_DECL_NOTHROW;
~QDateTime();
#ifdef Q_COMPILER_RVALUE_REFS