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Change meaning of offset in QStringData

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It used to be an index into the first element in 'd' that came after
'offset'. It is now the byte offset from the beginning of the
QStringData structure.

By no longer using an actual array to access characters, we also steer
clear of GCC bug #43247:

    http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43247

This aligns this data structure with QArrayData. The intention is to
have QVector, QString and QByteArray share the same memory layout and
possibly code.

Change-Id: I4850813e1bd47c3cb670c50c9a8ccc1bff2e8597
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
João Abecasis 2012-02-17 14:18:45 +01:00 committed by Qt by Nokia
parent 3fe1eed053
commit a5233b6b22
3 changed files with 26 additions and 25 deletions
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32
src/corelib/tools/qstring.cpp
View File

@ -94,6 +94,8 @@
#define ULLONG_MAX quint64_C(18446744073709551615)
#endif
#define IS_RAW_DATA(d) ((d)->offset != sizeof(QStringData))
QT_BEGIN_NAMESPACE
#ifndef QT_NO_TEXTCODEC
@ -800,8 +802,8 @@ const QString::Null QString::null = { };
\sa split()
*/
const QStaticStringData<1> QString::shared_null = { { Q_REFCOUNT_INITIALIZE_STATIC, 0, 0, false, { 0 } }, { 0 } };
const QStaticStringData<1> QString::shared_empty = { { Q_REFCOUNT_INITIALIZE_STATIC, 0, 0, false, { 0 } }, { 0 } };
const QStaticStringData<1> QString::shared_null = { { Q_REFCOUNT_INITIALIZE_STATIC, 0, 0, false, sizeof(QStringData) }, { 0 } };
const QStaticStringData<1> QString::shared_empty = { { Q_REFCOUNT_INITIALIZE_STATIC, 0, 0, false, sizeof(QStringData) }, { 0 } };
int QString::grow(int size)
{
@ -1052,7 +1054,7 @@ QString::QString(const QChar *unicode, int size)
d->size = size;
d->alloc = (uint) size;
d->capacityReserved = false;
d->offset = 0;
d->offset = sizeof(QStringData);
memcpy(d->data(), unicode, size * sizeof(QChar));
d->data()[size] = '\0';
}
@ -1076,7 +1078,7 @@ QString::QString(int size, QChar ch)
d->size = size;
d->alloc = (uint) size;
d->capacityReserved = false;
d->offset = 0;
d->offset = sizeof(QStringData);
d->data()[size] = '\0';
ushort *i = d->data() + size;
ushort *b = d->data();
@ -1100,7 +1102,7 @@ QString::QString(int size, Qt::Initialization)
d->size = size;
d->alloc = (uint) size;
d->capacityReserved = false;
d->offset = 0;
d->offset = sizeof(QStringData);
d->data()[size] = '\0';
}
@ -1122,7 +1124,7 @@ QString::QString(QChar ch)
d->size = 1;
d->alloc = 1;
d->capacityReserved = false;
d->offset = 0;
d->offset = sizeof(QStringData);
d->data()[0] = ch.unicode();
d->data()[1] = '\0';
}
@ -1220,7 +1222,7 @@ void QString::resize(int size)
if (size < 0)
size = 0;
if (d->offset && !d->ref.isShared() && size < d->size) {
if (IS_RAW_DATA(d) && !d->ref.isShared() && size < d->size) {
d->size = size;
return;
}
@ -1294,14 +1296,14 @@ void QString::resize(int size)
// ### Qt 5: rename reallocData() to avoid confusion. 197625
void QString::realloc(int alloc)
{
if (d->ref.isShared() || d->offset) {
if (d->ref.isShared() || IS_RAW_DATA(d)) {
Data *x = static_cast<Data *>(::malloc(sizeof(Data) + (alloc+1) * sizeof(QChar)));
Q_CHECK_PTR(x);
x->ref.initializeOwned();
x->size = qMin(alloc, d->size);
x->alloc = (uint) alloc;
x->capacityReserved = d->capacityReserved;
x->offset =0;
x->offset = sizeof(QStringData);
::memcpy(x->data(), d->data(), x->size * sizeof(QChar));
x->data()[x->size] = 0;
if (!d->ref.deref())
@ -1312,7 +1314,7 @@ void QString::realloc(int alloc)
Q_CHECK_PTR(p);
d = p;
d->alloc = alloc;
d->offset = 0;
d->offset = sizeof(QStringData);
}
}
@ -3741,7 +3743,7 @@ QString::Data *QString::fromLatin1_helper(const char *str, int size)
d->size = size;
d->alloc = (uint) size;
d->capacityReserved = false;
d->offset = 0;
d->offset = sizeof(QStringData);
d->data()[size] = '\0';
ushort *dst = d->data();
/* SIMD:
@ -4769,7 +4771,7 @@ int QString::localeAwareCompare_helper(const QChar *data1, int length1,
const ushort *QString::utf16() const
{
if (d->offset)
if (IS_RAW_DATA(d))
const_cast<QString*>(this)->realloc(); // ensure '\\0'-termination for ::fromRawData strings
return d->data();
}
@ -7050,7 +7052,7 @@ QString QString::fromRawData(const QChar *unicode, int size)
x->size = size;
x->alloc = 0;
x->capacityReserved = false;
x->offset = (const ushort *)unicode - (x->d + sizeof(qptrdiff)/sizeof(ushort));
x->offset = reinterpret_cast<const char *>(unicode) - reinterpret_cast<char *>(x);
}
return QString(x, 0);
}
@ -7076,9 +7078,9 @@ QString &QString::setRawData(const QChar *unicode, int size)
} else {
if (unicode) {
d->size = size;
d->offset = (const ushort *)unicode - (d->d + sizeof(qptrdiff)/sizeof(ushort));
d->offset = reinterpret_cast<const char *>(unicode) - reinterpret_cast<char *>(d);
} else {
d->offset = 0;
d->offset = sizeof(QStringData);
d->size = 0;
}
}

17
src/corelib/tools/qstring.h
View File

@ -75,12 +75,11 @@ struct QStringData {
int size;
uint alloc : 31;
uint capacityReserved : 1;
union {
qptrdiff offset; // will always work as we add/subtract from a ushort ptr
ushort d[sizeof(qptrdiff)/sizeof(ushort)];
};
inline ushort *data() { return d + sizeof(qptrdiff)/sizeof(ushort) + offset; }
inline const ushort *data() const { return d + sizeof(qptrdiff)/sizeof(ushort) + offset; }
qptrdiff offset;
inline ushort *data() { return reinterpret_cast<ushort *>(reinterpret_cast<char *>(this) + offset); }
inline const ushort *data() const { return reinterpret_cast<const ushort *>(reinterpret_cast<const char *>(this) + offset); }
};
template<int N> struct QStaticStringData;
@ -126,7 +125,7 @@ template<int N> struct QStaticStringData
# define QStringLiteral(str) ([]() -> QStaticStringDataPtr<sizeof(QT_UNICODE_LITERAL(str))/2 - 1> { \
enum { Size = sizeof(QT_UNICODE_LITERAL(str))/2 - 1 }; \
static const QStaticStringData<Size> qstring_literal = \
{ { Q_REFCOUNT_INITIALIZE_STATIC, Size, 0, 0, { 0 } }, QT_UNICODE_LITERAL(str) }; \
{ { Q_REFCOUNT_INITIALIZE_STATIC, Size, 0, 0, sizeof(QStringData) }, QT_UNICODE_LITERAL(str) }; \
QStaticStringDataPtr<Size> holder = { &qstring_literal }; \
return holder; }())
@ -139,7 +138,7 @@ template<int N> struct QStaticStringData
__extension__ ({ \
enum { Size = sizeof(QT_UNICODE_LITERAL(str))/2 - 1 }; \
static const QStaticStringData<Size> qstring_literal = \
{ { Q_REFCOUNT_INITIALIZE_STATIC, Size, 0, 0, { 0 } }, QT_UNICODE_LITERAL(str) }; \
{ { Q_REFCOUNT_INITIALIZE_STATIC, Size, 0, 0, sizeof(QStringData) }, QT_UNICODE_LITERAL(str) }; \
QStaticStringDataPtr<Size> holder = { &qstring_literal }; \
holder; })
# endif
@ -705,7 +704,7 @@ inline QChar *QString::data()
inline const QChar *QString::constData() const
{ return reinterpret_cast<const QChar*>(d->data()); }
inline void QString::detach()
{ if (d->ref.isShared() || d->offset) realloc(); }
{ if (d->ref.isShared() || (d->offset != sizeof(QStringData))) realloc(); }
inline bool QString::isDetached() const
{ return !d->ref.isShared(); }
inline QString &QString::operator=(const QLatin1String &s)

2
tests/auto/corelib/tools/qstring/tst_qstring.cpp
View File

@ -5150,7 +5150,7 @@ void tst_QString::literals()
QVERIFY(str.length() == 4);
QVERIFY(str == QLatin1String("abcd"));
QVERIFY(str.data_ptr()->ref.isStatic());
QVERIFY(str.data_ptr()->offset == 0);
QVERIFY(str.data_ptr()->offset == sizeof(QStringData));
const QChar *s = str.constData();
QString str2 = str;