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QMetaTypeId: use QByteArray, not QVarLengthArray, to construct type names

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So far, type-name strings for class template instantiations were constructed
in QMetaTypeId::qt_metatype_id() by concatenating various bits and pieces
into a QVarLengthArray<char>, presumably to avoid the dynamic memory
allocation for small strings.

Yet, when passing the result to qRegisterNormalisedMetaType, which takes
a QByteArray, the QVarLengthArray was copied from, not by
QByteArray::fromRawData(), but by QByteArray(const char*,int), which
unconditionally results in a dynamic memory allocation after all.

What's worse: the characters are copied twice: First into the QVarLengthArray,
and then into the QByteArray.

Remove the first of these copies by using QByteArray+reserve() to copy
directly into the final QByteArray.

Change-Id: Id915798a318fe97279a7cc0aca176544f99c7e86
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
This commit is contained in:
Marc Mutz 2012-08-27 10:39:16 +02:00 committed by The Qt Project
parent 04ebd8e56f
commit c400e16a58
1 changed files with 34 additions and 27 deletions
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59
src/corelib/kernel/qmetatype.h
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@ -670,12 +670,12 @@ struct QMetaTypeIdQObject<T*, /* isPointerToTypeDerivedFromQObject */ true>
static QBasicAtomicInt metatype_id = Q_BASIC_ATOMIC_INITIALIZER(0);
if (const int id = metatype_id.loadAcquire())
return id;
const int len = int(strlen(T::staticMetaObject.className()));
QVarLengthArray<char, 16> classNameStar;
classNameStar.append(T::staticMetaObject.className(), len);
classNameStar.append('*');
const int newId = qRegisterNormalizedMetaType<T*>( \
QByteArray(classNameStar.constData(), classNameStar.size()),
const char * const cName = T::staticMetaObject.className();
QByteArray typeName;
typeName.reserve(strlen(cName) + 1);
typeName.append(cName).append('*');
const int newId = qRegisterNormalizedMetaType<T*>(
typeName,
reinterpret_cast<T**>(quintptr(-1)));
metatype_id.storeRelease(newId);
return newId;
@ -757,17 +757,18 @@ struct QMetaTypeId< SINGLE_ARG_TEMPLATE<T> > \
static QBasicAtomicInt metatype_id = Q_BASIC_ATOMIC_INITIALIZER(0); \
if (const int id = metatype_id.load()) \
return id; \
QVarLengthArray<char, 24> name; \
name.append(#SINGLE_ARG_TEMPLATE, int(sizeof(#SINGLE_ARG_TEMPLATE)) - 1); \
name.append('<'); \
const char *tName = QMetaType::typeName(qMetaTypeId<T>()); \
Q_ASSERT(tName); \
name.append(tName, int(strlen(tName))); \
if (name.last() == '>') \
name.append(' '); \
name.append('>'); \
const int tNameLen = qstrlen(tName); \
QByteArray typeName; \
typeName.reserve(sizeof(#SINGLE_ARG_TEMPLATE) + 1 + tNameLen + 1 + 1); \
typeName.append(#SINGLE_ARG_TEMPLATE, sizeof(#SINGLE_ARG_TEMPLATE) - 1) \
.append('<').append(tName, tNameLen); \
if (typeName.endsWith('>')) \
typeName.append(' '); \
typeName.append('>'); \
const int newId = qRegisterNormalizedMetaType< SINGLE_ARG_TEMPLATE<T> >( \
QByteArray(name.constData(), name.size()), \
typeName, \
reinterpret_cast< SINGLE_ARG_TEMPLATE<T> *>(quintptr(-1))); \
metatype_id.storeRelease(newId); \
return newId; \
@ -786,21 +787,21 @@ struct QMetaTypeId< DOUBLE_ARG_TEMPLATE<T, U> > \
static QBasicAtomicInt metatype_id = Q_BASIC_ATOMIC_INITIALIZER(0); \
if (const int id = metatype_id.loadAcquire()) \
return id; \
QVarLengthArray<char, 24> name; \
name.append(#DOUBLE_ARG_TEMPLATE, sizeof(#DOUBLE_ARG_TEMPLATE) - 1); \
name.append('<'); \
const char *tName = QMetaType::typeName(qMetaTypeId<T>()); \
Q_ASSERT(tName); \
name.append(tName, int(strlen(tName))); \
name.append(','); \
const char *uName = QMetaType::typeName(qMetaTypeId<U>()); \
Q_ASSERT(tName); \
Q_ASSERT(uName); \
name.append(uName, int(strlen(uName))); \
if (name.last() == '>') \
name.append(' '); \
name.append('>'); \
const int tNameLen = qstrlen(tName); \
const int uNameLen = qstrlen(uName); \
QByteArray typeName; \
typeName.reserve(sizeof(#DOUBLE_ARG_TEMPLATE) + 1 + tNameLen + 1 + uNameLen + 1 + 1); \
typeName.append(#DOUBLE_ARG_TEMPLATE, sizeof(#DOUBLE_ARG_TEMPLATE) - 1) \
.append('<').append(tName, tNameLen).append(',').append(uName, uNameLen); \
if (typeName.endsWith('>')) \
typeName.append(' '); \
typeName.append('>'); \
const int newId = qRegisterNormalizedMetaType< DOUBLE_ARG_TEMPLATE<T, U> >(\
QByteArray(name.constData(), name.size()), \
typeName, \
reinterpret_cast< DOUBLE_ARG_TEMPLATE<T, U> *>(quintptr(-1))); \
metatype_id.storeRelease(newId); \
return newId; \
@ -827,7 +828,13 @@ struct QMetaTypeId_ ## SMART_POINTER ## _QObjectStar<T, true> \
static QBasicAtomicInt metatype_id = Q_BASIC_ATOMIC_INITIALIZER(0); \
if (const int id = metatype_id.loadAcquire()) \
return id; \
const int newId = qRegisterNormalizedMetaType< SMART_POINTER<T> >( #SMART_POINTER "<" + QByteArray(T::staticMetaObject.className()) + ">", \
const char * const cName = T::staticMetaObject.className(); \
QByteArray typeName; \
typeName.reserve(sizeof(#SMART_POINTER) + 1 + strlen(cName) + 1); \
typeName.append(#SMART_POINTER, sizeof(#SMART_POINTER) - 1) \
.append('<').append(cName).append('>'); \
const int newId = qRegisterNormalizedMetaType< SMART_POINTER<T> >( \
typeName, \
reinterpret_cast< SMART_POINTER<T> *>(quintptr(-1))); \
metatype_id.storeRelease(newId); \
return newId; \