From 20cf632ad5f3ffe7b0fd231724c971f4e07304eb Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C4=99drzej=20Nowacki?= Date: Thu, 26 Jun 2014 13:02:54 +0200 Subject: Reading QJsonObject property should not modify the object itself. Before this change such code: QJsonObject o; o["blah"]; would create property "blah" and assign null value to it, while this code: const QJsonObject o; o["blah"]; would not. The change unifies the confusing behavior. Now reading a non-existing property, is not causing a property to be added in any visible way. Internally QJsonObject stores a special hash of undefined, but referenced values. Such reference is supposed to not live long, only to the first compacting or assignment. Change-Id: Ib022acf74ff49bad88d45d65d7093c4281d468f1 Reviewed-by: Thiago Macieira Reviewed-by: Lars Knoll --- src/corelib/json/qjson_p.h | 71 ++++++++++++++++++++++++++++++++++++++++ src/corelib/json/qjsonobject.cpp | 14 ++++---- src/corelib/json/qjsonvalue.cpp | 7 ++-- src/corelib/json/qjsonvalue.h | 2 ++ 4 files changed, 83 insertions(+), 11 deletions(-) (limited to 'src/corelib/json') diff --git a/src/corelib/json/qjson_p.h b/src/corelib/json/qjson_p.h index 7d0162938d..92330175ba 100644 --- a/src/corelib/json/qjson_p.h +++ b/src/corelib/json/qjson_p.h @@ -61,6 +61,8 @@ #include #include #include +#include +#include #include #include @@ -776,6 +778,75 @@ private: Q_DISABLE_COPY(Data) }; +struct ObjectUndefinedKeys +{ + static void insertKey(const QJsonObject *object, int index, const QString &key) + { + QMutexLocker lock(&mutex); + keys()[object][index] = key; + } + static QString takeKey(const QJsonObject *object, int index) + { + QMutexLocker lock(&mutex); + return keys()[object].take(index); + } + static void removeKeys(const QJsonObject *object) + { + QMutexLocker lock(&mutex); + keys().remove(object); + } +private: + typedef QHash > KeysHash; + static KeysHash &keys() + { + static KeysHash keys; + return keys; + } + static QBasicMutex mutex; +}; + +} // namespace QJsonPrivate + +struct QJsonValueRef::UnionHelper +{ + static inline QJsonObject *untaggedPointer(QJsonObject *object) + { + const quintptr Mask = ~quintptr(0) << 2; + return reinterpret_cast(quintptr(object) & Mask); + } + static inline QJsonObject *taggedPointer(QJsonObject *object) + { + const quintptr Mask = 1; + return reinterpret_cast(quintptr(object) | Mask); + } + + static void setValueAt(QJsonValueRef *ref, QJsonValue value) + { + using namespace QJsonPrivate; + QJsonObject *object = untaggedPointer(ref->o); + if (ref->o != object) + object->insert(ObjectUndefinedKeys::takeKey(object, ref->index), value); + else + object->setValueAt(ref->index, value); + } + + static QJsonValue valueAt(const QJsonValueRef *ref) + { + QJsonObject *object = untaggedPointer(ref->o); + if (ref->o != object) + return QJsonValue::Undefined; + return ref->o->valueAt(ref->index); + } +}; + +/*! + \internal + Constructor that creates reference to an undefined value in \a object. +*/ +inline QJsonValueRef::QJsonValueRef(QJsonObject *object, const QString &key) + : o(UnionHelper::taggedPointer(object)), is_object(true), index(qHash(key)) +{ + QJsonPrivate::ObjectUndefinedKeys::insertKey(object, index, key); } QT_END_NAMESPACE diff --git a/src/corelib/json/qjsonobject.cpp b/src/corelib/json/qjsonobject.cpp index fb975c65e0..94ec9a2818 100644 --- a/src/corelib/json/qjsonobject.cpp +++ b/src/corelib/json/qjsonobject.cpp @@ -134,6 +134,7 @@ QJsonObject::~QJsonObject() { if (d && !d->ref.deref()) delete d; + QJsonPrivate::ObjectUndefinedKeys::removeKeys(this); // ### Qt6 move it to ~QJsonValueRef } /*! @@ -290,14 +291,9 @@ QJsonValue QJsonObject::operator [](const QString &key) const */ QJsonValueRef QJsonObject::operator [](const QString &key) { - // ### somewhat inefficient, as we lookup the key twice if it doesn't yet exist bool keyExists = false; int index = o ? o->indexOf(key, &keyExists) : -1; - if (!keyExists) { - iterator i = insert(key, QJsonValue()); - index = i.i; - } - return QJsonValueRef(this, index); + return keyExists ? QJsonValueRef(this, index) : QJsonValueRef(this, key); } /*! @@ -1001,7 +997,9 @@ void QJsonObject::compact() detach(); d->compact(); - o = static_cast(d->header->root()); + using namespace QJsonPrivate; + o = static_cast(d->header->root()); + ObjectUndefinedKeys::removeKeys(this); // ### Qt6 move it to ~QJsonValueRef } /*! @@ -1038,6 +1036,8 @@ void QJsonObject::setValueAt(int i, const QJsonValue &val) insert(e->key(), val); } +QBasicMutex QJsonPrivate::ObjectUndefinedKeys::mutex; + #if !defined(QT_NO_DEBUG_STREAM) && !defined(QT_JSON_READONLY) QDebug operator<<(QDebug dbg, const QJsonObject &o) { diff --git a/src/corelib/json/qjsonvalue.cpp b/src/corelib/json/qjsonvalue.cpp index 4c4838d314..1224a24709 100644 --- a/src/corelib/json/qjsonvalue.cpp +++ b/src/corelib/json/qjsonvalue.cpp @@ -669,11 +669,10 @@ void QJsonValue::detach() However, they are not explicitly documented here. */ - QJsonValueRef &QJsonValueRef::operator =(const QJsonValue &val) { if (is_object) - o->setValueAt(index, val); + UnionHelper::setValueAt(this, val); else a->replace(index, val); @@ -683,7 +682,7 @@ QJsonValueRef &QJsonValueRef::operator =(const QJsonValue &val) QJsonValueRef &QJsonValueRef::operator =(const QJsonValueRef &ref) { if (is_object) - o->setValueAt(index, ref); + UnionHelper::setValueAt(this, ref); else a->replace(index, ref); @@ -704,7 +703,7 @@ QJsonValue QJsonValueRef::toValue() const { if (!is_object) return a->at(index); - return o->valueAt(index); + return UnionHelper::valueAt(this); } #if !defined(QT_NO_DEBUG_STREAM) && !defined(QT_JSON_READONLY) diff --git a/src/corelib/json/qjsonvalue.h b/src/corelib/json/qjsonvalue.h index 97e20b574d..a00bc0b72f 100644 --- a/src/corelib/json/qjsonvalue.h +++ b/src/corelib/json/qjsonvalue.h @@ -149,6 +149,7 @@ public: : a(array), is_object(false), index(idx) {} QJsonValueRef(QJsonObject *object, int idx) : o(object), is_object(true), index(idx) {} + inline QJsonValueRef(QJsonObject *object, const QString &key); inline operator QJsonValue() const { return toValue(); } QJsonValueRef &operator = (const QJsonValue &val); @@ -188,6 +189,7 @@ private: }; uint is_object : 1; uint index : 31; + struct UnionHelper; }; #if !defined(QT_NO_DEBUG_STREAM) && !defined(QT_JSON_READONLY) -- cgit v1.2.3