/**************************************************************************** ** ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). ** Contact: Nokia Corporation (qt-info@nokia.com) ** ** This file is part of the QtCore module of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:LGPL$ ** No Commercial Usage ** This file contains pre-release code and may not be distributed. ** You may use this file in accordance with the terms and conditions ** contained in the either Technology Preview License Agreement or the ** Beta Release License Agreement. ** ** GNU Lesser General Public License Usage ** Alternatively, this file may be used under the terms of the GNU Lesser ** General Public License version 2.1 as published by the Free Software ** Foundation and appearing in the file LICENSE.LGPL included in the ** packaging of this file. Please review the following information to ** ensure the GNU Lesser General Public License version 2.1 requirements ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. ** ** In addition, as a special exception, Nokia gives you certain ** additional rights. These rights are described in the Nokia Qt LGPL ** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this ** package. ** ** GNU General Public License Usage ** Alternatively, this file may be used under the terms of the GNU ** General Public License version 3.0 as published by the Free Software ** Foundation and appearing in the file LICENSE.GPL included in the ** packaging of this file. Please review the following information to ** ensure the GNU General Public License version 3.0 requirements will be ** met: http://www.gnu.org/copyleft/gpl.html. ** ** If you are unsure which license is appropriate for your use, please ** contact the sales department at http://qt.nokia.com/contact. ** $QT_END_LICENSE$ ** ****************************************************************************/ #include "qmap.h" #include #ifdef QT_QMAP_DEBUG # include # include #endif QT_BEGIN_NAMESPACE QMapData QMapData::shared_null = { &shared_null, { &shared_null, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, Q_BASIC_ATOMIC_INITIALIZER(1), 0, 0, 0, false, true }; QMapData *QMapData::createData() { QMapData *d = new QMapData; Q_CHECK_PTR(d); Node *e = reinterpret_cast(d); e->backward = e; e->forward[0] = e; d->ref = 1; d->topLevel = 0; d->size = 0; d->randomBits = 0; d->insertInOrder = false; d->sharable = true; return d; } void QMapData::continueFreeData(int offset) { Node *e = reinterpret_cast(this); Node *cur = e->forward[0]; Node *prev; while (cur != e) { prev = cur; cur = cur->forward[0]; qFree(reinterpret_cast(prev) - offset); } delete this; } /*! Creates a new node inside the data structure. \a update is an array with pointers to the node after which the new node should be inserted. Because of the strange skip list data structure there could be several pointers to this node on different levels. \a offset is an amount of bytes that needs to reserved just before the QMapData::Node structure. */ QMapData::Node *QMapData::node_create(Node *update[], int offset) { int level = 0; uint mask = (1 << Sparseness) - 1; while ((randomBits & mask) == mask && level < LastLevel) { ++level; mask <<= Sparseness; } if (level > topLevel) { Node *e = reinterpret_cast(this); level = ++topLevel; e->forward[level] = e; update[level] = e; } ++randomBits; if (level == 3 && !insertInOrder) randomBits = qrand(); void *concreteNode = qMalloc(offset + sizeof(Node) + level * sizeof(Node *)); Q_CHECK_PTR(concreteNode); Node *abstractNode = reinterpret_cast(reinterpret_cast(concreteNode) + offset); abstractNode->backward = update[0]; update[0]->forward[0]->backward = abstractNode; for (int i = level; i >= 0; i--) { abstractNode->forward[i] = update[i]->forward[i]; update[i]->forward[i] = abstractNode; update[i] = abstractNode; } // update[level+1]=reinterpret_cast(this); ++size; return abstractNode; } void QMapData::node_delete(Node *update[], int offset, Node *node) { node->forward[0]->backward = node->backward; for (int i = 0; i <= topLevel; ++i) { if (update[i]->forward[i] != node) break; update[i]->forward[i] = node->forward[i]; } --size; qFree(reinterpret_cast(node) - offset); } #ifdef QT_QMAP_DEBUG uint QMapData::adjust_ptr(Node *node) { if (node == reinterpret_cast(this)) { return (uint)0xDEADBEEF; } else { return (uint)node; } } void QMapData::dump() { qDebug("Map data (ref = %d, size = %d, randomBits = %#.8x)", int(ref), size, randomBits); QString preOutput; QVector output(topLevel + 1); Node *e = reinterpret_cast(this); QString str; str.sprintf(" %.8x", adjust_ptr(reinterpret_cast(this))); preOutput += str; Node *update[LastLevel + 1]; for (int i = 0; i <= topLevel; ++i) { str.sprintf("%d: [%.8x] -", i, adjust_ptr(reinterpret_cast(forward[i]))); output[i] += str; update[i] = reinterpret_cast(forward[i]); } Node *node = reinterpret_cast(forward[0]); while (node != e) { int level = 0; while (level < topLevel && update[level + 1] == node) ++level; str.sprintf(" %.8x", adjust_ptr(node)); preOutput += str; for (int i = 0; i <= level; ++i) { str.sprintf("-> [%.8x] -", adjust_ptr(node->forward[i])); output[i] += str; update[i] = node->forward[i]; } for (int j = level + 1; j <= topLevel; ++j) output[j] += QString("---------------"); node = node->forward[0]; } qDebug("%s", preOutput.ascii()); for (int i = 0; i <= topLevel; ++i) qDebug("%s", output[i].ascii()); } #endif /*! \class QMap \brief The QMap class is a template class that provides a skip-list-based dictionary. \ingroup tools \ingroup shared \mainclass \reentrant QMap\ is one of Qt's generic \l{container classes}. It stores (key, value) pairs and provides fast lookup of the value associated with a key. QMap and QHash provide very similar functionality. The differences are: \list \i QHash provides faster lookups than QMap. (See \l{Algorithmic Complexity} for details.) \i When iterating over a QHash, the items are arbitrarily ordered. With QMap, the items are always sorted by key. \i The key type of a QHash must provide operator==() and a global qHash(Key) function. The key type of a QMap must provide operator<() specifying a total order. \endlist Here's an example QMap with QString keys and \c int values: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 0 To insert a (key, value) pair into the map, you can use operator[](): \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 1 This inserts the following three (key, value) pairs into the QMap: ("one", 1), ("three", 3), and ("seven", 7). Another way to insert items into the map is to use insert(): \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 2 To look up a value, use operator[]() or value(): \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 3 If there is no item with the specified key in the map, these functions return a \l{default-constructed value}. If you want to check whether the map contains a certain key, use contains(): \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 4 There is also a value() overload that uses its second argument as a default value if there is no item with the specified key: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 5 In general, we recommend that you use contains() and value() rather than operator[]() for looking up a key in a map. The reason is that operator[]() silently inserts an item into the map if no item exists with the same key (unless the map is const). For example, the following code snippet will create 1000 items in memory: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 6 To avoid this problem, replace \c map[i] with \c map.value(i) in the code above. If you want to navigate through all the (key, value) pairs stored in a QMap, you can use an iterator. QMap provides both \l{Java-style iterators} (QMapIterator and QMutableMapIterator) and \l{STL-style iterators} (QMap::const_iterator and QMap::iterator). Here's how to iterate over a QMap using a Java-style iterator: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 7 Here's the same code, but using an STL-style iterator this time: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 8 The items are traversed in ascending key order. Normally, a QMap allows only one value per key. If you call insert() with a key that already exists in the QMap, the previous value will be erased. For example: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 9 However, you can store multiple values per key by using insertMulti() instead of insert() (or using the convenience subclass QMultiMap). If you want to retrieve all the values for a single key, you can use values(const Key &key), which returns a QList: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 10 The items that share the same key are available from most recently to least recently inserted. Another approach is to call find() to get the STL-style iterator for the first item with a key and iterate from there: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 11 If you only need to extract the values from a map (not the keys), you can also use \l{foreach}: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 12 Items can be removed from the map in several ways. One way is to call remove(); this will remove any item with the given key. Another way is to use QMutableMapIterator::remove(). In addition, you can clear the entire map using clear(). QMap's key and value data types must be \l{assignable data types}. This covers most data types you are likely to encounter, but the compiler won't let you, for example, store a QWidget as a value; instead, store a QWidget *. In addition, QMap's key type must provide operator<(). QMap uses it to keep its items sorted, and assumes that two keys \c x and \c y are equal if neither \c{x < y} nor \c{y < x} is true. Example: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 13 In the example, we start by comparing the employees' names. If they're equal, we compare their dates of birth to break the tie. \sa QMapIterator, QMutableMapIterator, QHash, QSet */ /*! \fn QMap::QMap() Constructs an empty map. \sa clear() */ /*! \fn QMap::QMap(const QMap &other) Constructs a copy of \a other. This operation occurs in \l{constant time}, because QMap is \l{implicitly shared}. This makes returning a QMap from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), and this takes \l{linear time}. \sa operator=() */ /*! \fn QMap::QMap(const std::map & other) Constructs a copy of \a other. This function is only available if Qt is configured with STL compatibility enabled. \sa toStdMap() */ /*! \fn std::map QMap::toStdMap() const Returns an STL map equivalent to this QMap. This function is only available if Qt is configured with STL compatibility enabled. */ /*! \fn QMap::~QMap() Destroys the map. References to the values in the map, and all iterators over this map, become invalid. */ /*! \fn QMap &QMap::operator=(const QMap &other) Assigns \a other to this map and returns a reference to this map. */ /*! \fn bool QMap::operator==(const QMap &other) const Returns true if \a other is equal to this map; otherwise returns false. Two maps are considered equal if they contain the same (key, value) pairs. This function requires the value type to implement \c operator==(). \sa operator!=() */ /*! \fn bool QMap::operator!=(const QMap &other) const Returns true if \a other is not equal to this map; otherwise returns false. Two maps are considered equal if they contain the same (key, value) pairs. This function requires the value type to implement \c operator==(). \sa operator==() */ /*! \fn int QMap::size() const Returns the number of (key, value) pairs in the map. \sa isEmpty(), count() */ /*! \fn bool QMap::isEmpty() const Returns true if the map contains no items; otherwise returns false. \sa size() */ /*! \fn void QMap::detach() \internal Detaches this map from any other maps with which it may share data. \sa isDetached() */ /*! \fn bool QMap::isDetached() const \internal Returns true if the map's internal data isn't shared with any other map object; otherwise returns false. \sa detach() */ /*! \fn void QMap::setSharable(bool sharable) \internal */ /*! \fn void QMap::setInsertInOrder(bool sharable) \internal */ /*! \fn void QMap::clear() Removes all items from the map. \sa remove() */ /*! \fn int QMap::remove(const Key &key) Removes all the items that have the key \a key from the map. Returns the number of items removed which is usually 1 but will be 0 if the key isn't in the map, or \> 1 if insertMulti() has been used with the \a key. \sa clear(), take(), QMultiMap::remove() */ /*! \fn T QMap::take(const Key &key) Removes the item with the key \a key from the map and returns the value associated with it. If the item does not exist in the map, the function simply returns a \l{default-constructed value}. If there are multiple items for \a key in the map, only the most recently inserted one is removed and returned. If you don't use the return value, remove() is more efficient. \sa remove() */ /*! \fn bool QMap::contains(const Key &key) const Returns true if the map contains an item with key \a key; otherwise returns false. \sa count(), QMultiMap::contains() */ /*! \fn const T QMap::value(const Key &key) const Returns the value associated with the key \a key. If the map contains no item with key \a key, the function returns a \l{default-constructed value}. If there are multiple items for \a key in the map, the value of the most recently inserted one is returned. \sa key(), values(), contains(), operator[]() */ /*! \fn const T QMap::value(const Key &key, const T &defaultValue) const \overload If the map contains no item with key \a key, the function returns \a defaultValue. */ /*! \fn T &QMap::operator[](const Key &key) Returns the value associated with the key \a key as a modifiable reference. If the map contains no item with key \a key, the function inserts a \l{default-constructed value} into the map with key \a key, and returns a reference to it. If the map contains multiple items with key \a key, this function returns a reference to the most recently inserted value. \sa insert(), value() */ /*! \fn const T QMap::operator[](const Key &key) const \overload Same as value(). */ /*! \fn QList QMap::uniqueKeys() const \since 4.2 Returns a list containing all the keys in the map in ascending order. Keys that occur multiple times in the map (because items were inserted with insertMulti(), or unite() was used) occur only once in the returned list. \sa keys(), values() */ /*! \fn QList QMap::keys() const Returns a list containing all the keys in the map in ascending order. Keys that occur multiple times in the map (because items were inserted with insertMulti(), or unite() was used) also occur multiple times in the list. To obtain a list of unique keys, where each key from the map only occurs once, use uniqueKeys(). The order is guaranteed to be the same as that used by values(). \sa uniqueKeys(), values(), key() */ /*! \fn QList QMap::keys(const T &value) const \overload Returns a list containing all the keys associated with value \a value in ascending order. This function can be slow (\l{linear time}), because QMap's internal data structure is optimized for fast lookup by key, not by value. */ /*! \fn Key QMap::key(const T &value) const Returns the first key with value \a value. If the map contains no item with value \a value, the function returns a \link {default-constructed value} default-constructed key \endlink. This function can be slow (\l{linear time}), because QMap's internal data structure is optimized for fast lookup by key, not by value. \sa value(), keys() */ /*! \fn Key QMap::key(const T &value, const Key &defaultKey) const \since 4.3 \overload Returns the first key with value \a value, or \a defaultKey if the map contains no item with value \a value. This function can be slow (\l{linear time}), because QMap's internal data structure is optimized for fast lookup by key, not by value. */ /*! \fn QList QMap::values() const Returns a list containing all the values in the map, in ascending order of their keys. If a key is associated with multiple values, all of its values will be in the list, and not just the most recently inserted one. \sa keys(), value() */ /*! \fn QList QMap::values(const Key &key) const \overload Returns a list containing all the values associated with key \a key, from the most recently inserted to the least recently inserted one. \sa count(), insertMulti() */ /*! \fn int QMap::count(const Key &key) const Returns the number of items associated with key \a key. \sa contains(), insertMulti(), QMultiMap::count() */ /*! \fn int QMap::count() const \overload Same as size(). */ /*! \fn QMap::iterator QMap::begin() Returns an \l{STL-style iterator} pointing to the first item in the map. \sa constBegin(), end() */ /*! \fn QMap::const_iterator QMap::begin() const \overload */ /*! \fn QMap::const_iterator QMap::constBegin() const Returns a const \l{STL-style iterator} pointing to the first item in the map. \sa begin(), constEnd() */ /*! \fn QMap::iterator QMap::end() Returns an \l{STL-style iterator} pointing to the imaginary item after the last item in the map. \sa begin(), constEnd() */ /*! \fn QMap::const_iterator QMap::end() const \overload */ /*! \fn QMap::const_iterator QMap::constEnd() const Returns a const \l{STL-style iterator} pointing to the imaginary item after the last item in the map. \sa constBegin(), end() */ /*! \fn QMap::iterator QMap::erase(iterator pos) Removes the (key, value) pair pointed to by the iterator \a pos from the map, and returns an iterator to the next item in the map. \sa remove() */ /*! \fn QMap::iterator QMap::find(const Key &key) Returns an iterator pointing to the item with key \a key in the map. If the map contains no item with key \a key, the function returns end(). If the map contains multiple items with key \a key, this function returns an iterator that points to the most recently inserted value. The other values are accessible by incrementing the iterator. For example, here's some code that iterates over all the items with the same key: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 14 \sa constFind(), value(), values(), lowerBound(), upperBound(), QMultiMap::find() */ /*! \fn QMap::const_iterator QMap::find(const Key &key) const \overload */ /*! \fn QMap::iterator QMap::constFind(const Key &key) const \since 4.1 Returns an const iterator pointing to the item with key \a key in the map. If the map contains no item with key \a key, the function returns constEnd(). \sa find(), QMultiMap::constFind() */ /*! \fn QMap::iterator QMap::lowerBound(const Key &key) Returns an iterator pointing to the first item with key \a key in the map. If the map contains no item with key \a key, the function returns an iterator to the nearest item with a greater key. Example: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 15 If the map contains multiple items with key \a key, this function returns an iterator that points to the most recently inserted value. The other values are accessible by incrementing the iterator. For example, here's some code that iterates over all the items with the same key: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 16 \sa qLowerBound(), upperBound(), find() */ /*! \fn QMap::const_iterator QMap::lowerBound(const Key &key) const \overload */ /*! \fn QMap::iterator QMap::upperBound(const Key &key) Returns an iterator pointing to the item that immediately follows the last item with key \a key in the map. If the map contains no item with key \a key, the function returns an iterator to the nearest item with a greater key. Example: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 17 \sa qUpperBound(), lowerBound(), find() */ /*! \fn QMap::const_iterator QMap::upperBound(const Key &key) const \overload */ /*! \fn QMap::iterator QMap::insert(const Key &key, const T &value) Inserts a new item with the key \a key and a value of \a value. If there is already an item with the key \a key, that item's value is replaced with \a value. If there are multiple items with the key \a key, the most recently inserted item's value is replaced with \a value. \sa insertMulti() */ /*! \fn QMap::iterator QMap::insertMulti(const Key &key, const T &value) Inserts a new item with the key \a key and a value of \a value. If there is already an item with the same key in the map, this function will simply create a new one. (This behavior is different from insert(), which overwrites the value of an existing item.) \sa insert(), values() */ /*! \fn QMap &QMap::unite(const QMap &other) Inserts all the items in the \a other map into this map. If a key is common to both maps, the resulting map will contain the key multiple times. \sa insertMulti() */ /*! \typedef QMap::Iterator Qt-style synonym for QMap::iterator. */ /*! \typedef QMap::ConstIterator Qt-style synonym for QMap::const_iterator. */ /*! \typedef QMap::difference_type Typedef for ptrdiff_t. Provided for STL compatibility. */ /*! \typedef QMap::key_type Typedef for Key. Provided for STL compatibility. */ /*! \typedef QMap::mapped_type Typedef for T. Provided for STL compatibility. */ /*! \typedef QMap::size_type Typedef for int. Provided for STL compatibility. */ /*! \fn bool QMap::empty() const This function is provided for STL compatibility. It is equivalent to isEmpty(), returning true if the map is empty; otherwise returning false. */ /*! \class QMap::iterator \brief The QMap::iterator class provides an STL-style non-const iterator for QMap and QMultiMap. QMap features both \l{STL-style iterators} and \l{Java-style iterators}. The STL-style iterators are more low-level and more cumbersome to use; on the other hand, they are slightly faster and, for developers who already know STL, have the advantage of familiarity. QMap\::iterator allows you to iterate over a QMap (or QMultiMap) and to modify the value (but not the key) stored under a particular key. If you want to iterate over a const QMap, you should use QMap::const_iterator. It is generally good practice to use QMap::const_iterator on a non-const QMap as well, unless you need to change the QMap through the iterator. Const iterators are slightly faster, and can improve code readability. The default QMap::iterator constructor creates an uninitialized iterator. You must initialize it using a QMap function like QMap::begin(), QMap::end(), or QMap::find() before you can start iterating. Here's a typical loop that prints all the (key, value) pairs stored in a map: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 18 Unlike QHash, which stores its items in an arbitrary order, QMap stores its items ordered by key. Items that share the same key (because they were inserted using QMap::insertMulti(), or due to a unite()) will appear consecutively, from the most recently to the least recently inserted value. Let's see a few examples of things we can do with a QMap::iterator that we cannot do with a QMap::const_iterator. Here's an example that increments every value stored in the QMap by 2: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 19 Here's an example that removes all the items whose key is a string that starts with an underscore character: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 20 The call to QMap::erase() removes the item pointed to by the iterator from the map, and returns an iterator to the next item. Here's another way of removing an item while iterating: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 21 It might be tempting to write code like this: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 22 However, this will potentially crash in \c{++i}, because \c i is a dangling iterator after the call to erase(). Multiple iterators can be used on the same map. If you add items to the map, existing iterators will remain valid. If you remove items from the map, iterators that point to the removed items will become dangling iterators. \sa QMap::const_iterator, QMutableMapIterator */ /*! \fn QMap::iterator::operator QMapData::Node *() const \internal */ /*! \typedef QMap::iterator::difference_type \internal */ /*! \typedef QMap::iterator::iterator_category A synonym for \e {std::bidirectional_iterator_tag} indicating this iterator is a bidirectional iterator. */ /*! \typedef QMap::iterator::pointer \internal */ /*! \typedef QMap::iterator::reference \internal */ /*! \typedef QMap::iterator::value_type \internal */ /*! \fn QMap::iterator::iterator() Constructs an uninitialized iterator. Functions like key(), value(), and operator++() must not be called on an uninitialized iterator. Use operator=() to assign a value to it before using it. \sa QMap::begin() QMap::end() */ /*! \fn QMap::iterator::iterator(QMapData::Node *node) \internal */ /*! \fn const Key &QMap::iterator::key() const Returns the current item's key as a const reference. There is no direct way of changing an item's key through an iterator, although it can be done by calling QMap::erase() followed by QMap::insert() or QMap::insertMulti(). \sa value() */ /*! \fn T &QMap::iterator::value() const Returns a modifiable reference to the current item's value. You can change the value of an item by using value() on the left side of an assignment, for example: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 23 \sa key(), operator*() */ /*! \fn T &QMap::iterator::operator*() const Returns a modifiable reference to the current item's value. Same as value(). \sa key() */ /*! \fn T *QMap::iterator::operator->() const Returns a pointer to the current item's value. \sa value() */ /*! \fn bool QMap::iterator::operator==(const iterator &other) const \fn bool QMap::iterator::operator==(const const_iterator &other) const Returns true if \a other points to the same item as this iterator; otherwise returns false. \sa operator!=() */ /*! \fn bool QMap::iterator::operator!=(const iterator &other) const \fn bool QMap::iterator::operator!=(const const_iterator &other) const Returns true if \a other points to a different item than this iterator; otherwise returns false. \sa operator==() */ /*! \fn QMap::iterator QMap::iterator::operator++() The prefix ++ operator (\c{++i}) advances the iterator to the next item in the map and returns an iterator to the new current item. Calling this function on QMap::end() leads to undefined results. \sa operator--() */ /*! \fn QMap::iterator QMap::iterator::operator++(int) \overload The postfix ++ operator (\c{i++}) advances the iterator to the next item in the map and returns an iterator to the previously current item. */ /*! \fn QMap::iterator QMap::iterator::operator--() The prefix -- operator (\c{--i}) makes the preceding item current and returns an iterator pointing to the new current item. Calling this function on QMap::begin() leads to undefined results. \sa operator++() */ /*! \fn QMap::iterator QMap::iterator::operator--(int) \overload The prefix -- operator (\c{--i}) makes the preceding item current and returns an iterator pointing to the previously current item. */ /*! \fn QMap::iterator QMap::iterator::operator+(int j) const Returns an iterator to the item at \a j positions forward from this iterator. (If \a j is negative, the iterator goes backward.) This operation can be slow for large \a j values. \sa operator-() */ /*! \fn QMap::iterator QMap::iterator::operator-(int j) const Returns an iterator to the item at \a j positions backward from this iterator. (If \a j is negative, the iterator goes forward.) This operation can be slow for large \a j values. \sa operator+() */ /*! \fn QMap::iterator &QMap::iterator::operator+=(int j) Advances the iterator by \a j items. (If \a j is negative, the iterator goes backward.) \sa operator-=(), operator+() */ /*! \fn QMap::iterator &QMap::iterator::operator-=(int j) Makes the iterator go back by \a j items. (If \a j is negative, the iterator goes forward.) \sa operator+=(), operator-() */ /*! \class QMap::const_iterator \brief The QMap::const_iterator class provides an STL-style const iterator for QMap and QMultiMap. QMap features both \l{STL-style iterators} and \l{Java-style iterators}. The STL-style iterators are more low-level and more cumbersome to use; on the other hand, they are slightly faster and, for developers who already know STL, have the advantage of familiarity. QMap\::const_iterator allows you to iterate over a QMap (or a QMultiMap). If you want to modify the QMap as you iterate over it, you must use QMap::iterator instead. It is generally good practice to use QMap::const_iterator on a non-const QMap as well, unless you need to change the QMap through the iterator. Const iterators are slightly faster, and can improve code readability. The default QMap::const_iterator constructor creates an uninitialized iterator. You must initialize it using a QMap function like QMap::constBegin(), QMap::constEnd(), or QMap::find() before you can start iterating. Here's a typical loop that prints all the (key, value) pairs stored in a map: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 24 Unlike QHash, which stores its items in an arbitrary order, QMap stores its items ordered by key. Items that share the same key (because they were inserted using QMap::insertMulti()) will appear consecutively, from the most recently to the least recently inserted value. Multiple iterators can be used on the same map. If you add items to the map, existing iterators will remain valid. If you remove items from the map, iterators that point to the removed items will become dangling iterators. \sa QMap::iterator, QMapIterator */ /*! \fn QMap::const_iterator::operator QMapData::Node *() const \internal */ /*! \typedef QMap::const_iterator::difference_type \internal */ /*! \typedef QMap::const_iterator::iterator_category A synonym for \e {std::bidirectional_iterator_tag} indicating this iterator is a bidirectional iterator. */ /*! \typedef QMap::const_iterator::pointer \internal */ /*! \typedef QMap::const_iterator::reference \internal */ /*! \typedef QMap::const_iterator::value_type \internal */ /*! \fn QMap::const_iterator::const_iterator() Constructs an uninitialized iterator. Functions like key(), value(), and operator++() must not be called on an uninitialized iterator. Use operator=() to assign a value to it before using it. \sa QMap::constBegin() QMap::constEnd() */ /*! \fn QMap::const_iterator::const_iterator(QMapData::Node *node) \internal */ /*! \fn QMap::const_iterator::const_iterator(const iterator &other) Constructs a copy of \a other. */ /*! \fn const Key &QMap::const_iterator::key() const Returns the current item's key. \sa value() */ /*! \fn const T &QMap::const_iterator::value() const Returns the current item's value. \sa key(), operator*() */ /*! \fn const T &QMap::const_iterator::operator*() const Returns the current item's value. Same as value(). \sa key() */ /*! \fn const T *QMap::const_iterator::operator->() const Returns a pointer to the current item's value. \sa value() */ /*! \fn bool QMap::const_iterator::operator==(const const_iterator &other) const Returns true if \a other points to the same item as this iterator; otherwise returns false. \sa operator!=() */ /*! \fn bool QMap::const_iterator::operator!=(const const_iterator &other) const Returns true if \a other points to a different item than this iterator; otherwise returns false. \sa operator==() */ /*! \fn QMap::const_iterator QMap::const_iterator::operator++() The prefix ++ operator (\c{++i}) advances the iterator to the next item in the map and returns an iterator to the new current item. Calling this function on QMap::end() leads to undefined results. \sa operator--() */ /*! \fn QMap::const_iterator QMap::const_iterator::operator++(int) \overload The postfix ++ operator (\c{i++}) advances the iterator to the next item in the map and returns an iterator to the previously current item. */ /*! \fn QMap::const_iterator &QMap::const_iterator::operator--() The prefix -- operator (\c{--i}) makes the preceding item current and returns an iterator pointing to the new current item. Calling this function on QMap::begin() leads to undefined results. \sa operator++() */ /*! \fn QMap::const_iterator QMap::const_iterator::operator--(int) \overload The postfix -- operator (\c{i--}) makes the preceding item current and returns an iterator pointing to the previously current item. */ /*! \fn QMap::const_iterator QMap::const_iterator::operator+(int j) const Returns an iterator to the item at \a j positions forward from this iterator. (If \a j is negative, the iterator goes backward.) This operation can be slow for large \a j values. \sa operator-() */ /*! \fn QMap::const_iterator QMap::const_iterator::operator-(int j) const Returns an iterator to the item at \a j positions backward from this iterator. (If \a j is negative, the iterator goes forward.) This operation can be slow for large \a j values. \sa operator+() */ /*! \fn QMap::const_iterator &QMap::const_iterator::operator+=(int j) Advances the iterator by \a j items. (If \a j is negative, the iterator goes backward.) This operation can be slow for large \a j values. \sa operator-=(), operator+() */ /*! \fn QMap::const_iterator &QMap::const_iterator::operator-=(int j) Makes the iterator go back by \a j items. (If \a j is negative, the iterator goes forward.) This operation can be slow for large \a j values. \sa operator+=(), operator-() */ /*! \fn QDataStream &operator<<(QDataStream &out, const QMap &map) \relates QMap Writes the map \a map to stream \a out. This function requires the key and value types to implement \c operator<<(). \sa \link datastreamformat.html Format of the QDataStream operators \endlink */ /*! \fn QDataStream &operator>>(QDataStream &in, QMap &map) \relates QMap Reads a map from stream \a in into \a map. This function requires the key and value types to implement \c operator>>(). \sa \link datastreamformat.html Format of the QDataStream operators \endlink */ /*! \class QMultiMap \brief The QMultiMap class is a convenience QMap subclass that provides multi-valued maps. \ingroup tools \ingroup shared \mainclass \reentrant QMultiMap\ is one of Qt's generic \l{container classes}. It inherits QMap and extends it with a few convenience functions that make it more suitable than QMap for storing multi-valued maps. A multi-valued map is a map that allows multiple values with the same key; QMap normally doesn't allow that, unless you call QMap::insertMulti(). Because QMultiMap inherits QMap, all of QMap's functionality also applies to QMultiMap. For example, you can use isEmpty() to test whether the map is empty, and you can traverse a QMultiMap using QMap's iterator classes (for example, QMapIterator). But in addition, it provides an insert() function that corresponds to QMap::insertMulti(), and a replace() function that corresponds to QMap::insert(). It also provides convenient operator+() and operator+=(). Example: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 25 Unlike QMap, QMultiMap provides no operator[]. Use value() or replace() if you want to access the most recently inserted item with a certain key. If you want to retrieve all the values for a single key, you can use values(const Key &key), which returns a QList: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 26 The items that share the same key are available from most recently to least recently inserted. If you prefer the STL-style iterators, you can call find() to get the iterator for the first item with a key and iterate from there: \snippet doc/src/snippets/code/src_corelib_tools_qmap.cpp 27 QMultiMap's key and value data types must be \l{assignable data types}. This covers most data types you are likely to encounter, but the compiler won't let you, for example, store a QWidget as a value; instead, store a QWidget *. In addition, QMultiMap's key type must provide operator<(). See the QMap documentation for details. \sa QMap, QMapIterator, QMutableMapIterator, QMultiHash */ /*! \fn QMultiMap::QMultiMap() Constructs an empty map. */ /*! \fn QMultiMap::QMultiMap(const QMap &other) Constructs a copy of \a other (which can be a QMap or a QMultiMap). \sa operator=() */ /*! \fn QMultiMap::iterator QMultiMap::replace(const Key &key, const T &value) Inserts a new item with the key \a key and a value of \a value. If there is already an item with the key \a key, that item's value is replaced with \a value. If there are multiple items with the key \a key, the most recently inserted item's value is replaced with \a value. \sa insert() */ /*! \fn QMultiMap::iterator QMultiMap::insert(const Key &key, const T &value) Inserts a new item with the key \a key and a value of \a value. If there is already an item with the same key in the map, this function will simply create a new one. (This behavior is different from replace(), which overwrites the value of an existing item.) \sa replace() */ /*! \fn QMultiMap &QMultiMap::operator+=(const QMultiMap &other) Inserts all the items in the \a other map into this map and returns a reference to this map. \sa insert(), operator+() */ /*! \fn QMultiMap QMultiMap::operator+(const QMultiMap &other) const Returns a map that contains all the items in this map in addition to all the items in \a other. If a key is common to both maps, the resulting map will contain the key multiple times. \sa operator+=() */ /*! \fn bool QMultiMap::contains(const Key &key, const T &value) const \since 4.3 Returns true if the map contains an item with key \a key and value \a value; otherwise returns false. \sa QMap::contains() */ /*! \fn bool QMultiMap::contains(const Key &key) const \overload \sa QMap::contains() */ /*! \fn int QMultiMap::remove(const Key &key, const T &value) \since 4.3 Removes all the items that have the key \a key and the value \a value from the map. Returns the number of items removed. \sa QMap::remove() */ /*! \fn int QMultiMap::remove(const Key &key) \overload \sa QMap::remove() */ /*! \fn int QMultiMap::count(const Key &key, const T &value) const \since 4.3 Returns the number of items with key \a key and value \a value. \sa QMap::count() */ /*! \fn int QMultiMap::count(const Key &key) const \overload \sa QMap::count() */ /*! \fn int QMultiMap::count() const \overload \sa QMap::count() */ /*! \fn typename QMap::iterator QMultiMap::find(const Key &key, const T &value) \since 4.3 Returns an iterator pointing to the item with key \a key and value \a value in the map. If the map contains no such item, the function returns end(). If the map contains multiple items with key \a key, this function returns an iterator that points to the most recently inserted value. \sa QMap::find() */ /*! \fn typename QMap::iterator QMultiMap::find(const Key &key) \overload \sa QMap::find() */ /*! \fn typename QMap::const_iterator QMultiMap::find(const Key &key, const T &value) const \since 4.3 \overload Returns a const iterator pointing to the item with the given \a key and \a value in the map. If the map contains no such item, the function returns end(). If the map contains multiple items with the specified \a key, this function returns a const iterator that points to the most recently inserted value. \sa QMap::find() */ /*! \fn typename QMap::const_iterator QMultiMap::find(const Key &key) const \since 4.3 \overload \sa QMap::find() */ /*! \fn typename QMap::const_iterator QMultiMap::constFind(const Key &key, const T &value) const \since 4.3 Returns an iterator pointing to the item with key \a key and the value \a value in the map. If the map contains no such item, the function returns constEnd(). \sa QMap::constFind() */ /*! \fn typename QMap::const_iterator QMultiMap::constFind(const Key &key) const \overload \sa QMap::constFind() */ /*! \fn T &QMap::iterator::data() const Use value() instead. */ /*! \fn const T &QMap::const_iterator::data() const Use value() instead. */ /*! \fn iterator QMap::remove(iterator it) Use erase(\a it) instead. */ /*! \fn void QMap::erase(const Key &key) Use remove(\a key) instead. */ /*! \fn iterator QMap::insert(const Key &key, const T &value, bool overwrite); Use the two-argument insert() overload instead. If you don't want to overwrite, call contains() beforehand. \oldcode QMap map; ... map.insert("delay", 30000, false); \newcode QMap map; ... if (!map.contains("delay")) map.insert("delay", 30000); \endcode */ /*! \fn iterator QMap::replace(const Key &key, const T &value) Use remove() then insert(). */ QT_END_NAMESPACE