QCborMap Class▲
-
Header: QCborMap
-
Since: Qt 5.12
-
CMake:
find_package(Qt6 REQUIRED COMPONENTS Core)
target_link_libraries(mytarget PRIVATE Qt6::Core)
-
qmake: QT += core
-
Group: QCborMap is part of CBOR Support in Qt, qtserialization
Detailed Description▲
This class can be used to hold an associative container in CBOR, a map between a key and a value type. CBOR is the Concise Binary Object Representation, a very compact form of binary data encoding that is a superset of JSON. It was created by the IETF Constrained RESTful Environments (CoRE) WG, which has used it in many new RFCs. It is meant to be used alongside the CoAP protocol.
Unlike JSON and QVariantMap, CBOR map keys can be of any type, not just strings. For that reason, QCborMap is effectively a map between QCborValue keys to QCborValue value elements.
However, for all member functions that take a key parameter, QCborMap provides overloads that will work efficiently with integers and strings. In fact, the use of integer keys is encouraged, since they occupy fewer bytes to transmit and are simpler to encode and decode. Newer protocols designed by the IETF CoRE WG to work specifically with CBOR are known to use them.
QCborMap is not sorted, because of that, searching for keys has linear complexity (O(n)). QCborMap actually keeps the elements in the order that they were inserted, which means that it is possible to make sorted QCborMaps by carefully inserting elements in sorted order. CBOR does not require sorting, but recommends it.
QCborMap can also be converted to and from QVariantMap and QJsonObject. However, when performing the conversion, any non-string keys will be stringified using a one-way method that the conversion back to QCborMap will not undo.
See Also▲
Member Type Documentation▲
QCborMap::const_iterator▲
A synonym for QCborMap::ConstIterator
QCborMap::iterator▲
A synonym for QCborMap::Iterator.
QCborMap::key_type▲
The key type for this map. Since QCborMap keys can be any CBOR type, this is a QCborValue.
QCborMap::mapped_type▲
The type that is mapped to (the value), that is, a QCborValue.
QCborMap::size_type▲
The type that QCborMap uses for sizes.
QCborMap::value_type▲
The value that is stored in this container: a pair of QCborValues
Member Function Documentation▲
QCborMap::iterator QCborMap::find(qint64 key)▲
QCborMap::const_iterator QCborMap::find(qint64 key) const
Returns a map iterator to the key-value pair whose key is key, if the map contains such a pair. If it doesn't, this function returns end().
CBOR recommends using integer keys, since they occupy less space and are simpler to encode and decode.
If the map contains more than one key equal to key, it is undefined which one this function will find. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
See Also▲
QCborMap::iterator QCborMap::find(QLatin1StringView key)▲
QCborMap::const_iterator QCborMap::find(QLatin1StringView key) const
This is an overloaded function.
Returns a map iterator to the key-value pair whose key is key, if the map contains such a pair. If it doesn't, this function returns end().
If the map contains more than one key equal to key, it is undefined which one this function will find. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
See Also▲
QCborMap::iterator QCborMap::find(const QString &key)▲
QCborMap::const_iterator QCborMap::find(const QString &key) const
This is an overloaded function.
Returns a map iterator to the key-value pair whose key is key, if the map contains such a pair. If it doesn't, this function returns end().
If the map contains more than one key equal to key, it is undefined which one this function will find. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
See Also▲
QCborMap::iterator QCborMap::find(const QCborValue &key)▲
QCborMap::const_iterator QCborMap::find(const QCborValue &key) const
This is an overloaded function.
Returns a map iterator to the key-value pair whose key is key, if the map contains such a pair. If it doesn't, this function returns end().
If the map contains more than one key equal to key, it is undefined which one this function will find. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
See Also▲
QCborValue QCborMap::extract(QCborMap::const_iterator it)▲
QCborValue QCborMap::extract(QCborMap::iterator it)
Extracts a value from the map at the position indicated by iterator it and returns the value so extracted.
See Also▲
QCborMap::QCborMap()▲
QCborMap::QCborMap(std::initializer_list<value_type> args)▲
Constructs a QCborMap with items from a brace-initialization list found in args, as in the following example:
QCborMap map = {
{0, "Hello"},
{1, "World"},
{"foo", nullptr},
{"bar", QCborArray{0, 1, 2, 3, 4}}
};QCborMap::QCborMap(const QCborMap &other)▲
Creates a QCborMap object that is a copy of other.
QCborMap::~QCborMap()▲
Destroys this QCborMap object and frees any associated resources it owns.
QCborMap::iterator QCborMap::begin()▲
Returns a map iterator pointing to the first key-value pair of this map. If this map is empty, the returned iterator will be the same as end().
See Also▲
See also constBegin(), end()
QCborMap::const_iterator QCborMap::begin() const▲
Returns a map iterator pointing to the first key-value pair of this map. If this map is empty, the returned iterator will be the same as constEnd().
See Also▲
QCborMap::const_iterator QCborMap::cbegin() const▲
Returns a map iterator pointing to the first key-value pair of this map. If this map is empty, the returned iterator will be the same as constEnd().
See Also▲
QCborMap::const_iterator QCborMap::cend() const▲
Returns a map iterator representing an element just past the last element in the map.
See Also▲
See also begin(), constBegin(), find(), constFind()
void QCborMap::clear()▲
int QCborMap::compare(const QCborMap &other) const▲
Compares this map and other, comparing each element in sequence, and returns an integer that indicates whether this map should be sorted prior to (if the result is negative) or after other (if the result is positive). If this function returns 0, the two maps are equal and contain the same elements.
Note that CBOR maps are unordered, which means that two maps containing the very same pairs but in different order will still compare differently. To avoid this, it is recommended to insert elements into the map in a predictable order, such as by ascending key value. In fact, maps with keys in sorted order are required for Canonical CBOR representation.
For more information on CBOR sorting order, see QCborValue::compare().
See Also▲
See also QCborValue::compare(), QCborArray::compare(), operator==()
QCborMap::const_iterator QCborMap::constBegin() const▲
Returns a map iterator pointing to the first key-value pair of this map. If this map is empty, the returned iterator will be the same as constEnd().
See Also▲
QCborMap::const_iterator QCborMap::constEnd() const▲
Returns a map iterator representing an element just past the last element in the map.
See Also▲
See also begin(), constBegin(), find(), constFind()
QCborMap::const_iterator QCborMap::constFind(qint64 key) const▲
Returns a map iterator to the key-value pair whose key is key, if the map contains such a pair. If it doesn't, this function returns constEnd().
CBOR recommends using integer keys, since they occupy less space and are simpler to encode and decode.
If the map contains more than one key equal to key, it is undefined which one this function will find. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
See Also▲
QCborMap::const_iterator QCborMap::constFind(QLatin1StringView key) const▲
This is an overloaded function.
Returns a map iterator to the key-value pair whose key is key, if the map contains such a pair. If it doesn't, this function returns constEnd().
If the map contains more than one key equal to key, it is undefined which one this function will find. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
See Also▲
QCborMap::const_iterator QCborMap::constFind(const QString &key) const▲
This is an overloaded function.
Returns a map iterator to the key-value pair whose key is key, if the map contains such a pair. If it doesn't, this function returns constEnd().
If the map contains more than one key equal to key, it is undefined which one this function will find. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
See Also▲
QCborMap::const_iterator QCborMap::constFind(const QCborValue &key) const▲
This is an overloaded function.
Returns a map iterator to the key-value pair whose key is key, if the map contains such a pair. If it doesn't, this function returns constEnd().
If the map contains more than one key equal to key, it is undefined which one this function will find. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
See Also▲
bool QCborMap::contains(qint64 key) const▲
Returns true if this map contains a key-value pair identified by key key. CBOR recommends using integer keys, since they occupy less space and are simpler to encode and decode.
See Also▲
bool QCborMap::contains(QLatin1StringView key) const▲
This is an overloaded function.
Returns true if this map contains a key-value pair identified by key key.
See Also▲
bool QCborMap::contains(const QString &key) const▲
This is an overloaded function.
Returns true if this map contains a key-value pair identified by key key.
See Also▲
bool QCborMap::contains(const QCborValue &key) const▲
Returns true if this map contains a key-value pair identified by key key.
See Also▲
bool QCborMap::empty() const▲
Synonym for isEmpty(). This function is provided for compatibility with generic code that uses the Standard Library API.
Returns true if this map is empty (size() == 0).
See Also▲
QCborMap::iterator QCborMap::end()▲
Returns a map iterator representing an element just past the last element in the map.
See Also▲
See also begin(), constBegin(), find(), constFind()
QCborMap::const_iterator QCborMap::end() const▲
Returns a map iterator representing an element just past the last element in the map.
See Also▲
See also begin(), constBegin(), find(), constFind()
QCborMap::iterator QCborMap::erase(QCborMap::const_iterator it)▲
Removes the key-value pair pointed to by the map iterator it and returns a pointer to the next element, after removal.
See Also▲
QCborMap::iterator QCborMap::erase(QCborMap::iterator it)▲
This is an overloaded function.
Removes the key-value pair pointed to by the map iterator it and returns a pointer to the next element, after removal.
See Also▲
[static] QCborMap QCborMap::fromJsonObject(const QJsonObject &obj)▲
Converts all JSON items found in the obj object to CBOR using QCborValue::fromJson(), and returns the map composed of those elements.
This conversion is lossless, as the CBOR type system is a superset of JSON's. Moreover, the map returned by this function can be converted back to the original obj by using toJsonObject().
See Also▲
See also toJsonObject(), toVariantMap(), QCborValue::fromJsonValue(), QCborArray::fromJsonArray()
[static, since 6.3] QCborMap QCborMap::fromJsonObject(QJsonObject &&obj)▲
This is an overloaded function.
This function was introduced in Qt 6.3.
[static] QCborMap QCborMap::fromVariantHash(const QVariantHash &hash)▲
Converts all the items in hash to CBOR using QCborValue::fromVariant() and returns the map composed of those elements.
Conversion from QVariant is not completely lossless. Please see the documentation in QCborValue::fromVariant() for more information.
See Also▲
See also toVariantHash(), fromVariantMap(), fromJsonObject(), QCborValue::fromVariant()
[static] QCborMap QCborMap::fromVariantMap(const QVariantMap &map)▲
Converts all the items in map to CBOR using QCborValue::fromVariant() and returns the map composed of those elements.
Conversion from QVariant is not completely lossless. Please see the documentation in QCborValue::fromVariant() for more information.
See Also▲
See also toVariantMap(), fromVariantHash(), fromJsonObject(), QCborValue::fromVariant()
QCborMap::iterator QCborMap::insert(qint64 key, const QCborValue &value)▲
This is an overloaded function.
Inserts the key key and value value into this map and returns a map iterator pointing to the newly inserted pair.
If the map already had a key equal to key, its value will be overwritten by value.
See Also▲
QCborMap::iterator QCborMap::insert(QLatin1StringView key, const QCborValue &value)▲
This is an overloaded function.
Inserts the key key and value value into this map and returns a map iterator pointing to the newly inserted pair.
If the map already had a key equal to key, its value will be overwritten by value.
See Also▲
QCborMap::iterator QCborMap::insert(const QString &key, const QCborValue &value)▲
This is an overloaded function.
Inserts the key key and value value into this map and returns a map iterator pointing to the newly inserted pair.
If the map already had a key equal to key, its value will be overwritten by value.
See Also▲
QCborMap::iterator QCborMap::insert(const QCborValue &key, const QCborValue &value)▲
This is an overloaded function.
Inserts the key key and value value into this map and returns a map iterator pointing to the newly inserted pair.
If the map already had a key equal to key, its value will be overwritten by value.
See Also▲
QCborMap::iterator QCborMap::insert(QCborMap::value_type v)▲
This is an overloaded function.
Inserts the key-value pair in v into this map and returns a map iterator pointing to the newly inserted pair.
If the map already had a key equal to v.first, its value will be overwritten by v.second.
See Also▲
See also operator[], erase(), extract()
bool QCborMap::isEmpty() const▲
QList<QCborValue> QCborMap::keys() const▲
void QCborMap::remove(qint64 key)▲
Removes the key key and the corresponding value from the map, if it is found. If the map contains no such key, this function does nothing.
If the map contains more than one key equal to key, it is undefined which one this function will remove. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
remove(QLatin1StringView), remove(const QString &), remove(const QCborValue &)
See Also▲
See also value(qint64), operator[](qint64), find(qint64), contains(qint64)
void QCborMap::remove(QLatin1StringView key)▲
This is an overloaded function.
Removes the key key and the corresponding value from the map, if it is found. If the map contains no such key, this function does nothing.
If the map contains more than one key equal to key, it is undefined which one this function will remove. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
See Also▲
void QCborMap::remove(const QString &key)▲
This is an overloaded function.
Removes the key key and the corresponding value from the map, if it is found. If the map contains no such key, this function does nothing.
If the map contains more than one key equal to key, it is undefined which one this function will remove. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
remove(qint64), remove(QLatin1StringView), remove(const QCborValue &)
See Also▲
See also value(const QString &), operator[](const QString &), find(const QString &), contains(const QString &)
void QCborMap::remove(const QCborValue &key)▲
Removes the key key and the corresponding value from the map, if it is found. If the map contains no such key, this function does nothing.
If the map contains more than one key equal to key, it is undefined which one this function will remove. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
remove(qint64), remove(QLatin1StringView), remove(const QString &)
See Also▲
See also value(const QCborValue &), operator[](const QCborValue &), find(const QCborValue &), contains(const QCborValue &)
qsizetype QCborMap::size() const▲
void QCborMap::swap(QCborMap &other)▲
Swaps the contents of this map and other.
QCborValue QCborMap::take(qint64 key)▲
Removes the key key and the corresponding value from the map and returns the value, if it is found. If the map contains no such key, this function does nothing.
If the map contains more than one key equal to key, it is undefined which one this function will remove. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
See Also▲
QCborValue QCborMap::take(QLatin1StringView key)▲
Removes the key key and the corresponding value from the map and returns the value, if it is found. If the map contains no such key, this function does nothing.
If the map contains more than one key equal to key, it is undefined which one this function will remove. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
See Also▲
QCborValue QCborMap::take(const QString &key)▲
Removes the key key and the corresponding value from the map and returns the value, if it is found. If the map contains no such key, this function does nothing.
If the map contains more than one key equal to key, it is undefined which one this function will remove. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
See Also▲
QCborValue QCborMap::take(const QCborValue &key)▲
Removes the key key and the corresponding value from the map and returns the value, if it is found. If the map contains no such key, this function does nothing.
If the map contains more than one key equal to key, it is undefined which one this function will remove. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
See Also▲
QCborValue QCborMap::toCborValue() const▲
Explicitly constructs a QCborValue object that represents this map. This function is usually not necessary since QCborValue has a constructor for QCborMap, so the conversion is implicit.
Converting QCborMap to QCborValue allows it to be used in any context where QCborValues can be used, including as keys and mapped types in QCborMap, as well as QCborValue::toCbor().
See Also▲
See also QCborValue::QCborValue(const QCborMap &)
QJsonObject QCborMap::toJsonObject() const▲
Recursively converts every QCborValue value in this map to JSON using QCborValue::toJsonValue() and creates a string key for all keys that aren't strings, then returns the corresponding QJsonObject composed of those associations.
Please note that CBOR contains a richer and wider type set than JSON, so some information may be lost in this conversion. For more details on what conversions are applied, see QCborValue::toJsonValue().
Map key conversion to string▲
JSON objects are defined as having string keys, unlike CBOR, so the conversion of a QCborMap to QJsonObject will imply a step of "stringification" of the key values. The conversion will use the special handling of tags and extended types from above and will also convert the rest of the types as follows:
|
Type |
Transformation |
|---|---|
|
Bool |
"true" and "false" |
|
Null |
"null" |
|
Undefined |
"undefined" |
|
Integer |
The decimal string form of the number |
|
Double |
The decimal string form of the number |
|
Byte array |
Unless tagged differently (see above), encoded as Base64url |
|
Array |
Replaced by the compact form of its Diagnostic notation |
|
Map |
Replaced by the compact form of its Diagnostic notation |
|
Tags and extended types |
Tag number is dropped and the tagged value is converted to string |
Notes▲
See Also▲
See also fromJsonObject(), QCborValue::toJsonValue(), QCborArray::toJsonArray(), toVariantMap()
QVariantHash QCborMap::toVariantHash() const▲
Converts the CBOR values to QVariant using QCborValue::toVariant() and "stringifies" all the CBOR keys in this map, returning the QVariantHash that results from that association list.
QVariantMaps have string keys, unlike CBOR, so the conversion of a QCborMap to QVariantMap will imply a step of "stringification" of the key values. See QCborMap::toJsonObject() for details.
In addition, the conversion to QVariant is not completely lossless. Please see the documentation in QCborValue::toVariant() for more information.
See Also▲
See also fromVariantHash(), toVariantMap(), toJsonObject(), QCborValue::toVariant(), QCborArray::toVariantList()
QVariantMap QCborMap::toVariantMap() const▲
Converts the CBOR values to QVariant using QCborValue::toVariant() and "stringifies" all the CBOR keys in this map, returning the QVariantMap that results from that association list.
QVariantMaps have string keys, unlike CBOR, so the conversion of a QCborMap to QVariantMap will imply a step of "stringification" of the key values. See QCborMap::toJsonObject() for details.
In addition, the conversion to QVariant is not completely lossless. Please see the documentation in QCborValue::toVariant() for more information.
See Also▲
See also fromVariantMap(), toVariantHash(), toJsonObject(), QCborValue::toVariant(), QCborArray::toVariantList()
QCborValue QCborMap::value(qint64 key) const▲
Returns the QCborValue element in this map that corresponds to key key, if there is one. CBOR recommends using integer keys, since they occupy less space and are simpler to encode and decode.
If the map does not contain key key, this function returns a QCborValue containing an undefined value. For that reason, it is not possible with this function to tell apart the situation where the key was not present from the situation where the key was mapped to an undefined value.
If the map contains more than one key equal to key, it is undefined which one the return from function will reference. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
value(QLatin1StringView), value(const QString &), value(const QCborValue &)
See Also▲
See also operator[](qint64), find(qint64), constFind(qint64), remove(qint64), contains(qint64)
QCborValue QCborMap::value(QLatin1StringView key) const▲
This is an overloaded function.
Returns the QCborValue element in this map that corresponds to key key, if there is one.
If the map does not contain key key, this function returns a QCborValue containing an undefined value. For that reason, it is not possible with this function to tell apart the situation where the key was not present from the situation where the key was mapped to an undefined value.
If the map contains more than one key equal to key, it is undefined which one this function will return. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
value(qint64), value(const QString &), value(const QCborValue &)
See Also▲
See also operator[](QLatin1StringView), find(QLatin1StringView), constFind(QLatin1StringView), remove(QLatin1StringView), contains(QLatin1StringView)
QCborValue QCborMap::value(const QString &key) const▲
This is an overloaded function.
Returns the QCborValue element in this map that corresponds to key key, if there is one.
If the map does not contain key key, this function returns a QCborValue containing an undefined value. For that reason, it is not possible with this function to tell apart the situation where the key was not present from the situation where the key was mapped to an undefined value.
If the map contains more than one key equal to key, it is undefined which one this function will return. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
value(qint64), value(QLatin1StringView), value(const QCborValue &)
See Also▲
See also operator[](const QString &), find(const QString &), constFind(const QString &), remove(const QString &), contains(const QString &)
QCborValue QCborMap::value(const QCborValue &key) const▲
Returns the QCborValue element in this map that corresponds to key key, if there is one.
If the map does not contain key key, this function returns a QCborValue containing an undefined value. For that reason, it is not possible with this function to tell apart the situation where the key was not present from the situation where the key was mapped to an undefined value.
If the map contains more than one key equal to key, it is undefined which one this function will return. QCborMap does not allow inserting duplicate keys, but it is possible to create such a map by decoding a CBOR stream with them. They are usually not permitted and having duplicate keys is usually an indication of a problem in the sender.
value(qint64), value(QLatin1StringView), value(const QString &)
See Also▲
See also operator[](const QCborValue &), find(const QCborValue &), constFind(const QCborValue &), remove(const QCborValue &), contains(const QCborValue &)
bool QCborMap::operator!=(const QCborMap &other) const▲
Compares this map and other, comparing each element in sequence, and returns true if the two maps contains any different elements or elements in different orders, false otherwise.
Note that CBOR maps are unordered, which means that two maps containing the very same pairs but in different order will still compare differently. To avoid this, it is recommended to insert elements into the map in a predictable order, such as by ascending key value. In fact, maps with keys in sorted order are required for Canonical CBOR representation.
For more information on CBOR equality in Qt, see, QCborValue::compare().
See Also▲
See also compare(), QCborValue::operator==(), QCborMap::operator==(), operator==(), operator<()
bool QCborMap::operator<(const QCborMap &other) const▲
Compares this map and other, comparing each element in sequence, and returns true if this map should be sorted before other, false otherwise.
Note that CBOR maps are unordered, which means that two maps containing t