Basics¶
Standard types¶
Below are Qt equivalents to MessagePack types listed in spec:
| MessagePack type | Qt or C++ type |
|---|---|
| positive fixint | quint8 |
| fixmap, map | QMap, QHash |
| fixarray,array | QList |
| fixstr, str | QString |
| nil | QVariant() |
| false, true | bool |
| bin | QByteArray |
| float 32 | float |
| float 64 | double |
| uint 8 | quint8 |
| uint 16 | quint16 |
| uint 32 | quint32 |
| uint 64 | quint64 |
| int 8 | qint8 |
| int 16 | qint16 |
| int 32 | qint32, int |
| int 64 | qint64 |
| negative fixint | qint8 |
You can pack and unpack any of those types right away:
Packing¶
Pass QVariant to MsgPack::pack() function:
QVariant v = 123;
QByteArray packed = MsgPack::pack(v);
qDebug() << packed.toHex();
Of course QVariant can contain a QVarianList or a QVariantMap:
QList<QVariant> list;
list << 123 << 4.56 << true;
QByteArray packed = MsgPack::pack(list);
qDebug() << packed.toHex();
Note
If you want to pack QList<int> for example see: REF TO MsgPackStream
Unpacking¶
Unpacking is handled by MsgPack::unpack() function:
QByteArray packed = MsgPack::pack("qwerty");
QVariant unpacked = MsgPack::unpack(packed);
qDebug() << unpacked.toString();
Tip
If packed data contains only one msgpack type (fixstr of fixmap for example), unpack will return it as QVariant(QString()) and QVariant(QMap()) respectively.
But if there are several values packed, QVariant(QList()) will be returned (consider this 5 bool values packed without msgpack’s list: [0xc3, 0xc3, 0xc3, 0xc3, 0xc3])
More types¶
There are built in packers and unpackers (basic and stream ones) for following types:
QPoint, QSize, QRect, QTime, QDate, QDateTime, QColor, QGeoCoordinate.
But since there is no such types in msgpack spec, ext type is used.
Example:
MsgPack::registerType(QMetaType::QPoint, 37); // 37 is msgpack user type id
QByteArray ba = MsgPack::pack(QPoint(12, 34));
qDebug() << MsgPack::unpack(ba).toPoint();
Note, that QColor and QGeoCoordinate is enabled by default only in qmake project.
Thread safety¶
All methods are thread safe, except MsgPack::setCompatibilityModeEnabled which is not.
pack() and unpack() do not use any global variables except user packers and unpackers, access to them is controlled via QReadLocker (and QWriteLocker when registering a new one), so readers do not block each other.
Warning
User packers and unpackers can break thread-safety! But in most cases they are so simple, so this is not a problem.
Compatibility mode¶
You can enable compatibility mode this way: MsgPack::setCompatibilityModeEnabled(true), after that there will be no str8, and QByteArray will be packed to str.