CopperSpice API  1.7.2
QUuid Class Reference

The QUuid class stores a Universally Unique Identifier (UUID). More...

Public Types

enum  Variant
 
enum  Version
 

Public Methods

constexpr QUuid ()
 
constexpr QUuid (const GUID &guid)
 
 QUuid (const QByteArray &text)
 
 QUuid (const QString &text)
 
constexpr QUuid (uint l, ushort w1, ushort w2, uchar b1, uchar b2, uchar b3, uchar b4, uchar b5, uchar b6, uchar b7, uchar b8)
 
bool isNull () const
 
 operator GUID () const
 
constexpr bool operator!= (const GUID &guid) const
 
constexpr bool operator!= (const QUuid &other) const
 
bool operator< (const QUuid &other) const
 
constexpr QUuid & operator= (const GUID &guid)
 
constexpr bool operator== (const GUID &guid) const
 
constexpr bool operator== (const QUuid &other) const
 
bool operator> (const QUuid &other) const
 
QByteArray toByteArray () const
 
QByteArray toRfc4122 () const
 
QString toString () const
 
QUuid::Variant variant () const
 
QUuid::Version version () const
 

Static Public Methods

static QUuid createUuid ()
 
static QUuid createUuidV3 (const QUuid &ns, const QByteArray &baseData)
 
static QUuid createUuidV3 (const QUuid &ns, const QString &baseData)
 
static QUuid createUuidV5 (const QUuid &ns, const QByteArray &baseData)
 
static QUuid createUuidV5 (const QUuid &ns, const QString &baseData)
 
static QUuid fromRfc4122 (const QByteArray &bytes)
 

Related Functions

These are not member functions

QDataStreamoperator<< (QDataStream &s, const QUuid &id)
 
QDataStreamoperator>> (QDataStream &s, QUuid &id)
 

Detailed Description

The QUuid class stores a Universally Unique Identifier (UUID).

Using Universally Unique IDentifiers (UUID) is a standard way to uniquely identify entities in a distributed computing environment. A UUID is a 16-byte (128-bit) number generated by some algorithm that is meant to guarantee that the UUID will be unique in the distributed computing environment where it is used. The acronym GUID is often used instead, Globally Unique IDentifiers, but it refers to the same thing.

Actually, the GUID is one variant of UUID. Multiple variants are in use. Each UUID contains a bit field that specifies which type (variant) of UUID it is. Call variant() to discover which type of UUID an instance of QUuid contains. It extracts the three most significant bits of byte 8 of the 16 bytes. In QUuid, byte 8 is QUuid::data4[0]. If you create instances of QUuid using the constructor that accepts all the numeric values as parameters, use the following table to set the three most significant bits of parameter b1, which becomes QUuid::data4[0] and contains the variant field in its three most significant bits. In the table, 'x' means do not care.

msb0msb1msb2Variant
0xxNCS (Network Computing System)
10xDCE (Distributed Computing Environment)
110Microsoft (GUID)
111Reserved for future expansion

If variant() returns QUuid::DCE, the UUID also contains a version field in the four most significant bits of QUuid::data3, and you can call version() to discover which version your QUuid contains. If you create instances of QUuid using the constructor that accepts all the numeric values as parameters, use the following table to set the four most significant bits of parameter w2, which becomes QUuid::data3 and contains the version field in its four most significant bits.

msb0msb1msb2msb3Version
0001Time
0010Embedded POSIX
0011Name
0100Random

The field layouts for the DCE versions listed in the table above are specified in the Network Working Group UUID Specification.

Most platforms provide a tool for generating new UUIDs, e.g. uuidgen and guidgen. You can also use createUuid(). UUIDs generated by createUuid() are of the random type. Their QUuid::Version bits are set to QUuid::Random, and their QUuid::Variant bits are set to QUuid::DCE. The rest of the UUID is composed of random numbers. Theoretically, this means there is a small chance that a UUID generated by createUuid() will not be unique. But it is a very small chance.

UUIDs can be constructed from numeric values or from strings, or using the static createUuid() function. They can be converted to a string with toString(). UUIDs have a variant() and a version(), and null UUIDs return true from isNull().

See also
toString(), QUuid()

Member Enumeration Documentation

This enum defines the values used in the variant field of the UUID. The value in the variant field determines the layout of the 128-bit value.

ConstantValueDescription
QUuid::VarUnknown-1Variant is unknown
QUuid::NCS0Reserved for NCS (Network Computing System) backward compatibility
QUuid::DCE2Distributed Computing Environment, the scheme used by QUuid
QUuid::Microsoft6Reserved for Microsoft backward compatibility (GUID)
QUuid::Reserved7Reserved for future definition

This enum defines the values used in the version field of the UUID. The version field is meaningful only if the value in the variant field is QUuid::DCE.

ConstantValueDescription
QUuid::VerUnknown-1 Version is unknown
QUuid::Time1 Time based by using timestamp, clock sequence, and MAC network card address (if available) for the node sections
QUuid::EmbeddedPOSIX2 DCE Security version, with embedded POSIX UUIDs
QUuid::Name3 Name based by using values from a name for all sections
QUuid::Random4 Random based by using random numbers for all sections

Constructor & Destructor Documentation

constexpr QUuid::QUuid ( )
inlineconstexpr

Creates the null UUID. toString() will output the null UUID as "{00000000-0000-0000-0000-000000000000}".

constexpr QUuid::QUuid ( uint  l,
ushort  w1,
ushort  w2,
uchar  b1,
uchar  b2,
uchar  b3,
uchar  b4,
uchar  b5,
uchar  b6,
uchar  b7,
uchar  b8 
)
inlineconstexpr

Creates a UUID with the value specified by the parameters, l, w1, w2, b1, b2, b3, b4, b5, b6, b7, b8.

// {67C8770B-44F1-410A-AB9A-F9B5446F13EE}
QUuid IID_MyInterface(0x67c8770b, 0x44f1, 0x410a, 0xab, 0x9a, 0xf9, 0xb5, 0x44, 0x6f, 0x13, 0xee)
QUuid::QUuid ( const QString text)

Creates a QUuid object from the string text, which must be formatted as five hex fields separated by '-', e.g., "{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}" where 'x' is a hex digit. The curly braces shown here are optional, but it is normal to include them. If the conversion fails, a null UUID is created. See toString() for an explanation of how the five hex fields map to the public data members in QUuid.

See also
toString(), QUuid()
QUuid::QUuid ( const QByteArray text)

Creates a QUuid object from the QByteArray text, which must be formatted as five hex fields separated by '-', e.g., "{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}" where 'x' is a hex digit. The curly braces shown here are optional, but it is normal to include them. If the conversion fails, a null UUID is created. See toByteArray() for an explanation of how the five hex fields map to the public data members in QUuid.

See also
toByteArray(), QUuid()
constexpr QUuid::QUuid ( const GUID &  guid)
inlineconstexpr

Casts a Windows guid to a QUuid.

Warning
This function is only for Windows.

Method Documentation

QUuid QUuid::createUuid ( )
static

On any platform other than Windows, this function returns a new UUID with variant QUuid::DCE and version QUuid::Random. If the /dev/urandom device exists, then the numbers used to construct the UUID will be of cryptographic quality, which will make the UUID unique. Otherwise, the numbers of the UUID will be obtained from the local pseudo-random number generator (qrand(), which is seeded by qsrand()) which is usually not of cryptographic quality, which means that the UUID can not be guaranteed to be unique.

On a Windows platform, a GUID is generated, which almost certainly will be unique, on this or any other system, networked or not.

See also
variant(), version()
QUuid QUuid::createUuidV3 ( const QUuid &  ns,
const QByteArray baseData 
)
static

This function returns a new UUID with variant QUuid::DCE and version QUuid::Md5. ns is the namespace and baseData is the basic data as described by RFC 4122.

See also
variant(), version(), createUuidV5()
QUuid QUuid::createUuidV3 ( const QUuid &  ns,
const QString baseData 
)
inlinestatic

This function returns a new UUID with variant QUuid::DCE and version QUuid::Md5. ns is the namespace and baseData is the basic data as described by RFC 4122.

See also
variant(), version(), createUuidV5()
QUuid QUuid::createUuidV5 ( const QUuid &  ns,
const QByteArray baseData 
)
static

This function returns a new UUID with variant QUuid::DCE and version QUuid::Sha1. ns is the namespace and baseData is the basic data as described by RFC 4122.

See also
variant(), version(), createUuidV3()
QUuid QUuid::createUuidV5 ( const QUuid &  ns,
const QString baseData 
)
inlinestatic

This function returns a new UUID with variant QUuid::DCE and version QUuid::Sha1. ns is the namespace and baseData is the basic data as described by RFC 4122.

See also
variant(), version(), createUuidV3()
QUuid QUuid::fromRfc4122 ( const QByteArray bytes)
static

Creates a QUuid object from the binary representation of the UUID given by bytes, as specified by RFC 4122 section 4.1.2. See toRfc4122() for a further explanation of the order of bytes required.

The byte array accepted is not a human readable format.

If the conversion fails, a null UUID is created.

See also
toRfc4122(), QUuid()
bool QUuid::isNull ( ) const

Returns true if this is the null UUID {00000000-0000-0000-0000-000000000000}, otherwise returns false.

QUuid::operator GUID ( ) const
inline

Returns a Windows GUID from a QUuid.

Warning
This method is only for Windows platforms.
constexpr bool QUuid::operator!= ( const GUID &  guid) const
inlineconstexpr

Returns true if this UUID is not equal to the Windows GUID guid, otherwise returns false.

constexpr bool QUuid::operator!= ( const QUuid &  other) const
inlineconstexpr

Returns true if this QUuid and the other QUuid are different, otherwise returns false.

bool QUuid::operator< ( const QUuid &  other) const

Returns true if this QUuid has the same variant field as the other QUuid and is lexicographically before the other QUuid. If the other QUuid has a different variant field, the return value is determined by comparing the two variants.

See also
variant()
constexpr QUuid & QUuid::operator= ( const GUID &  guid)
inlineconstexpr

Assigns a Windows guid to a QUuid.

Warning
This function is only for Windows platforms.
constexpr bool QUuid::operator== ( const GUID &  guid) const
inlineconstexpr

Returns true if this UUID is equal to the Windows GUID guid, otherwise returns false.

constexpr bool QUuid::operator== ( const QUuid &  other) const
inlineconstexpr

Returns true if this QUuid and the other QUuid are identical, otherwise returns false.

bool QUuid::operator> ( const QUuid &  other) const

Returns true if this QUuid has the same variant field as the other QUuid and is lexicographically after the other QUuid. If the other QUuid has a different variant field, the return value is determined by comparing the two variants.

See also
variant()
QByteArray QUuid::toByteArray ( ) const

Returns the binary representation of this QUuid. The byte array is formatted as five hex fields separated by '-' and enclosed in curly braces, i.e., "{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}" where 'x' is a hex digit. From left to right, the five hex fields are obtained from the four public data members in QUuid as follows:

Field #Source
1data1
2data2
3data3
4data4[0] .. data4[1]
5data4[2] .. data4[7]
QByteArray QUuid::toRfc4122 ( ) const

Returns the binary representation of this QUuid. The byte array is in big endian format, and formatted according to RFC 4122, section 4.1.2 - "Layout and byte order".

The order is as follows:

Field #Source
1data1
2data2
3data3
4data4[0] .. data4[7]
QString QUuid::toString ( ) const

Returns the string representation of this QUuid. The string is formatted as five hex fields separated by '-' and enclosed in curly braces, i.e., "{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}" where 'x' is a hex digit. From left to right, the five hex fields are obtained from the four public data members in QUuid as follows:

Field #Source
1data1
2data2
3data3
4data4[0] .. data4[1]
5data4[2] .. data4[7]
QUuid::Variant QUuid::variant ( ) const

Returns the value in the variant field of the UUID. If the return value is QUuid::DCE, call version() to see which layout it uses. The null UUID is considered to be of an unknown variant.

See also
version()
QUuid::Version QUuid::version ( ) const

Returns the version field of the UUID, if the UUID's variant field is QUuid::DCE. Otherwise it returns QUuid::VerUnknown.

See also
variant()

Friends And Related Function Documentation

QDataStream & operator<< ( QDataStream s,
const QUuid &  id 
)
related

Writes the UUID id to the data stream s.

QDataStream & operator>> ( QDataStream s,
QUuid &  id 
)
related

Reads a UUID from the stream s into id.