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# QUuid Class Reference
[QtCore module]

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

### Types

- enum Variant { VarUnknown, NCS, DCE, Microsoft, Reserved }
- enum Version { VerUnknown, Time, EmbeddedPOSIX, Name, Random }

### Methods

- __init__ (self)
- __init__ (self, int l, int w1, int w2, str b1, str b2, str b3, str b4, str b5, str b6, str b7, str b8)
- __init__ (self, QString)
- __init__ (self, QByteArray)
- __init__ (self, QUuid)
- bool isNull (self)
- QByteArray toByteArray (self)
- QByteArray toRfc4122 (self)
- QString toString (self)
- Variant variant (self)
- Version version (self)

### Static Methods

- QUuid createUuid ()
- QUuid fromRfc4122 (QByteArray)

### Special Methods

- bool __eq__ (self, QUuid orig)
- bool __ge__ (self, QUuid other)
- bool __gt__ (self, QUuid other)
- bool __le__ (self, QUuid other)
- bool __lt__ (self, QUuid other)
- bool __ne__ (self, QUuid orig)
- str __repr__ (self)

## 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 signifcant 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 don't care.

msb0 | msb1 | msb2 | Variant
--- | --- | --- | ---
0 | x | x | NCS (Network Computing System)
1 | 0 | x | DCE (Distributed Computing Environment)
1 | 1 | 0 | Microsoft (GUID)
1 | 1 | 1 | Reserved 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.

msb0 | msb1 | msb2 | msb3 | Version
--- | --- | --- | --- | ---
0 | 0 | 0 | 1 | Time
0 | 0 | 1 | 0 | Embedded POSIX
0 | 0 | 1 | 1 | Name
0 | 1 | 0 | 0 | Random

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().

## Type Documentation

### QUuid.Variant

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.

Constant | Value | Description
--- | --- | ---
`QUuid.VarUnknown` | `-1` | Variant is unknown
`QUuid.NCS` | `0` | Reserved for NCS (Network Computing System) backward compatibility
`QUuid.DCE` | `2` | Distributed Computing Environment, the scheme used by QUuid
`QUuid.Microsoft` | `6` | Reserved for Microsoft backward compatibility (GUID)
`QUuid.Reserved` | `7` | Reserved for future definition

### QUuid.Version

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.

Constant | Value | Description
--- | --- | ---
`QUuid.VerUnknown` | `-1` | Version is unknown
`QUuid.Time` | `1` | Time-based, by using timestamp, clock sequence, and MAC network card address (if available) for the node sections
`QUuid.EmbeddedPOSIX` | `2` | DCE Security version, with embedded POSIX UUIDs
`QUuid.Name` | `3` | Name-based, by using values from a name for all sections
`QUuid.Random` | `4` | Random-based, by using random numbers for all sections

## Method Documentation

### QUuid.__init__ (self)

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

### QUuid.__init__ (self, int l, int w1, int w2, str b1, str b2, str b3, str b4, str b5, str b6, str b7, str b8)

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

Example:

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

### QUuid.__init__ (self, QString)

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() and QUuid().

### QUuid.__init__ (self, QByteArray)

### QUuid.__init__ (self, QUuid)

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.

This function was introduced in Qt 4.8.

See also toByteArray() and QUuid().

### QUuid QUuid.createUuid ()

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 cryptograhic quality, which means that the UUID can't 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() and version().

### QUuid QUuid.fromRfc4122 (QByteArray)

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.

This function was introduced in Qt 4.8.

See also toRfc4122() and QUuid().

### bool QUuid.isNull (self)

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

### QByteArray QUuid.toByteArray (self)

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
--- | ---
1 | data1
2 | data2
3 | data3
4 | data4[0] .. data4[1]
5 | data4[2] .. data4[7]

This function was introduced in Qt 4.8.

### QByteArray QUuid.toRfc4122 (self)

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
--- | ---
1 | data1
2 | data2
3 | data3
4 | data4[0] .. data4[7]

This function was introduced in Qt 4.8.

### QString QUuid.toString (self)

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
--- | ---
1 | data1
2 | data2
3 | data3
4 | data4[0] .. data4[1]
5 | data4[2] .. data4[7]

### Variant QUuid.variant (self)

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().

### Version QUuid.version (self)

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

See also variant().

### bool QUuid.__eq__ (self, QUuid orig)

### bool QUuid.__ge__ (self, QUuid other)

### bool QUuid.__gt__ (self, QUuid other)

### bool QUuid.__le__ (self, QUuid other)

### bool QUuid.__lt__ (self, QUuid other)

### bool QUuid.__ne__ (self, QUuid orig)

### str QUuid.__repr__ (self)