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Published: Aug 27, 2018 License: BSD-3-Clause Imports: 16 Imported by: 0


uuid build status

The uuid package generates and inspects UUIDs based on RFC 4122 and DCE 1.1: Authentication and Security Services.

This package is based on the github.com/pborman/uuid package (previously named code.google.com/p/go-uuid). It differs from these earlier packages in that a UUID is a 16 byte array rather than a byte slice. One loss due to this change is the ability to represent an invalid UUID (vs a NIL UUID).


go get github.com/google/uuid



Full go doc style documentation for the package can be viewed online without installing this package by using the GoDoc site here: http://godoc.org/github.com/google/uuid



Package uuid generates and inspects UUIDs.

UUIDs are based on RFC 4122 and DCE 1.1: Authentication and Security Services.

A UUID is a 16 byte (128 bit) array. UUIDs may be used as keys to maps or compared directly.



View Source
const (
	Person = Domain(0)
	Group  = Domain(1)
	Org    = Domain(2)

Domain constants for DCE Security (Version 2) UUIDs.

View Source
const (
	Invalid   = Variant(iota) // Invalid UUID
	RFC4122                   // The variant specified in RFC4122
	Reserved                  // Reserved, NCS backward compatibility.
	Microsoft                 // Reserved, Microsoft Corporation backward compatibility.
	Future                    // Reserved for future definition.

Constants returned by Variant.


View Source
var (
	NameSpaceDNS  = Must(Parse("6ba7b810-9dad-11d1-80b4-00c04fd430c8"))
	NameSpaceURL  = Must(Parse("6ba7b811-9dad-11d1-80b4-00c04fd430c8"))
	NameSpaceOID  = Must(Parse("6ba7b812-9dad-11d1-80b4-00c04fd430c8"))
	NameSpaceX500 = Must(Parse("6ba7b814-9dad-11d1-80b4-00c04fd430c8"))
	Nil           UUID // empty UUID, all zeros

Well known namespace IDs and UUIDs


func ClockSequence

func ClockSequence() int

ClockSequence returns the current clock sequence, generating one if not already set. The clock sequence is only used for Version 1 UUIDs.

The uuid package does not use global static storage for the clock sequence or the last time a UUID was generated. Unless SetClockSequence is used, a new random clock sequence is generated the first time a clock sequence is requested by ClockSequence, GetTime, or NewUUID. (section

func NodeID

func NodeID() []byte

NodeID returns a slice of a copy of the current Node ID, setting the Node ID if not already set.

func NodeInterface

func NodeInterface() string

NodeInterface returns the name of the interface from which the NodeID was derived. The interface "user" is returned if the NodeID was set by SetNodeID.

func SetClockSequence

func SetClockSequence(seq int)

SetClockSequence sets the clock sequence to the lower 14 bits of seq. Setting to -1 causes a new sequence to be generated.

func SetNodeID

func SetNodeID(id []byte) bool

SetNodeID sets the Node ID to be used for Version 1 UUIDs. The first 6 bytes of id are used. If id is less than 6 bytes then false is returned and the Node ID is not set.

func SetNodeInterface

func SetNodeInterface(name string) bool

SetNodeInterface selects the hardware address to be used for Version 1 UUIDs. If name is "" then the first usable interface found will be used or a random Node ID will be generated. If a named interface cannot be found then false is returned.

SetNodeInterface never fails when name is "".

func SetRand

func SetRand(r io.Reader)

SetRand sets the random number generator to r, which implements io.Reader. If r.Read returns an error when the package requests random data then a panic will be issued.

Calling SetRand with nil sets the random number generator to the default generator.


type Domain

type Domain byte

A Domain represents a Version 2 domain

func (Domain) String

func (d Domain) String() string

type Time

type Time int64

A Time represents a time as the number of 100's of nanoseconds since 15 Oct 1582.

func GetTime

func GetTime() (Time, uint16, error)

GetTime returns the current Time (100s of nanoseconds since 15 Oct 1582) and clock sequence as well as adjusting the clock sequence as needed. An error is returned if the current time cannot be determined.

func (Time) UnixTime

func (t Time) UnixTime() (sec, nsec int64)

UnixTime converts t the number of seconds and nanoseconds using the Unix epoch of 1 Jan 1970.

type UUID

type UUID [16]byte

A UUID is a 128 bit (16 byte) Universal Unique IDentifier as defined in RFC 4122.

func FromBytes

func FromBytes(b []byte) (uuid UUID, err error)

FromBytes creates a new UUID from a byte slice. Returns an error if the slice does not have a length of 16. The bytes are copied from the slice.

func Must

func Must(uuid UUID, err error) UUID

Must returns uuid if err is nil and panics otherwise.

func New

func New() UUID

New creates a new random UUID or panics. New is equivalent to the expression


func NewDCEGroup

func NewDCEGroup() (UUID, error)

NewDCEGroup returns a DCE Security (Version 2) UUID in the group domain with the id returned by os.Getgid.

NewDCESecurity(Group, uint32(os.Getgid()))

func NewDCEPerson

func NewDCEPerson() (UUID, error)

NewDCEPerson returns a DCE Security (Version 2) UUID in the person domain with the id returned by os.Getuid.

NewDCESecurity(Person, uint32(os.Getuid()))

func NewDCESecurity

func NewDCESecurity(domain Domain, id uint32) (UUID, error)

NewDCESecurity returns a DCE Security (Version 2) UUID.

The domain should be one of Person, Group or Org. On a POSIX system the id should be the users UID for the Person domain and the users GID for the Group. The meaning of id for the domain Org or on non-POSIX systems is site defined.

For a given domain/id pair the same token may be returned for up to 7 minutes and 10 seconds.

func NewHash

func NewHash(h hash.Hash, space UUID, data []byte, version int) UUID

NewHash returns a new UUID derived from the hash of space concatenated with data generated by h. The hash should be at least 16 byte in length. The first 16 bytes of the hash are used to form the UUID. The version of the UUID will be the lower 4 bits of version. NewHash is used to implement NewMD5 and NewSHA1.

func NewMD5

func NewMD5(space UUID, data []byte) UUID

NewMD5 returns a new MD5 (Version 3) UUID based on the supplied name space and data. It is the same as calling:

NewHash(md5.New(), space, data, 3)

func NewRandom

func NewRandom() (UUID, error)

NewRandom returns a Random (Version 4) UUID.

The strength of the UUIDs is based on the strength of the crypto/rand package.

A note about uniqueness derived from the UUID Wikipedia entry:

Randomly generated UUIDs have 122 random bits.  One's annual risk of being
hit by a meteorite is estimated to be one chance in 17 billion, that
means the probability is about 0.00000000006 (6 × 10−11),
equivalent to the odds of creating a few tens of trillions of UUIDs in a
year and having one duplicate.

func NewSHA1

func NewSHA1(space UUID, data []byte) UUID

NewSHA1 returns a new SHA1 (Version 5) UUID based on the supplied name space and data. It is the same as calling:

NewHash(sha1.New(), space, data, 5)

func NewUUID

func NewUUID() (UUID, error)

NewUUID returns a Version 1 UUID based on the current NodeID and clock sequence, and the current time. If the NodeID has not been set by SetNodeID or SetNodeInterface then it will be set automatically. If the NodeID cannot be set NewUUID returns nil. If clock sequence has not been set by SetClockSequence then it will be set automatically. If GetTime fails to return the current NewUUID returns nil and an error.

In most cases, New should be used.

func Parse

func Parse(s string) (UUID, error)

Parse decodes s into a UUID or returns an error. Both the UUID form of xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx and urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx are decoded.

func ParseBytes

func ParseBytes(b []byte) (UUID, error)

ParseBytes is like Parse, except it parses a byte slice instead of a string.

func (UUID) ClockSequence

func (uuid UUID) ClockSequence() int

ClockSequence returns the clock sequence encoded in uuid. The clock sequence is only well defined for version 1 and 2 UUIDs.

func (UUID) Domain

func (uuid UUID) Domain() Domain

Domain returns the domain for a Version 2 UUID. Domains are only defined for Version 2 UUIDs.

func (UUID) ID

func (uuid UUID) ID() uint32

ID returns the id for a Version 2 UUID. IDs are only defined for Version 2 UUIDs.

func (UUID) MarshalBinary

func (uuid UUID) MarshalBinary() ([]byte, error)

MarshalBinary implements encoding.BinaryMarshaler.

func (UUID) MarshalText

func (uuid UUID) MarshalText() ([]byte, error)

MarshalText implements encoding.TextMarshaler.

func (UUID) NodeID

func (uuid UUID) NodeID() []byte

NodeID returns the 6 byte node id encoded in uuid. It returns nil if uuid is not valid. The NodeID is only well defined for version 1 and 2 UUIDs.

func (*UUID) Scan

func (uuid *UUID) Scan(src interface{}) error

Scan implements sql.Scanner so UUIDs can be read from databases transparently Currently, database types that map to string and []byte are supported. Please consult database-specific driver documentation for matching types.

func (UUID) String

func (uuid UUID) String() string

String returns the string form of uuid, xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx , or "" if uuid is invalid.

func (UUID) Time

func (uuid UUID) Time() Time

Time returns the time in 100s of nanoseconds since 15 Oct 1582 encoded in uuid. The time is only defined for version 1 and 2 UUIDs.

func (UUID) URN

func (uuid UUID) URN() string

URN returns the RFC 2141 URN form of uuid, urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx, or "" if uuid is invalid.

func (*UUID) UnmarshalBinary

func (uuid *UUID) UnmarshalBinary(data []byte) error

UnmarshalBinary implements encoding.BinaryUnmarshaler.

func (*UUID) UnmarshalText

func (uuid *UUID) UnmarshalText(data []byte) error

UnmarshalText implements encoding.TextUnmarshaler.

func (UUID) Value

func (uuid UUID) Value() (driver.Value, error)

Value implements sql.Valuer so that UUIDs can be written to databases transparently. Currently, UUIDs map to strings. Please consult database-specific driver documentation for matching types.

func (UUID) Variant

func (uuid UUID) Variant() Variant

Variant returns the variant encoded in uuid.

func (UUID) Version

func (uuid UUID) Version() Version

Version returns the version of uuid.

type Variant

type Variant byte

A Variant represents a UUID's variant.

func (Variant) String

func (v Variant) String() string

type Version

type Version byte

A Version represents a UUID's version.

func (Version) String

func (v Version) String() string

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