uuid

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README

UUID

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Package uuid provides a pure Go implementation of Universally Unique Identifiers (UUID) variant as defined in RFC-4122. This package supports both the creation and parsing of UUIDs in different formats.

This package supports the following UUID versions:

  • Version 1, based on timestamp and MAC address (RFC-4122)
  • Version 3, based on MD5 hashing of a named value (RFC-4122)
  • Version 4, based on random numbers (RFC-4122)
  • Version 5, based on SHA-1 hashing of a named value (RFC-4122)

Project History

This project was originally forked from the github.com/satori/go.uuid repository after it appeared to be no longer maintained, while exhibiting critical flaws. We have decided to take over this project to ensure it receives regular maintenance for the benefit of the larger Go community.

We'd like to thank Maxim Bublis for his hard work on the original iteration of the package.

License

This source code of this package is released under the MIT License. Please see the LICENSE for the full content of the license.

We recommend using v2.0.0+ of this package, as versions prior to 2.0.0 were created before our fork of the original package and have some known deficiencies.

Installation

It is recommended to use a package manager like dep that understands tagged releases of a package, as well as semantic versioning.

If you are unable to make use of a dependency manager with your project, you can use the go get command to download it directly:

$ go get github.com/gofrs/uuid

Requirements

Due to subtests not being supported in older versions of Go, this package is only regularly tested against Go 1.7+. This package may work perfectly fine with Go 1.2+, but support for these older versions is not actively maintained.

Go 1.11 Modules

As of v3.2.0, this repository no longer adopts Go modules, and v3.2.0 no longer has a go.mod file. As a result, v3.2.0 also drops support for the github.com/gofrs/uuid/v3 import path. Only module-based consumers are impacted. With the v3.2.0 release, all gofrs/uuid consumers should use the github.com/gofrs/uuid import path.

An existing module-based consumer will continue to be able to build using the github.com/gofrs/uuid/v3 import path using any valid consumer go.mod that worked prior to the publishing of v3.2.0, but any module-based consumer should start using the github.com/gofrs/uuid import path when possible and must use the github.com/gofrs/uuid import path prior to upgrading to v3.2.0.

Please refer to Issue #61 and Issue #66 for more details.

Usage

Here is a quick overview of how to use this package. For more detailed documentation, please see the GoDoc Page.

package main

import (
	"log"

	"github.com/gofrs/uuid"
)

// Create a Version 4 UUID, panicking on error.
// Use this form to initialize package-level variables.
var u1 = uuid.Must(uuid.NewV4())

func main() {
	// Create a Version 4 UUID.
	u2, err := uuid.NewV4()
	if err != nil {
		log.Fatalf("failed to generate UUID: %v", err)
	}
	log.Printf("generated Version 4 UUID %v", u2)

	// Parse a UUID from a string.
	s := "6ba7b810-9dad-11d1-80b4-00c04fd430c8"
	u3, err := uuid.FromString(s)
	if err != nil {
		log.Fatalf("failed to parse UUID %q: %v", s, err)
	}
	log.Printf("successfully parsed UUID %v", u3)
}

References

Documentation

Overview

Package uuid provides implementations of the Universally Unique Identifier (UUID), as specified in RFC-4122 and the Peabody RFC Draft (revision 02).

RFC-4122[1] provides the specification for versions 1, 3, 4, and 5. The Peabody UUID RFC Draft[2] provides the specification for the new k-sortable UUIDs, versions 6 and 7.

DCE 1.1[3] provides the specification for version 2, but version 2 support was removed from this package in v4 due to some concerns with the specification itself. Reading the spec, it seems that it would result in generating UUIDs that aren't very unique. In having read the spec it seemed that our implementation did not meet the spec. It also seems to be at-odds with RFC 4122, meaning we would need quite a bit of special code to support it. Lastly, there were no Version 2 implementations that we could find to ensure we were understanding the specification correctly.

[1] https://tools.ietf.org/html/rfc4122 [2] https://datatracker.ietf.org/doc/html/draft-peabody-dispatch-new-uuid-format-02 [3] http://pubs.opengroup.org/onlinepubs/9696989899/chap5.htm#tagcjh_08_02_01_01

Index

Constants

View Source 
const (
	V1 byte // Version 1 (date-time and MAC address)

	V3 // Version 3 (namespace name-based)
	V4 // Version 4 (random)
	V5 // Version 5 (namespace name-based)
	V6 // Version 6 (k-sortable timestamp and random data) [peabody draft]
	V7 // Version 7 (k-sortable timestamp, with configurable precision, and random data) [peabody draft]

)

UUID versions.

View Source 
const (
	VariantNCS byte = iota
	VariantRFC4122
	VariantMicrosoft
	VariantFuture
)

UUID layout variants.

View Source 
const (
	DomainPerson = iota
	DomainGroup
	DomainOrg
)

UUID DCE domains.

View Source 
const Size = 16

Size of a UUID in bytes.

Variables

View Source 
var (
	NamespaceDNS  = Must(FromString("6ba7b810-9dad-11d1-80b4-00c04fd430c8"))
	NamespaceURL  = Must(FromString("6ba7b811-9dad-11d1-80b4-00c04fd430c8"))
	NamespaceOID  = Must(FromString("6ba7b812-9dad-11d1-80b4-00c04fd430c8"))
	NamespaceX500 = Must(FromString("6ba7b814-9dad-11d1-80b4-00c04fd430c8"))
)

Predefined namespace UUIDs.

View Source 
var Nil = UUID{}

Nil is the nil UUID, as specified in RFC-4122, that has all 128 bits set to zero.

Functions

This section is empty.

Types

type Gen 

type Gen struct {
	// contains filtered or unexported fields
}

Gen is a reference UUID generator based on the specifications laid out in RFC-4122 and DCE 1.1: Authentication and Security Services. This type satisfies the Generator interface as defined in this package.

For consumers who are generating V1 UUIDs, but don't want to expose the MAC address of the node generating the UUIDs, the NewGenWithHWAF() function has been provided as a convenience. See the function's documentation for more info.

The authors of this package do not feel that the majority of users will need to obfuscate their MAC address, and so we recommend using NewGen() to create a new generator.

func NewGen 

func NewGen() *Gen

NewGen returns a new instance of Gen with some default values set. Most people should use this.

func NewGenWithHWAF 

func NewGenWithHWAF(hwaf HWAddrFunc) *Gen

NewGenWithHWAF builds a new UUID generator with the HWAddrFunc provided. Most consumers should use NewGen() instead.

This is used so that consumers can generate their own MAC addresses, for use in the generated UUIDs, if there is some concern about exposing the physical address of the machine generating the UUID.

The Gen generator will only invoke the HWAddrFunc once, and cache that MAC address for all the future UUIDs generated by it. If you'd like to switch the MAC address being used, you'll need to create a new generator using this function.

func (*Gen) NewV1 

func (g *Gen) NewV1() (UUID, error)

NewV1 returns a UUID based on the current timestamp and MAC address.

func (*Gen) NewV3 

func (g *Gen) NewV3(ns UUID, name string) UUID

NewV3 returns a UUID based on the MD5 hash of the namespace UUID and name.

func (*Gen) NewV4 

func (g *Gen) NewV4() (UUID, error)

NewV4 returns a randomly generated UUID.

func (*Gen) NewV5 

func (g *Gen) NewV5(ns UUID, name string) UUID

NewV5 returns a UUID based on SHA-1 hash of the namespace UUID and name.

func (*Gen) NewV6 

func (g *Gen) NewV6() (UUID, error)

NewV6 returns a k-sortable UUID based on a timestamp and 48 bits of pseudorandom data. The timestamp in a V6 UUID is the same as V1, with the bit order being adjusted to allow the UUID to be k-sortable.

This is implemented based on revision 02 of the Peabody UUID draft, and may be subject to change pending further revisions. Until the final specification revision is finished, changes required to implement updates to the spec will not be considered a breaking change. They will happen as a minor version releases until the spec is final.

func (*Gen) NewV7 

func (g *Gen) NewV7(p Precision) (UUID, error)

NewV7 returns a k-sortable UUID based on the current UNIX epoch, with the ability to configure the timestamp's precision from millisecond all the way to nanosecond. The additional precision is supported by reducing the amount of pseudorandom data that makes up the rest of the UUID.

If an unknown Precision argument is passed to this method it will panic. As such it's strongly encouraged to use the package-provided constants for this value.

This is implemented based on revision 02 of the Peabody UUID draft, and may be subject to change pending further revisions. Until the final specification revision is finished, changes required to implement updates to the spec will not be considered a breaking change. They will happen as a minor version releases until the spec is final.

type Generator added in v1.2.0 

type Generator interface {
	NewV1() (UUID, error)
	NewV3(ns UUID, name string) UUID
	NewV4() (UUID, error)
	NewV5(ns UUID, name string) UUID
	NewV6() (UUID, error)
	NewV7(Precision) (UUID, error)
}

Generator provides an interface for generating UUIDs. 

var DefaultGenerator Generator = NewGen()

DefaultGenerator is the default UUID Generator used by this package.

type HWAddrFunc 

type HWAddrFunc func() (net.HardwareAddr, error)

HWAddrFunc is the function type used to provide hardware (MAC) addresses.

type NullUUID added in v1.1.0 

type NullUUID struct {
	UUID  UUID
	Valid bool
}

NullUUID can be used with the standard sql package to represent a UUID value that can be NULL in the database.

func (NullUUID) MarshalJSON 

func (u NullUUID) MarshalJSON() ([]byte, error)

MarshalJSON marshals the NullUUID as null or the nested UUID

func (*NullUUID) Scan added in v1.1.0 

func (u *NullUUID) Scan(src interface{}) error

Scan implements the sql.Scanner interface.

func (*NullUUID) UnmarshalJSON 

func (u *NullUUID) UnmarshalJSON(b []byte) error

UnmarshalJSON unmarshals a NullUUID

func (NullUUID) Value added in v1.1.0 

func (u NullUUID) Value() (driver.Value, error)

Value implements the driver.Valuer interface.

type Precision 

type Precision byte

Precision is used to configure the V7 generator, to specify how precise the timestamp within the UUID should be. 

const (
	NanosecondPrecision Precision = iota
	MicrosecondPrecision
	MillisecondPrecision
)

func (Precision) Duration 

func (p Precision) Duration() time.Duration

Duration returns the time.Duration for a specific precision. If the Precision value is not known, this returns 0.

func (Precision) String 

func (p Precision) String() string

type Timestamp 

type Timestamp uint64

Timestamp is the count of 100-nanosecond intervals since 00:00:00.00, 15 October 1582 within a V1 UUID. This type has no meaning for other UUID versions since they don't have an embedded timestamp.

func TimestampFromV1 

func TimestampFromV1(u UUID) (Timestamp, error)

TimestampFromV1 returns the Timestamp embedded within a V1 UUID. Returns an error if the UUID is any version other than 1.

func TimestampFromV6 

func TimestampFromV6(u UUID) (Timestamp, error)

TimestampFromV6 returns the Timestamp embedded within a V6 UUID. This function returns an error if the UUID is any version other than 6.

This is implemented based on revision 01 of the Peabody UUID draft, and may be subject to change pending further revisions. Until the final specification revision is finished, changes required to implement updates to the spec will not be considered a breaking change. They will happen as a minor version releases until the spec is final.

func (Timestamp) Time 

func (t Timestamp) Time() (time.Time, error)

Time returns the UTC time.Time representation of a Timestamp

type UUID 

type UUID [Size]byte

UUID is an array type to represent the value of a UUID, as defined in RFC-4122.

func FromBytes 

func FromBytes(input []byte) (UUID, error)

FromBytes returns a UUID generated from the raw byte slice input. It will return an error if the slice isn't 16 bytes long.

func FromBytesOrNil 

func FromBytesOrNil(input []byte) UUID

FromBytesOrNil returns a UUID generated from the raw byte slice input. Same behavior as FromBytes(), but returns uuid.Nil instead of an error.

func FromString 

func FromString(input string) (UUID, error)

FromString returns a UUID parsed from the input string. Input is expected in a form accepted by UnmarshalText.

func FromStringOrNil 

func FromStringOrNil(input string) UUID

FromStringOrNil returns a UUID parsed from the input string. Same behavior as FromString(), but returns uuid.Nil instead of an error.

func Must added in v1.2.0 

func Must(u UUID, err error) UUID

Must is a helper that wraps a call to a function returning (UUID, error) and panics if the error is non-nil. It is intended for use in variable initializations such as 

var packageUUID = uuid.Must(uuid.FromString("123e4567-e89b-12d3-a456-426655440000"))

func NewV1 

func NewV1() (UUID, error)

NewV1 returns a UUID based on the current timestamp and MAC address.

func NewV3 

func NewV3(ns UUID, name string) UUID

NewV3 returns a UUID based on the MD5 hash of the namespace UUID and name.

func NewV4 

func NewV4() (UUID, error)

NewV4 returns a randomly generated UUID.

func NewV5 

func NewV5(ns UUID, name string) UUID

NewV5 returns a UUID based on SHA-1 hash of the namespace UUID and name.

func NewV6 

func NewV6() (UUID, error)

NewV6 returns a k-sortable UUID based on a timestamp and 48 bits of pseudorandom data. The timestamp in a V6 UUID is the same as V1, with the bit order being adjusted to allow the UUID to be k-sortable.

This is implemented based on revision 02 of the Peabody UUID draft, and may be subject to change pending further revisions. Until the final specification revision is finished, changes required to implement updates to the spec will not be considered a breaking change. They will happen as a minor version releases until the spec is final.

func NewV7 

func NewV7(p Precision) (UUID, error)

NewV7 returns a k-sortable UUID based on the current UNIX epoch, with the ability to configure the timestamp's precision from millisecond all the way to nanosecond. The additional precision is supported by reducing the amount of pseudorandom data that makes up the rest of the UUID.

If an unknown Precision argument is passed to this method it will panic. As such it's strongly encouraged to use the package-provided constants for this value.

This is implemented based on revision 02 of the Peabody UUID draft, and may be subject to change pending further revisions. Until the final specification revision is finished, changes required to implement updates to the spec will not be considered a breaking change. They will happen as a minor version releases until the spec is final.

func (UUID) Bytes 

func (u UUID) Bytes() []byte

Bytes returns a byte slice representation of the UUID.

func (UUID) Format 

func (u UUID) Format(f fmt.State, c rune)

Format implements fmt.Formatter for UUID values.

The behavior is as follows: The 'x' and 'X' verbs output only the hex digits of the UUID, using a-f for 'x' and A-F for 'X'. The 'v', '+v', 's' and 'q' verbs return the canonical RFC-4122 string representation. The 'S' verb returns the RFC-4122 format, but with capital hex digits. The '#v' verb returns the "Go syntax" representation, which is a 16 byte array initializer. All other verbs not handled directly by the fmt package (like '%p') are unsupported and will return "%!verb(uuid.UUID=value)" as recommended by the fmt package.

func (UUID) IsNil 

func (u UUID) IsNil() bool

IsNil returns if the UUID is equal to the nil UUID

func (UUID) MarshalBinary 

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

MarshalBinary implements the encoding.BinaryMarshaler interface.

func (UUID) MarshalText 

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

MarshalText implements the encoding.TextMarshaler interface. The encoding is the same as returned by the String() method.

func (*UUID) Scan 

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

Scan implements the sql.Scanner interface. A 16-byte slice will be handled by UnmarshalBinary, while a longer byte slice or a string will be handled by UnmarshalText.

func (*UUID) SetVariant 

func (u *UUID) SetVariant(v byte)

SetVariant sets the variant bits.

func (*UUID) SetVersion 

func (u *UUID) SetVersion(v byte)

SetVersion sets the version bits.

func (UUID) String 

func (u UUID) String() string

String returns a canonical RFC-4122 string representation of the UUID: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.

func (*UUID) UnmarshalBinary 

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

UnmarshalBinary implements the encoding.BinaryUnmarshaler interface. It will return an error if the slice isn't 16 bytes long.

func (*UUID) UnmarshalText 

func (u *UUID) UnmarshalText(text []byte) error

UnmarshalText implements the encoding.TextUnmarshaler interface. Following formats are supported: 

"6ba7b810-9dad-11d1-80b4-00c04fd430c8",
"{6ba7b810-9dad-11d1-80b4-00c04fd430c8}",
"urn:uuid:6ba7b810-9dad-11d1-80b4-00c04fd430c8"
"6ba7b8109dad11d180b400c04fd430c8"
"{6ba7b8109dad11d180b400c04fd430c8}",
"urn:uuid:6ba7b8109dad11d180b400c04fd430c8"

ABNF for supported UUID text representation follows: 

URN := 'urn'
UUID-NID := 'uuid'

hexdig := '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' |
          'a' | 'b' | 'c' | 'd' | 'e' | 'f' |
          'A' | 'B' | 'C' | 'D' | 'E' | 'F'

hexoct := hexdig hexdig
2hexoct := hexoct hexoct
4hexoct := 2hexoct 2hexoct
6hexoct := 4hexoct 2hexoct
12hexoct := 6hexoct 6hexoct

hashlike := 12hexoct
canonical := 4hexoct '-' 2hexoct '-' 2hexoct '-' 6hexoct

plain := canonical | hashlike
uuid := canonical | hashlike | braced | urn

braced := '{' plain '}' | '{' hashlike  '}'
urn := URN ':' UUID-NID ':' plain

func (UUID) Value 

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

Value implements the driver.Valuer interface.

func (UUID) Variant 

func (u UUID) Variant() byte

Variant returns the UUID layout variant.

func (UUID) Version 

func (u UUID) Version() byte

Version returns the algorithm version used to generate the UUID.

Source Files

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