Is there a method to generate a UUID with go language

问题:

I have code that looks like this:

u := make([]byte, 16) _, err := rand.Read(u) if err != nil {     return }  u[8] = (u[8] | 0x80) & 0xBF // what does this do? u[6] = (u[6] | 0x40) & 0x4F // what does this do?  return hex.EncodeToString(u)

It returns a string with a length of 32, but I don't think it is a valid UUID. If it is a real UUID, why is it a UUID, and what is the purpose of the code that modifies the value of u[8] and u[6].

Is there a better way of generating UUIDs?

回答1:

u[8] = (u[8] | 0x80) & 0xBF // what's the purpose ? u[6] = (u[6] | 0x40) & 0x4F // what's the purpose ?

These lines clamp the values of byte 6 and 8 to a specific range. rand.Read returns random bytes in the range 0-255, which are not all valid values for a UUID. As far as I can tell, this should be done for all the values in the slice though.

If you are on linux, you can alternatively call /usr/bin/uuidgen.

package main  import (     "fmt"     "log"     "os/exec" )  func main() {     out, err := exec.Command("uuidgen").Output()     if err != nil {         log.Fatal(err)     }     fmt.Printf("%s", out) }

Which yields:

$ go run uuid.go  dc9076e9-2fda-4019-bd2c-900a8284b9c4

回答2:

You can generate UUIDs using the go-uuid library. This can be installed with:

go get github.com/nu7hatch/gouuid

You can generate random (version 4) UUIDs with:

import "github.com/nu7hatch/gouuid"  ...  u, err := uuid.NewV4()

The returned UUID type is a 16 byte array, so you can retrieve the binary value easily. It also provides the standard hex string representation via its String() method.

The code you have also looks like it will also generate a valid version 4 UUID: the bitwise manipulation you perform at the end set the version and variant fields of the UUID to correctly identify it as version 4. This is done to distinguish random UUIDs from ones generated via other algorithms (e.g. version 1 UUIDs based on your MAC address and time).

回答3:

The go-uuid library is NOT RFC4122 compliant. The variant bits are not set correctly. There have been several attempts by community members to have this fixed but pull requests for the fix are not being accepted.

You can generate UUIDs using the Go uuid library I rewrote based on the go-uuid library. There are several fixes and improvements. This can be installed with:

go get github.com/twinj/uuid

You can generate random (version 4) UUIDs with:

import "github.com/twinj/uuid"  u := uuid.NewV4()

The returned UUID type is an interface and the underlying type is an array.

The library also generates v1 UUIDs and correctly generates v3 and 5 UUIDs. There are several new methods to help with printing and formatting and also new general methods to create UUIDs based off of existing data.

回答4:

"crypto/rand" is cross platform pkg for random bytes generattion

package main  import (     "crypto/rand"     "fmt" )  func pseudo_uuid() (uuid string) {      b := make([]byte, 16)     _, err := rand.Read(b)     if err != nil {         fmt.Println("Error: ", err)         return     }      uuid = fmt.Sprintf("%X-%X-%X-%X-%X", b[0:4], b[4:6], b[6:8], b[8:10], b[10:])      return }

回答5:

From Russ Cox's post:

There's no official library. Ignoring error checking, this seems like it would work fine:

f, _ := os.O