Is there a method to generate a UUID with go language

go uuid
hardPass picture hardPass · Feb 28, 2013 · Viewed 120.5k times · Source

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?

Answer

James Henstridge picture James Henstridge · Feb 28, 2013

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).

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