// Copyright 2016 Google Inc.  All rights reserved.

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

package uuid

import "io"

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

// the expression

//

//    uuid.Must(uuid.NewRandom())

func New() UUID {

	return Must(NewRandom())

}

// 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 NewRandom() (UUID, error) {

	var uuid UUID

	_, err := io.ReadFull(rander, uuid[:])

	if err != nil {

		return Nil, err

	}

	uuid[6] = (uuid[6] & 0x0f) | 0x40 // Version 4

	uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10

	return uuid, nil

}