| // Copyright 2011 Google Inc. All rights reserved. |
| // Author: borman@google.com (Paul Borman) |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| package uuid |
| |
| // Random returns a Random (Version 4) UUID or panics. |
| // |
| // The strength of the UUIDs is based on the strength of the crypto/rand |
| // package. |
| // |
| // A note about uniqueness derived from 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 { |
| uuid := make([]byte, 16) |
| randomBits([]byte(uuid)) |
| uuid[6] = (uuid[6] & 0x0f) | 0x40 // Version 4 |
| uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10 |
| return uuid |
| } |
