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76 lines
2.0 KiB
76 lines
2.0 KiB
// Copyright 2016 Google Inc. All rights reserved. |
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// Use of this source code is governed by a BSD-style |
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// license that can be found in the LICENSE file. |
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package uuid |
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import "io" |
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// New creates a new random UUID or panics. New is equivalent to |
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// the expression |
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// |
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// uuid.Must(uuid.NewRandom()) |
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func New() UUID { |
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return Must(NewRandom()) |
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} |
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// NewString creates a new random UUID and returns it as a string or panics. |
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// NewString is equivalent to the expression |
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// |
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// uuid.New().String() |
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func NewString() string { |
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return Must(NewRandom()).String() |
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} |
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// NewRandom returns a Random (Version 4) UUID. |
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// |
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// The strength of the UUIDs is based on the strength of the crypto/rand |
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// package. |
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// |
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// Uses the randomness pool if it was enabled with EnableRandPool. |
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// |
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// A note about uniqueness derived from the UUID Wikipedia entry: |
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// |
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// Randomly generated UUIDs have 122 random bits. One's annual risk of being |
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// hit by a meteorite is estimated to be one chance in 17 billion, that |
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// means the probability is about 0.00000000006 (6 × 10−11), |
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// equivalent to the odds of creating a few tens of trillions of UUIDs in a |
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// year and having one duplicate. |
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func NewRandom() (UUID, error) { |
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if !poolEnabled { |
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return NewRandomFromReader(rander) |
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} |
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return newRandomFromPool() |
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} |
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// NewRandomFromReader returns a UUID based on bytes read from a given io.Reader. |
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func NewRandomFromReader(r io.Reader) (UUID, error) { |
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var uuid UUID |
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_, err := io.ReadFull(r, uuid[:]) |
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if err != nil { |
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return Nil, err |
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} |
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uuid[6] = (uuid[6] & 0x0f) | 0x40 // Version 4 |
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uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10 |
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return uuid, nil |
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} |
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func newRandomFromPool() (UUID, error) { |
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var uuid UUID |
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poolMu.Lock() |
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if poolPos == randPoolSize { |
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_, err := io.ReadFull(rander, pool[:]) |
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if err != nil { |
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poolMu.Unlock() |
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return Nil, err |
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} |
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poolPos = 0 |
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} |
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copy(uuid[:], pool[poolPos:(poolPos+16)]) |
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poolPos += 16 |
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poolMu.Unlock() |
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uuid[6] = (uuid[6] & 0x0f) | 0x40 // Version 4 |
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uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10 |
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return uuid, nil |
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}
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