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// 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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