forked from golang/hotime
40 lines
1.3 KiB
Go
40 lines
1.3 KiB
Go
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// Copyright (C) MongoDB, Inc. 2022-present.
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may
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// not use this file except in compliance with the License. You may obtain
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// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
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// Package randutil provides common random number utilities.
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package randutil
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import (
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crand "crypto/rand"
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"fmt"
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"io"
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xrand "go.mongodb.org/mongo-driver/internal/randutil/rand"
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)
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// NewLockedRand returns a new "x/exp/rand" pseudo-random number generator seeded with a
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// cryptographically-secure random number.
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// It is safe to use from multiple goroutines.
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func NewLockedRand() *xrand.Rand {
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var randSrc = new(xrand.LockedSource)
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randSrc.Seed(cryptoSeed())
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return xrand.New(randSrc)
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}
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// cryptoSeed returns a random uint64 read from the "crypto/rand" random number generator. It is
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// intended to be used to seed pseudorandom number generators at package initialization. It panics
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// if it encounters any errors.
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func cryptoSeed() uint64 {
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var b [8]byte
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_, err := io.ReadFull(crand.Reader, b[:])
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if err != nil {
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panic(fmt.Errorf("failed to read 8 bytes from a \"crypto/rand\".Reader: %v", err))
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}
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return (uint64(b[0]) << 0) | (uint64(b[1]) << 8) | (uint64(b[2]) << 16) | (uint64(b[3]) << 24) |
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(uint64(b[4]) << 32) | (uint64(b[5]) << 40) | (uint64(b[6]) << 48) | (uint64(b[7]) << 56)
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}
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