service/vendor/go.mongodb.org/mongo-driver/internal/randutil/randutil.go

40 lines
1.3 KiB
Go

// Copyright (C) MongoDB, Inc. 2022-present.
//
// 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
// Package randutil provides common random number utilities.
package randutil
import (
crand "crypto/rand"
"fmt"
"io"
xrand "go.mongodb.org/mongo-driver/internal/randutil/rand"
)
// NewLockedRand returns a new "x/exp/rand" pseudo-random number generator seeded with a
// cryptographically-secure random number.
// It is safe to use from multiple goroutines.
func NewLockedRand() *xrand.Rand {
var randSrc = new(xrand.LockedSource)
randSrc.Seed(cryptoSeed())
return xrand.New(randSrc)
}
// cryptoSeed returns a random uint64 read from the "crypto/rand" random number generator. It is
// intended to be used to seed pseudorandom number generators at package initialization. It panics
// if it encounters any errors.
func cryptoSeed() uint64 {
var b [8]byte
_, err := io.ReadFull(crand.Reader, b[:])
if err != nil {
panic(fmt.Errorf("failed to read 8 bytes from a \"crypto/rand\".Reader: %v", err))
}
return (uint64(b[0]) << 0) | (uint64(b[1]) << 8) | (uint64(b[2]) << 16) | (uint64(b[3]) << 24) |
(uint64(b[4]) << 32) | (uint64(b[5]) << 40) | (uint64(b[6]) << 48) | (uint64(b[7]) << 56)
}