148 lines
2.7 KiB
Go
148 lines
2.7 KiB
Go
package unsafe
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import (
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crand "crypto/rand"
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mrand "math/rand"
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"sync"
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)
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const (
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strChars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" // 62 characters
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)
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// Rand is a prng, that is seeded with OS randomness.
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// The OS randomness is obtained from crypto/rand, however none of the provided
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// methods are suitable for cryptographic usage.
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// They all utilize math/rand's prng internally.
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//
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// All of the methods here are suitable for concurrent use.
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// This is achieved by using a mutex lock on all of the provided methods.
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type Rand struct {
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sync.Mutex
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rand *mrand.Rand
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}
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var grand *Rand
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func init() {
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grand = NewRand()
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}
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func NewRand() *Rand {
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rand := &Rand{}
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rand.init()
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return rand
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}
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func (r *Rand) init() {
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bz := cRandBytes(8)
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var seed uint64
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for i := 0; i < 8; i++ {
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seed |= uint64(bz[i])
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seed <<= 8
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}
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r.reset(int64(seed))
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}
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func (r *Rand) reset(seed int64) {
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r.rand = mrand.New(mrand.NewSource(seed))
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}
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//----------------------------------------
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// Global functions
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func Seed(seed int64) {
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grand.Seed(seed)
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}
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func Str(length int) string {
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return grand.Str(length)
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}
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func Int63() int64 {
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return grand.Int63()
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}
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func Int() int {
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return grand.Int()
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}
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func Bytes(n int) []byte {
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return grand.Bytes(n)
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}
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//----------------------------------------
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// Rand methods
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func (r *Rand) Seed(seed int64) {
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r.Lock()
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r.reset(seed)
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r.Unlock()
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}
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// Str constructs a random alphanumeric string of given length.
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func (r *Rand) Str(length int) string {
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if length <= 0 {
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return ""
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}
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chars := []byte{}
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MAIN_LOOP:
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for {
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val := r.Int63()
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for i := 0; i < 10; i++ {
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v := int(val & 0x3f) // rightmost 6 bits
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if v >= 62 { // only 62 characters in strChars
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val >>= 6
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continue
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} else {
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chars = append(chars, strChars[v])
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if len(chars) == length {
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break MAIN_LOOP
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}
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val >>= 6
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}
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}
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}
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return string(chars)
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}
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func (r *Rand) Int63() int64 {
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r.Lock()
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i63 := r.rand.Int63()
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r.Unlock()
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return i63
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}
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func (r *Rand) Int() int {
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r.Lock()
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i := r.rand.Int()
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r.Unlock()
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return i
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}
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// Bytes returns n random bytes generated from the internal
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// prng.
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func (r *Rand) Bytes(n int) []byte {
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// cRandBytes isn't guaranteed to be fast so instead
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// use random bytes generated from the internal PRNG
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bs := make([]byte, n)
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for i := 0; i < len(bs); i++ {
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bs[i] = byte(r.Int() & 0xFF)
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}
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return bs
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}
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// NOTE: This relies on the os's random number generator.
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// For real security, we should salt that with some seed.
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// See github.com/cometbft/cometbft/crypto for a more secure reader.
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func cRandBytes(numBytes int) []byte {
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b := make([]byte, numBytes)
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_, err := crand.Read(b)
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if err != nil {
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panic(err)
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}
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return b
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}
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