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Copy pathmain.go
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78 lines (67 loc) · 1.72 KB
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package random
import (
cryptoRand "crypto/rand"
"encoding/base64"
"fmt"
"math/rand"
mathRand "math/rand"
"net"
"time"
)
type Randomizer struct {
mathRand.Rand
}
// Bytes returns securely generated random bytes.
// It will return an error if the system's secure random
// number generator fails to function correctly, in which
// case the caller should not continue.
func (r *Randomizer) Bytes(n int) ([]byte, error) {
b := make([]byte, n)
_, err := cryptoRand.Read(b)
// Note that err == nil only if we read len(b) bytes.
if err != nil {
return nil, err
}
return b, nil
}
// String returns a URL-safe, base64 encoded
// securely generated random string.
func (r *Randomizer) String(s int) (string, error) {
b, err := r.Bytes(s)
return base64.URLEncoding.EncodeToString(b), err
}
// Number generates a number between 0 and n
func (r *Randomizer) Number(n int) int {
return mathRand.Intn(n)
}
// NumberBetween returns a random number between n and m
func (r *Randomizer) NumberBetween(n int, m int) int {
return mathRand.Intn(m-n) + n
}
// Port asks the kernel for an available port
func (r *Randomizer) Port() (int, error) {
addr, err := net.ResolveTCPAddr("tcp", "localhost:0")
if err != nil {
return 0, err
}
l, err := net.ListenTCP("tcp", addr)
if err != nil {
return 0, err
}
defer l.Close()
return l.Addr().(*net.TCPAddr).Port, nil
}
// Code returns a random code
func (r *Randomizer) Code() string {
return fmt.Sprintf("%016d", rand.Int63n(1e16))
}
// New returns a preseeded randomizer
func New() *Randomizer {
randomizer := mathRand.New(mathRand.NewSource(time.Now().UTC().UnixNano()))
if randomizer == nil {
panic("Failed to start random number generator")
}
return &Randomizer{
*randomizer,
}
}