/
rand.go
100 lines (81 loc) · 2.3 KB
/
rand.go
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package randx
import (
"bytes"
"crypto/rand"
"encoding/binary"
"log"
"math"
"math/big"
"time"
)
// from https://github.com/thanhpk/randstr
// list of default letters that can be used to make a random string when calling String
// function with no letters provided
var defLetters = []rune("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
// String generates a random string using only letters provided in the letters parameter
// if user ommit letters parameters, this function will use defLetters instead
func String(n int, letters ...string) string {
var letterRunes []rune
if len(letters) == 0 {
letterRunes = defLetters
} else {
letterRunes = []rune(letters[0])
}
var bb bytes.Buffer
bb.Grow(n)
l := uint32(len(letterRunes))
// on each loop, generate one random rune and append to output
for i := 0; i < n; i++ {
bb.WriteRune(letterRunes[binary.BigEndian.Uint32(Bytes(4))%l])
}
return bb.String()
}
// Bytes generates n random bytes.
func Bytes(n int) []byte {
b := make([]byte, n)
_, err := rand.Read(b)
if err != nil {
panic(err)
}
return b
}
var rander = rand.Reader // random function
func Time() time.Time {
min := time.Date(1970, 1, 0, 0, 0, 0, 0, time.UTC)
max := time.Date(2070, 1, 0, 0, 0, 0, 0, time.UTC)
return TimeBetween(min, max)
}
func TimeBetween(min, max time.Time) time.Time {
minUnit, maxUnix := min.Unix(), max.Unix()
n, _ := rand.Int(rander, big.NewInt(maxUnix-minUnit))
return time.Unix(n.Int64()+minUnit, 0)
}
func Bool() bool { return Int64Between(0, 1) == 0 }
func Int64() int64 { return Int64N(math.MaxInt64) }
func Int64N(n int64) int64 {
v, _ := rand.Int(rander, big.NewInt(n))
return v.Int64()
}
func Int64Between(min, max int64) (v int64) { return Int64N(max-min+1) + min }
func IntN(n int) int {
v, _ := rand.Int(rander, big.NewInt(int64(n)))
return int(v.Int64())
}
func Int() int { return int(Int32()) }
func IntBetween(min, max int) int { return IntN(max-min+1) + min }
func Int32N(n int) int32 {
v, _ := rand.Int(rander, big.NewInt(int64(n)))
return int32(v.Int64())
}
func Int32() int32 { return Int32N(math.MaxInt32) }
func Uint64N(n int64) uint64 {
v, _ := rand.Int(rander, big.NewInt(n))
return v.Uint64()
}
func Uint64() (v uint64) {
err := binary.Read(rander, binary.BigEndian, &v)
if err != nil {
log.Fatal(err)
}
return v
}