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package util
import (
"bytes"
srand "crypto/rand"
"encoding/binary"
"math/rand"
"net/http"
"net/url"
"sort"
"time"
)
const dictionary = "_0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
//CreateRandomString create random string
func CreateRandomString() string {
b := make([]byte, 32)
l := len(dictionary)
_, err := srand.Read(b)
if err != nil {
// fail back to insecure rand
rand.Seed(time.Now().UnixNano())
for i := range b {
b[i] = dictionary[rand.Int()%l]
}
} else {
for i, v := range b {
b[i] = dictionary[v%byte(l)]
}
}
return string(b)
}
// Encode encodes the values into ``URL encoded'' form
// ("acl&bar=baz&foo=quux") sorted by key.
func Encode(v url.Values) string {
if v == nil {
return ""
}
var buf bytes.Buffer
keys := make([]string, 0, len(v))
for k := range v {
keys = append(keys, k)
}
sort.Strings(keys)
for _, k := range keys {
vs := v[k]
prefix := url.QueryEscape(k)
for _, v := range vs {
if buf.Len() > 0 {
buf.WriteByte('&')
}
buf.WriteString(prefix)
if v != "" {
buf.WriteString("=")
buf.WriteString(url.QueryEscape(v))
}
}
}
return buf.String()
}
func GetGMTime() string {
return time.Now().UTC().Format(http.TimeFormat)
}
//
func randUint32() uint32 {
return randUint32Slice(1)[0]
}
func randUint32Slice(c int) []uint32 {
b := make([]byte, c*4)
_, err := srand.Read(b)
if err != nil {
// fail back to insecure rand
rand.Seed(time.Now().UnixNano())
for i := range b {
b[i] = byte(rand.Int())
}
}
n := make([]uint32, c)
for i := range n {
n[i] = binary.BigEndian.Uint32(b[i*4 : i*4+4])
}
return n
}
func toByte(n uint32, st, ed byte) byte {
return byte(n%uint32(ed-st+1) + uint32(st))
}
func toDigit(n uint32) byte {
return toByte(n, '0', '9')
}
func toLowerLetter(n uint32) byte {
return toByte(n, 'a', 'z')
}
func toUpperLetter(n uint32) byte {
return toByte(n, 'A', 'Z')
}
type convFunc func(uint32) byte
var convFuncs = []convFunc{toDigit, toLowerLetter, toUpperLetter}
// tools for generating a random ECS instance password
// from 8 to 30 char MUST contain digit upper, case letter and upper case letter
// http://docs.aliyun.com/#/pub/ecs/open-api/instance&createinstance
func GenerateRandomECSPassword() string {
// [8, 30]
l := int(randUint32()%23 + 8)
n := randUint32Slice(l)
b := make([]byte, l)
b[0] = toDigit(n[0])
b[1] = toLowerLetter(n[1])
b[2] = toUpperLetter(n[2])
for i := 3; i < l; i++ {
b[i] = convFuncs[n[i]%3](n[i])
}
s := make([]byte, l)
perm := rand.Perm(l)
for i, v := range perm {
s[v] = b[i]
}
return string(s)
}
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