github.com/lingyao2333/mo-zero@v1.4.1/core/stringx/random.go (about)

     1  package stringx
     2  
     3  import (
     4  	crand "crypto/rand"
     5  	"fmt"
     6  	"math/rand"
     7  	"sync"
     8  	"time"
     9  )
    10  
    11  const (
    12  	letterBytes    = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
    13  	letterIdxBits  = 6 // 6 bits to represent a letter index
    14  	idLen          = 8
    15  	defaultRandLen = 8
    16  	letterIdxMask  = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
    17  	letterIdxMax   = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
    18  )
    19  
    20  var src = newLockedSource(time.Now().UnixNano())
    21  
    22  type lockedSource struct {
    23  	source rand.Source
    24  	lock   sync.Mutex
    25  }
    26  
    27  func newLockedSource(seed int64) *lockedSource {
    28  	return &lockedSource{
    29  		source: rand.NewSource(seed),
    30  	}
    31  }
    32  
    33  func (ls *lockedSource) Int63() int64 {
    34  	ls.lock.Lock()
    35  	defer ls.lock.Unlock()
    36  	return ls.source.Int63()
    37  }
    38  
    39  func (ls *lockedSource) Seed(seed int64) {
    40  	ls.lock.Lock()
    41  	defer ls.lock.Unlock()
    42  	ls.source.Seed(seed)
    43  }
    44  
    45  // Rand returns a random string.
    46  func Rand() string {
    47  	return Randn(defaultRandLen)
    48  }
    49  
    50  // RandId returns a random id string.
    51  func RandId() string {
    52  	b := make([]byte, idLen)
    53  	_, err := crand.Read(b)
    54  	if err != nil {
    55  		return Randn(idLen)
    56  	}
    57  
    58  	return fmt.Sprintf("%x%x%x%x", b[0:2], b[2:4], b[4:6], b[6:8])
    59  }
    60  
    61  // Randn returns a random string with length n.
    62  func Randn(n int) string {
    63  	b := make([]byte, n)
    64  	// A src.Int63() generates 63 random bits, enough for letterIdxMax characters!
    65  	for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {
    66  		if remain == 0 {
    67  			cache, remain = src.Int63(), letterIdxMax
    68  		}
    69  		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
    70  			b[i] = letterBytes[idx]
    71  			i--
    72  		}
    73  		cache >>= letterIdxBits
    74  		remain--
    75  	}
    76  
    77  	return string(b)
    78  }
    79  
    80  // Seed sets the seed to seed.
    81  func Seed(seed int64) {
    82  	src.Seed(seed)
    83  }