github.com/sandwich-go/boost@v1.3.29/xrand/string.go (about)

     1  package xrand
     2  
     3  import (
     4  	"fmt"
     5  	"time"
     6  	"unsafe"
     7  )
     8  
     9  const (
    10  	letterBytes   = "abcdefghijklmnopqrstuvwxyz"
    11  	letterIdxBits = 6                    // 6 bits to represent a letter index
    12  	letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
    13  	letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
    14  )
    15  
    16  var nowFunc = time.Now
    17  
    18  // StringWithTimestamp 随机 n 个字符的字符串，并以当前时间戳做后缀
    19  func StringWithTimestamp(n int) string {
    20  	return fmt.Sprintf("%s_%d", String(n), nowFunc().Unix())
    21  }
    22  
    23  // String 随机 n 个字符的字符串
    24  func String(n int) string {
    25  	b := make([]byte, n)
    26  	// A src.Int63() generates 63 random bits, enough for letterIdxMax characters!
    27  	for i, cache, remain := n-1, FastRand(), letterIdxMax; i >= 0; {
    28  		if remain == 0 {
    29  			cache, remain = FastRand(), letterIdxMax
    30  		}
    31  		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
    32  			b[i] = letterBytes[idx]
    33  			i--
    34  		}
    35  		cache >>= letterIdxBits
    36  		remain--
    37  	}
    38  	return *(*string)(unsafe.Pointer(&b))
    39  }