Source file src/golang.conradwood.net/go-easyops/cmdline/utils.go

Documentation: golang.conradwood.net/go-easyops/cmdline

     1  package cmdline
     2  
     3  import (
     4  	"math/rand"
     5  	"time"
     6  )
     7  
     8  var (
     9  	randsrc = rand.New(rand.NewSource(time.Now().UnixNano()))
    10  )
    11  
    12  // copy of "utils", but avoiding import cycle
    13  func RandomString(n int) string {
    14  	const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
    15  	const (
    16  		letterIdxBits = 6                    // 6 bits to represent a letter index
    17  		letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
    18  		letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
    19  
    20  	)
    21  
    22  	b := make([]byte, n)
    23  	// A randsrc.Int63() generates 63 random bits, enough for letterIdxMax characters!
    24  	for i, cache, remain := n-1, randsrc.Int63(), letterIdxMax; i >= 0; {
    25  		if remain == 0 {
    26  			cache, remain = randsrc.Int63(), letterIdxMax
    27  		}
    28  		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
    29  			b[i] = letterBytes[idx]
    30  			i--
    31  		}
    32  		cache >>= letterIdxBits
    33  		remain--
    34  	}
    35  
    36  	return string(b)
    37  }
    38  

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