github.com/Anderson-Lu/gobox@v0.0.0-20191127065433-3e6c4c2da420/string/string_helper.go (about)

     1  package string
     2  
     3  import (
     4  	"math/rand"
     5  	"regexp"
     6  	"time"
     7  )
     8  
     9  var urlRegexp *regexp.Regexp
    10  var src = rand.NewSource(time.Now().UnixNano())
    11  
    12  const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
    13  const (
    14  	letterIdxBits = 6                    // 6 bits to represent a letter index
    15  	letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
    16  	letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
    17  )
    18  
    19  func init() {
    20  	urlRegexp = regexp.MustCompile(`(https?|ftp|file)://[-A-Za-z0-9+&@#/%?=~_|!:,.;]+[-A-Za-z0-9+&@#/%=~_|]`)
    21  }
    22  
    23  /*
    24  * Find urls from specific string
    25   */
    26  func FindUrl(raw string) []string {
    27  	return urlRegexp.FindAllString(raw, -1)
    28  }
    29  
    30  /*
    31  * Generate a random string
    32   */
    33  func RandStringBytesMaskImprSrc(n int) string {
    34  	b := make([]byte, n)
    35  	// A src.Int63() generates 63 random bits, enough for letterIdxMax characters!
    36  	for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {
    37  		if remain == 0 {
    38  			cache, remain = src.Int63(), letterIdxMax
    39  		}
    40  		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
    41  			b[i] = letterBytes[idx]
    42  			i--
    43  		}
    44  		cache >>= letterIdxBits
    45  		remain--
    46  	}
    47  
    48  	return string(b)
    49  }