ADD: randstr

app.go

@@ -1,6 +1,6 @@
 /*
  * @Author: NorthCity1984
- * @LastEditTime: 2022-04-03 09:31:39
+ * @LastEditTime: 2022-04-04 16:09:13
  * @Description:
  * @Website: https://grimoire.cn
  * Copyright (c) NorthCity1984 All rights reserved.
@@ -8,14 +8,28 @@
 package main
 
 import (
+	// "githuh"
+
 	"fmt"
-	"math"
+
+	"gitee.com/NorthCityChen/stl-go/randoom"
 )
 
 func main() {
-	// ans := math.Exp2(0)
-	ans := math.Sqrt(-8)
-	// ans2 := math1.Sqrt(-8)
-	fmt.Println(ans)
-	// fmt.Println(ans2)
+	// // ans := math.Exp2(0)
+	// ans := math.Sqrt(-8)
+	// // ans2 := math1.Sqrt(-8)
+	// fmt.Println(ans)
+	// // fmt.Println(ans2)
+	// string
+	// queue
+	// queue
+	// random.RandStringBytesMaskImprSrcSB(5)
+	// fmt.Println(r)
+	// ret := randoom.RandStr(45)
+	fmt.Println(randoom.RandStr(45))
+	fmt.Println(randoom.RandStr(45))
+	fmt.Println(randoom.RandStr(45))
+	fmt.Println(randoom.RandStr(45))
+	fmt.Println(randoom.RandStr(45))
 }

randoom/random.go

@@ -0,0 +1,40 @@
+/*
+ * @Author: NorthCity1984
+ * @LastEditTime: 2022-04-04 16:10:11
+ * @Description:
+ * @Website: https://grimoire.cn
+ * Copyright (c) NorthCity1984 All rights reserved.
+ */
+package randoom
+
+import (
+	"math/rand"
+	"strings"
+	"time"
+)
+
+const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+const (
+	letterIdxBits = 6                    // 6 bits to represent a letter index
+	letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
+	letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
+)
+
+var src = rand.NewSource(time.Now().UnixNano())
+
+func RandStr(strLen int) string {
+	str := strings.Builder{}
+	str.Grow(strLen)
+	for i, cache, remain := strLen-1, src.Int63(), letterIdxMax; i >= 0; {
+		if remain == 0 {
+			cache, remain = src.Int63(), letterIdxMax
+		}
+		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
+			str.WriteByte(letterBytes[idx])
+			i--
+		}
+		cache >>= letterIdxBits
+		remain--
+	}
+	return str.String()
+}