feat(utils):增加一个生成随机字符串的工具函数。

utils/verify_code.go

@@ -0,0 +1,36 @@
+package utils
+
+import (
+	"math/rand"
+	"time"
+	"unsafe"
+)
+
+const letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+
+var src = rand.NewSource(time.Now().UnixNano())
+
+const (
+	// 6 bits to represent a letter index
+	letterIdBits = 6
+	// All 1-bits as many as letterIdBits
+	letterIdMask = 1<<letterIdBits - 1
+	letterIdMax  = 63 / letterIdBits
+)
+
+func RandStr(n int) string {
+	b := make([]byte, n)
+	// A rand.Int63() generates 63 random bits, enough for letterIdMax letters!
+	for i, cache, remain := n-1, src.Int63(), letterIdMax; i >= 0; {
+		if remain == 0 {
+			cache, remain = src.Int63(), letterIdMax
+		}
+		if idx := int(cache & letterIdMask); idx < len(letters) {
+			b[i] = letters[idx]
+			i--
+		}
+		cache >>= letterIdBits
+		remain--
+	}
+	return *(*string)(unsafe.Pointer(&b))
+}