From 34739a83b8e01c6984b6415987d48323ddb49ade Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=BE=90=E6=B6=9B?= <midnite@outlook.com>
Date: Fri, 12 Aug 2022 10:10:30 +0800
Subject: [PATCH] =?UTF-8?q?feat(utils):=E5=A2=9E=E5=8A=A0=E4=B8=80?=
 =?UTF-8?q?=E4=B8=AA=E7=94=9F=E6=88=90=E9=9A=8F=E6=9C=BA=E5=AD=97=E7=AC=A6?=
 =?UTF-8?q?=E4=B8=B2=E7=9A=84=E5=B7=A5=E5=85=B7=E5=87=BD=E6=95=B0=E3=80=82?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 utils/verify_code.go | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 utils/verify_code.go

diff --git a/utils/verify_code.go b/utils/verify_code.go
new file mode 100644
index 0000000..7f3d7c4
--- /dev/null
+++ b/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))
+}