쿠폰 헬퍼 함수 추가

coupon/helper.go

@@ -0,0 +1,54 @@
+package coupon
+
+import (
+	"encoding/binary"
+	"encoding/hex"
+	"math/rand"
+	"strings"
+)
+
+func DisolveCouponCode(code string) (round string, key string) {
+	var final []byte
+	for _, n := range strings.Split(code, "-") {
+		nb, err := hex.DecodeString(n)
+		if err != nil {
+			// 형식 오류
+			return "", ""
+		}
+		final = append(final, nb...)
+	}
+
+	if len(final) != 8 {
+		// 형식 오류
+		return "", ""
+	}
+
+	uid := final[4:]
+	left := binary.BigEndian.Uint16(uid[0:2])
+	right := binary.BigEndian.Uint16(uid[2:4])
+
+	final = final[0:4]
+	xor := binary.LittleEndian.Uint32(final)
+	roundhashnum := xor ^ (uint32(left) * uint32(right))
+
+	roundhash := make([]byte, 4)
+	binary.BigEndian.PutUint32(roundhash, roundhashnum)
+
+	round = hex.EncodeToString(roundhash)
+	key = hex.EncodeToString(uid)
+
+	return
+}
+
+func MakeCouponRoundHash(name string) (hash string, roundNumber uint32) {
+	roundbt := make([]byte, 8)
+	copy(roundbt, []byte(strings.ToLower(name)))
+
+	roundseed := int64(binary.BigEndian.Uint64(roundbt))
+	roundhash := make([]byte, 4)
+	rand.New(rand.NewSource(roundseed)).Read(roundhash)
+	roundNumber = binary.BigEndian.Uint32(roundhash)
+	hash = hex.EncodeToString(roundhash)
+
+	return
+}