feat: add writer

utils.go

@@ -0,0 +1,36 @@
+package spb
+
+import "io"
+
+func ReadNum(r io.Reader) (n uint32, cnt uint32, err error) {
+	var buf [1]byte
+	for cnt < 5 {
+		_, err = r.Read(buf[:])
+		if err != nil {
+			return
+		}
+		n |= uint32(buf[0]&0x7f) << (7 * cnt)
+		cnt++
+		if buf[0]&0x80 == 0 {
+			break
+		}
+	}
+	return
+}
+
+func WriteNum(w io.Writer, n uint32) (cnt uint32, err error) {
+	var buf [1]byte
+	for n > 0 {
+		buf[0] = uint8(n & 0x7f)
+		if n>>7 > 0 {
+			buf[0] |= 0x80
+		}
+		_, err = w.Write(buf[:])
+		if err != nil {
+			return
+		}
+		n >>= 7
+		cnt++
+	}
+	return
+}