优化代码结构

helper.go

@@ -0,0 +1,20 @@
+package docxlib
+
+import (
+	"unsafe"
+)
+
+// BytesToString 没有内存开销的转换
+func BytesToString(b []byte) string {
+	return *(*string)(unsafe.Pointer(&b))
+}
+
+// StringToBytes 没有内存开销的转换
+func StringToBytes(s string) (b []byte) {
+	bh := (*slice)(unsafe.Pointer(&b))
+	sh := (*slice)(unsafe.Pointer(&s))
+	bh.data = sh.data
+	bh.len = sh.len
+	bh.cap = sh.len
+	return b
+}