security: Add digest calculation support in transformation

Change-Id: I8326c19aff580289b5301687351d81fd74af8a83
Refs: #3009
diff --git a/src/security/transform/transform-base.hpp b/src/security/transform/transform-base.hpp
index 5e3a72b..98faf6d 100644
--- a/src/security/transform/transform-base.hpp
+++ b/src/security/transform/transform-base.hpp
@@ -186,11 +186,20 @@
 
   /**
    * @brief Read the content from output buffer and write it into next module.
+   *
+   * It is not guaranteed that all the content in output buffer will be flushed to next module.
    */
   void
   flushOutputBuffer();
 
   /**
+   * @brief Read the all the content from output buffer and write it into next module.
+   * @post isOutputBufferEmpty() returns true.
+   */
+  void
+  flushAllOutput();
+
+  /**
    * @brief Set output buffer to @p buffer
    */
   void