diff --git a/aos/util/file.h b/aos/util/file.h
index 8089225..7c06ece 100644
--- a/aos/util/file.h
+++ b/aos/util/file.h
@@ -2,9 +2,12 @@
 #define AOS_UTIL_FILE_H_
 
 #include <sys/stat.h>
+
+#include <memory>
 #include <string>
 #include <string_view>
 
+#include "absl/types/span.h"
 #include "glog/logging.h"
 
 namespace aos {
@@ -32,6 +35,9 @@
 // runs across.
 void UnlinkRecursive(std::string_view path);
 
+// Maps file from disk into memory
+std::shared_ptr<absl::Span<uint8_t>> MMapFile(const std::string &path);
+
 }  // namespace util
 }  // namespace aos