diff --git a/lib/tar_cstruct.ml b/lib/tar_cstruct.ml
index e2055d5..186ffba 100644
--- a/lib/tar_cstruct.ml
+++ b/lib/tar_cstruct.ml
@@ -20,6 +20,12 @@ module Cstruct_io = struct
   let check_available ch len =
     min (Cstruct.length ch.data - ch.pos) len
 
+  let read_zerocopy ic len =
+    if check_available ic len <> len then raise End_of_file;
+    let r = Cstruct.sub ic.data ic.pos len in
+    ic.pos <- ic.pos + len;
+    r
+
   let really_read ic buf =
     let len = Cstruct.length buf in
     if check_available ic len <> len then raise End_of_file;
diff --git a/lib/tar_cstruct.mli b/lib/tar_cstruct.mli
index 979f421..c93e5ed 100644
--- a/lib/tar_cstruct.mli
+++ b/lib/tar_cstruct.mli
@@ -19,6 +19,10 @@ val really_read : in_channel -> Cstruct.t -> unit
 (** [really_read ic buf] fills [buf] with data from [ic] or raises
     {!Stdlib.End_of_file} *)
 
+val read_zerocopy : in_channel -> int -> Cstruct.t
+(** [read_zerocopy ic len] updates the position and returns a sub cstruct of
+    [ic] or raises {!Stdlib.End_of_file} *)
+
 val skip : in_channel -> int -> unit
 
 val really_write : out_channel -> Cstruct.t -> unit