Index: src/natools-s_expressions-atom_buffers.adb
==================================================================
--- src/natools-s_expressions-atom_buffers.adb
+++ src/natools-s_expressions-atom_buffers.adb
@@ -72,10 +72,26 @@
       Preallocate (Buffer, 1);
       Buffer.Ref.Update.Data.all (Buffer.Used + 1) := Data;
       Buffer.Used := Buffer.Used + 1;
    end Append;
 
+
+   procedure Append_Reverse (Buffer : in out Atom_Buffer; Data : in Atom) is
+      procedure Process (Target : in out Atom);
+
+      procedure Process (Target : in out Atom) is
+      begin
+         for I in reverse Data'Range loop
+            Buffer.Used := Buffer.Used + 1;
+            Target (Buffer.Used) := Data (I);
+         end loop;
+      end Process;
+   begin
+      Preallocate (Buffer, Data'Length);
+      Buffer.Ref.Update (Process'Access);
+   end Append_Reverse;
+
 
    function Length (Buffer : Atom_Buffer) return Count is
    begin
       return Buffer.Used;
    end Length;
@@ -142,10 +158,17 @@
    function Element (Buffer : Atom_Buffer; Position : Count) return Octet is
    begin
       return Buffer.Ref.Query.Data.all (Position);
    end Element;
 
+
+   procedure Pop (Buffer : in out Atom_Buffer; Data : out Octet) is
+   begin
+      Data := Buffer.Ref.Query.Data.all (Buffer.Used);
+      Buffer.Used := Buffer.Used - 1;
+   end Pop;
+
 
    procedure Hard_Reset (Buffer : in out Atom_Buffer) is
    begin
       Buffer.Ref.Reset;
       Buffer.Available := 0;

Index: src/natools-s_expressions-atom_buffers.ads
==================================================================
--- src/natools-s_expressions-atom_buffers.ads
+++ src/natools-s_expressions-atom_buffers.ads
@@ -40,10 +40,13 @@
       --  any further allocation.
 
    procedure Append (Buffer : in out Atom_Buffer; Data : in Atom);
    procedure Append (Buffer : in out Atom_Buffer; Data : in Octet);
       --  Append Data after the end of Buffer
+
+   procedure Append_Reverse (Buffer : in out Atom_Buffer; Data : in Atom);
+      --  Append bytes from Atom from last to first
 
    function Length (Buffer : Atom_Buffer) return Count;
    function Data (Buffer : Atom_Buffer) return Atom;
    procedure Query
      (Buffer : in Atom_Buffer;
@@ -52,10 +55,13 @@
      (Buffer : in Atom_Buffer;
       Data : out Atom;
       Length : out Count);
    function Element (Buffer : Atom_Buffer; Position : Count) return Octet;
       --  Accessors to the whole buffer as an Atom
+
+   procedure Pop (Buffer : in out Atom_Buffer; Data : out Octet);
+      --  Remove last octet from Buffer and store it in Data
 
    function Raw_Query (Buffer : Atom_Buffer) return Atom_Refs.Accessor;
       --  Accessor to the whole allocated memory
 
    procedure Hard_Reset (Buffer : in out Atom_Buffer);