Add tag-peeling support

src/geef_nif.erl

@@ -101,6 +101,10 @@ blob_size(_ObjHandle) ->
 blob_content(_ObjHandle) ->
     nif_error(?LINE).
 
+-spec tag_peel(term()) -> {ok, atom(), term()} | {error, term()}.
+tag_peel(_Tag) ->
+    ?NIF_FN.
+
 -spec library_version() -> {integer, integer, integer}.
 library_version() ->
     nif_error(?LINE).

src/geef_tag.erl

@@ -0,0 +1,22 @@
+-module(geef_tag).
+
+-ifdef(TEST).
+-include_lib("eunit/include/eunit.hrl").
+-endif.
+
+-export([lookup/2, peel/1]).
+
+-include("geef_records.hrl").
+
+-spec lookup(pid(), geef_oid() | iolist()) -> {ok, geef_object()} | {error, term()}.
+lookup(Repo, Id) ->
+    geef_object:lookup(Repo, Id, tag).
+
+-spec peel(geef_object()) -> {ok, geef_object()} | {error, term()}.
+peel(#geef_object{type=tag, handle=Handle}) ->
+    case geef_nif:tag_peel(Handle) of
+    	{ok, Type, PeeledHandle} ->
+	    {ok, #geef_object{type=Type, handle=PeeledHandle}};
+	Err = {error, _} ->
+	    Err
+    end.