Clean up handling of .asn1db files

There is (differenct) code for reading .asn1db files both in
asn1ct and asn1_db. Consolidate the reading into one routine
in asn1db.

Another problem is that the encoding rule that the .asn1db
file was created for is not in the .asn1db, but only in the
generated Erlang module. It is much easier and safer to put
the encoding rule in the .asn1db file itself. We will also
put the version number of the asn1 application into the file,
to ensure that we don't use an old .asn1db file that could
potentially be incompatible.

1 files changed, 89 insertions, 27 deletions

diff --git a/lib/asn1/src/asn1_db.erl b/lib/asn1/src/asn1_db.erl
index 869b36ddbd..48d9dd16d7 100644
--- a/lib/asn1/src/asn1_db.erl
+++ b/lib/asn1/src/asn1_db.erl
@@ -19,25 +19,37 @@
 %%
 -module(asn1_db).
 
--export([dbstart/1,dbnew/1,dbsave/2,dbput/3,dbget/2]).
+-export([dbstart/1,dbnew/2,dbload/1,dbload/3,dbsave/2,dbput/3,dbget/2]).
 -export([dbstop/0]).
 
 -record(state, {parent, monitor, includes, table}).
 
 %% Interface
-dbstart(Includes) ->
+dbstart(Includes0) ->
+    Includes = case Includes0 of
+		   [] -> ["."];
+		   [_|_] -> Includes0
+	       end,
     Parent = self(),
     undefined = get(?MODULE),			%Assertion.
     put(?MODULE, spawn_link(fun() -> init(Parent, Includes) end)),
     ok.
 
-dbnew(Module)              -> req({new, Module}).
+dbload(Module, Erule, Mtime) ->
+    req({load, Module, Erule, Mtime}).
+
+dbload(Module) ->
+    req({load, Module, any, {{0,0,0},{0,0,0}}}).
+
+dbnew(Module, Erule)       -> req({new, Module, Erule}).
 dbsave(OutFile, Module)    -> cast({save, OutFile, Module}).
 dbput(Module, K, V)        -> cast({set, Module, K, V}).
 dbget(Module, K)           -> req({get, Module, K}).
 dbstop()                   -> Resp = req(stop), erase(?MODULE), Resp.
 
 %% Internal functions
+-define(MAGIC_KEY, '__version_and_erule__').
+
 req(Request) ->
     DbPid = get(?MODULE),
     Ref = erlang:monitor(process,DbPid),
@@ -71,47 +83,57 @@ loop(#state{parent = Parent, monitor = MRef, table = Table,
             ets:insert(Modtab, {K2, V}),
             loop(State);
         {From, {get, Mod, K2}} ->
-            Result = case ets:lookup(Table, Mod) of
-                         []            -> opentab(Table, Mod, Includes);
-                         [{_, Modtab}] -> {ok, Modtab}
-                     end,
-            case Result of
-                {ok, Newtab} -> reply(From, lookup(Newtab, K2));
-                _Error       -> reply(From, undefined)
+	    %% XXX If there is no information for Mod, get_table/3
+	    %% will attempt to load information from an .asn1db
+	    %% file, without comparing its timestamp against the
+	    %% source file. This is known to happen when check_*
+	    %% functions for DER are generated, but it could possibly
+	    %% happen in other circumstances. Ideally, this issue should
+	    %% be rectified in some way, perhaps by ensuring that
+	    %% the module has been loaded (using dbload/4) prior
+	    %% to calling dbget/2.
+            case get_table(Table, Mod, Includes) of
+                {ok,Tab} -> reply(From, lookup(Tab, K2));
+                error -> reply(From, undefined)
             end,
             loop(State);
         {save, OutFile, Mod} ->
             [{_,Mtab}] = ets:lookup(Table, Mod),
             ok = ets:tab2file(Mtab, OutFile),
             loop(State);
-        {From, {new, Mod}} ->
+        {From, {new, Mod, Erule}} ->
             [] = ets:lookup(Table, Mod),	%Assertion.
             ModTableId = ets:new(list_to_atom(lists:concat(["asn1_",Mod])), []),
             ets:insert(Table, {Mod, ModTableId}),
+	    ets:insert(ModTableId, {?MAGIC_KEY, info(Erule)}),
             reply(From, ok),
             loop(State);
+	{From, {load, Mod, Erule, Mtime}} ->
+	    case ets:member(Table, Mod) of
+		true ->
+		    reply(From, ok);
+		false ->
+		    case load_table(Mod, Erule, Mtime, Includes) of
+			{ok, ModTableId} ->
+			    ets:insert(Table, {Mod, ModTableId}),
+			    reply(From, ok);
+			error ->
+			    reply(From, error)
+		    end
+	    end,
+	    loop(State);
         {From, stop} ->
             reply(From, stopped); %% Nothing to store
         {'DOWN', MRef, process, Parent, Reason} ->
             exit(Reason)
     end.
 
-opentab(Tab, Mod, []) ->
-    opentab(Tab, Mod, ["."]);
-opentab(Tab, Mod, Includes) ->
-    Base = lists:concat([Mod, ".asn1db"]),
-    opentab2(Tab, Base, Mod, Includes, ok).
-
-opentab2(_Tab, _Base, _Mod, [], Error) ->
-    Error;
-opentab2(Tab, Base, Mod, [Ih|It], _Error) ->
-    File = filename:join(Ih, Base),
-    case ets:file2tab(File) of
-        {ok, Modtab} ->
-            ets:insert(Tab, {Mod, Modtab}),
-            {ok, Modtab};
-        NewErr ->
-            opentab2(Tab, Base, Mod, It, NewErr)
+get_table(Table, Mod, Includes) ->
+    case ets:lookup(Table, Mod) of
+	[{Mod,Tab}] ->
+	    {ok,Tab};
+	[] ->
+	    load_table(Mod, any, {{0,0,0},{0,0,0}}, Includes)
     end.
 
 lookup(Tab, K) ->
@@ -119,3 +141,43 @@ lookup(Tab, K) ->
         []      -> undefined;
         [{K,V}] -> V
     end.
+
+info(Erule) ->
+    {asn1ct:vsn(),Erule}.
+
+load_table(Mod, Erule, Mtime, Includes) ->
+    Base = lists:concat([Mod, ".asn1db"]),
+    case path_find(Includes, Mtime, Base) of
+	error ->
+	    error;
+	{ok,ModTab} when Erule =:= any ->
+	    {ok,ModTab};
+	{ok,ModTab} ->
+	    Vsn = asn1ct:vsn(),
+	    case ets:lookup(ModTab, ?MAGIC_KEY) of
+		[{_,{Vsn,Erule}}] ->
+		    %% Correct version and encoding rule.
+		    {ok,ModTab};
+		_ ->
+		    %% Missing key or wrong version/encoding rule.
+		    ets:delete(ModTab),
+		    error
+	    end
+    end.
+
+path_find([H|T], Mtime, Base) ->
+    File = filename:join(H, Base),
+    case filelib:last_modified(File) of
+	0 ->
+	    path_find(T, Mtime, Base);
+	DbMtime when DbMtime >= Mtime ->
+	    case ets:file2tab(File) of
+		{ok,_}=Ret ->
+		    Ret;
+		_ ->
+		    path_find(T, Mtime, Base)
+	    end;
+	_ ->
+	    path_find(T, Mtime, Base)
+    end;
+path_find([], _, _) -> error.