1 files changed, 66 insertions, 0 deletions
diff --git a/erts/example/next_perm.erl b/erts/example/next_perm.erl
new file mode 100644
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+++ b/erts/example/next_perm.erl
@@ -0,0 +1,66 @@
+%%
+%% %CopyrightBegin%
+%% 
+%% Copyright Ericsson AB 2006-2009. All Rights Reserved.
+%% 
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%% 
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%% 
+%% %CopyrightEnd%
+%%
+-module(next_perm).
+
+-export([next_perm/1, prev_perm/1, load/0, all_perm/1]).
+
+load() ->
+    case whereis(next_perm) of
+	undefined ->
+	    case erl_ddll:load_driver(".", "next_perm") of
+		ok -> ok;
+		{error, already_loaded} -> ok;
+		E -> exit(E)
+	    end,
+	    Port = open_port({spawn, "next_perm"}, []),
+	    register(next_perm, Port);
+	_ ->
+	    ok
+    end.
+
+list_to_integer_binaries(L) ->
+    [<<I:32/integer-native>> || I <- L].
+
+next_perm(L) ->
+    next_perm(L, 1).
+
+prev_perm(L) ->
+    next_perm(L, 2).
+
+next_perm(L, Nxt) ->
+    load(),
+    B = list_to_integer_binaries(L),
+    Port = whereis(next_perm),
+    port_command(Port, [Nxt, B]),
+    receive
+	[Port | Result] ->
+	    Result
+    end.
+
+all_perm(L) ->
+    New = prev_perm(L),
+    all_perm(New, L, [New]).
+
+all_perm(L, L, Acc) ->
+    Acc;
+all_perm(L, Orig, Acc) ->
+    New = prev_perm(L),
+    all_perm(New, Orig, [New | Acc]).
+
+