First pass at implementing a wrapper library.

Manually stub out the term_to_natural and 
natural_to_term functions for the time being, 
because the actual implementation is most likely 
not going to scale.

src/vclock.erl

@@ -0,0 +1,141 @@
+%% @doc Provide a wrapper library which provides the same interface
+%%      as riak_core's vclock library, but uses the vvclock library to
+%%      support use of the verified version.
+%%
+%%      Manually stub out the natural/term conversion calls for the time
+%%      being to optimize for testing the library with the current test
+%%      suite.
+%%
+
+-module(vclock).
+
+-export([fresh/0,
+         descends/2,
+         merge/1,
+         get_counter/2,
+         get_timestamp/2,
+         increment/2,
+         increment/3,
+         all_nodes/1,
+         equal/2,
+         prune/3,
+         timestamp/0]).
+
+%% @doc Return natural timestamp.
+timestamp() ->
+    calendar:datetime_to_gregorian_seconds(erlang:universaltime()).
+
+%% @doc Generate a fresh vector clock.
+fresh() ->
+    vvclock:fresh().
+
+%% @doc Increment a vector clock for a particular actor.
+increment(Actor, VClock) ->
+    vvclock:increment(term_to_peano(Actor), VClock).
+
+%% @doc Increment a vector clock with a particular timestamp.
+increment(_Actor, _Timestamp, _VClock) ->
+    %% Not implementing this one for now.
+    erlang:error(deprecated).
+
+%% @doc Return counter for a particular actor.
+get_counter(Actor, VClock) ->
+    Counter = vvclock:get_counter(term_to_peano(Actor), VClock),
+    peano_to_term(Counter).
+
+%% @doc Return timestamp for a particular actor.
+get_timestamp(Actor, VClock) ->
+    Timestamp = vvclock:get_timestamp(term_to_peano(Actor), VClock),
+    peano_to_term(Timestamp).
+
+%% @doc Determine if one vector clock is an ancestor of another.
+descends(VClock1, VClock2) ->
+    case vvclock:descends(VClock1, VClock2) of
+        'True' ->
+            true;
+        'False' ->
+            false
+    end.
+
+%% @doc Return list of all actors that have ever touched the vclock.
+all_nodes(VClock) ->
+    [peano_to_term(Node) || Node <- vvclock:all_nodes(VClock)].
+
+%% @doc Prune vclocks.
+prune(VClock, _Timestamp, BProps) ->
+    Old = get_property(old_vclock, BProps),
+    Young = get_property(young_vclock, BProps),
+    Large = get_property(large_vclock, BProps),
+    Small = get_property(small_vclock, BProps),
+    vvclock:prune(VClock, Small, Large, Young, Old).
+
+%% @doc Merge function which operates on a list of vector clocks.
+merge([VClock1,VClock2|VClocks]) ->
+    merge([vvclock:merge(VClock1, VClock2)|VClocks]);
+merge([VClock]) ->
+    VClock;
+merge([]) ->
+    [].
+
+%% @doc Compare equality of two vclocks.
+equal(VClock1, VClock2) ->
+    vvclock:equal(VClock1, VClock2).
+
+%% @doc Convert a peano number back into an erlang term.
+peano_to_term(Peano) ->
+    natural_to_term(peano_to_natural(Peano)).
+
+%% @doc Convert an erlang term into a peano number.
+term_to_peano(Term) ->
+    natural_to_peano(term_to_natural(Term)).
+
+%% @doc Convert a natural number to an erlang term.
+natural_to_term(Natural) ->
+    case Natural of
+        1 ->
+            a;
+        2 ->
+            b;
+        3 ->
+            c;
+        4 ->
+            d;
+        _ ->
+            erlang:error(not_supported)
+    end.
+
+%% @doc Convert an erlang term to a natural number.
+term_to_natural(Term) ->
+    case Term of
+        a ->
+            1;
+        b ->
+            2;
+        c ->
+            3;
+        d ->
+            4;
+        _ ->
+            erlang:error(not_supported)
+    end.
+
+%% @doc Convert a natural number into a peano.
+natural_to_peano(0) ->
+    'O';
+natural_to_peano(Natural) ->
+    {'S', natural_to_peano(Natural - 1)}.
+
+%% @doc Convert a peano number into a natural.
+peano_to_natural('O') ->
+    0;
+peano_to_natural({'S', Peano}) ->
+    1 + Peano.
+
+%% @doc Extract property from bucket properties.
+get_property(Key, PairList) ->
+    case lists:keyfind(Key, 1, PairList) of
+      {_Key, Value} ->
+        Value;
+      false ->
+        undefined
+    end.