better cpu topology test coverage
diff --git a/src/folsom_vm_metrics.erl b/src/folsom_vm_metrics.erl
index f3708de..9984c37 100644
--- a/src/folsom_vm_metrics.erl
+++ b/src/folsom_vm_metrics.erl
@@ -35,7 +35,7 @@
         ]).
 
 %% exported for eunit test
--export([convert_cpu_topology/2]).
+-export([convert_system_info/1]).
 
 -include("folsom.hrl").
 
diff --git a/test/cpu_topo_data b/test/cpu_topo_data
new file mode 100644
index 0000000..1ec265a
--- /dev/null
+++ b/test/cpu_topo_data
@@ -0,0 +1,137 @@
+[
+%% Intel(R) Xeon(R) CPU X5647 @ 2.93GHz (Dual CPU)
+
+[{node,[{processor,[{core,[{thread,{logical,1}},
+                           {thread,{logical,9}}]},
+                    {core,[{thread,{logical,3}},{thread,{logical,11}}]},
+                    {core,[{thread,{logical,5}},{thread,{logical,13}}]},
+                    {core,[{thread,{logical,7}},{thread,{logical,15}}]}]}]},
+ {node,[{processor,[{core,[{thread,{logical,0}},
+                           {thread,{logical,8}}]},
+                    {core,[{thread,{logical,2}},{thread,{logical,10}}]},
+                    {core,[{thread,{logical,4}},{thread,{logical,12}}]},
+                    {core,[{thread,{logical,6}},{thread,{logical,14}}]}]}]}],
+
+%% Intel(R) Xeon(R) CPU X5647 @ 2.93GHz
+
+[{processor,[{core,[{thread,{logical,0}},
+                    {thread,{logical,4}}]},
+             {core,[{thread,{logical,1}},{thread,{logical,5}}]},
+             {core,[{thread,{logical,2}},{thread,{logical,6}}]},
+             {core,[{thread,{logical,3}},{thread,{logical,7}}]}]}],
+
+%% Intel Core 2 Quad Q8300 LGA775 'Yorkfield' 2.5GHz 4MB-cache (1333FSB) Processor
+
+[{processor,[{core,{logical,0}},
+             {core,{logical,1}},
+             {core,{logical,2}},
+             {core,{logical,3}}]}],
+
+%% Intel® Xeon® Six Core E5-2620 (2.0 GHz, 7.20 GT/s, 15M L3 Cache)
+
+[{processor,[{core,[{thread,{logical,0}},
+                    {thread,{logical,6}}]},
+             {core,[{thread,{logical,1}},{thread,{logical,7}}]},
+             {core,[{thread,{logical,2}},{thread,{logical,8}}]},
+             {core,[{thread,{logical,3}},{thread,{logical,9}}]},
+             {core,[{thread,{logical,4}},{thread,{logical,10}}]},
+             {core,[{thread,{logical,5}},{thread,{logical,11}}]}]}],
+
+%% OSX
+
+undefined,
+
+%% Intel(R) Xeon(R) CPU W3530 @ 2.80GHz
+
+[{processor,[{core,[{thread,{logical,0}},
+                    {thread,{logical,4}}]},
+             {core,[{thread,{logical,1}},{thread,{logical,5}}]},
+             {core,[{thread,{logical,2}},{thread,{logical,6}}]},
+             {core,[{thread,{logical,3}},{thread,{logical,7}}]}]}],
+
+%% Intel(R) Atom(TM) CPU N2800 @ 1.86GHz (8GB memory)
+
+[{processor,[{core,[{thread,{logical,0}},
+                    {thread,{logical,1}}]},
+             {core,[{thread,{logical,2}},{thread,{logical,3}}]}]}],
+
+%% Intel(R) Core(TM) i7-2675QM CPU @ 2.20GHz
+
+[{processor,[{core,[{thread,{logical,0}},
+                    {thread,{logical,4}}]},
+             {core,[{thread,{logical,1}},{thread,{logical,5}}]},
+             {core,[{thread,{logical,2}},{thread,{logical,6}}]},
+             {core,[{thread,{logical,3}},{thread,{logical,7}}]}]}],
+
+%% Intel(R) Xeon(R) CPU L3426  @ 1.87GHz
+
+[{processor,[{core,[{thread,{logical,0}},
+                    {thread,{logical,4}}]},
+             {core,[{thread,{logical,1}},{thread,{logical,5}}]},
+             {core,[{thread,{logical,2}},{thread,{logical,6}}]},
+             {core,[{thread,{logical,3}},{thread,{logical,7}}]}]}],
+
+%% Intel(R) Core(TM) i7 CPU M 640  @ 2.80GHz (in a vmware fusion vm, one cpu enabled)
+
+[{processor,{logical,0}}],
+
+%% Intel(R) Core(TM) i7 CPU M 640  @ 2.80GHz (in a vmware fusion vm, two cpus enabled)
+
+[{processor,{logical,0}},{processor,{logical,1}}],
+
+%% Intel(R) Core(TM) i7 CPU M 640  @ 2.80GHz (in a vmware fusion vm, four cpus enabled)
+
+[{processor,{logical,0}},
+ {processor,{logical,1}},
+ {processor,{logical,2}},
+ {processor,{logical,3}}],
+
+%% Intel(R) Xeon(R) CPU E5620  @ 2.40GHz (EC2 hi1.4xlarge)
+
+[{processor,[{thread,{logical,0}},
+             {thread,{logical,1}},
+             {thread,{logical,2}},
+             {thread,{logical,3}},
+             {thread,{logical,4}},
+             {thread,{logical,5}},
+             {thread,{logical,6}},
+             {thread,{logical,7}},
+             {thread,{logical,8}},
+             {thread,{logical,9}},
+             {thread,{logical,10}},
+             {thread,{logical,11}},
+             {thread,{logical,12}},
+             {thread,{logical,13}},
+             {thread,{logical,14}},
+             {thread,{logical,15}}]}],
+
+%% Intel(R) Xeon(R) CPU E5-2670 0 @ 2.60GHz (EC2 cc2.8xlarge)
+
+[{processor,[{core,[{thread,{logical,0}},
+                    {thread,{logical,16}}]},
+             {core,[{thread,{logical,1}},{thread,{logical,17}}]},
+             {core,[{thread,{logical,2}},{thread,{logical,18}}]},
+             {core,[{thread,{logical,3}},{thread,{logical,19}}]},
+             {core,[{thread,{logical,4}},{thread,{logical,20}}]},
+             {core,[{thread,{logical,5}},{thread,{logical,21}}]},
+             {core,[{thread,{logical,6}},{thread,{logical,22}}]},
+             {core,[{thread,{logical,7}},{thread,{logical,23}}]}]},
+ {processor,[{core,[{thread,{logical,8}},
+                    {thread,{logical,24}}]},
+             {core,[{thread,{logical,9}},{thread,{logical,25}}]},
+             {core,[{thread,{logical,10}},{thread,{logical,26}}]},
+             {core,[{thread,{logical,11}},{thread,{logical,27}}]},
+             {core,[{thread,{logical,12}},{thread,{logical,28}}]},
+             {core,[{thread,{logical,13}},{thread,{logical,29}}]},
+             {core,[{thread,{logical,14}},{thread,{logical,30}}]},
+             {core,[{thread,{logical,15}},{thread,{logical,31}}]}]}],
+
+%% Unknown
+
+[{processor,{logical,0}},{processor,{logical,1}}],
+
+%% single-core ppc32
+
+{logical,0}
+
+].
diff --git a/test/folsom_erlang_checks.erl b/test/folsom_erlang_checks.erl
index 31a681a..8057d8c 100644
--- a/test/folsom_erlang_checks.erl
+++ b/test/folsom_erlang_checks.erl
@@ -338,27 +338,14 @@
     for(N, LoopCount + 1, Counter).
 
 cpu_topology() ->
-    Test = [{node,[{processor,[{core,[{thread,{logical,1}},{thread,{logical,9}}]},
-                               {core,[{thread,{logical,3}},{thread,{logical,11}}]},
-                               {core,[{thread,{logical,5}},{thread,{logical,13}}]},
-                               {core,[{thread,{logical,7}},{thread,{logical,15}}]}]}]},
-            {node,[{processor,[{core,[{thread,{logical,0}},{thread,{logical,8}}]},
-                               {core,[{thread,{logical,2}},{thread,{logical,10}}]},
-                               {core,[{thread,{logical,4}},{thread,{logical,12}}]},
-                               {core,[{thread,{logical,6}},{thread,{logical,14}}]}]}]}],
+    {ok, [Data]} = file:consult("./cpu_topo_data"),
+    [run_convert_and_jsonify(Item) || Item <- Data].
 
-    ExpectedResult = [{node,[{processor,[{core,[{thread,[logical,1]},{thread,[logical,9]}]},
-                                         {core,[{thread,[logical,3]},{thread,[logical,11]}]},
-                                         {core,[{thread,[logical,5]},{thread,[logical,13]}]},
-                                         {core,[{thread,[logical,7]},{thread,[logical,15]}]}]}]},
-                      {node,[{processor,[{core,[{thread,[logical,0]},{thread,[logical,8]}]},
-                                         {core,[{thread,[logical,2]},{thread,[logical,10]}]},
-                                         {core,[{thread,[logical,4]},{thread,[logical,12]}]},
-                                         {core,[{thread,[logical,6]},{thread,[logical,14]}]}]}]}],
 
-    ExpectedResult = folsom_vm_metrics:convert_cpu_topology(Test, []),
-
-    [{logical, 0}] = folsom_vm_metrics:convert_cpu_topology({logical, 0}, []).
+run_convert_and_jsonify(Item) ->
+    io:format("Converting ... ~n~p~n", [Item]),
+    Result = folsom_vm_metrics:convert_system_info({cpu_topology, Item}),
+    io:format("~p~n", [mochijson2:encode(Result)]).
 
 duration_check(Duration) ->
     [?assert(lists:keymember(Key, 1, Duration)) || Key <-
diff --git a/test/mochijson2.erl b/test/mochijson2.erl
new file mode 100644
index 0000000..954a07d
--- /dev/null
+++ b/test/mochijson2.erl
@@ -0,0 +1,849 @@
+%% @author Bob Ippolito <bob@mochimedia.com>
+%% @copyright 2007 Mochi Media, Inc.
+
+%% @doc Yet another JSON (RFC 4627) library for Erlang. mochijson2 works
+%%      with binaries as strings, arrays as lists (without an {array, _})
+%%      wrapper and it only knows how to decode UTF-8 (and ASCII).
+%%
+%%      JSON terms are decoded as follows (javascript -> erlang):
+%%      <ul>
+%%          <li>{"key": "value"} ->
+%%              {struct, [{&lt;&lt;"key">>, &lt;&lt;"value">>}]}</li>
+%%          <li>["array", 123, 12.34, true, false, null] ->
+%%              [&lt;&lt;"array">>, 123, 12.34, true, false, null]
+%%          </li>
+%%      </ul>
+%%      <ul>
+%%          <li>Strings in JSON decode to UTF-8 binaries in Erlang</li>
+%%          <li>Objects decode to {struct, PropList}</li>
+%%          <li>Numbers decode to integer or float</li>
+%%          <li>true, false, null decode to their respective terms.</li>
+%%      </ul>
+%%      The encoder will accept the same format that the decoder will produce,
+%%      but will also allow additional cases for leniency:
+%%      <ul>
+%%          <li>atoms other than true, false, null will be considered UTF-8
+%%              strings (even as a proplist key)
+%%          </li>
+%%          <li>{json, IoList} will insert IoList directly into the output
+%%              with no validation
+%%          </li>
+%%          <li>{array, Array} will be encoded as Array
+%%              (legacy mochijson style)
+%%          </li>
+%%          <li>A non-empty raw proplist will be encoded as an object as long
+%%              as the first pair does not have an atom key of json, struct,
+%%              or array
+%%          </li>
+%%      </ul>
+
+-module(mochijson2).
+-author('bob@mochimedia.com').
+-export([encoder/1, encode/1]).
+-export([decoder/1, decode/1]).
+
+% This is a macro to placate syntax highlighters..
+-define(Q, $\").
+-define(ADV_COL(S, N), S#decoder{offset=N+S#decoder.offset,
+                                 column=N+S#decoder.column}).
+-define(INC_COL(S), S#decoder{offset=1+S#decoder.offset,
+                              column=1+S#decoder.column}).
+-define(INC_LINE(S), S#decoder{offset=1+S#decoder.offset,
+                               column=1,
+                               line=1+S#decoder.line}).
+-define(INC_CHAR(S, C),
+        case C of
+            $\n ->
+                S#decoder{column=1,
+                          line=1+S#decoder.line,
+                          offset=1+S#decoder.offset};
+            _ ->
+                S#decoder{column=1+S#decoder.column,
+                          offset=1+S#decoder.offset}
+        end).
+-define(IS_WHITESPACE(C),
+        (C =:= $\s orelse C =:= $\t orelse C =:= $\r orelse C =:= $\n)).
+
+%% @type iolist() = [char() | binary() | iolist()]
+%% @type iodata() = iolist() | binary()
+%% @type json_string() = atom | binary()
+%% @type json_number() = integer() | float()
+%% @type json_array() = [json_term()]
+%% @type json_object() = {struct, [{json_string(), json_term()}]}
+%% @type json_iolist() = {json, iolist()}
+%% @type json_term() = json_string() | json_number() | json_array() |
+%%                     json_object() | json_iolist()
+
+-record(encoder, {handler=null,
+                  utf8=false}).
+
+-record(decoder, {object_hook=null,
+                  offset=0,
+                  line=1,
+                  column=1,
+                  state=null}).
+
+%% @spec encoder([encoder_option()]) -> function()
+%% @doc Create an encoder/1 with the given options.
+%% @type encoder_option() = handler_option() | utf8_option()
+%% @type utf8_option() = boolean(). Emit unicode as utf8 (default - false)
+encoder(Options) ->
+    State = parse_encoder_options(Options, #encoder{}),
+    fun (O) -> json_encode(O, State) end.
+
+%% @spec encode(json_term()) -> iolist()
+%% @doc Encode the given as JSON to an iolist.
+encode(Any) ->
+    json_encode(Any, #encoder{}).
+
+%% @spec decoder([decoder_option()]) -> function()
+%% @doc Create a decoder/1 with the given options.
+decoder(Options) ->
+    State = parse_decoder_options(Options, #decoder{}),
+    fun (O) -> json_decode(O, State) end.
+
+%% @spec decode(iolist()) -> json_term()
+%% @doc Decode the given iolist to Erlang terms.
+decode(S) ->
+    json_decode(S, #decoder{}).
+
+%% Internal API
+
+parse_encoder_options([], State) ->
+    State;
+parse_encoder_options([{handler, Handler} | Rest], State) ->
+    parse_encoder_options(Rest, State#encoder{handler=Handler});
+parse_encoder_options([{utf8, Switch} | Rest], State) ->
+    parse_encoder_options(Rest, State#encoder{utf8=Switch}).
+
+parse_decoder_options([], State) ->
+    State;
+parse_decoder_options([{object_hook, Hook} | Rest], State) ->
+    parse_decoder_options(Rest, State#decoder{object_hook=Hook}).
+
+json_encode(true, _State) ->
+    <<"true">>;
+json_encode(false, _State) ->
+    <<"false">>;
+json_encode(null, _State) ->
+    <<"null">>;
+json_encode(I, _State) when is_integer(I) ->
+    integer_to_list(I);
+json_encode(F, _State) when is_float(F) ->
+    mochinum:digits(F);
+json_encode(S, State) when is_binary(S); is_atom(S) ->
+    json_encode_string(S, State);
+json_encode([{K, _}|_] = Props, State) when (K =/= struct andalso
+                                             K =/= array andalso
+                                             K =/= json) ->
+    json_encode_proplist(Props, State);
+json_encode({struct, Props}, State) when is_list(Props) ->
+    json_encode_proplist(Props, State);
+json_encode(Array, State) when is_list(Array) ->
+    json_encode_array(Array, State);
+json_encode({array, Array}, State) when is_list(Array) ->
+    json_encode_array(Array, State);
+json_encode({json, IoList}, _State) ->
+    IoList;
+json_encode(Bad, #encoder{handler=null}) ->
+    exit({json_encode, {bad_term, Bad}});
+json_encode(Bad, State=#encoder{handler=Handler}) ->
+    json_encode(Handler(Bad), State).
+
+json_encode_array([], _State) ->
+    <<"[]">>;
+json_encode_array(L, State) ->
+    F = fun (O, Acc) ->
+                [$,, json_encode(O, State) | Acc]
+        end,
+    [$, | Acc1] = lists:foldl(F, "[", L),
+    lists:reverse([$\] | Acc1]).
+
+json_encode_proplist([], _State) ->
+    <<"{}">>;
+json_encode_proplist(Props, State) ->
+    F = fun ({K, V}, Acc) ->
+                KS = json_encode_string(K, State),
+                VS = json_encode(V, State),
+                [$,, VS, $:, KS | Acc]
+        end,
+    [$, | Acc1] = lists:foldl(F, "{", Props),
+    lists:reverse([$\} | Acc1]).
+
+json_encode_string(A, State) when is_atom(A) ->
+    L = atom_to_list(A),
+    case json_string_is_safe(L) of
+        true ->
+            [?Q, L, ?Q];
+        false ->
+            json_encode_string_unicode(xmerl_ucs:from_utf8(L), State, [?Q])
+    end;
+json_encode_string(B, State) when is_binary(B) ->
+    case json_bin_is_safe(B) of
+        true ->
+            [?Q, B, ?Q];
+        false ->
+            json_encode_string_unicode(xmerl_ucs:from_utf8(B), State, [?Q])
+    end;
+json_encode_string(I, _State) when is_integer(I) ->
+    [?Q, integer_to_list(I), ?Q];
+json_encode_string(L, State) when is_list(L) ->
+    case json_string_is_safe(L) of
+        true ->
+            [?Q, L, ?Q];
+        false ->
+            json_encode_string_unicode(L, State, [?Q])
+    end.
+
+json_string_is_safe([]) ->
+    true;
+json_string_is_safe([C | Rest]) ->
+    case C of
+        ?Q ->
+            false;
+        $\\ ->
+            false;
+        $\b ->
+            false;
+        $\f ->
+            false;
+        $\n ->
+            false;
+        $\r ->
+            false;
+        $\t ->
+            false;
+        C when C >= 0, C < $\s; C >= 16#7f, C =< 16#10FFFF ->
+            false;
+        C when C < 16#7f ->
+            json_string_is_safe(Rest);
+        _ ->
+            false
+    end.
+
+json_bin_is_safe(<<>>) ->
+    true;
+json_bin_is_safe(<<C, Rest/binary>>) ->
+    case C of
+        ?Q ->
+            false;
+        $\\ ->
+            false;
+        $\b ->
+            false;
+        $\f ->
+            false;
+        $\n ->
+            false;
+        $\r ->
+            false;
+        $\t ->
+            false;
+        C when C >= 0, C < $\s; C >= 16#7f ->
+            false;
+        C when C < 16#7f ->
+            json_bin_is_safe(Rest)
+    end.
+
+json_encode_string_unicode([], _State, Acc) ->
+    lists:reverse([$\" | Acc]);
+json_encode_string_unicode([C | Cs], State, Acc) ->
+    Acc1 = case C of
+               ?Q ->
+                   [?Q, $\\ | Acc];
+               %% Escaping solidus is only useful when trying to protect
+               %% against "</script>" injection attacks which are only
+               %% possible when JSON is inserted into a HTML document
+               %% in-line. mochijson2 does not protect you from this, so
+               %% if you do insert directly into HTML then you need to
+               %% uncomment the following case or escape the output of encode.
+               %%
+               %% $/ ->
+               %%    [$/, $\\ | Acc];
+               %%
+               $\\ ->
+                   [$\\, $\\ | Acc];
+               $\b ->
+                   [$b, $\\ | Acc];
+               $\f ->
+                   [$f, $\\ | Acc];
+               $\n ->
+                   [$n, $\\ | Acc];
+               $\r ->
+                   [$r, $\\ | Acc];
+               $\t ->
+                   [$t, $\\ | Acc];
+               C when C >= 0, C < $\s ->
+                   [unihex(C) | Acc];
+               C when C >= 16#7f, C =< 16#10FFFF, State#encoder.utf8 ->
+                   [xmerl_ucs:to_utf8(C) | Acc];
+               C when  C >= 16#7f, C =< 16#10FFFF, not State#encoder.utf8 ->
+                   [unihex(C) | Acc];
+               C when C < 16#7f ->
+                   [C | Acc];
+               _ ->
+                   exit({json_encode, {bad_char, C}})
+           end,
+    json_encode_string_unicode(Cs, State, Acc1).
+
+hexdigit(C) when C >= 0, C =< 9 ->
+    C + $0;
+hexdigit(C) when C =< 15 ->
+    C + $a - 10.
+
+unihex(C) when C < 16#10000 ->
+    <<D3:4, D2:4, D1:4, D0:4>> = <<C:16>>,
+    Digits = [hexdigit(D) || D <- [D3, D2, D1, D0]],
+    [$\\, $u | Digits];
+unihex(C) when C =< 16#10FFFF ->
+    N = C - 16#10000,
+    S1 = 16#d800 bor ((N bsr 10) band 16#3ff),
+    S2 = 16#dc00 bor (N band 16#3ff),
+    [unihex(S1), unihex(S2)].
+
+json_decode(L, S) when is_list(L) ->
+    json_decode(iolist_to_binary(L), S);
+json_decode(B, S) ->
+    {Res, S1} = decode1(B, S),
+    {eof, _} = tokenize(B, S1#decoder{state=trim}),
+    Res.
+
+decode1(B, S=#decoder{state=null}) ->
+    case tokenize(B, S#decoder{state=any}) of
+        {{const, C}, S1} ->
+            {C, S1};
+        {start_array, S1} ->
+            decode_array(B, S1);
+        {start_object, S1} ->
+            decode_object(B, S1)
+    end.
+
+make_object(V, #decoder{object_hook=null}) ->
+    V;
+make_object(V, #decoder{object_hook=Hook}) ->
+    Hook(V).
+
+decode_object(B, S) ->
+    decode_object(B, S#decoder{state=key}, []).
+
+decode_object(B, S=#decoder{state=key}, Acc) ->
+    case tokenize(B, S) of
+        {end_object, S1} ->
+            V = make_object({struct, lists:reverse(Acc)}, S1),
+            {V, S1#decoder{state=null}};
+        {{const, K}, S1} ->
+            {colon, S2} = tokenize(B, S1),
+            {V, S3} = decode1(B, S2#decoder{state=null}),
+            decode_object(B, S3#decoder{state=comma}, [{K, V} | Acc])
+    end;
+decode_object(B, S=#decoder{state=comma}, Acc) ->
+    case tokenize(B, S) of
+        {end_object, S1} ->
+            V = make_object({struct, lists:reverse(Acc)}, S1),
+            {V, S1#decoder{state=null}};
+        {comma, S1} ->
+            decode_object(B, S1#decoder{state=key}, Acc)
+    end.
+
+decode_array(B, S) ->
+    decode_array(B, S#decoder{state=any}, []).
+
+decode_array(B, S=#decoder{state=any}, Acc) ->
+    case tokenize(B, S) of
+        {end_array, S1} ->
+            {lists:reverse(Acc), S1#decoder{state=null}};
+        {start_array, S1} ->
+            {Array, S2} = decode_array(B, S1),
+            decode_array(B, S2#decoder{state=comma}, [Array | Acc]);
+        {start_object, S1} ->
+            {Array, S2} = decode_object(B, S1),
+            decode_array(B, S2#decoder{state=comma}, [Array | Acc]);
+        {{const, Const}, S1} ->
+            decode_array(B, S1#decoder{state=comma}, [Const | Acc])
+    end;
+decode_array(B, S=#decoder{state=comma}, Acc) ->
+    case tokenize(B, S) of
+        {end_array, S1} ->
+            {lists:reverse(Acc), S1#decoder{state=null}};
+        {comma, S1} ->
+            decode_array(B, S1#decoder{state=any}, Acc)
+    end.
+
+tokenize_string(B, S=#decoder{offset=O}) ->
+    case tokenize_string_fast(B, O) of
+        {escape, O1} ->
+            Length = O1 - O,
+            S1 = ?ADV_COL(S, Length),
+            <<_:O/binary, Head:Length/binary, _/binary>> = B,
+            tokenize_string(B, S1, lists:reverse(binary_to_list(Head)));
+        O1 ->
+            Length = O1 - O,
+            <<_:O/binary, String:Length/binary, ?Q, _/binary>> = B,
+            {{const, String}, ?ADV_COL(S, Length + 1)}
+    end.
+
+tokenize_string_fast(B, O) ->
+    case B of
+        <<_:O/binary, ?Q, _/binary>> ->
+            O;
+        <<_:O/binary, $\\, _/binary>> ->
+            {escape, O};
+        <<_:O/binary, C1, _/binary>> when C1 < 128 ->
+            tokenize_string_fast(B, 1 + O);
+        <<_:O/binary, C1, C2, _/binary>> when C1 >= 194, C1 =< 223,
+                C2 >= 128, C2 =< 191 ->
+            tokenize_string_fast(B, 2 + O);
+        <<_:O/binary, C1, C2, C3, _/binary>> when C1 >= 224, C1 =< 239,
+                C2 >= 128, C2 =< 191,
+                C3 >= 128, C3 =< 191 ->
+            tokenize_string_fast(B, 3 + O);
+        <<_:O/binary, C1, C2, C3, C4, _/binary>> when C1 >= 240, C1 =< 244,
+                C2 >= 128, C2 =< 191,
+                C3 >= 128, C3 =< 191,
+                C4 >= 128, C4 =< 191 ->
+            tokenize_string_fast(B, 4 + O);
+        _ ->
+            throw(invalid_utf8)
+    end.
+
+tokenize_string(B, S=#decoder{offset=O}, Acc) ->
+    case B of
+        <<_:O/binary, ?Q, _/binary>> ->
+            {{const, iolist_to_binary(lists:reverse(Acc))}, ?INC_COL(S)};
+        <<_:O/binary, "\\\"", _/binary>> ->
+            tokenize_string(B, ?ADV_COL(S, 2), [$\" | Acc]);
+        <<_:O/binary, "\\\\", _/binary>> ->
+            tokenize_string(B, ?ADV_COL(S, 2), [$\\ | Acc]);
+        <<_:O/binary, "\\/", _/binary>> ->
+            tokenize_string(B, ?ADV_COL(S, 2), [$/ | Acc]);
+        <<_:O/binary, "\\b", _/binary>> ->
+            tokenize_string(B, ?ADV_COL(S, 2), [$\b | Acc]);
+        <<_:O/binary, "\\f", _/binary>> ->
+            tokenize_string(B, ?ADV_COL(S, 2), [$\f | Acc]);
+        <<_:O/binary, "\\n", _/binary>> ->
+            tokenize_string(B, ?ADV_COL(S, 2), [$\n | Acc]);
+        <<_:O/binary, "\\r", _/binary>> ->
+            tokenize_string(B, ?ADV_COL(S, 2), [$\r | Acc]);
+        <<_:O/binary, "\\t", _/binary>> ->
+            tokenize_string(B, ?ADV_COL(S, 2), [$\t | Acc]);
+        <<_:O/binary, "\\u", C3, C2, C1, C0, Rest/binary>> ->
+            C = erlang:list_to_integer([C3, C2, C1, C0], 16),
+            if C > 16#D7FF, C < 16#DC00 ->
+                %% coalesce UTF-16 surrogate pair
+                <<"\\u", D3, D2, D1, D0, _/binary>> = Rest,
+                D = erlang:list_to_integer([D3,D2,D1,D0], 16),
+                [CodePoint] = xmerl_ucs:from_utf16be(<<C:16/big-unsigned-integer,
+                    D:16/big-unsigned-integer>>),
+                Acc1 = lists:reverse(xmerl_ucs:to_utf8(CodePoint), Acc),
+                tokenize_string(B, ?ADV_COL(S, 12), Acc1);
+            true ->
+                Acc1 = lists:reverse(xmerl_ucs:to_utf8(C), Acc),
+                tokenize_string(B, ?ADV_COL(S, 6), Acc1)
+            end;
+        <<_:O/binary, C1, _/binary>> when C1 < 128 ->
+            tokenize_string(B, ?INC_CHAR(S, C1), [C1 | Acc]);
+        <<_:O/binary, C1, C2, _/binary>> when C1 >= 194, C1 =< 223,
+                C2 >= 128, C2 =< 191 ->
+            tokenize_string(B, ?ADV_COL(S, 2), [C2, C1 | Acc]);
+        <<_:O/binary, C1, C2, C3, _/binary>> when C1 >= 224, C1 =< 239,
+                C2 >= 128, C2 =< 191,
+                C3 >= 128, C3 =< 191 ->
+            tokenize_string(B, ?ADV_COL(S, 3), [C3, C2, C1 | Acc]);
+        <<_:O/binary, C1, C2, C3, C4, _/binary>> when C1 >= 240, C1 =< 244,
+                C2 >= 128, C2 =< 191,
+                C3 >= 128, C3 =< 191,
+                C4 >= 128, C4 =< 191 ->
+            tokenize_string(B, ?ADV_COL(S, 4), [C4, C3, C2, C1 | Acc]);
+        _ ->
+            throw(invalid_utf8)
+    end.
+
+tokenize_number(B, S) ->
+    case tokenize_number(B, sign, S, []) of
+        {{int, Int}, S1} ->
+            {{const, list_to_integer(Int)}, S1};
+        {{float, Float}, S1} ->
+            {{const, list_to_float(Float)}, S1}
+    end.
+
+tokenize_number(B, sign, S=#decoder{offset=O}, []) ->
+    case B of
+        <<_:O/binary, $-, _/binary>> ->
+            tokenize_number(B, int, ?INC_COL(S), [$-]);
+        _ ->
+            tokenize_number(B, int, S, [])
+    end;
+tokenize_number(B, int, S=#decoder{offset=O}, Acc) ->
+    case B of
+        <<_:O/binary, $0, _/binary>> ->
+            tokenize_number(B, frac, ?INC_COL(S), [$0 | Acc]);
+        <<_:O/binary, C, _/binary>> when C >= $1 andalso C =< $9 ->
+            tokenize_number(B, int1, ?INC_COL(S), [C | Acc])
+    end;
+tokenize_number(B, int1, S=#decoder{offset=O}, Acc) ->
+    case B of
+        <<_:O/binary, C, _/binary>> when C >= $0 andalso C =< $9 ->
+            tokenize_number(B, int1, ?INC_COL(S), [C | Acc]);
+        _ ->
+            tokenize_number(B, frac, S, Acc)
+    end;
+tokenize_number(B, frac, S=#decoder{offset=O}, Acc) ->
+    case B of
+        <<_:O/binary, $., C, _/binary>> when C >= $0, C =< $9 ->
+            tokenize_number(B, frac1, ?ADV_COL(S, 2), [C, $. | Acc]);
+        <<_:O/binary, E, _/binary>> when E =:= $e orelse E =:= $E ->
+            tokenize_number(B, esign, ?INC_COL(S), [$e, $0, $. | Acc]);
+        _ ->
+            {{int, lists:reverse(Acc)}, S}
+    end;
+tokenize_number(B, frac1, S=#decoder{offset=O}, Acc) ->
+    case B of
+        <<_:O/binary, C, _/binary>> when C >= $0 andalso C =< $9 ->
+            tokenize_number(B, frac1, ?INC_COL(S), [C | Acc]);
+        <<_:O/binary, E, _/binary>> when E =:= $e orelse E =:= $E ->
+            tokenize_number(B, esign, ?INC_COL(S), [$e | Acc]);
+        _ ->
+            {{float, lists:reverse(Acc)}, S}
+    end;
+tokenize_number(B, esign, S=#decoder{offset=O}, Acc) ->
+    case B of
+        <<_:O/binary, C, _/binary>> when C =:= $- orelse C=:= $+ ->
+            tokenize_number(B, eint, ?INC_COL(S), [C | Acc]);
+        _ ->
+            tokenize_number(B, eint, S, Acc)
+    end;
+tokenize_number(B, eint, S=#decoder{offset=O}, Acc) ->
+    case B of
+        <<_:O/binary, C, _/binary>> when C >= $0 andalso C =< $9 ->
+            tokenize_number(B, eint1, ?INC_COL(S), [C | Acc])
+    end;
+tokenize_number(B, eint1, S=#decoder{offset=O}, Acc) ->
+    case B of
+        <<_:O/binary, C, _/binary>> when C >= $0 andalso C =< $9 ->
+            tokenize_number(B, eint1, ?INC_COL(S), [C | Acc]);
+        _ ->
+            {{float, lists:reverse(Acc)}, S}
+    end.
+
+tokenize(B, S=#decoder{offset=O}) ->
+    case B of
+        <<_:O/binary, C, _/binary>> when ?IS_WHITESPACE(C) ->
+            tokenize(B, ?INC_CHAR(S, C));
+        <<_:O/binary, "{", _/binary>> ->
+            {start_object, ?INC_COL(S)};
+        <<_:O/binary, "}", _/binary>> ->
+            {end_object, ?INC_COL(S)};
+        <<_:O/binary, "[", _/binary>> ->
+            {start_array, ?INC_COL(S)};
+        <<_:O/binary, "]", _/binary>> ->
+            {end_array, ?INC_COL(S)};
+        <<_:O/binary, ",", _/binary>> ->
+            {comma, ?INC_COL(S)};
+        <<_:O/binary, ":", _/binary>> ->
+            {colon, ?INC_COL(S)};
+        <<_:O/binary, "null", _/binary>> ->
+            {{const, null}, ?ADV_COL(S, 4)};
+        <<_:O/binary, "true", _/binary>> ->
+            {{const, true}, ?ADV_COL(S, 4)};
+        <<_:O/binary, "false", _/binary>> ->
+            {{const, false}, ?ADV_COL(S, 5)};
+        <<_:O/binary, "\"", _/binary>> ->
+            tokenize_string(B, ?INC_COL(S));
+        <<_:O/binary, C, _/binary>> when (C >= $0 andalso C =< $9)
+                                         orelse C =:= $- ->
+            tokenize_number(B, S);
+        <<_:O/binary>> ->
+            trim = S#decoder.state,
+            {eof, S}
+    end.
+%%
+%% Tests
+%%
+-ifdef(TEST).
+-include_lib("eunit/include/eunit.hrl").
+
+
+%% testing constructs borrowed from the Yaws JSON implementation.
+
+%% Create an object from a list of Key/Value pairs.
+
+obj_new() ->
+    {struct, []}.
+
+is_obj({struct, Props}) ->
+    F = fun ({K, _}) when is_binary(K) -> true end,
+    lists:all(F, Props).
+
+obj_from_list(Props) ->
+    Obj = {struct, Props},
+    ?assert(is_obj(Obj)),
+    Obj.
+
+%% Test for equivalence of Erlang terms.
+%% Due to arbitrary order of construction, equivalent objects might
+%% compare unequal as erlang terms, so we need to carefully recurse
+%% through aggregates (tuples and objects).
+
+equiv({struct, Props1}, {struct, Props2}) ->
+    equiv_object(Props1, Props2);
+equiv(L1, L2) when is_list(L1), is_list(L2) ->
+    equiv_list(L1, L2);
+equiv(N1, N2) when is_number(N1), is_number(N2) -> N1 == N2;
+equiv(B1, B2) when is_binary(B1), is_binary(B2) -> B1 == B2;
+equiv(A, A) when A =:= true orelse A =:= false orelse A =:= null -> true.
+
+%% Object representation and traversal order is unknown.
+%% Use the sledgehammer and sort property lists.
+
+equiv_object(Props1, Props2) ->
+    L1 = lists:keysort(1, Props1),
+    L2 = lists:keysort(1, Props2),
+    Pairs = lists:zip(L1, L2),
+    true = lists:all(fun({{K1, V1}, {K2, V2}}) ->
+                             equiv(K1, K2) and equiv(V1, V2)
+                     end, Pairs).
+
+%% Recursively compare tuple elements for equivalence.
+
+equiv_list([], []) ->
+    true;
+equiv_list([V1 | L1], [V2 | L2]) ->
+    equiv(V1, V2) andalso equiv_list(L1, L2).
+
+decode_test() ->
+    [1199344435545.0, 1] = decode(<<"[1199344435545.0,1]">>),
+    <<16#F0,16#9D,16#9C,16#95>> = decode([34,"\\ud835","\\udf15",34]).
+
+e2j_vec_test() ->
+    test_one(e2j_test_vec(utf8), 1).
+
+test_one([], _N) ->
+    %% io:format("~p tests passed~n", [N-1]),
+    ok;
+test_one([{E, J} | Rest], N) ->
+    %% io:format("[~p] ~p ~p~n", [N, E, J]),
+    true = equiv(E, decode(J)),
+    true = equiv(E, decode(encode(E))),
+    test_one(Rest, 1+N).
+
+e2j_test_vec(utf8) ->
+    [
+     {1, "1"},
+     {3.1416, "3.14160"}, %% text representation may truncate, trail zeroes
+     {-1, "-1"},
+     {-3.1416, "-3.14160"},
+     {12.0e10, "1.20000e+11"},
+     {1.234E+10, "1.23400e+10"},
+     {-1.234E-10, "-1.23400e-10"},
+     {10.0, "1.0e+01"},
+     {123.456, "1.23456E+2"},
+     {10.0, "1e1"},
+     {<<"foo">>, "\"foo\""},
+     {<<"foo", 5, "bar">>, "\"foo\\u0005bar\""},
+     {<<"">>, "\"\""},
+     {<<"\n\n\n">>, "\"\\n\\n\\n\""},
+     {<<"\" \b\f\r\n\t\"">>, "\"\\\" \\b\\f\\r\\n\\t\\\"\""},
+     {obj_new(), "{}"},
+     {obj_from_list([{<<"foo">>, <<"bar">>}]), "{\"foo\":\"bar\"}"},
+     {obj_from_list([{<<"foo">>, <<"bar">>}, {<<"baz">>, 123}]),
+      "{\"foo\":\"bar\",\"baz\":123}"},
+     {[], "[]"},
+     {[[]], "[[]]"},
+     {[1, <<"foo">>], "[1,\"foo\"]"},
+
+     %% json array in a json object
+     {obj_from_list([{<<"foo">>, [123]}]),
+      "{\"foo\":[123]}"},
+
+     %% json object in a json object
+     {obj_from_list([{<<"foo">>, obj_from_list([{<<"bar">>, true}])}]),
+      "{\"foo\":{\"bar\":true}}"},
+
+     %% fold evaluation order
+     {obj_from_list([{<<"foo">>, []},
+                     {<<"bar">>, obj_from_list([{<<"baz">>, true}])},
+                     {<<"alice">>, <<"bob">>}]),
+      "{\"foo\":[],\"bar\":{\"baz\":true},\"alice\":\"bob\"}"},
+
+     %% json object in a json array
+     {[-123, <<"foo">>, obj_from_list([{<<"bar">>, []}]), null],
+      "[-123,\"foo\",{\"bar\":[]},null]"}
+    ].
+
+%% test utf8 encoding
+encoder_utf8_test() ->
+    %% safe conversion case (default)
+    [34,"\\u0001","\\u0442","\\u0435","\\u0441","\\u0442",34] =
+        encode(<<1,"\321\202\320\265\321\201\321\202">>),
+
+    %% raw utf8 output (optional)
+    Enc = mochijson2:encoder([{utf8, true}]),
+    [34,"\\u0001",[209,130],[208,181],[209,129],[209,130],34] =
+        Enc(<<1,"\321\202\320\265\321\201\321\202">>).
+
+input_validation_test() ->
+    Good = [
+        {16#00A3, <<?Q, 16#C2, 16#A3, ?Q>>}, %% pound
+        {16#20AC, <<?Q, 16#E2, 16#82, 16#AC, ?Q>>}, %% euro
+        {16#10196, <<?Q, 16#F0, 16#90, 16#86, 16#96, ?Q>>} %% denarius
+    ],
+    lists:foreach(fun({CodePoint, UTF8}) ->
+        Expect = list_to_binary(xmerl_ucs:to_utf8(CodePoint)),
+        Expect = decode(UTF8)
+    end, Good),
+
+    Bad = [
+        %% 2nd, 3rd, or 4th byte of a multi-byte sequence w/o leading byte
+        <<?Q, 16#80, ?Q>>,
+        %% missing continuations, last byte in each should be 80-BF
+        <<?Q, 16#C2, 16#7F, ?Q>>,
+        <<?Q, 16#E0, 16#80,16#7F, ?Q>>,
+        <<?Q, 16#F0, 16#80, 16#80, 16#7F, ?Q>>,
+        %% we don't support code points > 10FFFF per RFC 3629
+        <<?Q, 16#F5, 16#80, 16#80, 16#80, ?Q>>,
+        %% escape characters trigger a different code path
+        <<?Q, $\\, $\n, 16#80, ?Q>>
+    ],
+    lists:foreach(
+      fun(X) ->
+              ok = try decode(X) catch invalid_utf8 -> ok end,
+              %% could be {ucs,{bad_utf8_character_code}} or
+              %%          {json_encode,{bad_char,_}}
+              {'EXIT', _} = (catch encode(X))
+      end, Bad).
+
+inline_json_test() ->
+    ?assertEqual(<<"\"iodata iodata\"">>,
+                 iolist_to_binary(
+                   encode({json, [<<"\"iodata">>, " iodata\""]}))),
+    ?assertEqual({struct, [{<<"key">>, <<"iodata iodata">>}]},
+                 decode(
+                   encode({struct,
+                           [{key, {json, [<<"\"iodata">>, " iodata\""]}}]}))),
+    ok.
+
+big_unicode_test() ->
+    UTF8Seq = list_to_binary(xmerl_ucs:to_utf8(16#0001d120)),
+    ?assertEqual(
+       <<"\"\\ud834\\udd20\"">>,
+       iolist_to_binary(encode(UTF8Seq))),
+    ?assertEqual(
+       UTF8Seq,
+       decode(iolist_to_binary(encode(UTF8Seq)))),
+    ok.
+
+custom_decoder_test() ->
+    ?assertEqual(
+       {struct, [{<<"key">>, <<"value">>}]},
+       (decoder([]))("{\"key\": \"value\"}")),
+    F = fun ({struct, [{<<"key">>, <<"value">>}]}) -> win end,
+    ?assertEqual(
+       win,
+       (decoder([{object_hook, F}]))("{\"key\": \"value\"}")),
+    ok.
+
+atom_test() ->
+    %% JSON native atoms
+    [begin
+         ?assertEqual(A, decode(atom_to_list(A))),
+         ?assertEqual(iolist_to_binary(atom_to_list(A)),
+                      iolist_to_binary(encode(A)))
+     end || A <- [true, false, null]],
+    %% Atom to string
+    ?assertEqual(
+       <<"\"foo\"">>,
+       iolist_to_binary(encode(foo))),
+    ?assertEqual(
+       <<"\"\\ud834\\udd20\"">>,
+       iolist_to_binary(encode(list_to_atom(xmerl_ucs:to_utf8(16#0001d120))))),
+    ok.
+
+key_encode_test() ->
+    %% Some forms are accepted as keys that would not be strings in other
+    %% cases
+    ?assertEqual(
+       <<"{\"foo\":1}">>,
+       iolist_to_binary(encode({struct, [{foo, 1}]}))),
+    ?assertEqual(
+       <<"{\"foo\":1}">>,
+       iolist_to_binary(encode({struct, [{<<"foo">>, 1}]}))),
+    ?assertEqual(
+       <<"{\"foo\":1}">>,
+       iolist_to_binary(encode({struct, [{"foo", 1}]}))),
+	?assertEqual(
+       <<"{\"foo\":1}">>,
+       iolist_to_binary(encode([{foo, 1}]))),
+    ?assertEqual(
+       <<"{\"foo\":1}">>,
+       iolist_to_binary(encode([{<<"foo">>, 1}]))),
+    ?assertEqual(
+       <<"{\"foo\":1}">>,
+       iolist_to_binary(encode([{"foo", 1}]))),
+    ?assertEqual(
+       <<"{\"\\ud834\\udd20\":1}">>,
+       iolist_to_binary(
+         encode({struct, [{[16#0001d120], 1}]}))),
+    ?assertEqual(
+       <<"{\"1\":1}">>,
+       iolist_to_binary(encode({struct, [{1, 1}]}))),
+    ok.
+
+unsafe_chars_test() ->
+    Chars = "\"\\\b\f\n\r\t",
+    [begin
+         ?assertEqual(false, json_string_is_safe([C])),
+         ?assertEqual(false, json_bin_is_safe(<<C>>)),
+         ?assertEqual(<<C>>, decode(encode(<<C>>)))
+     end || C <- Chars],
+    ?assertEqual(
+       false,
+       json_string_is_safe([16#0001d120])),
+    ?assertEqual(
+       false,
+       json_bin_is_safe(list_to_binary(xmerl_ucs:to_utf8(16#0001d120)))),
+    ?assertEqual(
+       [16#0001d120],
+       xmerl_ucs:from_utf8(
+         binary_to_list(
+           decode(encode(list_to_atom(xmerl_ucs:to_utf8(16#0001d120))))))),
+    ?assertEqual(
+       false,
+       json_string_is_safe([16#110000])),
+    ?assertEqual(
+       false,
+       json_bin_is_safe(list_to_binary(xmerl_ucs:to_utf8([16#110000])))),
+    %% solidus can be escaped but isn't unsafe by default
+    ?assertEqual(
+       <<"/">>,
+       decode(<<"\"\\/\"">>)),
+    ok.
+
+int_test() ->
+    ?assertEqual(0, decode("0")),
+    ?assertEqual(1, decode("1")),
+    ?assertEqual(11, decode("11")),
+    ok.
+
+large_int_test() ->
+    ?assertEqual(<<"-2147483649214748364921474836492147483649">>,
+        iolist_to_binary(encode(-2147483649214748364921474836492147483649))),
+    ?assertEqual(<<"2147483649214748364921474836492147483649">>,
+        iolist_to_binary(encode(2147483649214748364921474836492147483649))),
+    ok.
+
+float_test() ->
+    ?assertEqual(<<"-2147483649.0">>, iolist_to_binary(encode(-2147483649.0))),
+    ?assertEqual(<<"2147483648.0">>, iolist_to_binary(encode(2147483648.0))),
+    ok.
+
+handler_test() ->
+    ?assertEqual(
+       {'EXIT',{json_encode,{bad_term,{}}}},
+       catch encode({})),
+    F = fun ({}) -> [] end,
+    ?assertEqual(
+       <<"[]">>,
+       iolist_to_binary((encoder([{handler, F}]))({}))),
+    ok.
+
+-endif.