gistfile1.hrl

-module(bm).

-export([funs/4]).

-define(INDENT, 10).

funs(Module, Prefix, Args, N) when is_atom(Prefix) ->
    Funs = [Fun || {Fun, Arity} <- Module:module_info(exports),
		   is_matched(Fun, Prefix),
		   Arity =:= length(Args)],
    funs(Module, Funs, Args, N);
funs(Module, Funs, Args, N) when is_list(Funs) ->
    Results = lists:foldl(fun(Fun, Results) ->
				  clear_line(),
				  io:format("~p...", [Fun]),
				  [{Fun, tc(Module, Fun, Args, N)} | Results]
			  end, [], Funs),
    clear_line(),

    print_results(lists:keysort(2, Results)).

is_matched(Fun, Prefix) ->
    lists:prefix(atom_to_list(Prefix), atom_to_list(Fun)).

clear_line() ->
    Columns = element(2, io:columns()) - 1,
    io:format("\r~s\r", [lists:duplicate(Columns, $\s)]).

tc(Module, Fun, Args, N) ->
    statistics(runtime),
    statistics(wall_clock),
    repeat(Module, Fun, Args, N),
    {_, Runtime} = statistics(runtime),
    {_, WallClock} = statistics(wall_clock),

    {Runtime, WallClock}.

repeat(_, _, _, 0) ->
    ok;
repeat(Module, Fun, Args, N) ->
    apply(Module, Fun, Args),
    repeat(Module, Fun, Args, N - 1).

print_results(Results) ->
    FieldWidth = field_with(Results),
    lists:foreach(fun({Fun, {Runtime, WallClock}}) ->
			  io:format("~*...w~p (~p) ms.~n", [-FieldWidth, Fun, Runtime, WallClock])
		  end, Results).

field_with(Results) ->
    lists:foldl(fun({Fun, _}, MaxLen) ->
			lists:max([MaxLen, length(atom_to_list(Fun))])
		end, 0, Results) + ?INDENT.

gistfile2.hrl

-module(sample).
-compile(export_all).

bm() ->
    bm:funs(?MODULE, decompress, [<<1,0,3,0,4,0,10,0,15,0,150>>], 500000).

bm2() ->
    bm:funs(?MODULE, [decompress_1, decompress_2], [<<1,0,3,0,4,0,10,0,15,0,150>>], 500000).

decompress_1(Bin) when is_binary(Bin) ->
    decompress_1(Bin, []).
decompress_1(<<0, Count, Tail/binary>>, Acc) ->
    decompress_1(Tail, [<<0:(Count * 8)>> | Acc]);
decompress_1(<<Head, Tail/binary>>, Acc) ->
    decompress_1(Tail, [Head | Acc]);
decompress_1(<<>>, Acc) ->
    list_to_binary(lists:reverse(Acc)).

decompress_2(Bin) when is_binary(Bin) ->
    decompress_2(Bin, <<>>).
decompress_2(<<0, Count, Tail/binary>>, Acc) ->
    decompress_2(Tail, <<Acc/binary, 0:(Count * 8)>>);
decompress_2(<<Head, Tail/binary>>, Acc) ->
    decompress_2(Tail, <<Acc/binary, Head>>);
decompress_2(<<>>, Acc) ->
    Acc.

decompress_3(Bin) when is_binary(Bin) ->
    decompress_3(Bin, []).
decompress_3(<<0, Count, Tail/binary>>, Acc) ->
    decompress_3(Tail, [Acc, <<0:(Count * 8)>>]);
decompress_3(<<Head, Tail/binary>>, Acc) ->
    decompress_3(Tail, [Acc, Head]);
decompress_3(<<>>, Acc) ->
    list_to_binary(Acc).