%%%-------------------------------------------------------------------
%%% File    : get_fields.erl
%%% Author  : Jay Nelson <jay@duomark.com>
%%% Description : 
%%%   Benchmark for stream_extract_nth/3 performance.
%%%
%%% Created : 25 Jun 2005 by Jay Nelson <jay@duomark.com>
%%%-------------------------------------------------------------------
-module(get_fields).

%% API
-export([
	 sampleRecord/1, setOfRecords/1,
	 time/2, test/4, convert_db_to_list/2,
	 slow_collect/3, normal_collect/3, fast_collect/3, fastest_collect/3
	 ]).


%%====================================================================
%% Tests
%%====================================================================
sampleRecord(Num) ->
    <<"This is record #", Num:32/integer>>.
setOfRecords(Count) ->
    RecNums = lists:seq(1, Count),
    concat_binary([sampleRecord(Num) || Num <- RecNums]).
    
time(Type=slow, _Size=small) ->
    Bin = setOfRecords(25),
    timer:tc(get_fields, test, [Type, Bin, 7, 20]);
time(Type=normal, _Size=small) ->
    Bin = setOfRecords(25),
    timer:tc(get_fields, test, [Type, Bin, 7, 20]);
time(Type=fast, _Size=small) ->
    Bin = setOfRecords(25),
    timer:tc(get_fields, test, [Type, Bin, 7, 20]);
time(Type=fastest, _Size=small) ->
    Bin = setOfRecords(25),
    timer:tc(get_fields, test, [Type, Bin, 7, 20]);

time(Type=slow, _Size=large) ->
    Bin = setOfRecords(25000),
    timer:tc(get_fields, test, [Type, Bin, 7, 20]);
time(Type=normal, _Size=large) ->
    Bin = setOfRecords(25000),
    timer:tc(get_fields, test, [Type, Bin, 7, 20]);
time(Type=fast, _Size=large) ->
    Bin = setOfRecords(25000),
    timer:tc(get_fields, test, [Type, Bin, 7, 20]);
time(Type=fastest, _Size=large) ->
    Bin = setOfRecords(25000),
    timer:tc(get_fields, test, [Type, Bin, 7, 20]);

time(Type=slow, _Size=long) ->
    Bin = setOfRecords(25000),
    timer:tc(get_fields, test, [Type, Bin, 1700, 5000]);
time(Type=normal, _Size=long) ->
    Bin = setOfRecords(25000),
    timer:tc(get_fields, test, [Type, Bin, 1700, 5000]);
time(Type=fast, _Size=long) ->
    Bin = setOfRecords(25000),
    timer:tc(get_fields, test, [Type, Bin, 1700, 5000]);
time(Type=fastest, _Size=long) ->
    Bin = setOfRecords(25000),
    timer:tc(get_fields, test, [Type, Bin, 1700, 5000]).

test(slow, DB, FieldSize, RecSize) ->
    L = slow_collect(DB, FieldSize, RecSize),
    length(L);
test(normal, DB, FieldSize, RecSize) ->
    L = normal_collect(DB, FieldSize, RecSize),
    length(L);
test(fast, DB, FieldSize, RecSize) ->
    L = fast_collect(DB, FieldSize, RecSize),
    length(L);
test(fastest, DB, FieldSize, RecSize) ->
    L = fastest_collect(DB, FieldSize, RecSize),
    length(L).


%%====================================================================
%% API
%%====================================================================
slow_collect(DB, FieldSize, RecSize) ->
    LDB = binary_to_list(DB),
    slow_collect(LDB, FieldSize, RecSize, []).

slow_collect([], _FieldSize, _RecSize, FieldsCollected) ->
    lists:reverse(FieldsCollected);
slow_collect(DB, FieldSize, RecSize, FieldsCollected) ->
    ThisField = lists:sublist(DB, 1, FieldSize),
    Rest = lists:nthtail(RecSize, DB),
    slow_collect(Rest, FieldSize, RecSize,
		 [list_to_binary(ThisField) | FieldsCollected]).


normal_collect(DB, FieldSize, RecSize) ->
    LDB = convert_db_to_list(DB, RecSize),
    normal_collect1(LDB, FieldSize, []).

normal_collect1([], _FieldSize, FieldsCollected) ->
    lists:reverse(FieldsCollected);
normal_collect1([ThisRec | Rest], FieldSize, FieldsCollected) ->
    <<ThisField:FieldSize/binary, _More/binary>> = ThisRec,
    normal_collect1(Rest, FieldSize, [ThisField | FieldsCollected]).


fast_collect(DB, FieldSize, RecSize) ->
    fast_collect(DB, FieldSize, RecSize, 0, []).

fast_collect(DB, _FieldSize, _Length, Pos, FieldsCollected) when Pos >= size(DB) ->
    lists:reverse(FieldsCollected);
fast_collect(DB, FieldSize, Length, Pos, FieldsCollected) ->
    << _Skip:Pos/binary, ThisField:FieldSize/binary, _More/binary>> = DB,
    fast_collect(DB, FieldSize, Length, Pos + Length,
		 [ThisField | FieldsCollected]).


fastest_collect(DB, ExtractSize, RecSize) ->
    stream_extract_nth(DB, ExtractSize, RecSize).


%%====================================================================
%% Internal functions
%%====================================================================
convert_db_to_list(DB, Length) ->
    convert_db_to_list(DB, Length, 0, size(DB), []).

convert_db_to_list(_DB, _Length, Pos, DBSize, RecsCollected) when Pos >= DBSize ->
    lists:reverse(RecsCollected);
convert_db_to_list(DB, Length, Pos, DBSize, RecsCollected) ->
    <<_Skip:Pos/binary, Rec:Length/binary, _Rest/binary>> = DB,
    convert_db_to_list(DB, Length, Pos + Length, DBSize, [Rec | RecsCollected]).