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%% The contents of this file are subject to the Mozilla Public License
%% Version 1.1 (the "License"); you may not use this file except in
%% compliance with the License. You may obtain a copy of the License at
%% http://www.mozilla.org/MPL/
%%
%% 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.
%%
%% The Original Code is RabbitMQ.
%%
%% The Initial Developers of the Original Code are LShift Ltd,
%% Cohesive Financial Technologies LLC, and Rabbit Technologies Ltd.
%%
%% Portions created before 22-Nov-2008 00:00:00 GMT by LShift Ltd,
%% Cohesive Financial Technologies LLC, or Rabbit Technologies Ltd
%% are Copyright (C) 2007-2008 LShift Ltd, Cohesive Financial
%% Technologies LLC, and Rabbit Technologies Ltd.
%%
%% Portions created by LShift Ltd are Copyright (C) 2007-2009 LShift
%% Ltd. Portions created by Cohesive Financial Technologies LLC are
%% Copyright (C) 2007-2009 Cohesive Financial Technologies
%% LLC. Portions created by Rabbit Technologies Ltd are Copyright
%% (C) 2007-2009 Rabbit Technologies Ltd.
%%
%% All Rights Reserved.
%%
%% Contributor(s): ______________________________________.
%%
-module(bpqueue).
%% Block-prefixed queue. This implements a queue of queues, but
%% supporting the normal queue interface. Each block has a prefix and
%% it is guaranteed that no two consecutive blocks have the same
%% prefix. len/1 returns the flattened length of the queue and is O(1)
-export([new/0, is_empty/1, len/1, in/3, in_r/3, out/1, out_r/1, join/2,
fold/3, from_list/1, to_list/1, map_fold_filter_l/4,
map_fold_filter_r/4]).
%%----------------------------------------------------------------------------
-ifdef(use_specs).
-type(bpqueue() :: {non_neg_integer(), queue()}).
-type(prefix() :: any()).
-type(value() :: any()).
-type(result() :: {'empty', bpqueue()} |
{{'value', prefix(), value()}, bpqueue()}).
-spec(new/0 :: () -> bpqueue()).
-spec(is_empty/1 :: (bpqueue()) -> boolean()).
-spec(len/1 :: (bpqueue()) -> non_neg_integer()).
-spec(in/3 :: (prefix(), value(), bpqueue()) -> bpqueue()).
-spec(in_r/3 :: (prefix(), value(), bpqueue()) -> bpqueue()).
-spec(out/1 :: (bpqueue()) -> result()).
-spec(out_r/1 :: (bpqueue()) -> result()).
-spec(join/2 :: (bpqueue(), bpqueue()) -> bpqueue()).
-spec(fold/3 :: (fun ((prefix(), value(), B) -> B), B, bpqueue()) -> B).
-spec(from_list/1 :: ([{prefix(), [value()]}]) -> bpqueue()).
-spec(to_list/1 :: (bpqueue()) -> [{prefix(), [value()]}]).
-spec(map_fold_filter_l/4 ::
(fun ((prefix()) -> boolean()),
fun ((value(), B) -> {prefix(), value(), B}), B, bpqueue()) ->
{bpqueue(), B}).
-spec(map_fold_filter_r/4 ::
(fun ((prefix()) -> boolean()),
fun ((value(), B) -> {prefix(), value(), B}), B, bpqueue()) ->
{bpqueue(), B}).
-endif.
%%----------------------------------------------------------------------------
new() ->
{0, queue:new()}.
is_empty({0, _Q}) ->
true;
is_empty(_BPQ) ->
false.
len({N, _Q}) ->
N.
in(Prefix, Value, {0, Q}) ->
{1, queue:in({Prefix, queue:in(Value, Q)}, Q)};
in(Prefix, Value, {N, Q}) ->
{N+1,
case queue:out_r(Q) of
{{value, {Prefix, InnerQ}}, Q1} ->
queue:in({Prefix, queue:in(Value, InnerQ)}, Q1);
{{value, {_Prefix, _InnerQ}}, _Q1} ->
queue:in({Prefix, queue:in(Value, queue:new())}, Q)
end}.
in_r(Prefix, Value, {0, Q}) ->
{1, queue:in({Prefix, queue:in(Value, Q)}, Q)};
in_r(Prefix, Value, {N, Q}) ->
{N+1,
case queue:out(Q) of
{{value, {Prefix, InnerQ}}, Q1} ->
queue:in_r({Prefix, queue:in_r(Value, InnerQ)}, Q1);
{{value, {_Prefix, _InnerQ}}, _Q1} ->
queue:in_r({Prefix, queue:in(Value, queue:new())}, Q)
end}.
out({0, _Q} = BPQ) ->
{empty, BPQ};
out({N, Q}) ->
{{value, {Prefix, InnerQ}}, Q1} = queue:out(Q),
{{value, Value}, InnerQ1} = queue:out(InnerQ),
Q2 = case queue:is_empty(InnerQ1) of
true -> Q1;
false -> queue:in_r({Prefix, InnerQ1}, Q1)
end,
{{value, Prefix, Value}, {N-1, Q2}}.
out_r({0, _Q} = BPQ) ->
{empty, BPQ};
out_r({N, Q}) ->
{{value, {Prefix, InnerQ}}, Q1} = queue:out_r(Q),
{{value, Value}, InnerQ1} = queue:out_r(InnerQ),
Q2 = case queue:is_empty(InnerQ1) of
true -> Q1;
false -> queue:in({Prefix, InnerQ1}, Q1)
end,
{{value, Prefix, Value}, {N-1, Q2}}.
join({0, _Q}, BPQ) ->
BPQ;
join(BPQ, {0, _Q}) ->
BPQ;
join({NHead, QHead}, {NTail, QTail}) ->
{{value, {Prefix, InnerQHead}}, QHead1} = queue:out_r(QHead),
{NHead + NTail,
case queue:out(QTail) of
{{value, {Prefix, InnerQTail}}, QTail1} ->
queue:join(
queue:in({Prefix, queue:join(InnerQHead, InnerQTail)}, QHead1),
QTail1);
{{value, {_Prefix, _InnerQTail}}, _QTail1} ->
queue:join(QHead, QTail)
end}.
fold(_Fun, Init, {0, _Q}) ->
Init;
fold(Fun, Init, {_N, Q}) ->
fold1(Fun, Init, Q).
fold1(Fun, Init, Q) ->
case queue:out(Q) of
{empty, _Q} ->
Init;
{{value, {Prefix, InnerQ}}, Q1} ->
fold1(Fun, fold1(Fun, Prefix, Init, InnerQ), Q1)
end.
fold1(Fun, Prefix, Init, InnerQ) ->
case queue:out(InnerQ) of
{empty, _Q} ->
Init;
{{value, Value}, InnerQ1} ->
fold1(Fun, Prefix, Fun(Prefix, Value, Init), InnerQ1)
end.
from_list(List) ->
{FinalPrefix, FinalInnerQ, ListOfPQs1, Len} =
lists:foldl(
fun ({_Prefix, []}, Acc) ->
Acc;
({Prefix, InnerList}, {Prefix, InnerQ, ListOfPQs, LenAcc}) ->
{Prefix, queue:join(InnerQ, queue:from_list(InnerList)),
ListOfPQs, LenAcc + length(InnerList)};
({Prefix1, InnerList}, {Prefix, InnerQ, ListOfPQs, LenAcc}) ->
{Prefix1, queue:from_list(InnerList),
[{Prefix, InnerQ} | ListOfPQs], LenAcc + length(InnerList)}
end, {undefined, queue:new(), [], 0}, List),
ListOfPQs2 = [{FinalPrefix, FinalInnerQ} | ListOfPQs1],
[{undefined, InnerQ1} | Rest] = All = lists:reverse(ListOfPQs2),
{Len, queue:from_list(case queue:is_empty(InnerQ1) of
true -> Rest;
false -> All
end)}.
to_list({0, _Q}) ->
[];
to_list({_N, Q}) ->
lists:map(fun to_list1/1, queue:to_list(Q)).
to_list1({Prefix, InnerQ}) ->
{Prefix, queue:to_list(InnerQ)}.
%% map_fold_filter_[lr](FilterFun, Fun, Init, BPQ) -> {BPQ, Init}
%% where FilterFun(Prefix) -> boolean()
%% Fun(Value, Init) -> {Prefix, Value, Init}
%%
%% The filter fun allows you to skip very quickly over blocks that
%% you're not interested in. Such blocks appear in the resulting bpq
%% without modification. The Fun is then used both to map the value,
%% which also allows you to change the prefix (and thus block) of the
%% value, and also to modify the Init/Acc (just like a fold).
map_fold_filter_l(_PFilter, _Fun, Init, BPQ = {0, _Q}) ->
{BPQ, Init};
map_fold_filter_l(PFilter, Fun, Init, {_N, Q}) ->
map_fold_filter_l1(PFilter, Fun, Init, Q, new()).
map_fold_filter_l1(PFilter, Fun, Init, Q, QNew) ->
case queue:out(Q) of
{empty, _Q} ->
{QNew, Init};
{{value, {Prefix, InnerQ}}, Q1} ->
InnerList = queue:to_list(InnerQ),
{Init1, QNew1} =
case PFilter(Prefix) of
true ->
lists:foldl(
fun (Value, {Acc, QNew2}) ->
{Prefix1, Value1, Acc1} = Fun(Value, Acc),
{Acc1, in(Prefix1, Value1, QNew2)}
end, {Init, QNew}, InnerList);
false ->
{Init, join(QNew, from_list([{Prefix, InnerList}]))}
end,
map_fold_filter_l1(PFilter, Fun, Init1, Q1, QNew1)
end.
map_fold_filter_r(_PFilter, _Fun, Init, BPQ = {0, _Q}) ->
{BPQ, Init};
map_fold_filter_r(PFilter, Fun, Init, {_N, Q}) ->
map_fold_filter_r1(PFilter, Fun, Init, Q, new()).
map_fold_filter_r1(PFilter, Fun, Init, Q, QNew) ->
case queue:out_r(Q) of
{empty, _Q} ->
{QNew, Init};
{{value, {Prefix, InnerQ}}, Q1} ->
InnerList = queue:to_list(InnerQ),
{Init1, QNew1} =
case PFilter(Prefix) of
true ->
lists:foldr(
fun (Value, {Acc, QNew2}) ->
{Prefix1, Value1, Acc1} = Fun(Value, Acc),
{Acc1, in_r(Prefix1, Value1, QNew2)}
end, {Init, QNew}, InnerList);
false ->
{Init, join(from_list([{Prefix, InnerList}]), QNew)}
end,
map_fold_filter_r1(PFilter, Fun, Init1, Q1, QNew1)
end.
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