diff options
Diffstat (limited to 'lib/hipe/misc/hipe_segment_trees.erl')
| -rw-r--r-- | lib/hipe/misc/hipe_segment_trees.erl | 49 |
1 files changed, 40 insertions, 9 deletions
diff --git a/lib/hipe/misc/hipe_segment_trees.erl b/lib/hipe/misc/hipe_segment_trees.erl index cbee328125..22146396c3 100644 --- a/lib/hipe/misc/hipe_segment_trees.erl +++ b/lib/hipe/misc/hipe_segment_trees.erl @@ -17,19 +17,16 @@ %%% %%% %CopyrightEnd% %%% -%%% Segment trees. +%%% Segment trees, with a delete operation. %%% %%% Keys are the (0-based) indices into the list passed to build/1. %%% %%% Range bounds are inclusive. %%% -%%% TODO: Change the shape of the tree to a perfect binary tree, and pack it as -%%% an implicit data structure into tuples (like a binary heap would be) for -%%% improved efficiency. -module(hipe_segment_trees). --export([build/1, intersect/2]). +-export([build/1, intersect/2, delete/4]). -record(segment_tree, { lo :: integer(), @@ -75,9 +72,7 @@ empty_tree_from_endpoints(Endpoints) -> leaves([Endpoint]) -> [?POINT_LEAF(Endpoint)]; leaves([A | [B|_] = Tail]) -> - %% We could omit the range leaf if it's empty, but we want to pack this data - %% structure into an array (tuple) eventually, and then we *really* want - %% every other leaf to be a range + %% We omit the range leaf if it's empty case A<B-1 of true -> [?POINT_LEAF(A),?RANGE_LEAF(A+1,B-1) | leaves(Tail)]; false -> [?POINT_LEAF(A) | leaves(Tail)] @@ -121,7 +116,7 @@ insert_interval(I, {_Lo,_Hi}, _NLo, _NHi, Leaf) -> [I|Leaf]. intervals_intersect(ALo, AHi, BLo, BHi) -> (ALo =< AHi) andalso (BLo =< BHi) %% both nonempty - andalso (BLo =< AHi) andalso (ALo =< BHi). + andalso nonempty_intervals_intersect(ALo, AHi, BLo, BHi). %% Purely optional optimisation squash_empty_subtrees(?NODE(Left0, Right0, Mid, Segs)) -> @@ -148,3 +143,39 @@ intersect_1(Point, ?NODE(Left, Right, Mid, Segs), Acc0) -> Child = if Point =< Mid -> Left; true -> Right end, intersect_1(Point, Child, Segs ++ Acc0); intersect_1(_, LeafSegs, Acc) -> LeafSegs ++ Acc. + +%% @doc Deletes the interval {Lo, Hi}, which had index Index in the list passed +%% to build/1. +-spec delete(non_neg_integer(), integer(), integer(), tree()) -> tree(). +delete(_, _, _, nil) -> nil; +delete(_, Lo, Hi, Tree) when Lo > Hi -> Tree; +delete(_, Lo, Hi, Tree = #segment_tree{lo=TLo, hi=THi}) + when Hi < TLo; Lo > THi -> Tree; +delete(Index, Lo, Hi, Tree = #segment_tree{lo=TLo, hi=THi, root=Root0}) + when is_integer(Lo), is_integer(Hi) -> + Root = delete_1(Index, Lo, Hi, TLo, THi, Root0), + Tree#segment_tree{root=Root}. + +delete_1(I, Lo, Hi, NLo, NHi, ?NODE(Left0, Right0, Mid, Segments)) -> + if Lo =< NLo, NHi =< Hi -> + ?NODE(Left0, Right0, Mid, delete_2(Segments, I)); + true -> + Left = case nonempty_intervals_intersect(Lo, Hi, NLo, Mid) of + true -> delete_1(I, Lo, Hi, NLo, Mid, Left0); + false -> Left0 + end, + Right = case nonempty_intervals_intersect(Lo, Hi, Mid+1, NHi) of + true -> delete_1(I, Lo, Hi, Mid+1, NHi, Right0); + false -> Right0 + end, + %% We could do build_squash_node here, is it worth it? + ?NODE(Left, Right, Mid, Segments) + end; +delete_1(I, _Lo, _Hi, _NLo, _NHi, Leaf) -> delete_2(Leaf, I). + +delete_2([I|Segs], I) -> Segs; +delete_2([S|Segs], I) -> [S|delete_2(Segs,I)]. + +-compile({inline,nonempty_intervals_intersect/4}). +nonempty_intervals_intersect(ALo, AHi, BLo, BHi) -> + (BLo =< AHi) andalso (ALo =< BHi). |