Function iterator_from/2.

walter-weinmann · Nov 8, 2016 · 1a0e0aa · 1a0e0aa
1 parent cab8e62
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diff --git a/src/b_trees.erl b/src/b_trees.erl
@@ -69,6 +69,11 @@
 %%   The main advantage of the iterator approach is that it does not require the
 %%   complete list of all elements to be built in memory at one time.
 %%
+%% - iterator_from(K, B): Returns an iterator that can be used for traversing the
+%%   entries of B-Tree B; see next/1. The difference as compared to the iterator
+%%   returned by iterator/1 is that the first key greater than or equal to Key K
+%%   is returned.
+%%
 %% - keys(B): returns an ordered list of all keys in B-tree B.
 %%
 %% - largest(B): returns tuple {K, V}, where K is the largest key in B-tree B,
@@ -128,6 +133,7 @@
     is_defined/2,
     is_empty/1,
     iterator/1,
+    iterator_from/2,
     keys/1,
     largest/1,
     lookup/2,
@@ -821,6 +827,27 @@ iterator_1({KeyValues, Subtrees}, Iterator) ->
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
+-spec iterator_from(key(), b_tree()) -> iterator().
+
+iterator_from(_Key, {_, _, 0, nil}) ->
+    [];
+iterator_from(Key, {_, _, _, Tree}) ->
+    iterator_from_1(Key, Tree, []).
+
+-spec iterator_from_1(key(), tree(), iterator()) -> iterator().
+
+% The most left key / value.
+iterator_from_1(Key, {KeyNo, 0, KeyValues, []} = _Next, Iterator) ->
+    {_, Pos} = binary_search(Key, KeyValues, KeyNo, 1, KeyNo),
+    [{lists:sublist(KeyValues, Pos, KeyNo), []} | Iterator];
+% The most left subtree.
+iterator_from_1(Key, {KeyNo, SubtreeNo, KeyValues, Subtrees} = _Next, Iterator) ->
+    {_, Pos} = binary_search(Key, KeyValues, KeyNo, 1, KeyNo),
+    {KeyNo_1, SubtreeNo_1, KeyValues_1, Subtrees_1} = _NextIterator = lists:nth(Pos, Subtrees),
+    iterator_from_1(Key, {KeyNo_1, SubtreeNo_1, KeyValues_1, Subtrees_1}, [{lists:sublist(KeyValues, Pos, KeyNo), lists:sublist(Subtrees, Pos, SubtreeNo)} | Iterator]).
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
 -spec keys(b_tree()) -> keys().
 
 keys({_, _, 0, nil}) ->
@@ -910,7 +937,7 @@ next([{[], _}, {[], _} = Iterator | TailIterator]) ->
 % End of leaf node.
 next([{[], _}, {[{Key, Value} | TailKeyValues], [_ | TailSubtrees]} | TailIterator]) ->
     {Key, Value, iterator_1({TailKeyValues, TailSubtrees}, TailIterator)};
-% Processing a leaf node..
+% Processing a leaf node.
 next([{[{Key, Value} | KeyValues], []} | Iterator]) ->
     {Key, Value, [{KeyValues, []} | Iterator]};
 % End of iterator.

diff --git a/test/b_trees_SUITE.erl b/test/b_trees_SUITE.erl
@@ -53,6 +53,16 @@ all() ->
         insert_error_test,
         is_defined_test,
         is_empty_test,
+        iterator_from_next_00_test,
+        iterator_from_next_01_test,
+        iterator_from_next_02_test,
+        iterator_from_next_03_test,
+        iterator_from_next_04_test,
+        iterator_from_next_04_16_test,
+        iterator_from_next_06_test,
+        iterator_from_next_08_256_test,
+        iterator_from_next_16_test,
+        iterator_from_next_17_test,
         iterator_next_test,
         keys_test,
         largest_test,
@@ -678,6 +688,190 @@ is_empty_test(_Config) ->
 
     ok.
 
+%%--------------------------------------------------------------------
+%% TEST CASES: iterator_from & next
+%%--------------------------------------------------------------------
+
+iterator_from_next_00_test(_Config) ->
+    BTree_04_00 = b_trees:empty(4),
+    _Iterator_04_00_00 = b_trees:iterator_from("k_01", BTree_04_00),
+    ?assertEqual(none, b_trees:next(_Iterator_04_00_00)),
+
+    BTree_04_01 = test_generator:generate_b_tree_from_number(4, 1, 2),
+    Iterator_04_01_00 = b_trees:iterator_from("k_00", BTree_04_01),
+    {_Key_04_01_01, _Value_04_01_01, _Iterator_04_01_01} = b_trees:next(Iterator_04_01_00),
+    ?assertEqual({"k_01", "v_01"}, {_Key_04_01_01, _Value_04_01_01}),
+    ?assertEqual(none, b_trees:next(_Iterator_04_01_01)),
+
+    BTree_04_16 = test_generator:generate_b_tree_from_number(4, 16, 2),
+    Iterator_04_16_01 = b_trees:iterator_from("k_00", BTree_04_16),
+    {_Key_04_16_01, _Value_04_16_01, Iterator_04_16_02} = b_trees:next(Iterator_04_16_01),
+    ?assertEqual({"k_01", "v_01"}, {_Key_04_16_01, _Value_04_16_01}),
+    {_Key_04_16_02, _Value_04_16_02, _Iterator_04_16_03} = b_trees:next(Iterator_04_16_02),
+    ?assertEqual({"k_02", "v_02"}, {_Key_04_16_02, _Value_04_16_02}),
+
+    ok.
+
+%%--------------------------------------------------------------------
+%% TEST CASES: iterator_from & next
+%%--------------------------------------------------------------------
+
+iterator_from_next_01_test(_Config) ->
+    BTree_04_16 = test_generator:generate_b_tree_from_number(4, 16, 2),
+    Iterator_04_16_01 = b_trees:iterator_from("k_01", BTree_04_16),
+    {_Key_04_16_01, _Value_04_16_01, Iterator_04_16_02} = b_trees:next(Iterator_04_16_01),
+    ?assertEqual({"k_01", "v_01"}, {_Key_04_16_01, _Value_04_16_01}),
+    {_Key_04_16_02, _Value_04_16_02, _Iterator_04_16_03} = b_trees:next(Iterator_04_16_02),
+    ?assertEqual({"k_02", "v_02"}, {_Key_04_16_02, _Value_04_16_02}),
+
+    ok.
+
+%%--------------------------------------------------------------------
+%% TEST CASES: iterator_from & next
+%%--------------------------------------------------------------------
+
+iterator_from_next_02_test(_Config) ->
+    BTree_04_16 = test_generator:generate_b_tree_from_number(4, 16, 2),
+    Iterator_04_16_02 = b_trees:iterator_from("k_02", BTree_04_16),
+    {_Key_04_16_02, _Value_04_16_02, Iterator_04_16_03} = b_trees:next(Iterator_04_16_02),
+    ?assertEqual({"k_02", "v_02"}, {_Key_04_16_02, _Value_04_16_02}),
+    {_Key_04_16_03, _Value_04_16_03, _Iterator_04_16_04} = b_trees:next(Iterator_04_16_03),
+    ?assertEqual({"k_03", "v_03"}, {_Key_04_16_03, _Value_04_16_03}),
+
+    ok.
+
+%%--------------------------------------------------------------------
+%% TEST CASES: iterator_from & next
+%%--------------------------------------------------------------------
+
+iterator_from_next_03_test(_Config) ->
+    BTree_04_16 = test_generator:generate_b_tree_from_number(4, 16, 2),
+    Iterator_04_16_03 = b_trees:iterator_from("k_03", BTree_04_16),
+    {_Key_04_16_03, _Value_04_16_03, Iterator_04_16_04} = b_trees:next(Iterator_04_16_03),
+    ?assertEqual({"k_03", "v_03"}, {_Key_04_16_03, _Value_04_16_03}),
+    {_Key_04_16_04, _Value_04_16_04, _Iterator_04_16_05} = b_trees:next(Iterator_04_16_04),
+    ?assertEqual({"k_04", "v_04"}, {_Key_04_16_04, _Value_04_16_04}),
+
+    ok.
+
+%%--------------------------------------------------------------------
+%% TEST CASES: iterator_from & next
+%%--------------------------------------------------------------------
+
+iterator_from_next_04_test(_Config) ->
+    BTree_04_16 = test_generator:generate_b_tree_from_number(4, 16, 2),
+    Iterator_04_16_04 = b_trees:iterator_from("k_04", BTree_04_16),
+    {_Key_04_16_04, _Value_04_16_04, Iterator_04_16_05} = b_trees:next(Iterator_04_16_04),
+    ?assertEqual({"k_04", "v_04"}, {_Key_04_16_04, _Value_04_16_04}),
+    {_Key_04_16_05, _Value_04_16_05, _Iterator_04_16_06} = b_trees:next(Iterator_04_16_05),
+    ?assertEqual({"k_05", "v_05"}, {_Key_04_16_05, _Value_04_16_05}),
+
+    ok.
+
+%%--------------------------------------------------------------------
+%% TEST CASES: iterator_from & next
+%%--------------------------------------------------------------------
+
+iterator_from_next_04_16_test(_Config) ->
+    Number = 16,
+
+    BTree = test_generator:generate_b_tree_from_number(4, Number, 2),
+    KeyValues = test_generator:generate_key_values_from(Number, 2),
+
+    ?assertEqual(lists:sublist(KeyValues, 1, Number), iterate_next_b_tree(b_trees:iterator_from("k_00", BTree), Number - 0, [])),
+    ?assertEqual(lists:sublist(KeyValues, 2, Number), iterate_next_b_tree(b_trees:iterator_from("k_02", BTree), Number - 1, [])),
+    ?assertEqual(lists:sublist(KeyValues, 3, Number), iterate_next_b_tree(b_trees:iterator_from("k_03", BTree), Number - 2, [])),
+    ?assertEqual(lists:sublist(KeyValues, 4, Number), iterate_next_b_tree(b_trees:iterator_from("k_04", BTree), Number - 3, [])),
+    ?assertEqual(lists:sublist(KeyValues, 5, Number), iterate_next_b_tree(b_trees:iterator_from("k_05", BTree), Number - 4, [])),
+    ?assertEqual(lists:sublist(KeyValues, 6, Number), iterate_next_b_tree(b_trees:iterator_from("k_06", BTree), Number - 5, [])),
+    ?assertEqual(lists:sublist(KeyValues, 7, Number), iterate_next_b_tree(b_trees:iterator_from("k_07", BTree), Number - 6, [])),
+    ?assertEqual(lists:sublist(KeyValues, 8, Number), iterate_next_b_tree(b_trees:iterator_from("k_08", BTree), Number - 7, [])),
+    ?assertEqual(lists:sublist(KeyValues, 9, Number), iterate_next_b_tree(b_trees:iterator_from("k_09", BTree), Number - 8, [])),
+    ?assertEqual(lists:sublist(KeyValues, 10, Number), iterate_next_b_tree(b_trees:iterator_from("k_10", BTree), Number - 9, [])),
+    ?assertEqual(lists:sublist(KeyValues, 11, Number), iterate_next_b_tree(b_trees:iterator_from("k_11", BTree), Number - 10, [])),
+    ?assertEqual(lists:sublist(KeyValues, 12, Number), iterate_next_b_tree(b_trees:iterator_from("k_12", BTree), Number - 11, [])),
+    ?assertEqual(lists:sublist(KeyValues, 13, Number), iterate_next_b_tree(b_trees:iterator_from("k_13", BTree), Number - 12, [])),
+    ?assertEqual(lists:sublist(KeyValues, 14, Number), iterate_next_b_tree(b_trees:iterator_from("k_14", BTree), Number - 13, [])),
+    ?assertEqual(lists:sublist(KeyValues, 15, Number), iterate_next_b_tree(b_trees:iterator_from("k_15", BTree), Number - 14, [])),
+    ?assertEqual(lists:sublist(KeyValues, 16, Number), iterate_next_b_tree(b_trees:iterator_from("k_16", BTree), Number - 15, [])),
+
+    ok.
+
+%%--------------------------------------------------------------------
+%% TEST CASES: iterator_from & next
+%%--------------------------------------------------------------------
+
+iterator_from_next_06_test(_Config) ->
+    BTree_04_16 = test_generator:generate_b_tree_from_number(4, 16, 2),
+    Iterator_04_16_06 = b_trees:iterator_from("k_06", BTree_04_16),
+    {_Key_04_16_06, _Value_04_16_06, Iterator_04_16_07} = b_trees:next(Iterator_04_16_06),
+    ?assertEqual({"k_06", "v_06"}, {_Key_04_16_06, _Value_04_16_06}),
+    {_Key_04_16_07, _Value_04_16_07, _Iterator_04_16_08} = b_trees:next(Iterator_04_16_07),
+    ?assertEqual({"k_07", "v_07"}, {_Key_04_16_07, _Value_04_16_07}),
+
+    ok.
+
+%%--------------------------------------------------------------------
+%% TEST CASES: iterator_from & next
+%%--------------------------------------------------------------------
+
+iterator_from_next_08_256_test(_Config) ->
+    Number = 256,
+
+    BTree = test_generator:generate_b_tree_from_number(4, Number, 3),
+    KeyValues = test_generator:generate_key_values_from(Number, 3),
+
+    ?assertEqual(lists:sublist(KeyValues, 1, Number), iterate_next_b_tree(b_trees:iterator_from("k_000", BTree), Number - 0, [])),
+    ?assertEqual(lists:sublist(KeyValues, 2, Number), iterate_next_b_tree(b_trees:iterator_from("k_002", BTree), Number - 1, [])),
+    ?assertEqual(lists:sublist(KeyValues, 3, Number), iterate_next_b_tree(b_trees:iterator_from("k_003", BTree), Number - 2, [])),
+    ?assertEqual(lists:sublist(KeyValues, 4, Number), iterate_next_b_tree(b_trees:iterator_from("k_004", BTree), Number - 3, [])),
+    ?assertEqual(lists:sublist(KeyValues, 5, Number), iterate_next_b_tree(b_trees:iterator_from("k_005", BTree), Number - 4, [])),
+    ?assertEqual(lists:sublist(KeyValues, 7, Number), iterate_next_b_tree(b_trees:iterator_from("k_007", BTree), Number - 6, [])),
+    ?assertEqual(lists:sublist(KeyValues, 8, Number), iterate_next_b_tree(b_trees:iterator_from("k_008", BTree), Number - 7, [])),
+    ?assertEqual(lists:sublist(KeyValues, 11, Number), iterate_next_b_tree(b_trees:iterator_from("k_011", BTree), Number - 10, [])),
+    ?assertEqual(lists:sublist(KeyValues, 13, Number), iterate_next_b_tree(b_trees:iterator_from("k_013", BTree), Number - 12, [])),
+    ?assertEqual(lists:sublist(KeyValues, 16, Number), iterate_next_b_tree(b_trees:iterator_from("k_016", BTree), Number - 15, [])),
+    ?assertEqual(lists:sublist(KeyValues, 17, Number), iterate_next_b_tree(b_trees:iterator_from("k_017", BTree), Number - 16, [])),
+    ?assertEqual(lists:sublist(KeyValues, 19, Number), iterate_next_b_tree(b_trees:iterator_from("k_019", BTree), Number - 18, [])),
+    ?assertEqual(lists:sublist(KeyValues, 23, Number), iterate_next_b_tree(b_trees:iterator_from("k_023", BTree), Number - 22, [])),
+    ?assertEqual(lists:sublist(KeyValues, 29, Number), iterate_next_b_tree(b_trees:iterator_from("k_029", BTree), Number - 28, [])),
+    ?assertEqual(lists:sublist(KeyValues, 31, Number), iterate_next_b_tree(b_trees:iterator_from("k_031", BTree), Number - 30, [])),
+    ?assertEqual(lists:sublist(KeyValues, 32, Number), iterate_next_b_tree(b_trees:iterator_from("k_032", BTree), Number - 31, [])),
+    ?assertEqual(lists:sublist(KeyValues, 37, Number), iterate_next_b_tree(b_trees:iterator_from("k_037", BTree), Number - 36, [])),
+    ?assertEqual(lists:sublist(KeyValues, 41, Number), iterate_next_b_tree(b_trees:iterator_from("k_041", BTree), Number - 40, [])),
+    ?assertEqual(lists:sublist(KeyValues, 43, Number), iterate_next_b_tree(b_trees:iterator_from("k_043", BTree), Number - 42, [])),
+    ?assertEqual(lists:sublist(KeyValues, 47, Number), iterate_next_b_tree(b_trees:iterator_from("k_047", BTree), Number - 46, [])),
+    ?assertEqual(lists:sublist(KeyValues, 49, Number), iterate_next_b_tree(b_trees:iterator_from("k_049", BTree), Number - 48, [])),
+    ?assertEqual(lists:sublist(KeyValues, 64, Number), iterate_next_b_tree(b_trees:iterator_from("k_064", BTree), Number - 63, [])),
+    ?assertEqual(lists:sublist(KeyValues, 128, Number), iterate_next_b_tree(b_trees:iterator_from("k_128", BTree), Number - 127, [])),
+    ?assertEqual(lists:sublist(KeyValues, 256, Number), iterate_next_b_tree(b_trees:iterator_from("k_256", BTree), Number - 255, [])),
+
+    ok.
+
+%%--------------------------------------------------------------------
+%% TEST CASES: iterator_from & next
+%%--------------------------------------------------------------------
+
+iterator_from_next_16_test(_Config) ->
+    BTree_04_16 = test_generator:generate_b_tree_from_number(4, 16, 2),
+    Iterator_04_16_16 = b_trees:iterator_from("k_16", BTree_04_16),
+    {_Key_04_16_16, _Value_04_16_16, Iterator_04_16_17} = b_trees:next(Iterator_04_16_16),
+    ?assertEqual({"k_16", "v_16"}, {_Key_04_16_16, _Value_04_16_16}),
+    none = b_trees:next(Iterator_04_16_17),
+
+    ok.
+
+%%--------------------------------------------------------------------
+%% TEST CASES: iterator_from & next
+%%--------------------------------------------------------------------
+
+iterator_from_next_17_test(_Config) ->
+    BTree_04_16 = test_generator:generate_b_tree_from_number(4, 16, 2),
+    Iterator_04_16_17 = b_trees:iterator_from("k_17", BTree_04_16),
+    none = b_trees:next(Iterator_04_16_17),
+
+    ok.
+
 %%--------------------------------------------------------------------
 %% TEST CASES: iterator & next
 %%--------------------------------------------------------------------
@@ -1107,3 +1301,13 @@ values_test(_Config) ->
     ?assertEqual(16, length(b_trees:values(?B_TREE_06_16))),
 
     ok.
+
+%%--------------------------------------------------------------------
+%% Helper functions.
+%%--------------------------------------------------------------------
+
+iterate_next_b_tree(_, 0, KeyValues) ->
+    KeyValues;
+iterate_next_b_tree(Iterator, Count, KeyValues) ->
+    {Key, Value, IteratorNew} = b_trees:next(Iterator),
+    iterate_next_b_tree(IteratorNew, Count - 1, KeyValues ++ [{Key, Value}]).