1 /*
2 * *************************************************************************************************************************************************************
3 *
4 * TheseFoolishThings: Miscellaneous utilities
5 * http://tidalwave.it/projects/thesefoolishthings
6 *
7 * Copyright (C) 2009 - 2024 by Tidalwave s.a.s. (http://tidalwave.it)
8 *
9 * *************************************************************************************************************************************************************
10 *
11 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.
12 * You may obtain a copy of the License at
13 *
14 * http://www.apache.org/licenses/LICENSE-2.0
15 *
16 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
17 * CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
18 *
19 * *************************************************************************************************************************************************************
20 *
21 * git clone https://bitbucket.org/tidalwave/thesefoolishthings-src
22 * git clone https://github.com/tidalwave-it/thesefoolishthings-src
23 *
24 * *************************************************************************************************************************************************************
25 */
26 package it.tidalwave.util;
27
28 import javax.annotation.Nonnull;
29 import java.time.Instant;
30 import java.time.LocalDateTime;
31 import java.time.ZoneId;
32 import java.time.ZoneOffset;
33 import java.util.Random;
34 import java.util.Spliterator;
35 import java.util.Spliterators;
36 import java.util.function.BiFunction;
37 import java.util.function.Consumer;
38 import java.util.stream.Stream;
39 import java.util.stream.StreamSupport;
40 import lombok.AccessLevel;
41 import lombok.NoArgsConstructor;
42
43 /***************************************************************************************************************************************************************
44 *
45 * A collection of operations on {@link Stream}s.
46 *
47 * @author Fabrizio Giudici
48 * @since 3.2-ALPHA-12
49 * @it.tidalwave.javadoc.draft
50 *
51 **************************************************************************************************************************************************************/
52 @NoArgsConstructor(access = AccessLevel.PRIVATE)
53 public final class StreamUtils
54 {
55 /***********************************************************************************************************************************************************
56 * Zips two streams.
57 *
58 * @param streamA the first {@link Stream}
59 * @param streamB the second {@link Stream}
60 * @param <A> the type of elements of the first {@link Stream}
61 * @param <B> the type of elements of the second {@link Stream}
62 * @return the zipped {@link Stream} of {@link Pair}s
63 * @see #zip(Stream, Stream, BiFunction)
64 * @since 3.2-ALPHA-20
65 **********************************************************************************************************************************************************/
66 @Nonnull
67 public static <A, B> Stream<Pair<A, B>> zip (@Nonnull final Stream<? extends A> streamA,
68 @Nonnull final Stream<? extends B> streamB)
69 {
70 return zip(streamA, streamB, Pair::of);
71 }
72
73 /***********************************************************************************************************************************************************
74 * Zips two streams.
75 *
76 * @param streamA the first {@link Stream}
77 * @param streamB the second {@link Stream}
78 * @param zipper the zipping function
79 * @param <A> the type of elements of the first {@link Stream}
80 * @param <B> the type of elements of the second {@link Stream}
81 * @param <R> the type of elements of the zipped {@link Stream}
82 * @return the zipped {@link Stream}
83 * @see #zip(Stream, Stream)
84 * @since 3.2-ALPHA-12
85 **********************************************************************************************************************************************************/
86 @Nonnull
87 public static <A, B, R> Stream<R> zip (@Nonnull final Stream<? extends A> streamA,
88 @Nonnull final Stream<? extends B> streamB,
89 @Nonnull final BiFunction<? super A, ? super B, ? extends R> zipper)
90 {
91 final var parallel = streamA.isParallel() || streamB.isParallel();
92 final var sa = streamA.spliterator();
93 final var sb = streamB.spliterator();
94 final var characteristics =
95 sa.characteristics() & sb.characteristics() & (Spliterator.SIZED | Spliterator.ORDERED);
96 final var a = Spliterators.iterator(sa);
97 final var b = Spliterators.iterator(sb);
98 final var estSize = Math.min(sa.estimateSize(), sb.estimateSize());
99 return StreamSupport.stream(new Spliterators.AbstractSpliterator<R>(estSize, characteristics)
100 {
101 @Override
102 public boolean tryAdvance (@Nonnull final Consumer<? super R> action)
103 {
104 if (a.hasNext() && b.hasNext())
105 {
106 action.accept(zipper.apply(a.next(), b.next()));
107 return true;
108 }
109
110 return false;
111 }
112 },
113 parallel)
114 .onClose(streamA::close)
115 .onClose(streamB::close);
116 }
117
118 /***********************************************************************************************************************************************************
119 * Returns a {@code Stream} of random {@link LocalDateTime}s, in the given range.
120 *
121 * @param seed the random seed
122 * @param from the lower bound of the range (included)
123 * @param to the upper bound of the range (excluded)
124 * @return the stream
125 * @since 3.2-ALPHA-19
126 **********************************************************************************************************************************************************/
127 @Nonnull
128 public static Stream<LocalDateTime> randomLocalDateTimeStream (final long seed,
129 @Nonnull final LocalDateTime from,
130 @Nonnull final LocalDateTime to)
131 {
132 final var zo = ZoneOffset.UTC;
133 return new Random(seed)
134 .longs(from.toEpochSecond(zo), to.toEpochSecond(zo))
135 .mapToObj(l -> LocalDateTime.ofInstant(Instant.ofEpochSecond(l), ZoneId.of(zo.getId())));
136 }
137 }