1 /* 2 * Copyright (c) 2012, 2021, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 package java.util.stream; 26 27 import java.util.Spliterator; 28 import java.util.function.IntFunction; 29 30 /** 31 * Helper class for executing <a href="package-summary.html#StreamOps"> 32 * stream pipelines</a>, capturing all of the information about a stream 33 * pipeline (output shape, intermediate operations, stream flags, parallelism, 34 * etc) in one place. 35 * 36 * <p> 37 * A {@code PipelineHelper} describes the initial segment of a stream pipeline, 38 * including its source, intermediate operations, and may additionally 39 * incorporate information about the terminal (or stateful) operation which 40 * follows the last intermediate operation described by this 41 * {@code PipelineHelper}. The {@code PipelineHelper} is passed to the 42 * {@link TerminalOp#evaluateParallel(PipelineHelper, java.util.Spliterator)}, 43 * {@link TerminalOp#evaluateSequential(PipelineHelper, java.util.Spliterator)}, 44 * and {@link AbstractPipeline#opEvaluateParallel(PipelineHelper, java.util.Spliterator, 45 * java.util.function.IntFunction)}, methods, which can use the 46 * {@code PipelineHelper} to access information about the pipeline such as 47 * head shape, stream flags, and size, and use the helper methods 48 * such as {@link #wrapAndCopyInto(Sink, Spliterator)}, 49 * {@link #copyInto(Sink, Spliterator)}, and {@link #wrapSink(Sink)} to execute 50 * pipeline operations. 51 * 52 * @param <P_OUT> type of output elements from the pipeline 53 * @since 1.8 54 * @hide Visible for CTS testing only (OpenJDK8 tests). 55 */ 56 // Android-changed: Made public for CTS tests only. 57 public abstract class PipelineHelper<P_OUT> { 58 59 /** 60 * Gets the stream shape for the source of the pipeline segment. 61 * 62 * @return the stream shape for the source of the pipeline segment. 63 */ getSourceShape()64 abstract StreamShape getSourceShape(); 65 66 /** 67 * Gets the combined stream and operation flags for the output of the described 68 * pipeline. This will incorporate stream flags from the stream source, all 69 * the intermediate operations and the terminal operation. 70 * 71 * @return the combined stream and operation flags 72 * @see StreamOpFlag 73 */ 74 // Android-changed: Made public for CTS tests only. getStreamAndOpFlags()75 public abstract int getStreamAndOpFlags(); 76 77 /** 78 * Returns the exact output size of the portion of the output resulting from 79 * applying the pipeline stages described by this {@code PipelineHelper} to 80 * the portion of the input described by the provided 81 * {@code Spliterator}, if known. If not known or known infinite, will 82 * return {@code -1}. 83 * 84 * @apiNote 85 * The exact output size is known if the {@code Spliterator} has the 86 * {@code SIZED} characteristic, and the operation flags 87 * {@link StreamOpFlag#SIZED} is known on the combined stream and operation 88 * flags. The exact output size may differ from spliterator size, 89 * if pipeline contains a slice operation. 90 * 91 * @param spliterator the spliterator describing the relevant portion of the 92 * source data 93 * @return the exact size if known, or -1 if infinite or unknown 94 */ exactOutputSizeIfKnown(Spliterator<P_IN> spliterator)95 abstract<P_IN> long exactOutputSizeIfKnown(Spliterator<P_IN> spliterator); 96 97 /** 98 * Applies the pipeline stages described by this {@code PipelineHelper} to 99 * the provided {@code Spliterator} and send the results to the provided 100 * {@code Sink}. 101 * 102 * @implSpec 103 * The implementation behaves as if: 104 * <pre>{@code 105 * copyInto(wrapSink(sink), spliterator); 106 * }</pre> 107 * 108 * @param sink the {@code Sink} to receive the results 109 * @param spliterator the spliterator describing the source input to process 110 */ wrapAndCopyInto(S sink, Spliterator<P_IN> spliterator)111 abstract<P_IN, S extends Sink<P_OUT>> S wrapAndCopyInto(S sink, Spliterator<P_IN> spliterator); 112 113 /** 114 * Pushes elements obtained from the {@code Spliterator} into the provided 115 * {@code Sink}. If the stream pipeline is known to have short-circuiting 116 * stages in it (see {@link StreamOpFlag#SHORT_CIRCUIT}), the 117 * {@link Sink#cancellationRequested()} is checked after each 118 * element, stopping if cancellation is requested. 119 * 120 * @implSpec 121 * This method conforms to the {@code Sink} protocol of calling 122 * {@code Sink.begin} before pushing elements, via {@code Sink.accept}, and 123 * calling {@code Sink.end} after all elements have been pushed. 124 * 125 * @param wrappedSink the destination {@code Sink} 126 * @param spliterator the source {@code Spliterator} 127 */ copyInto(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator)128 abstract<P_IN> void copyInto(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator); 129 130 /** 131 * Pushes elements obtained from the {@code Spliterator} into the provided 132 * {@code Sink}, checking {@link Sink#cancellationRequested()} after each 133 * element, and stopping if cancellation is requested. 134 * 135 * @implSpec 136 * This method conforms to the {@code Sink} protocol of calling 137 * {@code Sink.begin} before pushing elements, via {@code Sink.accept}, and 138 * calling {@code Sink.end} after all elements have been pushed or if 139 * cancellation is requested. 140 * 141 * @param wrappedSink the destination {@code Sink} 142 * @param spliterator the source {@code Spliterator} 143 * @return true if the cancellation was requested 144 */ copyIntoWithCancel(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator)145 abstract <P_IN> boolean copyIntoWithCancel(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator); 146 147 /** 148 * Takes a {@code Sink} that accepts elements of the output type of the 149 * {@code PipelineHelper}, and wrap it with a {@code Sink} that accepts 150 * elements of the input type and implements all the intermediate operations 151 * described by this {@code PipelineHelper}, delivering the result into the 152 * provided {@code Sink}. 153 * 154 * @param sink the {@code Sink} to receive the results 155 * @return a {@code Sink} that implements the pipeline stages and sends 156 * results to the provided {@code Sink} 157 */ 158 // Android-changed: Made public for CTS tests only. wrapSink(Sink<P_OUT> sink)159 public abstract<P_IN> Sink<P_IN> wrapSink(Sink<P_OUT> sink); 160 161 /** 162 * 163 * @param spliterator 164 * @param <P_IN> 165 * @return 166 */ wrapSpliterator(Spliterator<P_IN> spliterator)167 abstract<P_IN> Spliterator<P_OUT> wrapSpliterator(Spliterator<P_IN> spliterator); 168 169 /** 170 * Constructs a @{link Node.Builder} compatible with the output shape of 171 * this {@code PipelineHelper}. 172 * 173 * @param exactSizeIfKnown if >=0 then a builder will be created that has a 174 * fixed capacity of exactly sizeIfKnown elements; if < 0 then the 175 * builder has variable capacity. A fixed capacity builder will fail 176 * if an element is added after the builder has reached capacity. 177 * @param generator a factory function for array instances 178 * @return a {@code Node.Builder} compatible with the output shape of this 179 * {@code PipelineHelper} 180 */ makeNodeBuilder(long exactSizeIfKnown, IntFunction<P_OUT[]> generator)181 abstract Node.Builder<P_OUT> makeNodeBuilder(long exactSizeIfKnown, 182 IntFunction<P_OUT[]> generator); 183 184 /** 185 * Collects all output elements resulting from applying the pipeline stages 186 * to the source {@code Spliterator} into a {@code Node}. 187 * 188 * @implNote 189 * If the pipeline has no intermediate operations and the source is backed 190 * by a {@code Node} then that {@code Node} will be returned (or flattened 191 * and then returned). This reduces copying for a pipeline consisting of a 192 * stateful operation followed by a terminal operation that returns an 193 * array, such as: 194 * <pre>{@code 195 * stream.sorted().toArray(); 196 * }</pre> 197 * 198 * @param spliterator the source {@code Spliterator} 199 * @param flatten if true and the pipeline is a parallel pipeline then the 200 * {@code Node} returned will contain no children, otherwise the 201 * {@code Node} may represent the root in a tree that reflects the 202 * shape of the computation tree. 203 * @param generator a factory function for array instances 204 * @return the {@code Node} containing all output elements 205 */ 206 // Android-changed: Made public for CTS tests only. evaluate(Spliterator<P_IN> spliterator, boolean flatten, IntFunction<P_OUT[]> generator)207 public abstract<P_IN> Node<P_OUT> evaluate(Spliterator<P_IN> spliterator, 208 boolean flatten, 209 IntFunction<P_OUT[]> generator); 210 } 211