1 /* 2 * Copyright (c) 2012, 2013, 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 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. 89 * 90 * @param spliterator the spliterator describing the relevant portion of the 91 * source data 92 * @return the exact size if known, or -1 if infinite or unknown 93 */ exactOutputSizeIfKnown(Spliterator<P_IN> spliterator)94 abstract<P_IN> long exactOutputSizeIfKnown(Spliterator<P_IN> spliterator); 95 96 /** 97 * Applies the pipeline stages described by this {@code PipelineHelper} to 98 * the provided {@code Spliterator} and send the results to the provided 99 * {@code Sink}. 100 * 101 * @implSpec 102 * The implementation behaves as if: 103 * <pre>{@code 104 * intoWrapped(wrapSink(sink), spliterator); 105 * }</pre> 106 * 107 * @param sink the {@code Sink} to receive the results 108 * @param spliterator the spliterator describing the source input to process 109 */ wrapAndCopyInto(S sink, Spliterator<P_IN> spliterator)110 abstract<P_IN, S extends Sink<P_OUT>> S wrapAndCopyInto(S sink, Spliterator<P_IN> spliterator); 111 112 /** 113 * Pushes elements obtained from the {@code Spliterator} into the provided 114 * {@code Sink}. If the stream pipeline is known to have short-circuiting 115 * stages in it (see {@link StreamOpFlag#SHORT_CIRCUIT}), the 116 * {@link Sink#cancellationRequested()} is checked after each 117 * element, stopping if cancellation is requested. 118 * 119 * @implSpec 120 * This method conforms to the {@code Sink} protocol of calling 121 * {@code Sink.begin} before pushing elements, via {@code Sink.accept}, and 122 * calling {@code Sink.end} after all elements have been pushed. 123 * 124 * @param wrappedSink the destination {@code Sink} 125 * @param spliterator the source {@code Spliterator} 126 */ copyInto(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator)127 abstract<P_IN> void copyInto(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator); 128 129 /** 130 * Pushes elements obtained from the {@code Spliterator} into the provided 131 * {@code Sink}, checking {@link Sink#cancellationRequested()} after each 132 * element, and stopping if cancellation is requested. 133 * 134 * @implSpec 135 * This method conforms to the {@code Sink} protocol of calling 136 * {@code Sink.begin} before pushing elements, via {@code Sink.accept}, and 137 * calling {@code Sink.end} after all elements have been pushed or if 138 * cancellation is requested. 139 * 140 * @param wrappedSink the destination {@code Sink} 141 * @param spliterator the source {@code Spliterator} 142 */ copyIntoWithCancel(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator)143 abstract <P_IN> void copyIntoWithCancel(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator); 144 145 /** 146 * Takes a {@code Sink} that accepts elements of the output type of the 147 * {@code PipelineHelper}, and wrap it with a {@code Sink} that accepts 148 * elements of the input type and implements all the intermediate operations 149 * described by this {@code PipelineHelper}, delivering the result into the 150 * provided {@code Sink}. 151 * 152 * @param sink the {@code Sink} to receive the results 153 * @return a {@code Sink} that implements the pipeline stages and sends 154 * results to the provided {@code Sink} 155 */ 156 // Android-changed: Made public for CTS tests only. wrapSink(Sink<P_OUT> sink)157 public abstract<P_IN> Sink<P_IN> wrapSink(Sink<P_OUT> sink); 158 159 /** 160 * 161 * @param spliterator 162 * @param <P_IN> 163 * @return 164 */ wrapSpliterator(Spliterator<P_IN> spliterator)165 abstract<P_IN> Spliterator<P_OUT> wrapSpliterator(Spliterator<P_IN> spliterator); 166 167 /** 168 * Constructs a @{link Node.Builder} compatible with the output shape of 169 * this {@code PipelineHelper}. 170 * 171 * @param exactSizeIfKnown if >=0 then a builder will be created that has a 172 * fixed capacity of exactly sizeIfKnown elements; if < 0 then the 173 * builder has variable capacity. A fixed capacity builder will fail 174 * if an element is added after the builder has reached capacity. 175 * @param generator a factory function for array instances 176 * @return a {@code Node.Builder} compatible with the output shape of this 177 * {@code PipelineHelper} 178 */ makeNodeBuilder(long exactSizeIfKnown, IntFunction<P_OUT[]> generator)179 abstract Node.Builder<P_OUT> makeNodeBuilder(long exactSizeIfKnown, 180 IntFunction<P_OUT[]> generator); 181 182 /** 183 * Collects all output elements resulting from applying the pipeline stages 184 * to the source {@code Spliterator} into a {@code Node}. 185 * 186 * @implNote 187 * If the pipeline has no intermediate operations and the source is backed 188 * by a {@code Node} then that {@code Node} will be returned (or flattened 189 * and then returned). This reduces copying for a pipeline consisting of a 190 * stateful operation followed by a terminal operation that returns an 191 * array, such as: 192 * <pre>{@code 193 * stream.sorted().toArray(); 194 * }</pre> 195 * 196 * @param spliterator the source {@code Spliterator} 197 * @param flatten if true and the pipeline is a parallel pipeline then the 198 * {@code Node} returned will contain no children, otherwise the 199 * {@code Node} may represent the root in a tree that reflects the 200 * shape of the computation tree. 201 * @param generator a factory function for array instances 202 * @return the {@code Node} containing all output elements 203 */ 204 // Android-changed: Made public for CTS tests only. evaluate(Spliterator<P_IN> spliterator, boolean flatten, IntFunction<P_OUT[]> generator)205 public abstract<P_IN> Node<P_OUT> evaluate(Spliterator<P_IN> spliterator, 206 boolean flatten, 207 IntFunction<P_OUT[]> generator); 208 } 209