PipelineHelper.java revision ff18b5f136f92154f2e05217e3953d10f459e561
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 */ 25package java.util.stream; 26 27import java.util.Spliterator; 28import 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 * @paramtype of output elements from the pipeline 53 * @since 1.8 54 */ 55abstract class PipelineHelper<P_OUT> { 56 57 /** 58 * Gets the stream shape for the source of the pipeline segment. 59 * 60 * @return the stream shape for the source of the pipeline segment. 61 */ 62 abstract StreamShape getSourceShape(); 63 64 /** 65 * Gets the combined stream and operation flags for the output of the described 66 * pipeline. This will incorporate stream flags from the stream source, all 67 * the intermediate operations and the terminal operation. 68 * 69 * @return the combined stream and operation flags 70 * @see StreamOpFlag 71 */ 72 abstract int getStreamAndOpFlags(); 73 74 /** 75 * Returns the exact output size of the portion of the output resulting from 76 * applying the pipeline stages described by this {@code PipelineHelper} to 77 * the the portion of the input described by the provided 78 * {@code Spliterator}, if known. If not known or known infinite, will 79 * return {@code -1}. 80 * 81 * @apiNote 82 * The exact output size is known if the {@code Spliterator} has the 83 * {@code SIZED} characteristic, and the operation flags 84 * {@link StreamOpFlag#SIZED} is known on the combined stream and operation 85 * flags. 86 * 87 * @param spliterator the spliterator describing the relevant portion of the 88 * source data 89 * @return the exact size if known, or -1 if infinite or unknown 90 */ 91 abstract<P_IN> long exactOutputSizeIfKnown(Spliterator<P_IN> spliterator); 92 93 /** 94 * Applies the pipeline stages described by this {@code PipelineHelper} to 95 * the provided {@code Spliterator} and send the results to the provided 96 * {@code Sink}. 97 * 98 * @implSpec 99 * The implementation behaves as if: 100 * <pre>{@code 101 * intoWrapped(wrapSink(sink), spliterator); 102 * }</pre> 103 * 104 * @param sink the {@code Sink} to receive the results 105 * @param spliterator the spliterator describing the source input to process 106 */ 107 abstract<P_IN, S extends Sink<P_OUT>> S wrapAndCopyInto(S sink, Spliterator<P_IN> spliterator); 108 109 /** 110 * Pushes elements obtained from the {@code Spliterator} into the provided 111 * {@code Sink}. If the stream pipeline is known to have short-circuiting 112 * stages in it (see {@link StreamOpFlag#SHORT_CIRCUIT}), the 113 * {@link Sink#cancellationRequested()} is checked after each 114 * element, stopping if cancellation is requested. 115 * 116 * @implSpec 117 * This method conforms to the {@code Sink} protocol of calling 118 * {@code Sink.begin} before pushing elements, via {@code Sink.accept}, and 119 * calling {@code Sink.end} after all elements have been pushed. 120 * 121 * @param wrappedSink the destination {@code Sink} 122 * @param spliterator the source {@code Spliterator} 123 */ 124 abstract<P_IN> void copyInto(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator); 125 126 /** 127 * Pushes elements obtained from the {@code Spliterator} into the provided 128 * {@code Sink}, checking {@link Sink#cancellationRequested()} after each 129 * element, and stopping if cancellation is requested. 130 * 131 * @implSpec 132 * This method conforms to the {@code Sink} protocol of calling 133 * {@code Sink.begin} before pushing elements, via {@code Sink.accept}, and 134 * calling {@code Sink.end} after all elements have been pushed or if 135 * cancellation is requested. 136 * 137 * @param wrappedSink the destination {@code Sink} 138 * @param spliterator the source {@code Spliterator} 139 */ 140 abstract <P_IN> void copyIntoWithCancel(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator); 141 142 /** 143 * Takes a {@code Sink} that accepts elements of the output type of the 144 * {@code PipelineHelper}, and wrap it with a {@code Sink} that accepts 145 * elements of the input type and implements all the intermediate operations 146 * described by this {@code PipelineHelper}, delivering the result into the 147 * provided {@code Sink}. 148 * 149 * @param sink the {@code Sink} to receive the results 150 * @return a {@code Sink} that implements the pipeline stages and sends 151 * results to the provided {@code Sink} 152 */ 153 abstract<P_IN> Sink<P_IN> wrapSink(Sink<P_OUT> sink); 154 155 /** 156 * 157 * @param spliterator 158 * @param 159 * @return 160 */ 161 abstract<P_IN> Spliterator<P_OUT> wrapSpliterator(Spliterator<P_IN> spliterator); 162 163 /** 164 * Constructs a @{link Node.Builder} compatible with the output shape of 165 * this {@code PipelineHelper}. 166 * 167 * @param exactSizeIfKnown if >=0 then a builder will be created that has a 168 * fixed capacity of exactly sizeIfKnown elements; if < 0 then the 169 * builder has variable capacity. A fixed capacity builder will fail 170 * if an element is added after the builder has reached capacity. 171 * @param generator a factory function for array instances 172 * @return a {@code Node.Builder} compatible with the output shape of this 173 * {@code PipelineHelper} 174 */ 175 abstract Node.Builder<P_OUT> makeNodeBuilder(long exactSizeIfKnown, 176 IntFunction<P_OUT[]> generator); 177 178 /** 179 * Collects all output elements resulting from applying the pipeline stages 180 * to the source {@code Spliterator} into a {@code Node}. 181 * 182 * @implNote 183 * If the pipeline has no intermediate operations and the source is backed 184 * by a {@code Node} then that {@code Node} will be returned (or flattened 185 * and then returned). This reduces copying for a pipeline consisting of a 186 * stateful operation followed by a terminal operation that returns an 187 * array, such as: 188 * <pre>{@code 189 * stream.sorted().toArray(); 190 * }</pre> 191 * 192 * @param spliterator the source {@code Spliterator} 193 * @param flatten if true and the pipeline is a parallel pipeline then the 194 * {@code Node} returned will contain no children, otherwise the 195 * {@code Node} may represent the root in a tree that reflects the 196 * shape of the computation tree. 197 * @param generator a factory function for array instances 198 * @return the {@code Node} containing all output elements 199 */ 200 abstract<P_IN> Node<P_OUT> evaluate(Spliterator<P_IN> spliterator, 201 boolean flatten, 202 IntFunction<P_OUT[]> generator); 203} 204