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 * @paramtype of output elements from the pipeline 53 * @since 1.8 54 * @hide Visible for CTS testing only (OpenJDK8 tests). 55 */ 56 public abstract class PipelineHelper<P_OUT> { 57 58 /** 59 * Gets the stream shape for the source of the pipeline segment. 60 * 61 * @return the stream shape for the source of the pipeline segment. 62 */ 63 abstract StreamShape getSourceShape(); 64 65 /** 66 * Gets the combined stream and operation flags for the output of the described 67 * pipeline. This will incorporate stream flags from the stream source, all 68 * the intermediate operations and the terminal operation. 69 * 70 * @return the combined stream and operation flags 71 * @see StreamOpFlag 72 */ 73 public abstract int getStreamAndOpFlags(); 74 75 /** 76 * Returns the exact output size of the portion of the output resulting from 77 * applying the pipeline stages described by this {@code PipelineHelper} to 78 * the the portion of the input described by the provided 79 * {@code Spliterator}, if known. If not known or known infinite, will 80 * return {@code -1}. 81 * 82 * @apiNote 83 * The exact output size is known if the {@code Spliterator} has the 84 * {@code SIZED} characteristic, and the operation flags 85 * {@link StreamOpFlag#SIZED} is known on the combined stream and operation 86 * flags. 87 * 88 * @param spliterator the spliterator describing the relevant portion of the 89 * source data 90 * @return the exact size if known, or -1 if infinite or unknown 91 */ 92 abstract<P_IN> long exactOutputSizeIfKnown(Spliterator<P_IN> spliterator); 93 94 /** 95 * Applies the pipeline stages described by this {@code PipelineHelper} to 96 * the provided {@code Spliterator} and send the results to the provided 97 * {@code Sink}. 98 * 99 * @implSpec 100 * The implementation behaves as if: 101 * <pre>{@code 102 * intoWrapped(wrapSink(sink), spliterator); 103 * }</pre> 104 * 105 * @param sink the {@code Sink} to receive the results 106 * @param spliterator the spliterator describing the source input to process 107 */ 108 abstract<P_IN, S extends Sink<P_OUT>> S wrapAndCopyInto(S sink, Spliterator<P_IN> spliterator); 109 110 /** 111 * Pushes elements obtained from the {@code Spliterator} into the provided 112 * {@code Sink}. If the stream pipeline is known to have short-circuiting 113 * stages in it (see {@link StreamOpFlag#SHORT_CIRCUIT}), the 114 * {@link Sink#cancellationRequested()} is checked after each 115 * element, stopping if cancellation is requested. 116 * 117 * @implSpec 118 * This method conforms to the {@code Sink} protocol of calling 119 * {@code Sink.begin} before pushing elements, via {@code Sink.accept}, and 120 * calling {@code Sink.end} after all elements have been pushed. 121 * 122 * @param wrappedSink the destination {@code Sink} 123 * @param spliterator the source {@code Spliterator} 124 */ 125 abstract<P_IN> void copyInto(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator); 126 127 /** 128 * Pushes elements obtained from the {@code Spliterator} into the provided 129 * {@code Sink}, checking {@link Sink#cancellationRequested()} after each 130 * element, and stopping if cancellation is requested. 131 * 132 * @implSpec 133 * This method conforms to the {@code Sink} protocol of calling 134 * {@code Sink.begin} before pushing elements, via {@code Sink.accept}, and 135 * calling {@code Sink.end} after all elements have been pushed or if 136 * cancellation is requested. 137 * 138 * @param wrappedSink the destination {@code Sink} 139 * @param spliterator the source {@code Spliterator} 140 */ 141 abstract <P_IN> void copyIntoWithCancel(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator); 142 143 /** 144 * Takes a {@code Sink} that accepts elements of the output type of the 145 * {@code PipelineHelper}, and wrap it with a {@code Sink} that accepts 146 * elements of the input type and implements all the intermediate operations 147 * described by this {@code PipelineHelper}, delivering the result into the 148 * provided {@code Sink}. 149 * 150 * @param sink the {@code Sink} to receive the results 151 * @return a {@code Sink} that implements the pipeline stages and sends 152 * results to the provided {@code Sink} 153 */ 154 public abstract<P_IN> Sink<P_IN> wrapSink(Sink<P_OUT> sink); 155 156 /** 157 * 158 * @param spliterator 159 * @param 160 * @return 161 */ 162 abstract<P_IN> Spliterator<P_OUT> wrapSpliterator(Spliterator<P_IN> spliterator); 163 164 /** 165 * Constructs a @{link Node.Builder} compatible with the output shape of 166 * this {@code PipelineHelper}. 167 * 168 * @param exactSizeIfKnown if >=0 then a builder will be created that has a 169 * fixed capacity of exactly sizeIfKnown elements; if < 0 then the 170 * builder has variable capacity. A fixed capacity builder will fail 171 * if an element is added after the builder has reached capacity. 172 * @param generator a factory function for array instances 173 * @return a {@code Node.Builder} compatible with the output shape of this 174 * {@code PipelineHelper} 175 */ 176 abstract Node.Builder<P_OUT> makeNodeBuilder(long exactSizeIfKnown, 177 IntFunction<P_OUT[]> generator); 178 179 /** 180 * Collects all output elements resulting from applying the pipeline stages 181 * to the source {@code Spliterator} into a {@code Node}. 182 * 183 * @implNote 184 * If the pipeline has no intermediate operations and the source is backed 185 * by a {@code Node} then that {@code Node} will be returned (or flattened 186 * and then returned). This reduces copying for a pipeline consisting of a 187 * stateful operation followed by a terminal operation that returns an 188 * array, such as: 189 * <pre>{@code 190 * stream.sorted().toArray(); 191 * }</pre> 192 * 193 * @param spliterator the source {@code Spliterator} 194 * @param flatten if true and the pipeline is a parallel pipeline then the 195 * {@code Node} returned will contain no children, otherwise the 196 * {@code Node} may represent the root in a tree that reflects the 197 * shape of the computation tree. 198 * @param generator a factory function for array instances 199 * @return the {@code Node} containing all output elements 200 */ 201 public abstract<P_IN> Node<P_OUT> evaluate(Spliterator<P_IN> spliterator, 202 boolean flatten, 203 IntFunction<P_OUT[]> generator); 204 } 205
