/* * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.util.stream; import java.util.Spliterator; import java.util.function.IntFunction; /** * Helper class for executing * stream pipelines, capturing all of the information about a stream * pipeline (output shape, intermediate operations, stream flags, parallelism, * etc) in one place. * *

* A {@code PipelineHelper} describes the initial segment of a stream pipeline, * including its source, intermediate operations, and may additionally * incorporate information about the terminal (or stateful) operation which * follows the last intermediate operation described by this * {@code PipelineHelper}. The {@code PipelineHelper} is passed to the * {@link TerminalOp#evaluateParallel(PipelineHelper, java.util.Spliterator)}, * {@link TerminalOp#evaluateSequential(PipelineHelper, java.util.Spliterator)}, * and {@link AbstractPipeline#opEvaluateParallel(PipelineHelper, java.util.Spliterator, * java.util.function.IntFunction)}, methods, which can use the * {@code PipelineHelper} to access information about the pipeline such as * head shape, stream flags, and size, and use the helper methods * such as {@link #wrapAndCopyInto(Sink, Spliterator)}, * {@link #copyInto(Sink, Spliterator)}, and {@link #wrapSink(Sink)} to execute * pipeline operations. * * @param type of output elements from the pipeline * @since 1.8 * @hide Visible for CTS testing only (OpenJDK8 tests). */ public abstract class PipelineHelper { /** * Gets the stream shape for the source of the pipeline segment. * * @return the stream shape for the source of the pipeline segment. */ abstract StreamShape getSourceShape(); /** * Gets the combined stream and operation flags for the output of the described * pipeline. This will incorporate stream flags from the stream source, all * the intermediate operations and the terminal operation. * * @return the combined stream and operation flags * @see StreamOpFlag */ public abstract int getStreamAndOpFlags(); /** * Returns the exact output size of the portion of the output resulting from * applying the pipeline stages described by this {@code PipelineHelper} to * the the portion of the input described by the provided * {@code Spliterator}, if known. If not known or known infinite, will * return {@code -1}. * * @apiNote * The exact output size is known if the {@code Spliterator} has the * {@code SIZED} characteristic, and the operation flags * {@link StreamOpFlag#SIZED} is known on the combined stream and operation * flags. * * @param spliterator the spliterator describing the relevant portion of the * source data * @return the exact size if known, or -1 if infinite or unknown */ abstract long exactOutputSizeIfKnown(Spliterator spliterator); /** * Applies the pipeline stages described by this {@code PipelineHelper} to * the provided {@code Spliterator} and send the results to the provided * {@code Sink}. * * @implSpec * The implementation behaves as if: *

{@code
     *     intoWrapped(wrapSink(sink), spliterator);
     * }
* * @param sink the {@code Sink} to receive the results * @param spliterator the spliterator describing the source input to process */ abstract> S wrapAndCopyInto(S sink, Spliterator spliterator); /** * Pushes elements obtained from the {@code Spliterator} into the provided * {@code Sink}. If the stream pipeline is known to have short-circuiting * stages in it (see {@link StreamOpFlag#SHORT_CIRCUIT}), the * {@link Sink#cancellationRequested()} is checked after each * element, stopping if cancellation is requested. * * @implSpec * This method conforms to the {@code Sink} protocol of calling * {@code Sink.begin} before pushing elements, via {@code Sink.accept}, and * calling {@code Sink.end} after all elements have been pushed. * * @param wrappedSink the destination {@code Sink} * @param spliterator the source {@code Spliterator} */ abstract void copyInto(Sink wrappedSink, Spliterator spliterator); /** * Pushes elements obtained from the {@code Spliterator} into the provided * {@code Sink}, checking {@link Sink#cancellationRequested()} after each * element, and stopping if cancellation is requested. * * @implSpec * This method conforms to the {@code Sink} protocol of calling * {@code Sink.begin} before pushing elements, via {@code Sink.accept}, and * calling {@code Sink.end} after all elements have been pushed or if * cancellation is requested. * * @param wrappedSink the destination {@code Sink} * @param spliterator the source {@code Spliterator} */ abstract void copyIntoWithCancel(Sink wrappedSink, Spliterator spliterator); /** * Takes a {@code Sink} that accepts elements of the output type of the * {@code PipelineHelper}, and wrap it with a {@code Sink} that accepts * elements of the input type and implements all the intermediate operations * described by this {@code PipelineHelper}, delivering the result into the * provided {@code Sink}. * * @param sink the {@code Sink} to receive the results * @return a {@code Sink} that implements the pipeline stages and sends * results to the provided {@code Sink} */ public abstract Sink wrapSink(Sink sink); /** * * @param spliterator * @param * @return */ abstract Spliterator wrapSpliterator(Spliterator spliterator); /** * Constructs a @{link Node.Builder} compatible with the output shape of * this {@code PipelineHelper}. * * @param exactSizeIfKnown if >=0 then a builder will be created that has a * fixed capacity of exactly sizeIfKnown elements; if < 0 then the * builder has variable capacity. A fixed capacity builder will fail * if an element is added after the builder has reached capacity. * @param generator a factory function for array instances * @return a {@code Node.Builder} compatible with the output shape of this * {@code PipelineHelper} */ abstract Node.Builder makeNodeBuilder(long exactSizeIfKnown, IntFunction generator); /** * Collects all output elements resulting from applying the pipeline stages * to the source {@code Spliterator} into a {@code Node}. * * @implNote * If the pipeline has no intermediate operations and the source is backed * by a {@code Node} then that {@code Node} will be returned (or flattened * and then returned). This reduces copying for a pipeline consisting of a * stateful operation followed by a terminal operation that returns an * array, such as: *
{@code
     *     stream.sorted().toArray();
     * }
* * @param spliterator the source {@code Spliterator} * @param flatten if true and the pipeline is a parallel pipeline then the * {@code Node} returned will contain no children, otherwise the * {@code Node} may represent the root in a tree that reflects the * shape of the computation tree. * @param generator a factory function for array instances * @return the {@code Node} containing all output elements */ public abstract Node evaluate(Spliterator spliterator, boolean flatten, IntFunction generator); }