| /* | |
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| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
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| * This code is free software; you can redistribute it and/or modify it | |
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| * particular file as subject to the "Classpath" exception as provided | |
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| * This code is distributed in the hope that it will be useful, but WITHOUT | |
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| * 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). | |
| * | |
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| */ | |
| package java.util.stream; | |
| import java.util.Spliterator; | |
| import java.util.function.IntFunction; | |
| /** | |
| * Helper class for executing <a href="package-summary.html#StreamOps"> | |
| * stream pipelines</a>, capturing all of the information about a stream | |
| * pipeline (output shape, intermediate operations, stream flags, parallelism, | |
| * etc) in one place. | |
| * | |
| * <p> | |
| * 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 <P_OUT> type of output elements from the pipeline | |
| * @since 1.8 | |
| */ | |
| abstract class PipelineHelper<P_OUT> { | |
| /** | |
| * 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 | |
| */ | |
| 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 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. The exact output size may differ from spliterator size, | |
| * if pipeline contains a slice operation. | |
| * | |
| * @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<P_IN> long exactOutputSizeIfKnown(Spliterator<P_IN> 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: | |
| * <pre>{@code | |
| * copyInto(wrapSink(sink), spliterator); | |
| * }</pre> | |
| * | |
| * @param sink the {@code Sink} to receive the results | |
| * @param spliterator the spliterator describing the source input to process | |
| */ | |
| abstract<P_IN, S extends Sink<P_OUT>> S wrapAndCopyInto(S sink, Spliterator<P_IN> 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<P_IN> void copyInto(Sink<P_IN> wrappedSink, Spliterator<P_IN> 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} | |
| * @return true if the cancellation was requested | |
| */ | |
| abstract <P_IN> boolean copyIntoWithCancel(Sink<P_IN> wrappedSink, Spliterator<P_IN> 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} | |
| */ | |
| abstract<P_IN> Sink<P_IN> wrapSink(Sink<P_OUT> sink); | |
| /** | |
| * | |
| * @param spliterator | |
| * @param <P_IN> | |
| * @return | |
| */ | |
| abstract<P_IN> Spliterator<P_OUT> wrapSpliterator(Spliterator<P_IN> 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<P_OUT> makeNodeBuilder(long exactSizeIfKnown, | |
| IntFunction<P_OUT[]> 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: | |
| * <pre>{@code | |
| * stream.sorted().toArray(); | |
| * }</pre> | |
| * | |
| * @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 | |
| */ | |
| abstract<P_IN> Node<P_OUT> evaluate(Spliterator<P_IN> spliterator, | |
| boolean flatten, | |
| IntFunction<P_OUT[]> generator); | |
| } |