211 lines
9.3 KiB
Java
211 lines
9.3 KiB
Java
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/*
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* Copyright (c) 2012, 2021, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.util.stream;
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import java.util.Spliterator;
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import java.util.function.IntFunction;
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/**
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* Helper class for executing <a href="package-summary.html#StreamOps">
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* stream pipelines</a>, capturing all of the information about a stream
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* pipeline (output shape, intermediate operations, stream flags, parallelism,
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* etc) in one place.
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*
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* <p>
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* A {@code PipelineHelper} describes the initial segment of a stream pipeline,
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* including its source, intermediate operations, and may additionally
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* incorporate information about the terminal (or stateful) operation which
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* follows the last intermediate operation described by this
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* {@code PipelineHelper}. The {@code PipelineHelper} is passed to the
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* {@link TerminalOp#evaluateParallel(PipelineHelper, java.util.Spliterator)},
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* {@link TerminalOp#evaluateSequential(PipelineHelper, java.util.Spliterator)},
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* and {@link AbstractPipeline#opEvaluateParallel(PipelineHelper, java.util.Spliterator,
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* java.util.function.IntFunction)}, methods, which can use the
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* {@code PipelineHelper} to access information about the pipeline such as
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* head shape, stream flags, and size, and use the helper methods
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* such as {@link #wrapAndCopyInto(Sink, Spliterator)},
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* {@link #copyInto(Sink, Spliterator)}, and {@link #wrapSink(Sink)} to execute
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* pipeline operations.
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*
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* @param <P_OUT> type of output elements from the pipeline
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* @since 1.8
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* @hide Visible for CTS testing only (OpenJDK8 tests).
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*/
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// Android-changed: Made public for CTS tests only.
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public abstract class PipelineHelper<P_OUT> {
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/**
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* Gets the stream shape for the source of the pipeline segment.
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*
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* @return the stream shape for the source of the pipeline segment.
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*/
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abstract StreamShape getSourceShape();
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/**
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* Gets the combined stream and operation flags for the output of the described
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* pipeline. This will incorporate stream flags from the stream source, all
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* the intermediate operations and the terminal operation.
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*
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* @return the combined stream and operation flags
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* @see StreamOpFlag
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*/
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// Android-changed: Made public for CTS tests only.
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public abstract int getStreamAndOpFlags();
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/**
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* Returns the exact output size of the portion of the output resulting from
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* applying the pipeline stages described by this {@code PipelineHelper} to
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* the portion of the input described by the provided
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* {@code Spliterator}, if known. If not known or known infinite, will
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* return {@code -1}.
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*
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* @apiNote
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* The exact output size is known if the {@code Spliterator} has the
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* {@code SIZED} characteristic, and the operation flags
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* {@link StreamOpFlag#SIZED} is known on the combined stream and operation
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* flags. The exact output size may differ from spliterator size,
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* if pipeline contains a slice operation.
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*
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* @param spliterator the spliterator describing the relevant portion of the
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* source data
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* @return the exact size if known, or -1 if infinite or unknown
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*/
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abstract<P_IN> long exactOutputSizeIfKnown(Spliterator<P_IN> spliterator);
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/**
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* Applies the pipeline stages described by this {@code PipelineHelper} to
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* the provided {@code Spliterator} and send the results to the provided
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* {@code Sink}.
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*
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* @implSpec
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* The implementation behaves as if:
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* <pre>{@code
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* copyInto(wrapSink(sink), spliterator);
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* }</pre>
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*
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* @param sink the {@code Sink} to receive the results
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* @param spliterator the spliterator describing the source input to process
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*/
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abstract<P_IN, S extends Sink<P_OUT>> S wrapAndCopyInto(S sink, Spliterator<P_IN> spliterator);
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/**
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* Pushes elements obtained from the {@code Spliterator} into the provided
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* {@code Sink}. If the stream pipeline is known to have short-circuiting
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* stages in it (see {@link StreamOpFlag#SHORT_CIRCUIT}), the
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* {@link Sink#cancellationRequested()} is checked after each
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* element, stopping if cancellation is requested.
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*
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* @implSpec
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* This method conforms to the {@code Sink} protocol of calling
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* {@code Sink.begin} before pushing elements, via {@code Sink.accept}, and
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* calling {@code Sink.end} after all elements have been pushed.
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*
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* @param wrappedSink the destination {@code Sink}
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* @param spliterator the source {@code Spliterator}
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*/
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abstract<P_IN> void copyInto(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator);
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/**
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* Pushes elements obtained from the {@code Spliterator} into the provided
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* {@code Sink}, checking {@link Sink#cancellationRequested()} after each
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* element, and stopping if cancellation is requested.
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*
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* @implSpec
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* This method conforms to the {@code Sink} protocol of calling
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* {@code Sink.begin} before pushing elements, via {@code Sink.accept}, and
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* calling {@code Sink.end} after all elements have been pushed or if
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* cancellation is requested.
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*
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* @param wrappedSink the destination {@code Sink}
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* @param spliterator the source {@code Spliterator}
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* @return true if the cancellation was requested
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*/
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abstract <P_IN> boolean copyIntoWithCancel(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator);
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/**
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* Takes a {@code Sink} that accepts elements of the output type of the
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* {@code PipelineHelper}, and wrap it with a {@code Sink} that accepts
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* elements of the input type and implements all the intermediate operations
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* described by this {@code PipelineHelper}, delivering the result into the
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* provided {@code Sink}.
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*
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* @param sink the {@code Sink} to receive the results
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* @return a {@code Sink} that implements the pipeline stages and sends
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* results to the provided {@code Sink}
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*/
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// Android-changed: Made public for CTS tests only.
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public abstract<P_IN> Sink<P_IN> wrapSink(Sink<P_OUT> sink);
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/**
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*
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* @param spliterator
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* @param <P_IN>
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* @return
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*/
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abstract<P_IN> Spliterator<P_OUT> wrapSpliterator(Spliterator<P_IN> spliterator);
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/**
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* Constructs a @{link Node.Builder} compatible with the output shape of
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* this {@code PipelineHelper}.
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*
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* @param exactSizeIfKnown if >=0 then a builder will be created that has a
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* fixed capacity of exactly sizeIfKnown elements; if < 0 then the
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* builder has variable capacity. A fixed capacity builder will fail
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* if an element is added after the builder has reached capacity.
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* @param generator a factory function for array instances
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* @return a {@code Node.Builder} compatible with the output shape of this
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* {@code PipelineHelper}
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*/
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abstract Node.Builder<P_OUT> makeNodeBuilder(long exactSizeIfKnown,
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IntFunction<P_OUT[]> generator);
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/**
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* Collects all output elements resulting from applying the pipeline stages
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* to the source {@code Spliterator} into a {@code Node}.
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*
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* @implNote
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* If the pipeline has no intermediate operations and the source is backed
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* by a {@code Node} then that {@code Node} will be returned (or flattened
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* and then returned). This reduces copying for a pipeline consisting of a
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* stateful operation followed by a terminal operation that returns an
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* array, such as:
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* <pre>{@code
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* stream.sorted().toArray();
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* }</pre>
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*
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* @param spliterator the source {@code Spliterator}
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* @param flatten if true and the pipeline is a parallel pipeline then the
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* {@code Node} returned will contain no children, otherwise the
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* {@code Node} may represent the root in a tree that reflects the
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* shape of the computation tree.
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* @param generator a factory function for array instances
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* @return the {@code Node} containing all output elements
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*/
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// Android-changed: Made public for CTS tests only.
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public abstract<P_IN> Node<P_OUT> evaluate(Spliterator<P_IN> spliterator,
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boolean flatten,
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IntFunction<P_OUT[]> generator);
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}
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