author | henryjen |
Mon, 08 Jul 2013 15:46:26 -0400 | |
changeset 18825 | 06636235cd12 |
parent 18789 | b518cd4045bc |
child 19220 | d3d40ccb544e |
permissions | -rw-r--r-- |
17182 | 1 |
/* |
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* Copyright (c) 2012, 2013, 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.Objects; |
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import java.util.Spliterator; |
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import java.util.function.IntFunction; |
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import java.util.function.Supplier; |
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/** |
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* Abstract base class for "pipeline" classes, which are the core |
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* implementations of the Stream interface and its primitive specializations. |
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* Manages construction and evaluation of stream pipelines. |
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* |
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* <p>An {@code AbstractPipeline} represents an initial portion of a stream |
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* pipeline, encapsulating a stream source and zero or more intermediate |
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* operations. The individual {@code AbstractPipeline} objects are often |
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* referred to as <em>stages</em>, where each stage describes either the stream |
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* source or an intermediate operation. |
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* |
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* <p>A concrete intermediate stage is generally built from an |
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* {@code AbstractPipeline}, a shape-specific pipeline class which extends it |
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* (e.g., {@code IntPipeline}) which is also abstract, and an operation-specific |
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* concrete class which extends that. {@code AbstractPipeline} contains most of |
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* the mechanics of evaluating the pipeline, and implements methods that will be |
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* used by the operation; the shape-specific classes add helper methods for |
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* dealing with collection of results into the appropriate shape-specific |
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* containers. |
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* |
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* <p>After chaining a new intermediate operation, or executing a terminal |
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* operation, the stream is considered to be consumed, and no more intermediate |
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* or terminal operations are permitted on this stream instance. |
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* |
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* @implNote |
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* <p>For sequential streams, and parallel streams without |
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* <a href="package-summary.html#StreamOps">stateful intermediate |
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* operations</a>, parallel streams, pipeline evaluation is done in a single |
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* pass that "jams" all the operations together. For parallel streams with |
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* stateful operations, execution is divided into segments, where each |
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* stateful operations marks the end of a segment, and each segment is |
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* evaluated separately and the result used as the input to the next |
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* segment. In all cases, the source data is not consumed until a terminal |
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* operation begins. |
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* |
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* @param <E_IN> type of input elements |
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* @param <E_OUT> type of output elements |
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* @param <S> type of the subclass implementing {@code BaseStream} |
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* @since 1.8 |
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*/ |
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abstract class AbstractPipeline<E_IN, E_OUT, S extends BaseStream<E_OUT, S>> |
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extends PipelineHelper<E_OUT> implements BaseStream<E_OUT, S> { |
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/** |
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* Backlink to the head of the pipeline chain (self if this is the source |
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* stage). |
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*/ |
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private final AbstractPipeline sourceStage; |
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/** |
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* The "upstream" pipeline, or null if this is the source stage. |
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*/ |
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private final AbstractPipeline previousStage; |
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/** |
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* The operation flags for the intermediate operation represented by this |
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* pipeline object. |
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*/ |
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protected final int sourceOrOpFlags; |
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/** |
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* The next stage in the pipeline, or null if this is the last stage. |
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* Effectively final at the point of linking to the next pipeline. |
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*/ |
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private AbstractPipeline nextStage; |
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/** |
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* The number of intermediate operations between this pipeline object |
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* and the stream source if sequential, or the previous stateful if parallel. |
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* Valid at the point of pipeline preparation for evaluation. |
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*/ |
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private int depth; |
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/** |
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* The combined source and operation flags for the source and all operations |
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* up to and including the operation represented by this pipeline object. |
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* Valid at the point of pipeline preparation for evaluation. |
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*/ |
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private int combinedFlags; |
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/** |
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* The source spliterator. Only valid for the head pipeline. |
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* Before the pipeline is consumed if non-null then {@code sourceSupplier} |
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* must be null. After the pipeline is consumed if non-null then is set to |
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* null. |
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*/ |
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private Spliterator<?> sourceSpliterator; |
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/** |
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* The source supplier. Only valid for the head pipeline. Before the |
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* pipeline is consumed if non-null then {@code sourceSpliterator} must be |
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* null. After the pipeline is consumed if non-null then is set to null. |
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*/ |
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private Supplier<? extends Spliterator<?>> sourceSupplier; |
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/** |
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* True if this pipeline has been linked or consumed |
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*/ |
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private boolean linkedOrConsumed; |
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/** |
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* True if there are any stateful ops in the pipeline; only valid for the |
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* source stage. |
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*/ |
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private boolean sourceAnyStateful; |
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/** |
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* True if pipeline is parallel, otherwise the pipeline is sequential; only |
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* valid for the source stage. |
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*/ |
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private boolean parallel; |
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/** |
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* Constructor for the head of a stream pipeline. |
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* |
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* @param source {@code Supplier<Spliterator>} describing the stream source |
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* @param sourceFlags The source flags for the stream source, described in |
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* {@link StreamOpFlag} |
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* @param parallel True if the pipeline is parallel |
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*/ |
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AbstractPipeline(Supplier<? extends Spliterator<?>> source, |
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int sourceFlags, boolean parallel) { |
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this.previousStage = null; |
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this.sourceSupplier = source; |
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this.sourceStage = this; |
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this.sourceOrOpFlags = sourceFlags & StreamOpFlag.STREAM_MASK; |
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// The following is an optimization of: |
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// StreamOpFlag.combineOpFlags(sourceOrOpFlags, StreamOpFlag.INITIAL_OPS_VALUE); |
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this.combinedFlags = (~(sourceOrOpFlags << 1)) & StreamOpFlag.INITIAL_OPS_VALUE; |
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this.depth = 0; |
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this.parallel = parallel; |
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} |
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/** |
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* Constructor for the head of a stream pipeline. |
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* |
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* @param source {@code Spliterator} describing the stream source |
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* @param sourceFlags the source flags for the stream source, described in |
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* {@link StreamOpFlag} |
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* @param parallel {@code true} if the pipeline is parallel |
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*/ |
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AbstractPipeline(Spliterator<?> source, |
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int sourceFlags, boolean parallel) { |
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this.previousStage = null; |
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this.sourceSpliterator = source; |
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this.sourceStage = this; |
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this.sourceOrOpFlags = sourceFlags & StreamOpFlag.STREAM_MASK; |
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// The following is an optimization of: |
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// StreamOpFlag.combineOpFlags(sourceOrOpFlags, StreamOpFlag.INITIAL_OPS_VALUE); |
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this.combinedFlags = (~(sourceOrOpFlags << 1)) & StreamOpFlag.INITIAL_OPS_VALUE; |
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this.depth = 0; |
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this.parallel = parallel; |
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} |
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/** |
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* Constructor for appending an intermediate operation stage onto an |
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* existing pipeline. |
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* |
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* @param previousStage the upstream pipeline stage |
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* @param opFlags the operation flags for the new stage, described in |
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* {@link StreamOpFlag} |
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*/ |
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AbstractPipeline(AbstractPipeline<?, E_IN, ?> previousStage, int opFlags) { |
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if (previousStage.linkedOrConsumed) |
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throw new IllegalStateException("stream has already been operated upon"); |
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previousStage.linkedOrConsumed = true; |
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previousStage.nextStage = this; |
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this.previousStage = previousStage; |
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this.sourceOrOpFlags = opFlags & StreamOpFlag.OP_MASK; |
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this.combinedFlags = StreamOpFlag.combineOpFlags(opFlags, previousStage.combinedFlags); |
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this.sourceStage = previousStage.sourceStage; |
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if (opIsStateful()) |
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sourceStage.sourceAnyStateful = true; |
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this.depth = previousStage.depth + 1; |
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} |
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// Terminal evaluation methods |
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/** |
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* Evaluate the pipeline with a terminal operation to produce a result. |
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* |
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* @param <R> the type of result |
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* @param terminalOp the terminal operation to be applied to the pipeline. |
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* @return the result |
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*/ |
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final <R> R evaluate(TerminalOp<E_OUT, R> terminalOp) { |
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assert getOutputShape() == terminalOp.inputShape(); |
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if (linkedOrConsumed) |
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throw new IllegalStateException("stream has already been operated upon"); |
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linkedOrConsumed = true; |
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return isParallel() |
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? (R) terminalOp.evaluateParallel(this, sourceSpliterator(terminalOp.getOpFlags())) |
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: (R) terminalOp.evaluateSequential(this, sourceSpliterator(terminalOp.getOpFlags())); |
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} |
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/** |
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* Collect the elements output from the pipeline stage. |
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* |
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* @param generator the array generator to be used to create array instances |
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* @return a flat array-backed Node that holds the collected output elements |
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*/ |
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final Node<E_OUT> evaluateToArrayNode(IntFunction<E_OUT[]> generator) { |
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if (linkedOrConsumed) |
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throw new IllegalStateException("stream has already been operated upon"); |
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linkedOrConsumed = true; |
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// If the last intermediate operation is stateful then |
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// evaluate directly to avoid an extra collection step |
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if (isParallel() && previousStage != null && opIsStateful()) { |
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return opEvaluateParallel(previousStage, previousStage.sourceSpliterator(0), generator); |
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} |
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else { |
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return evaluate(sourceSpliterator(0), true, generator); |
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} |
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} |
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/** |
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* Gets the source stage spliterator if this pipeline stage is the source |
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* stage. The pipeline is consumed after this method is called and |
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* returns successfully. |
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* |
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* @return the source stage spliterator |
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* @throws IllegalStateException if this pipeline stage is not the source |
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* stage. |
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*/ |
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final Spliterator<E_OUT> sourceStageSpliterator() { |
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if (this != sourceStage) |
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throw new IllegalStateException(); |
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if (linkedOrConsumed) |
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throw new IllegalStateException("stream has already been operated upon"); |
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linkedOrConsumed = true; |
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if (sourceStage.sourceSpliterator != null) { |
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Spliterator<E_OUT> s = sourceStage.sourceSpliterator; |
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sourceStage.sourceSpliterator = null; |
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return s; |
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} |
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else if (sourceStage.sourceSupplier != null) { |
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Spliterator<E_OUT> s = (Spliterator<E_OUT>) sourceStage.sourceSupplier.get(); |
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sourceStage.sourceSupplier = null; |
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return s; |
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} |
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else { |
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throw new IllegalStateException("source already consumed"); |
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} |
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} |
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// BaseStream |
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@Override |
17182 | 285 |
public final S sequential() { |
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sourceStage.parallel = false; |
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return (S) this; |
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} |
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@Override |
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public final S parallel() { |
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sourceStage.parallel = true; |
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return (S) this; |
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} |
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// Primitive specialization use co-variant overrides, hence is not final |
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@Override |
17182 | 298 |
public Spliterator<E_OUT> spliterator() { |
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if (linkedOrConsumed) |
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throw new IllegalStateException("stream has already been operated upon"); |
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linkedOrConsumed = true; |
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if (this == sourceStage) { |
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if (sourceStage.sourceSpliterator != null) { |
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Spliterator<E_OUT> s = sourceStage.sourceSpliterator; |
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sourceStage.sourceSpliterator = null; |
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return s; |
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} |
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else if (sourceStage.sourceSupplier != null) { |
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Supplier<Spliterator<E_OUT>> s = sourceStage.sourceSupplier; |
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sourceStage.sourceSupplier = null; |
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return lazySpliterator(s); |
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} |
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else { |
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throw new IllegalStateException("source already consumed"); |
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} |
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} |
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else { |
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return wrap(this, () -> sourceSpliterator(0), isParallel()); |
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} |
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} |
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||
18789 | 323 |
@Override |
17182 | 324 |
public final boolean isParallel() { |
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return sourceStage.parallel; |
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} |
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/** |
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* Returns the composition of stream flags of the stream source and all |
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* intermediate operations. |
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* |
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* @return the composition of stream flags of the stream source and all |
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* intermediate operations |
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* @see StreamOpFlag |
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*/ |
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final int getStreamFlags() { |
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return StreamOpFlag.toStreamFlags(combinedFlags); |
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} |
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/** |
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* Prepare the pipeline for a parallel execution. As the pipeline is built, |
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* the flags and depth indicators are set up for a sequential execution. |
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* If the execution is parallel, and there are any stateful operations, then |
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* some of these need to be adjusted, as well as adjusting for flags from |
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* the terminal operation (such as back-propagating UNORDERED). |
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* Need not be called for a sequential execution. |
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* |
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* @param terminalFlags Operation flags for the terminal operation |
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*/ |
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private void parallelPrepare(int terminalFlags) { |
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AbstractPipeline backPropagationHead = sourceStage; |
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if (sourceStage.sourceAnyStateful) { |
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int depth = 1; |
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for (AbstractPipeline u = sourceStage, p = sourceStage.nextStage; |
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p != null; |
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u = p, p = p.nextStage) { |
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int thisOpFlags = p.sourceOrOpFlags; |
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if (p.opIsStateful()) { |
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// If the stateful operation is a short-circuit operation |
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361 |
// then move the back propagation head forwards |
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// NOTE: there are no size-injecting ops |
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if (StreamOpFlag.SHORT_CIRCUIT.isKnown(thisOpFlags)) { |
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backPropagationHead = p; |
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18572
53b8b8c30086
8012987: Optimizations for Stream.limit/substream
psandoz
parents:
17182
diff
changeset
|
365 |
// Clear the short circuit flag for next pipeline stage |
53b8b8c30086
8012987: Optimizations for Stream.limit/substream
psandoz
parents:
17182
diff
changeset
|
366 |
// This stage encapsulates short-circuiting, the next |
53b8b8c30086
8012987: Optimizations for Stream.limit/substream
psandoz
parents:
17182
diff
changeset
|
367 |
// stage may not have any short-circuit operations, and |
53b8b8c30086
8012987: Optimizations for Stream.limit/substream
psandoz
parents:
17182
diff
changeset
|
368 |
// if so spliterator.forEachRemaining should be be used |
53b8b8c30086
8012987: Optimizations for Stream.limit/substream
psandoz
parents:
17182
diff
changeset
|
369 |
// for traversal |
53b8b8c30086
8012987: Optimizations for Stream.limit/substream
psandoz
parents:
17182
diff
changeset
|
370 |
thisOpFlags = thisOpFlags & ~StreamOpFlag.IS_SHORT_CIRCUIT; |
17182 | 371 |
} |
372 |
||
373 |
depth = 0; |
|
374 |
// The following injects size, it is equivalent to: |
|
375 |
// StreamOpFlag.combineOpFlags(StreamOpFlag.IS_SIZED, p.combinedFlags); |
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376 |
thisOpFlags = (thisOpFlags & ~StreamOpFlag.NOT_SIZED) | StreamOpFlag.IS_SIZED; |
|
377 |
} |
|
378 |
p.depth = depth++; |
|
379 |
p.combinedFlags = StreamOpFlag.combineOpFlags(thisOpFlags, u.combinedFlags); |
|
380 |
} |
|
381 |
} |
|
382 |
||
383 |
// Apply the upstream terminal flags |
|
384 |
if (terminalFlags != 0) { |
|
385 |
int upstreamTerminalFlags = terminalFlags & StreamOpFlag.UPSTREAM_TERMINAL_OP_MASK; |
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386 |
for (AbstractPipeline p = backPropagationHead; p.nextStage != null; p = p.nextStage) { |
|
387 |
p.combinedFlags = StreamOpFlag.combineOpFlags(upstreamTerminalFlags, p.combinedFlags); |
|
388 |
} |
|
389 |
||
390 |
combinedFlags = StreamOpFlag.combineOpFlags(terminalFlags, combinedFlags); |
|
391 |
} |
|
392 |
} |
|
393 |
||
394 |
/** |
|
395 |
* Get the source spliterator for this pipeline stage. For a sequential or |
|
396 |
* stateless parallel pipeline, this is the source spliterator. For a |
|
397 |
* stateful parallel pipeline, this is a spliterator describing the results |
|
398 |
* of all computations up to and including the most recent stateful |
|
399 |
* operation. |
|
400 |
*/ |
|
401 |
private Spliterator<?> sourceSpliterator(int terminalFlags) { |
|
402 |
// Get the source spliterator of the pipeline |
|
403 |
Spliterator<?> spliterator = null; |
|
404 |
if (sourceStage.sourceSpliterator != null) { |
|
405 |
spliterator = sourceStage.sourceSpliterator; |
|
406 |
sourceStage.sourceSpliterator = null; |
|
407 |
} |
|
408 |
else if (sourceStage.sourceSupplier != null) { |
|
409 |
spliterator = (Spliterator<?>) sourceStage.sourceSupplier.get(); |
|
410 |
sourceStage.sourceSupplier = null; |
|
411 |
} |
|
412 |
else { |
|
413 |
throw new IllegalStateException("source already consumed"); |
|
414 |
} |
|
415 |
||
416 |
if (isParallel()) { |
|
417 |
// @@@ Merge parallelPrepare with the loop below and use the |
|
418 |
// spliterator characteristics to determine if SIZED |
|
419 |
// should be injected |
|
420 |
parallelPrepare(terminalFlags); |
|
421 |
||
422 |
// Adapt the source spliterator, evaluating each stateful op |
|
423 |
// in the pipeline up to and including this pipeline stage |
|
424 |
for (AbstractPipeline u = sourceStage, p = sourceStage.nextStage, e = this; |
|
425 |
u != e; |
|
426 |
u = p, p = p.nextStage) { |
|
427 |
||
428 |
if (p.opIsStateful()) { |
|
429 |
spliterator = p.opEvaluateParallelLazy(u, spliterator); |
|
430 |
} |
|
431 |
} |
|
432 |
} |
|
433 |
else if (terminalFlags != 0) { |
|
434 |
combinedFlags = StreamOpFlag.combineOpFlags(terminalFlags, combinedFlags); |
|
435 |
} |
|
436 |
||
437 |
return spliterator; |
|
438 |
} |
|
439 |
||
440 |
||
441 |
// PipelineHelper |
|
442 |
||
443 |
@Override |
|
18572
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444 |
final StreamShape getSourceShape() { |
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|
445 |
AbstractPipeline p = AbstractPipeline.this; |
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|
446 |
while (p.depth > 0) { |
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|
447 |
p = p.previousStage; |
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|
448 |
} |
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449 |
return p.getOutputShape(); |
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|
450 |
} |
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|
451 |
|
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452 |
@Override |
17182 | 453 |
final <P_IN> long exactOutputSizeIfKnown(Spliterator<P_IN> spliterator) { |
454 |
return StreamOpFlag.SIZED.isKnown(getStreamAndOpFlags()) ? spliterator.getExactSizeIfKnown() : -1; |
|
455 |
} |
|
456 |
||
457 |
@Override |
|
458 |
final <P_IN, S extends Sink<E_OUT>> S wrapAndCopyInto(S sink, Spliterator<P_IN> spliterator) { |
|
459 |
copyInto(wrapSink(Objects.requireNonNull(sink)), spliterator); |
|
460 |
return sink; |
|
461 |
} |
|
462 |
||
463 |
@Override |
|
464 |
final <P_IN> void copyInto(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator) { |
|
465 |
Objects.requireNonNull(wrappedSink); |
|
466 |
||
467 |
if (!StreamOpFlag.SHORT_CIRCUIT.isKnown(getStreamAndOpFlags())) { |
|
468 |
wrappedSink.begin(spliterator.getExactSizeIfKnown()); |
|
469 |
spliterator.forEachRemaining(wrappedSink); |
|
470 |
wrappedSink.end(); |
|
471 |
} |
|
472 |
else { |
|
473 |
copyIntoWithCancel(wrappedSink, spliterator); |
|
474 |
} |
|
475 |
} |
|
476 |
||
477 |
@Override |
|
478 |
final <P_IN> void copyIntoWithCancel(Sink<P_IN> wrappedSink, Spliterator<P_IN> spliterator) { |
|
479 |
AbstractPipeline p = AbstractPipeline.this; |
|
480 |
while (p.depth > 0) { |
|
481 |
p = p.previousStage; |
|
482 |
} |
|
483 |
wrappedSink.begin(spliterator.getExactSizeIfKnown()); |
|
484 |
p.forEachWithCancel(spliterator, wrappedSink); |
|
485 |
wrappedSink.end(); |
|
486 |
} |
|
487 |
||
488 |
@Override |
|
489 |
final int getStreamAndOpFlags() { |
|
490 |
return combinedFlags; |
|
491 |
} |
|
492 |
||
493 |
final boolean isOrdered() { |
|
494 |
return StreamOpFlag.ORDERED.isKnown(combinedFlags); |
|
495 |
} |
|
496 |
||
497 |
@Override |
|
498 |
final <P_IN> Sink<P_IN> wrapSink(Sink<E_OUT> sink) { |
|
499 |
Objects.requireNonNull(sink); |
|
500 |
||
501 |
for (AbstractPipeline p=AbstractPipeline.this; p.depth > 0; p=p.previousStage) { |
|
502 |
sink = p.opWrapSink(p.previousStage.combinedFlags, sink); |
|
503 |
} |
|
504 |
return (Sink<P_IN>) sink; |
|
505 |
} |
|
506 |
||
507 |
@Override |
|
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508 |
final <P_IN> Spliterator<E_OUT> wrapSpliterator(Spliterator<P_IN> sourceSpliterator) { |
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|
509 |
if (depth == 0) { |
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|
510 |
return (Spliterator<E_OUT>) sourceSpliterator; |
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|
511 |
} |
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|
512 |
else { |
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|
513 |
return wrap(this, () -> sourceSpliterator, isParallel()); |
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|
514 |
} |
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|
515 |
} |
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|
516 |
|
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|
517 |
@Override |
17182 | 518 |
@SuppressWarnings("unchecked") |
519 |
final <P_IN> Node<E_OUT> evaluate(Spliterator<P_IN> spliterator, |
|
520 |
boolean flatten, |
|
521 |
IntFunction<E_OUT[]> generator) { |
|
522 |
if (isParallel()) { |
|
523 |
// @@@ Optimize if op of this pipeline stage is a stateful op |
|
524 |
return evaluateToNode(this, spliterator, flatten, generator); |
|
525 |
} |
|
526 |
else { |
|
527 |
Node.Builder<E_OUT> nb = makeNodeBuilder( |
|
528 |
exactOutputSizeIfKnown(spliterator), generator); |
|
529 |
return wrapAndCopyInto(nb, spliterator).build(); |
|
530 |
} |
|
531 |
} |
|
532 |
||
533 |
||
534 |
// Shape-specific abstract methods, implemented by XxxPipeline classes |
|
535 |
||
536 |
/** |
|
537 |
* Get the output shape of the pipeline. If the pipeline is the head, |
|
538 |
* then it's output shape corresponds to the shape of the source. |
|
539 |
* Otherwise, it's output shape corresponds to the output shape of the |
|
540 |
* associated operation. |
|
541 |
* |
|
542 |
* @return the output shape |
|
543 |
*/ |
|
544 |
abstract StreamShape getOutputShape(); |
|
545 |
||
546 |
/** |
|
547 |
* Collect elements output from a pipeline into a Node that holds elements |
|
548 |
* of this shape. |
|
549 |
* |
|
550 |
* @param helper the pipeline helper describing the pipeline stages |
|
551 |
* @param spliterator the source spliterator |
|
552 |
* @param flattenTree true if the returned node should be flattened |
|
553 |
* @param generator the array generator |
|
554 |
* @return a Node holding the output of the pipeline |
|
555 |
*/ |
|
556 |
abstract <P_IN> Node<E_OUT> evaluateToNode(PipelineHelper<E_OUT> helper, |
|
557 |
Spliterator<P_IN> spliterator, |
|
558 |
boolean flattenTree, |
|
559 |
IntFunction<E_OUT[]> generator); |
|
560 |
||
561 |
/** |
|
562 |
* Create a spliterator that wraps a source spliterator, compatible with |
|
563 |
* this stream shape, and operations associated with a {@link |
|
564 |
* PipelineHelper}. |
|
565 |
* |
|
566 |
* @param ph the pipeline helper describing the pipeline stages |
|
567 |
* @param supplier the supplier of a spliterator |
|
568 |
* @return a wrapping spliterator compatible with this shape |
|
569 |
*/ |
|
570 |
abstract <P_IN> Spliterator<E_OUT> wrap(PipelineHelper<E_OUT> ph, |
|
571 |
Supplier<Spliterator<P_IN>> supplier, |
|
572 |
boolean isParallel); |
|
573 |
||
574 |
/** |
|
575 |
* Create a lazy spliterator that wraps and obtains the supplied the |
|
576 |
* spliterator when a method is invoked on the lazy spliterator. |
|
577 |
* @param supplier the supplier of a spliterator |
|
578 |
*/ |
|
579 |
abstract Spliterator<E_OUT> lazySpliterator(Supplier<? extends Spliterator<E_OUT>> supplier); |
|
580 |
||
581 |
/** |
|
582 |
* Traverse the elements of a spliterator compatible with this stream shape, |
|
583 |
* pushing those elements into a sink. If the sink requests cancellation, |
|
584 |
* no further elements will be pulled or pushed. |
|
585 |
* |
|
586 |
* @param spliterator the spliterator to pull elements from |
|
587 |
* @param sink the sink to push elements to |
|
588 |
*/ |
|
589 |
abstract void forEachWithCancel(Spliterator<E_OUT> spliterator, Sink<E_OUT> sink); |
|
590 |
||
591 |
/** |
|
592 |
* Make a node builder compatible with this stream shape. |
|
593 |
* |
|
594 |
* @param exactSizeIfKnown if {@literal >=0}, then a node builder will be created that |
|
595 |
* has a fixed capacity of at most sizeIfKnown elements. If {@literal < 0}, |
|
596 |
* then the node builder has an unfixed capacity. A fixed capacity node |
|
597 |
* builder will throw exceptions if an element is added after builder has |
|
598 |
* reached capacity, or is built before the builder has reached capacity. |
|
599 |
* @param generator the array generator to be used to create instances of a |
|
600 |
* T[] array. For implementations supporting primitive nodes, this parameter |
|
601 |
* may be ignored. |
|
602 |
* @return a node builder |
|
603 |
*/ |
|
604 |
abstract Node.Builder<E_OUT> makeNodeBuilder(long exactSizeIfKnown, |
|
605 |
IntFunction<E_OUT[]> generator); |
|
606 |
||
607 |
||
608 |
// Op-specific abstract methods, implemented by the operation class |
|
609 |
||
610 |
/** |
|
611 |
* Returns whether this operation is stateful or not. If it is stateful, |
|
612 |
* then the method |
|
613 |
* {@link #opEvaluateParallel(PipelineHelper, java.util.Spliterator, java.util.function.IntFunction)} |
|
614 |
* must be overridden. |
|
615 |
* |
|
616 |
* @return {@code true} if this operation is stateful |
|
617 |
*/ |
|
618 |
abstract boolean opIsStateful(); |
|
619 |
||
620 |
/** |
|
621 |
* Accepts a {@code Sink} which will receive the results of this operation, |
|
622 |
* and return a {@code Sink} which accepts elements of the input type of |
|
623 |
* this operation and which performs the operation, passing the results to |
|
624 |
* the provided {@code Sink}. |
|
625 |
* |
|
626 |
* @apiNote |
|
627 |
* The implementation may use the {@code flags} parameter to optimize the |
|
628 |
* sink wrapping. For example, if the input is already {@code DISTINCT}, |
|
629 |
* the implementation for the {@code Stream#distinct()} method could just |
|
630 |
* return the sink it was passed. |
|
631 |
* |
|
632 |
* @param flags The combined stream and operation flags up to, but not |
|
633 |
* including, this operation |
|
634 |
* @param sink sink to which elements should be sent after processing |
|
635 |
* @return a sink which accepts elements, perform the operation upon |
|
636 |
* each element, and passes the results (if any) to the provided |
|
637 |
* {@code Sink}. |
|
638 |
*/ |
|
639 |
abstract Sink<E_IN> opWrapSink(int flags, Sink<E_OUT> sink); |
|
640 |
||
641 |
/** |
|
642 |
* Performs a parallel evaluation of the operation using the specified |
|
643 |
* {@code PipelineHelper} which describes the upstream intermediate |
|
644 |
* operations. Only called on stateful operations. If {@link |
|
645 |
* #opIsStateful()} returns true then implementations must override the |
|
646 |
* default implementation. |
|
647 |
* |
|
648 |
* @implSpec The default implementation always throw |
|
649 |
* {@code UnsupportedOperationException}. |
|
650 |
* |
|
651 |
* @param helper the pipeline helper describing the pipeline stages |
|
652 |
* @param spliterator the source {@code Spliterator} |
|
653 |
* @param generator the array generator |
|
654 |
* @return a {@code Node} describing the result of the evaluation |
|
655 |
*/ |
|
656 |
<P_IN> Node<E_OUT> opEvaluateParallel(PipelineHelper<E_OUT> helper, |
|
657 |
Spliterator<P_IN> spliterator, |
|
658 |
IntFunction<E_OUT[]> generator) { |
|
659 |
throw new UnsupportedOperationException("Parallel evaluation is not supported"); |
|
660 |
} |
|
661 |
||
662 |
/** |
|
663 |
* Returns a {@code Spliterator} describing a parallel evaluation of the |
|
664 |
* operation, using the specified {@code PipelineHelper} which describes the |
|
665 |
* upstream intermediate operations. Only called on stateful operations. |
|
666 |
* It is not necessary (though acceptable) to do a full computation of the |
|
667 |
* result here; it is preferable, if possible, to describe the result via a |
|
668 |
* lazily evaluated spliterator. |
|
669 |
* |
|
670 |
* @implSpec The default implementation behaves as if: |
|
671 |
* <pre>{@code |
|
672 |
* return evaluateParallel(helper, i -> (E_OUT[]) new |
|
673 |
* Object[i]).spliterator(); |
|
674 |
* }</pre> |
|
675 |
* and is suitable for implementations that cannot do better than a full |
|
676 |
* synchronous evaluation. |
|
677 |
* |
|
678 |
* @param helper the pipeline helper |
|
679 |
* @param spliterator the source {@code Spliterator} |
|
680 |
* @return a {@code Spliterator} describing the result of the evaluation |
|
681 |
*/ |
|
682 |
<P_IN> Spliterator<E_OUT> opEvaluateParallelLazy(PipelineHelper<E_OUT> helper, |
|
683 |
Spliterator<P_IN> spliterator) { |
|
684 |
return opEvaluateParallel(helper, spliterator, i -> (E_OUT[]) new Object[i]).spliterator(); |
|
685 |
} |
|
686 |
} |