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256 lines
10 KiB
Java
256 lines
10 KiB
Java
/*
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* Copyright (c) 2019, 2022, 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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*/
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package java.lang.foreign;
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import java.util.Objects;
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import java.util.Optional;
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import jdk.internal.javac.PreviewFeature;
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/**
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* A compound layout that denotes a repetition of a given <em>element layout</em>.
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* The repetition count is said to be the sequence layout's <em>element count</em>. A finite sequence can be thought of as a
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* group layout where the sequence layout's element layout is repeated a number of times that is equal to the sequence
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* layout's element count. In other words this layout:
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*
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* {@snippet lang=java :
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* MemoryLayout.sequenceLayout(3, ValueLayout.JAVA_INT.withOrder(ByteOrder.BIG_ENDIAN));
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* }
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*
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* is equivalent to the following layout:
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*
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* {@snippet lang=java :
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* MemoryLayout.structLayout(
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* ValueLayout.JAVA_INT.withOrder(ByteOrder.BIG_ENDIAN),
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* ValueLayout.JAVA_INT.withOrder(ByteOrder.BIG_ENDIAN),
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* ValueLayout.JAVA_INT.withOrder(ByteOrder.BIG_ENDIAN));
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* }
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*
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* @implSpec
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* This class is immutable, thread-safe and <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>.
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*
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* @since 19
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*/
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@PreviewFeature(feature=PreviewFeature.Feature.FOREIGN)
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public final class SequenceLayout extends AbstractLayout implements MemoryLayout {
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private final long elemCount;
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private final MemoryLayout elementLayout;
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SequenceLayout(long elemCount, MemoryLayout elementLayout) {
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this(elemCount, elementLayout, elementLayout.bitAlignment(), Optional.empty());
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}
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SequenceLayout(long elemCount, MemoryLayout elementLayout, long alignment, Optional<String> name) {
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super(Math.multiplyExact(elemCount, elementLayout.bitSize()), alignment, name);
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this.elemCount = elemCount;
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this.elementLayout = elementLayout;
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}
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/**
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* {@return the element layout associated with this sequence layout}
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*/
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public MemoryLayout elementLayout() {
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return elementLayout;
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}
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/**
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* {@return the element count of this sequence layout}
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*/
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public long elementCount() {
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return elemCount;
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}
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/**
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* Returns a sequence layout with the same element layout, alignment constraints and name as this sequence layout,
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* but with the specified element count.
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* @param elementCount the new element count.
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* @return a sequence layout with the given element count.
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* @throws IllegalArgumentException if {@code elementCount < 0}.
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*/
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public SequenceLayout withElementCount(long elementCount) {
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AbstractLayout.checkSize(elementCount, true);
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return new SequenceLayout(elementCount, elementLayout, alignment, name());
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}
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/**
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* Re-arrange the elements in this sequence layout into a multi-dimensional sequence layout.
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* The resulting layout is a sequence layout where element layouts in the flattened projection of this
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* sequence layout (see {@link #flatten()}) are re-arranged into one or more nested sequence layouts
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* according to the provided element counts. This transformation preserves the layout size;
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* that is, multiplying the provided element counts must yield the same element count
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* as the flattened projection of this sequence layout.
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* <p>
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* For instance, given a sequence layout of the kind:
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* {@snippet lang=java :
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* var seq = MemoryLayout.sequenceLayout(4, MemoryLayout.sequenceLayout(3, ValueLayout.JAVA_INT));
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* }
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* calling {@code seq.reshape(2, 6)} will yield the following sequence layout:
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* {@snippet lang=java :
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* var reshapeSeq = MemoryLayout.sequenceLayout(2, MemoryLayout.sequenceLayout(6, ValueLayout.JAVA_INT));
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* }
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* <p>
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* If one of the provided element count is the special value {@code -1}, then the element
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* count in that position will be inferred from the remaining element counts and the
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* element count of the flattened projection of this layout. For instance, a layout equivalent to
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* the above {@code reshapeSeq} can also be computed in the following ways:
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* {@snippet lang=java :
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* var reshapeSeqImplicit1 = seq.reshape(-1, 6);
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* var reshapeSeqImplicit2 = seq.reshape(2, -1);
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* }
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* @param elementCounts an array of element counts, of which at most one can be {@code -1}.
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* @return a sequence layout where element layouts in the flattened projection of this
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* sequence layout (see {@link #flatten()}) are re-arranged into one or more nested sequence layouts.
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* @throws UnsupportedOperationException if this sequence layout does not have an element count.
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* @throws IllegalArgumentException if two or more element counts are set to {@code -1}, or if one
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* or more element count is {@code <= 0} (but other than {@code -1}) or, if, after any required inference,
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* multiplying the element counts does not yield the same element count as the flattened projection of this
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* sequence layout.
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*/
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public SequenceLayout reshape(long... elementCounts) {
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Objects.requireNonNull(elementCounts);
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if (elementCounts.length == 0) {
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throw new IllegalArgumentException();
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}
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SequenceLayout flat = flatten();
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long expectedCount = flat.elementCount();
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long actualCount = 1;
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int inferPosition = -1;
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for (int i = 0 ; i < elementCounts.length ; i++) {
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if (elementCounts[i] == -1) {
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if (inferPosition == -1) {
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inferPosition = i;
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} else {
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throw new IllegalArgumentException("Too many unspecified element counts");
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}
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} else if (elementCounts[i] <= 0) {
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throw new IllegalArgumentException("Invalid element count: " + elementCounts[i]);
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} else {
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actualCount = elementCounts[i] * actualCount;
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}
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}
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// infer an unspecified element count (if any)
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if (inferPosition != -1) {
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long inferredCount = expectedCount / actualCount;
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elementCounts[inferPosition] = inferredCount;
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actualCount = actualCount * inferredCount;
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}
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if (actualCount != expectedCount) {
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throw new IllegalArgumentException("Element counts do not match expected size: " + expectedCount);
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}
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MemoryLayout res = flat.elementLayout();
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for (int i = elementCounts.length - 1 ; i >= 0 ; i--) {
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res = MemoryLayout.sequenceLayout(elementCounts[i], res);
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}
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return (SequenceLayout)res;
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}
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/**
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* Returns a flattened sequence layout. The element layout of the returned sequence layout
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* is the first non-sequence element layout found by recursively traversing the element layouts of this sequence layout.
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* This transformation preserves the layout size; nested sequence layout in this sequence layout will
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* be dropped and their element counts will be incorporated into that of the returned sequence layout.
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* For instance, given a sequence layout of the kind:
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* {@snippet lang=java :
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* var seq = MemoryLayout.sequenceLayout(4, MemoryLayout.sequenceLayout(3, ValueLayout.JAVA_INT));
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* }
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* calling {@code seq.flatten()} will yield the following sequence layout:
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* {@snippet lang=java :
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* var flattenedSeq = MemoryLayout.sequenceLayout(12, ValueLayout.JAVA_INT);
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* }
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* @return a sequence layout with the same size as this layout (but, possibly, with different
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* element count), whose element layout is not a sequence layout.
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* @throws UnsupportedOperationException if this sequence layout, or one of the nested sequence layouts being
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* flattened, does not have an element count.
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*/
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public SequenceLayout flatten() {
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long count = elementCount();
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MemoryLayout elemLayout = elementLayout();
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while (elemLayout instanceof SequenceLayout elemSeq) {
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count = count * elemSeq.elementCount();
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elemLayout = elemSeq.elementLayout();
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}
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return MemoryLayout.sequenceLayout(count, elemLayout);
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}
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@Override
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public String toString() {
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return decorateLayoutString(String.format("[%s:%s]",
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elemCount, elementLayout));
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}
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@Override
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public boolean equals(Object other) {
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if (this == other) {
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return true;
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}
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if (!super.equals(other)) {
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return false;
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}
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if (!(other instanceof SequenceLayout s)) {
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return false;
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}
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return elemCount == s.elemCount && elementLayout.equals(s.elementLayout);
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}
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@Override
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public int hashCode() {
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return Objects.hash(super.hashCode(), elemCount, elementLayout);
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}
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@Override
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SequenceLayout dup(long alignment, Optional<String> name) {
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return new SequenceLayout(elementCount(), elementLayout, alignment, name);
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}
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@Override
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boolean hasNaturalAlignment() {
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return alignment == elementLayout.bitAlignment();
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}
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//hack: the declarations below are to make javadoc happy; we could have used generics in AbstractLayout
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//but that causes issues with javadoc, see JDK-8224052
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/**
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* {@inheritDoc}
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*/
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@Override
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public SequenceLayout withName(String name) {
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return (SequenceLayout)super.withName(name);
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}
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/**
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* {@inheritDoc}
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*/
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@Override
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public SequenceLayout withBitAlignment(long alignmentBits) {
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return (SequenceLayout)super.withBitAlignment(alignmentBits);
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}
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}
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