1 /*
2 * Copyright (c) 2019, 2023, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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24 */
25
26 package java.lang.foreign;
27
28 import jdk.internal.foreign.layout.SequenceLayoutImpl;
29
30 /**
31 * A compound layout that denotes a homogeneous repetition of a given <em>element layout</em>.
32 * The repetition count is said to be the sequence layout's <em>element count</em>. A sequence layout can be thought of as a
33 * struct layout where the sequence layout's element layout is repeated a number of times that is equal to the sequence
34 * layout's element count. In other words this layout:
35 *
36 * {@snippet lang=java :
37 * MemoryLayout.sequenceLayout(3, ValueLayout.JAVA_INT.withOrder(ByteOrder.BIG_ENDIAN));
38 * }
39 *
40 * is equivalent to the following layout:
41 *
42 * {@snippet lang=java :
43 * MemoryLayout.structLayout(
44 * ValueLayout.JAVA_INT.withOrder(ByteOrder.BIG_ENDIAN),
45 * ValueLayout.JAVA_INT.withOrder(ByteOrder.BIG_ENDIAN),
46 * ValueLayout.JAVA_INT.withOrder(ByteOrder.BIG_ENDIAN));
47 * }
48 *
49 * @implSpec
50 * This class is immutable, thread-safe and <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>.
51 *
52 * @since 22
53 */
54 public sealed interface SequenceLayout extends MemoryLayout permits SequenceLayoutImpl {
55
56
57 /**
58 * {@return the element layout of this sequence layout}
59 */
60 MemoryLayout elementLayout();
61
62 /**
63 * {@return the element count of this sequence layout}
64 */
65 long elementCount();
66
67 /**
68 * {@return a sequence layout with the same characteristics of this layout, but with the given element count}
69 * @param elementCount the new element count.
70 * @throws IllegalArgumentException if {@code elementCount} is negative.
71 * @throws IllegalArgumentException if {@code elementLayout.bitSize() * elementCount} overflows.
72 */
73 SequenceLayout withElementCount(long elementCount);
74
75 /**
76 * Rearranges the elements in this sequence layout into a multi-dimensional sequence layout.
77 * The resulting layout is a sequence layout where element layouts in the {@linkplain #flatten() flattened projection}
78 * of this sequence layout are rearranged into one or more nested sequence layouts
79 * according to the provided element counts. This transformation preserves the layout size;
80 * that is, multiplying the provided element counts must yield the same element count
81 * as the flattened projection of this sequence layout.
82 * <p>
83 * For instance, given a sequence layout of the kind:
84 * {@snippet lang=java :
85 * var seq = MemoryLayout.sequenceLayout(4, MemoryLayout.sequenceLayout(3, ValueLayout.JAVA_INT));
86 * }
87 * calling {@code seq.reshape(2, 6)} will yield the following sequence layout:
88 * {@snippet lang=java :
89 * var reshapeSeq = MemoryLayout.sequenceLayout(2, MemoryLayout.sequenceLayout(6, ValueLayout.JAVA_INT));
90 * }
91 * <p>
92 * If one of the provided element count is the special value {@code -1}, then the element
93 * count in that position will be inferred from the remaining element counts and the
94 * element count of the flattened projection of this layout. For instance, a layout equivalent to
95 * the above {@code reshapeSeq} can also be computed in the following ways:
96 * {@snippet lang=java :
97 * var reshapeSeqImplicit1 = seq.reshape(-1, 6);
98 * var reshapeSeqImplicit2 = seq.reshape(2, -1);
99 * }
100 * @param elementCounts an array of element counts, of which at most one can be {@code -1}.
101 * @return a sequence layout where element layouts in the {@linkplain #flatten() flattened projection} of this
102 * sequence layout (see {@link #flatten()}) are re-arranged into one or more nested sequence layouts.
103 * @throws IllegalArgumentException if two or more element counts are set to {@code -1}, or if one
104 * or more element count is {@code <= 0} (but other than {@code -1}) or, if, after any required inference,
105 * multiplying the element counts does not yield the same element count as the flattened projection of this
106 * sequence layout.
107 */
108 SequenceLayout reshape(long... elementCounts);
109
110 /**
111 * Returns a flattened sequence layout. The element layout of the returned sequence layout
112 * is the first non-sequence layout found by inspecting (recursively, if needed) the element layout of this sequence layout:
113 * {@snippet lang=java :
114 * MemoryLayout flatElementLayout(SequenceLayout sequenceLayout) {
115 * return switch (sequenceLayout.elementLayout()) {
116 * case SequenceLayout nestedSequenceLayout -> flatElementLayout(nestedSequenceLayout);
117 * case MemoryLayout layout -> layout;
118 * };
119 * }
120 * }
121 * <p>
122 * This transformation preserves the layout size; nested sequence layout in this sequence layout will
123 * be dropped and their element counts will be incorporated into that of the returned sequence layout.
124 * For instance, given a sequence layout of the kind:
125 * {@snippet lang=java :
126 * var seq = MemoryLayout.sequenceLayout(4, MemoryLayout.sequenceLayout(3, ValueLayout.JAVA_INT));
127 * }
128 * calling {@code seq.flatten()} will yield the following sequence layout:
129 * {@snippet lang=java :
130 * var flattenedSeq = MemoryLayout.sequenceLayout(12, ValueLayout.JAVA_INT);
131 * }
132 * @return a sequence layout with the same size as this layout (but, possibly, with different
133 * element count), whose element layout is not a sequence layout.
134 */
135 SequenceLayout flatten();
136
137 /**
138 * {@inheritDoc}
139 */
140 @Override
141 SequenceLayout withName(String name);
142
143 /**
144 * {@inheritDoc}
145 */
146 @Override
147 MemoryLayout withoutName();
148
149 /**
150 * {@inheritDoc}
151 * @throws IllegalArgumentException {@inheritDoc}
152 * @throws IllegalArgumentException if {@code byteAlignment < elementLayout().byteAlignment()}.
153 */
154 SequenceLayout withByteAlignment(long byteAlignment);
155 }