8282191: Implementation of Foreign Function & Memory API (Preview)

Reviewed-by: erikj, jvernee, psandoz, dholmes, mchung

src/java.base/share/classes/java/lang/foreign/PaddingLayout.java

@@ -0,0 +1,100 @@
+/*
+ *  Copyright (c) 2019, 2022, Oracle and/or its affiliates. All rights reserved.
+ *  DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ *  This code is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 2 only, as
+ *  published by the Free Software Foundation.  Oracle designates this
+ *  particular file as subject to the "Classpath" exception as provided
+ *  by Oracle in the LICENSE file that accompanied this code.
+ *
+ *  This code is distributed in the hope that it will be useful, but WITHOUT
+ *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ *  version 2 for more details (a copy is included in the LICENSE file that
+ *  accompanied this code).
+ *
+ *  You should have received a copy of the GNU General Public License version
+ *  2 along with this work; if not, write to the Free Software Foundation,
+ *  Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ *   Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ *  or visit www.oracle.com if you need additional information or have any
+ *  questions.
+ *
+ */
+package java.lang.foreign;
+
+import java.util.Objects;
+import java.util.Optional;
+
+/**
+ * A padding layout. A padding layout specifies the size of extra space which is typically not accessed by applications,
+ * and is typically used for aligning member layouts around word boundaries.
+ *
+ * @implSpec
+ * This class is immutable, thread-safe and <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>.
+ */
+/* package-private */ final class PaddingLayout extends AbstractLayout implements MemoryLayout {
+
+    PaddingLayout(long size) {
+        this(size, 1, Optional.empty());
+    }
+
+    PaddingLayout(long size, long alignment, Optional<String> name) {
+        super(size, alignment, name);
+    }
+
+    @Override
+    public String toString() {
+        return decorateLayoutString("x" + bitSize());
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        if (this == other) {
+            return true;
+        }
+        if (!super.equals(other)) {
+            return false;
+        }
+        if (!(other instanceof PaddingLayout p)) {
+            return false;
+        }
+        return bitSize() == p.bitSize();
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(super.hashCode(), bitSize());
+    }
+
+    @Override
+    PaddingLayout dup(long alignment, Optional<String> name) {
+        return new PaddingLayout(bitSize(), alignment, name);
+    }
+
+    @Override
+    public boolean hasNaturalAlignment() {
+        return true;
+    }
+
+    //hack: the declarations below are to make javadoc happy; we could have used generics in AbstractLayout
+    //but that causes issues with javadoc, see JDK-8224052
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public PaddingLayout withName(String name) {
+        return (PaddingLayout)super.withName(name);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public PaddingLayout withBitAlignment(long alignmentBits) {
+        return (PaddingLayout)super.withBitAlignment(alignmentBits);
+    }
+}