--- /dev/null	2019-12-04 18:44:18.020007537 +0000
+++ new/src/jdk.incubator.foreign/share/classes/jdk/incubator/foreign/AbstractLayout.java	2019-12-09 18:15:26.023929462 +0000
@@ -0,0 +1,178 @@
+/*
+ *  Copyright (c) 2019, 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 jdk.incubator.foreign;
+
+import java.lang.constant.ClassDesc;
+import java.lang.constant.ConstantDesc;
+import java.lang.constant.ConstantDescs;
+import java.lang.constant.DirectMethodHandleDesc;
+import java.lang.constant.DynamicConstantDesc;
+import java.lang.constant.MethodHandleDesc;
+import java.lang.constant.MethodTypeDesc;
+import java.nio.ByteOrder;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.OptionalLong;
+
+abstract class AbstractLayout implements MemoryLayout {
+    private final OptionalLong size;
+    final long alignment;
+    private final Optional<String> name;
+
+    public AbstractLayout(OptionalLong size, long alignment, Optional<String> name) {
+        this.size = size;
+        this.alignment = alignment;
+        this.name = name;
+    }
+
+    Optional<String> optName() {
+        return name;
+    }
+
+    @Override
+    public AbstractLayout withName(String name) {
+        return dup(alignment, Optional.of(name));
+    }
+
+    @Override
+    public final Optional<String> name() {
+        return name;
+    }
+
+    abstract AbstractLayout dup(long alignment, Optional<String> name);
+
+    @Override
+    public AbstractLayout withBitAlignment(long alignmentBits) {
+        checkAlignment(alignmentBits);
+        return dup(alignmentBits, name);
+    }
+
+    void checkAlignment(long alignmentBitCount) {
+        if (((alignmentBitCount & (alignmentBitCount - 1)) != 0L) || //alignment must be a power of two
+                (alignmentBitCount < 8)) { //alignment must be greater than 8
+            throw new IllegalArgumentException("Invalid alignment: " + alignmentBitCount);
+        }
+    }
+
+    static void checkSize(long size) {
+        checkSize(size, false);
+    }
+
+    static void checkSize(long size, boolean includeZero) {
+        if (size < 0 || (!includeZero && size == 0)) {
+            throw new IllegalArgumentException("Invalid size for layout: " + size);
+        }
+    }
+
+    @Override
+    public final long bitAlignment() {
+        return alignment;
+    }
+
+    @Override
+    public long bitSize() {
+        return size.orElseThrow(this::badSizeException);
+    }
+
+    static OptionalLong optSize(MemoryLayout layout) {
+        return ((AbstractLayout)layout).size;
+    }
+
+    private UnsupportedOperationException badSizeException() {
+        return new UnsupportedOperationException("Cannot compute size of a layout which is, or depends on a sequence layout with unspecified size");
+    }
+
+    String decorateLayoutString(String s) {
+        if (name.isPresent()) {
+            s = String.format("%s(%s)", s, name.get());
+        }
+        if (!hasNaturalAlignment()) {
+            s = alignment + "%" + s;
+        }
+        return s;
+    }
+
+    boolean hasNaturalAlignment() {
+        return size.isPresent() && size.getAsLong() == alignment;
+    }
+
+    @Override
+    public int hashCode() {
+        return name.hashCode() << Long.hashCode(alignment);
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        if (this == other) {
+            return true;
+        }
+
+        if (!(other instanceof AbstractLayout)) {
+            return false;
+        }
+
+        return Objects.equals(name, ((AbstractLayout)other).name) &&
+                Objects.equals(alignment, ((AbstractLayout)other).alignment);
+    }
+
+    /*** Helper constants for implementing Layout::describeConstable ***/
+
+    public static final DirectMethodHandleDesc BSM_GET_STATIC_FINAL
+            = ConstantDescs.ofConstantBootstrap(ConstantDescs.CD_ConstantBootstraps, "getStaticFinal",
+            ConstantDescs.CD_Object, ConstantDescs.CD_Class);
+
+    static final ClassDesc CD_LAYOUT = MemoryLayout.class.describeConstable().get();
+
+    static final ClassDesc CD_VALUE_LAYOUT = ValueLayout.class.describeConstable().get();
+
+    static final ClassDesc CD_SEQUENCE_LAYOUT = SequenceLayout.class.describeConstable().get();
+
+    static final ClassDesc CD_GROUP_LAYOUT = GroupLayout.class.describeConstable().get();
+
+    static final ClassDesc CD_BYTEORDER = ByteOrder.class.describeConstable().get();
+
+    static final ConstantDesc BIG_ENDIAN = DynamicConstantDesc.ofNamed(BSM_GET_STATIC_FINAL, "BIG_ENDIAN", CD_BYTEORDER, CD_BYTEORDER);
+
+    static final ConstantDesc LITTLE_ENDIAN = DynamicConstantDesc.ofNamed(BSM_GET_STATIC_FINAL, "LITTLE_ENDIAN", CD_BYTEORDER, CD_BYTEORDER);
+
+    static final MethodHandleDesc MH_PADDING = MethodHandleDesc.ofMethod(DirectMethodHandleDesc.Kind.INTERFACE_STATIC, CD_LAYOUT, "ofPaddingBits",
+                MethodTypeDesc.of(CD_LAYOUT, ConstantDescs.CD_long));
+
+    static final MethodHandleDesc MH_VALUE = MethodHandleDesc.ofMethod(DirectMethodHandleDesc.Kind.INTERFACE_STATIC, CD_LAYOUT, "ofValueBits",
+                MethodTypeDesc.of(CD_VALUE_LAYOUT, ConstantDescs.CD_long, CD_BYTEORDER));
+
+    static final MethodHandleDesc MH_SIZED_SEQUENCE = MethodHandleDesc.ofMethod(DirectMethodHandleDesc.Kind.INTERFACE_STATIC, CD_LAYOUT, "ofSequence",
+                MethodTypeDesc.of(CD_SEQUENCE_LAYOUT, ConstantDescs.CD_long, CD_LAYOUT));
+
+    static final MethodHandleDesc MH_UNSIZED_SEQUENCE = MethodHandleDesc.ofMethod(DirectMethodHandleDesc.Kind.INTERFACE_STATIC, CD_LAYOUT, "ofSequence",
+                MethodTypeDesc.of(CD_SEQUENCE_LAYOUT, CD_LAYOUT));
+
+    static final MethodHandleDesc MH_STRUCT = MethodHandleDesc.ofMethod(DirectMethodHandleDesc.Kind.INTERFACE_STATIC, CD_LAYOUT, "ofStruct",
+                MethodTypeDesc.of(CD_GROUP_LAYOUT, CD_LAYOUT.arrayType()));
+
+    static final MethodHandleDesc MH_UNION = MethodHandleDesc.ofMethod(DirectMethodHandleDesc.Kind.INTERFACE_STATIC, CD_LAYOUT, "ofUnion",
+                MethodTypeDesc.of(CD_GROUP_LAYOUT, CD_LAYOUT.arrayType()));
+}