/*
 * Copyright (c) 2015, 2017, 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 com.oracle.svm.core;

import org.graalvm.nativeimage.ImageSingletons;
import org.graalvm.nativeimage.Platform;
import org.graalvm.nativeimage.Platforms;
import org.graalvm.nativeimage.hosted.Feature;

import com.oracle.svm.core.annotate.AutomaticFeature;
import com.oracle.svm.core.annotate.Uninterruptible;
import com.oracle.svm.core.annotate.UnknownObjectField;
import com.oracle.svm.core.meta.SharedField;

Static fields are represented as two arrays in the native image heap: one for Object fields and one for all primitive fields. The byte-offset into these arrays is stored in SharedField.getLocation. 

Implementation notes: The arrays are created after static analysis, but before compilation. We
need to know how many static fields are reachable in order to compute the appropriate size for
the arrays, which is only available after static analysis.
/**
 * Static fields are represented as two arrays in the native image heap: one for Object fields and
 * one for all primitive fields. The byte-offset into these arrays is stored in
 * {@link SharedField#getLocation}.
 * <p>
 * Implementation notes: The arrays are created after static analysis, but before compilation. We
 * need to know how many static fields are reachable in order to compute the appropriate size for
 * the arrays, which is only available after static analysis.
 */
public final class StaticFieldsSupport {

    @UnknownObjectField(types = {Object[].class}) private Object[] staticObjectFields;
    @UnknownObjectField(types = {byte[].class}) private byte[] staticPrimitiveFields;

    @Platforms(Platform.HOSTED_ONLY.class)
    protected StaticFieldsSupport() {
    }

    @Platforms(Platform.HOSTED_ONLY.class)
    public static void setData(Object[] staticObjectFields, byte[] staticPrimitiveFields) {
        StaticFieldsSupport support = ImageSingletons.lookup(StaticFieldsSupport.class);
        support.staticObjectFields = staticObjectFields;
        support.staticPrimitiveFields = staticPrimitiveFields;
    }

    @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
    public static Object[] getStaticObjectFields() {
        Object[] result = ImageSingletons.lookup(StaticFieldsSupport.class).staticObjectFields;
        assert result != null;
        return result;
    }

    @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
    public static byte[] getStaticPrimitiveFields() {
        byte[] result = ImageSingletons.lookup(StaticFieldsSupport.class).staticPrimitiveFields;
        assert result != null;
        return result;
    }
}

@AutomaticFeature
class StaticFieldsFeature implements Feature {
    @Override
    public void afterRegistration(AfterRegistrationAccess access) {
        ImageSingletons.add(StaticFieldsSupport.class, new StaticFieldsSupport());
    }
}