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/*
 * Copyright (c) 2018, 2018, 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.reflect.hosted;

// Checkstyle: allow reflection

import java.lang.reflect.Field;

import com.oracle.svm.core.annotate.RecomputeFieldValue.CustomFieldValueComputer;
import com.oracle.svm.core.util.VMError;
import com.oracle.svm.hosted.meta.HostedField;
import com.oracle.svm.hosted.meta.HostedMetaAccess;

import jdk.vm.ci.meta.MetaAccessProvider;
import jdk.vm.ci.meta.ResolvedJavaField;

public class FieldOffsetComputer implements CustomFieldValueComputer {

    @Override
    public Object compute(MetaAccessProvider metaAccess, ResolvedJavaField original, ResolvedJavaField annotated, Object receiver) {
        VMError.guarantee(metaAccess instanceof HostedMetaAccess, "Field offset computation must be done during compilation.");

        /*
         * We have to use `optionalLookupJavaField` as fields are omitted when there is no
         * reflective access in an image.
         */
        HostedField hostedField = ((HostedMetaAccess) metaAccess).optionalLookupJavaField((Field) receiver);
        if (hostedField != null && hostedField.wrapped.isUnsafeAccessed()) {
            int location = hostedField.getLocation();
            VMError.guarantee(location > 0, "Incorrect field location: " + location + " for " + hostedField.format("%H.%n"));
            return location;
        } else {
            /* A value of -1 signals that the field was not marked as unsafe accessed. */
            return -1;
        }
    }
}