/*
 * Copyright (c) 2017, 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.jni.access;

// Checkstyle: allow reflection

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;

import org.graalvm.nativeimage.Platform.HOSTED_ONLY;
import org.graalvm.nativeimage.Platforms;
import org.graalvm.word.UnsignedWord;
import org.graalvm.word.WordBase;
import org.graalvm.word.WordFactory;

import com.oracle.svm.core.StaticFieldsSupport;
import com.oracle.svm.hosted.FeatureImpl.CompilationAccessImpl;
import com.oracle.svm.hosted.meta.HostedField;
import com.oracle.svm.jni.nativeapi.JNIFieldId;

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

Information on a field that can be looked up and accessed via JNI.
/**
 * Information on a field that can be looked up and accessed via JNI.
 */
public final class JNIAccessibleField extends JNIAccessibleMember {
    private static final UnsignedWord ID_STATIC_FLAG = WordFactory.unsigned(-1L).unsignedShiftRight(1).add(1);
    private static final UnsignedWord ID_OBJECT_FLAG = ID_STATIC_FLAG.unsignedShiftRight(1);
    private static final UnsignedWord ID_OFFSET_MASK = ID_OBJECT_FLAG.subtract(1);

    
For instance fields, the offset of the field in an object of the declaring class. For static fields, depending on the field's type, the offset of the field in either StaticFieldsSupport.getStaticPrimitiveFields() or StaticFieldsSupport.getStaticObjectFields(). /**
     * For instance fields, the offset of the field in an object of the
     * {@linkplain JNIAccessibleMember#getDeclaringClass() declaring class}. For static fields,
     * depending on the field's type, the offset of the field in either
     * {@link StaticFieldsSupport#getStaticPrimitiveFields()} or
     * {@link StaticFieldsSupport#getStaticObjectFields()}.
     */
    public static WordBase getOffsetFromId(JNIFieldId id) {
        UnsignedWord result = ((UnsignedWord) id).and(ID_OFFSET_MASK);
        assert result.notEqual(0);
        return result;
    }

    private final String name;
    @Platforms(HOSTED_ONLY.class) private final UnsignedWord flags;
    private UnsignedWord id = WordFactory.zero();

    JNIAccessibleField(JNIAccessibleClass declaringClass, String name, JavaKind kind, int modifiers) {
        super(declaringClass);
        this.name = name;

        UnsignedWord bits = Modifier.isStatic(modifiers) ? ID_STATIC_FLAG : WordFactory.zero();
        bits = bits.or(kind.isObject() ? ID_OBJECT_FLAG : WordFactory.zero());
        this.flags = bits;
    }

    public JNIFieldId getId() {
        return (JNIFieldId) id;
    }

    public boolean isStatic() {
        assert !id.equal(0);
        return id.and(ID_STATIC_FLAG).notEqual(0);
    }

    void finishBeforeCompilation(CompilationAccessImpl access) {
        assert id.equal(0);
        try {
            Field reflField = getDeclaringClass().getClassObject().getDeclaredField(name);
            HostedField field = access.getMetaAccess().lookupJavaField(reflField);
            assert field.hasLocation();
            int offset = field.getLocation();
            assert ID_OFFSET_MASK.and(offset).equal(offset);
            this.id = flags.or(offset);
        } catch (NoSuchFieldException e) {
            throw new RuntimeException(e);
        }
        setHidingSubclasses(access.getMetaAccess(), sub -> anyMatchName(sub.getInstanceFields(false)) || anyMatchName(sub.getStaticFields()));
    }

    private boolean anyMatchName(ResolvedJavaField[] fields) {
        for (ResolvedJavaField field : fields) {
            if (field.getName().equals(name)) {
                return true;
            }
        }
        return false;
    }
}