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/*
 * 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;

import org.graalvm.nativeimage.Feature;
import org.graalvm.nativeimage.ImageSingletons;

import com.oracle.svm.core.SubstrateOptions;
import com.oracle.svm.hosted.thread.VMThreadMTFeature;

/**
 * Preallocates a {@link JNIThreadLocalEnvironment} for each thread at runtime.
 */
public class JNIThreadLocalEnvironmentFeature implements Feature {
    @Override
    public void beforeAnalysis(BeforeAnalysisAccess access) {
        if (SubstrateOptions.MultiThreaded.getValue()) {
            /*
             * The per-thread JNI environment is located at offset 0 of each thread's {@link
             * VMThread} structure. For that reason, it has the same address as the VMThread and can
             * be used to restore the designated VMThread register when transitioning from native to
             * Java.
             */
            VMThreadMTFeature mt = ImageSingletons.lookup(VMThreadMTFeature.class);
            mt.setThreadLocalAtOffsetZero(JNIThreadLocalEnvironment.jniFunctions);
        }
    }
}