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 *  DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *  This code is free software; you can redistribute it and/or modify it
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 *  published by the Free Software Foundation.  Oracle designates this
 *  particular file as subject to the "Classpath" exception as provided
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 *  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).
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package jdk.internal.foreign;

import jdk.incubator.foreign.MemoryAddress;
import jdk.incubator.foreign.MemoryHandles;
import jdk.internal.access.foreign.MemoryAddressProxy;
import jdk.internal.misc.VM;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.lang.invoke.VarHandle;
import java.util.Optional;
import java.util.function.Supplier;

This class contains misc helper functions to support creation of memory segments.
/**
 * This class contains misc helper functions to support creation of memory segments.
 */
public final class Utils {

    private static final String foreignRestrictedAccess = Optional.ofNullable(VM.getSavedProperty("foreign.restricted"))
            .orElse("deny");

    private static final MethodHandle ADDRESS_FILTER;

    static {
        try {
            ADDRESS_FILTER = MethodHandles.lookup().findStatic(Utils.class, "filterAddress",
                    MethodType.methodType(MemoryAddressProxy.class, MemoryAddress.class));
        } catch (Throwable ex) {
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static long alignUp(long n, long alignment) {
        return (n + alignment - 1) & -alignment;
    }

    public static long bitsToBytesOrThrow(long bits, Supplier<RuntimeException> exFactory) {
        if (bits % 8 == 0) {
            return bits / 8;
        } else {
            throw exFactory.get();
        }
    }

    public static VarHandle fixUpVarHandle(VarHandle handle) {
        // This adaptation is required, otherwise the memory access var handle will have type MemoryAddressProxy,
        // and not MemoryAddress (which the user expects), which causes performance issues with asType() adaptations.
        return MemoryHandles.filterCoordinates(handle, 0, ADDRESS_FILTER);
    }

    private static MemoryAddressProxy filterAddress(MemoryAddress addr) {
        return (MemoryAddressImpl)addr;
    }

    public static void checkRestrictedAccess(String method) {
        switch (foreignRestrictedAccess) {
            case "deny" -> throwIllegalAccessError(foreignRestrictedAccess, method);
            case "warn" -> System.err.println("WARNING: Accessing restricted foreign method: " + method);
            case "debug" -> {
                StringBuilder sb = new StringBuilder("DEBUG: restricted foreign method: \" + method");
                StackWalker.getInstance().forEach(f -> sb.append(System.lineSeparator())
                        .append("\tat ")
                        .append(f));
                System.err.println(sb.toString());
            }
            case "permit" -> {}
            default -> throwIllegalAccessError(foreignRestrictedAccess, method);
        }
    }

    private static void throwIllegalAccessError(String value, String method) {
        throw new IllegalAccessError("Illegal access to restricted foreign method: " + method +
                " ; system property 'foreign.restricted' is set to '" + value + "'");
    }
}