io.netty.util.internal.PlatformDependent - Netty 4.1.109.Final 源码

/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.util.internal;

import io.netty.util.CharsetUtil;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;
import org.jctools.queues.MpscArrayQueue;
import org.jctools.queues.MpscChunkedArrayQueue;
import org.jctools.queues.MpscUnboundedArrayQueue;
import org.jctools.queues.SpscLinkedQueue;
import org.jctools.queues.atomic.MpscAtomicArrayQueue;
import org.jctools.queues.atomic.MpscChunkedAtomicArrayQueue;
import org.jctools.queues.atomic.MpscUnboundedAtomicArrayQueue;
import org.jctools.queues.atomic.SpscLinkedAtomicQueue;
import org.jctools.util.Pow2;
import org.jctools.util.UnsafeAccess;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.file.Files;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Arrays;
import java.util.Collections;
import java.util.Deque;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Queue;
import java.util.Random;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentLinkedDeque;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.atomic.AtomicLong;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import static io.netty.util.internal.PlatformDependent0.HASH_CODE_ASCII_SEED;
import static io.netty.util.internal.PlatformDependent0.HASH_CODE_C1;
import static io.netty.util.internal.PlatformDependent0.HASH_CODE_C2;
import static io.netty.util.internal.PlatformDependent0.hashCodeAsciiSanitize;
import static io.netty.util.internal.PlatformDependent0.unalignedAccess;
import static java.lang.Math.max;
import static java.lang.Math.min;

/**
 * Utility that detects various properties specific to the current runtime
 * environment, such as Java version and the availability of the
 * {@code sun.misc.Unsafe} object.
 * <p>
 * You can disable the use of {@code sun.misc.Unsafe} if you specify
 * the system property <strong>io.netty.noUnsafe</strong>.
 */
public final class PlatformDependent {

    private static final InternalLogger logger = InternalLoggerFactory.getInstance(PlatformDependent.class);

    private static Pattern MAX_DIRECT_MEMORY_SIZE_ARG_PATTERN;
    private static final boolean MAYBE_SUPER_USER;

    private static final boolean CAN_ENABLE_TCP_NODELAY_BY_DEFAULT = !isAndroid();

    private static final Throwable UNSAFE_UNAVAILABILITY_CAUSE = unsafeUnavailabilityCause0();
    private static final boolean DIRECT_BUFFER_PREFERRED;
    private static final long MAX_DIRECT_MEMORY = estimateMaxDirectMemory();

    private static final int MPSC_CHUNK_SIZE =  1024;
    private static final int MIN_MAX_MPSC_CAPACITY =  MPSC_CHUNK_SIZE * 2;
    private static final int MAX_ALLOWED_MPSC_CAPACITY = Pow2.MAX_POW2;

    private static final long BYTE_ARRAY_BASE_OFFSET = byteArrayBaseOffset0();

    private static final File TMPDIR = tmpdir0();

    private static final int BIT_MODE = bitMode0();
    private static final String NORMALIZED_ARCH = normalizeArch(SystemPropertyUtil.get("os.arch", ""));
    private static final String NORMALIZED_OS = normalizeOs(SystemPropertyUtil.get("os.name", ""));

    // keep in sync with maven's pom.xml via os.detection.classifierWithLikes!
    private static final String[] ALLOWED_LINUX_OS_CLASSIFIERS = {"fedora", "suse", "arch"};
    private static final Set<String> LINUX_OS_CLASSIFIERS;

    private static final boolean IS_WINDOWS = isWindows0();
    private static final boolean IS_OSX = isOsx0();
    private static final boolean IS_J9_JVM = isJ9Jvm0();
    private static final boolean IS_IVKVM_DOT_NET = isIkvmDotNet0();

    private static final int ADDRESS_SIZE = addressSize0();
    private static final boolean USE_DIRECT_BUFFER_NO_CLEANER;
    private static final AtomicLong DIRECT_MEMORY_COUNTER;
    private static final long DIRECT_MEMORY_LIMIT;
    private static final ThreadLocalRandomProvider RANDOM_PROVIDER;
    private static final Cleaner CLEANER;
    private static final int UNINITIALIZED_ARRAY_ALLOCATION_THRESHOLD;
    // For specifications, see https://www.freedesktop.org/software/systemd/man/os-release.html
    private static final String[] OS_RELEASE_FILES = {"/etc/os-release", "/usr/lib/os-release"};
    private static final String LINUX_ID_PREFIX = "ID=";
    private static final String LINUX_ID_LIKE_PREFIX = "ID_LIKE=";
    public static final boolean BIG_ENDIAN_NATIVE_ORDER = ByteOrder.nativeOrder() == ByteOrder.BIG_ENDIAN;

    private static final Cleaner NOOP = new Cleaner() {
        @Override
        public void freeDirectBuffer(ByteBuffer buffer) {
            // NOOP
        }
    };

    static {
        if (javaVersion() >= 7) {
            RANDOM_PROVIDER = new ThreadLocalRandomProvider() {
                @Override
                @SuppressJava6Requirement(reason = "Usage guarded by java version check")
                public Random current() {
                    return java.util.concurrent.ThreadLocalRandom.current();
                }
            };
        } else {
            RANDOM_PROVIDER = new ThreadLocalRandomProvider() {
                @Override
                public Random current() {
                    return ThreadLocalRandom.current();
                }
            };
        }

        // Here is how the system property is used:
        //
        // * <  0  - Don't use cleaner, and inherit max direct memory from java. In this case the
        //           "practical max direct memory" would be 2 * max memory as defined by the JDK.
        // * == 0  - Use cleaner, Netty will not enforce max memory, and instead will defer to JDK.
        // * >  0  - Don't use cleaner. This will limit Netty's total direct memory
        //           (note: that JDK's direct memory limit is independent of this).
        long maxDirectMemory = SystemPropertyUtil.getLong("io.netty.maxDirectMemory", -1);

        if (maxDirectMemory == 0 || !hasUnsafe() || !PlatformDependent0.hasDirectBufferNoCleanerConstructor()) {
            USE_DIRECT_BUFFER_NO_CLEANER = false;
            DIRECT_MEMORY_COUNTER = null;
        } else {
            USE_DIRECT_BUFFER_NO_CLEANER = true;
            if (maxDirectMemory < 0) {
                maxDirectMemory = MAX_DIRECT_MEMORY;
                if (maxDirectMemory <= 0) {
                    DIRECT_MEMORY_COUNTER = null;
                } else {
                    DIRECT_MEMORY_COUNTER = new AtomicLong();
                }
            } else {
                DIRECT_MEMORY_COUNTER = new AtomicLong();
            }
        }
        logger.debug("-Dio.netty.maxDirectMemory: {} bytes", maxDirectMemory);
        DIRECT_MEMORY_LIMIT = maxDirectMemory >= 1 ? maxDirectMemory : MAX_DIRECT_MEMORY;

        int tryAllocateUninitializedArray =
                SystemPropertyUtil.getInt("io.netty.uninitializedArrayAllocationThreshold", 1024);
        UNINITIALIZED_ARRAY_ALLOCATION_THRESHOLD = javaVersion() >= 9 && PlatformDependent0.hasAllocateArrayMethod() ?
                tryAllocateUninitializedArray : -1;
        logger.debug("-Dio.netty.uninitializedArrayAllocationThreshold: {}", UNINITIALIZED_ARRAY_ALLOCATION_THRESHOLD);

        MAYBE_SUPER_USER = maybeSuperUser0();

        if (!isAndroid()) {
            // only direct to method if we are not running on android.
            // See https://github.com/netty/netty/issues/2604
            if (javaVersion() >= 9) {
                CLEANER = CleanerJava9.isSupported() ? new CleanerJava9() : NOOP;
            } else {
                CLEANER = CleanerJava6.isSupported() ? new CleanerJava6() : NOOP;
            }
        } else {
            CLEANER = NOOP;
        }

        // We should always prefer direct buffers by default if we can use a Cleaner to release direct buffers.
        DIRECT_BUFFER_PREFERRED = CLEANER != NOOP
                                  && !SystemPropertyUtil.getBoolean("io.netty.noPreferDirect", false);
        if (logger.isDebugEnabled()) {
            logger.debug("-Dio.netty.noPreferDirect: {}", !DIRECT_BUFFER_PREFERRED);
        }

        /*
         * We do not want to log this message if unsafe is explicitly disabled. Do not remove the explicit no unsafe
         * guard.
         */
        if (CLEANER == NOOP && !PlatformDependent0.isExplicitNoUnsafe()) {
            logger.info(
                    "Your platform does not provide complete low-level API for accessing direct buffers reliably. " +
                    "Unless explicitly requested, heap buffer will always be preferred to avoid potential system " +
                    "instability.");
        }

        final Set<String> allowedClassifiers = Collections.unmodifiableSet(
                new HashSet<String>(Arrays.asList(ALLOWED_LINUX_OS_CLASSIFIERS)));
        final Set<String> availableClassifiers = new LinkedHashSet<String>();

        if (!addPropertyOsClassifiers(allowedClassifiers, availableClassifiers)) {
            addFilesystemOsClassifiers(allowedClassifiers, availableClassifiers);
        }
        LINUX_OS_CLASSIFIERS = Collections.unmodifiableSet(availableClassifiers);
    }

    static void addFilesystemOsClassifiers(final Set<String> allowedClassifiers,
                                           final Set<String> availableClassifiers) {
        for (final String osReleaseFileName : OS_RELEASE_FILES) {
            final File file = new File(osReleaseFileName);
            boolean found = AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
                @Override
                public Boolean run() {
                    try {
                        if (file.exists()) {
                            BufferedReader reader = null;
                            try {
                                reader = new BufferedReader(
                                        new InputStreamReader(
                                                new FileInputStream(file), CharsetUtil.UTF_8));

                                String line;
                                while ((line = reader.readLine()) != null) {
                                    if (line.startsWith(LINUX_ID_PREFIX)) {
                                        String id = normalizeOsReleaseVariableValue(
                                                line.substring(LINUX_ID_PREFIX.length()));
                                        addClassifier(allowedClassifiers, availableClassifiers, id);
                                    } else if (line.startsWith(LINUX_ID_LIKE_PREFIX)) {
                                        line = normalizeOsReleaseVariableValue(
                                                line.substring(LINUX_ID_LIKE_PREFIX.length()));
                                        addClassifier(allowedClassifiers, availableClassifiers, line.split("[ ]+"));
                                    }
                                }
                            } catch (SecurityException e) {
                                logger.debug("Unable to read {}", osReleaseFileName, e);
                            } catch (IOException e) {
                                logger.debug("Error while reading content of {}", osReleaseFileName, e);
                            } finally {
                                if (reader != null) {
                                    try {
                                        reader.close();
                                    } catch (IOException ignored) {
                                        // Ignore
                                    }
                                }
                            }
                            // specification states we should only fall back if /etc/os-release does not exist
                            return true;
                        }
                    } catch (SecurityException e) {
                        logger.debug("Unable to check if {} exists", osReleaseFileName, e);
                    }
                    return false;
                }
            });

            if (found) {
                break;
            }
        }
    }

    static boolean addPropertyOsClassifiers(Set<String> allowedClassifiers, Set<String> availableClassifiers) {
        // empty: -Dio.netty.osClassifiers (no distro specific classifiers for native libs)
        // single ID: -Dio.netty.osClassifiers=ubuntu
        // pair ID, ID_LIKE: -Dio.netty.osClassifiers=ubuntu,debian
        // illegal otherwise
        String osClassifiersPropertyName = "io.netty.osClassifiers";
        String osClassifiers = SystemPropertyUtil.get(osClassifiersPropertyName);
        if (osClassifiers == null) {
            return false;
        }
        if (osClassifiers.isEmpty()) {
            // let users omit classifiers with just -Dio.netty.osClassifiers
            return true;
        }
        String[] classifiers = osClassifiers.split(",");
        if (classifiers.length == 0) {
            throw new IllegalArgumentException(
                    osClassifiersPropertyName + " property is not empty, but contains no classifiers: "
                            + osClassifiers);
        }
        // at most ID, ID_LIKE classifiers
        if (classifiers.length > 2) {
            throw new IllegalArgumentException(
                    osClassifiersPropertyName + " property contains more than 2 classifiers: " + osClassifiers);
        }
        for (String classifier : classifiers) {
            addClassifier(allowedClassifiers, availableClassifiers, classifier);
        }
        return true;
    }

    public static long byteArrayBaseOffset() {
        return BYTE_ARRAY_BASE_OFFSET;
    }

    public static boolean hasDirectBufferNoCleanerConstructor() {
        return PlatformDependent0.hasDirectBufferNoCleanerConstructor();
    }

    public static byte[] allocateUninitializedArray(int size) {
        return UNINITIALIZED_ARRAY_ALLOCATION_THRESHOLD < 0 || UNINITIALIZED_ARRAY_ALLOCATION_THRESHOLD > size ?
                new byte[size] : PlatformDependent0.allocateUninitializedArray(size);
    }

    /**
     * Returns {@code true} if and only if the current platform is Android
     */
    public static boolean isAndroid() {
        return PlatformDependent0.isAndroid();
    }

    /**
     * Return {@code true} if the JVM is running on Windows
     */
    public static boolean isWindows() {
        return IS_WINDOWS;
    }

    /**
     * Return {@code true} if the JVM is running on OSX / MacOS
     */
    public static boolean isOsx() {
        return IS_OSX;
    }

    /**
     * Return {@code true} if the current user may be a super-user. Be aware that this is just an hint and so it may
     * return false-positives.
     */
    public static boolean maybeSuperUser() {
        return MAYBE_SUPER_USER;
    }

    /**
     * Return the version of Java under which this library is used.
     */
    public static int javaVersion() {
        return PlatformDependent0.javaVersion();
    }

    /**
     * Returns {@code true} if and only if it is fine to enable TCP_NODELAY socket option by default.
     */
    public static boolean canEnableTcpNoDelayByDefault() {
        return CAN_ENABLE_TCP_NODELAY_BY_DEFAULT;
    }

    /**
     * Return {@code true} if {@code sun.misc.Unsafe} was found on the classpath and can be used for accelerated
     * direct memory access.
     */
    public static boolean hasUnsafe() {
        return UNSAFE_UNAVAILABILITY_CAUSE == null;
    }

    /**
     * Return the reason (if any) why {@code sun.misc.Unsafe} was not available.
     */
    public static Throwable getUnsafeUnavailabilityCause() {
        return UNSAFE_UNAVAILABILITY_CAUSE;
    }

    /**
     * {@code true} if and only if the platform supports unaligned access.
     *
     * @see <a href="https://en.wikipedia.org/wiki/Segmentation_fault#Bus_error">Wikipedia on segfault</a>
     */
    public static boolean isUnaligned() {
        return PlatformDependent0.isUnaligned();
    }

    /**
     * Returns {@code true} if the platform has reliable low-level direct buffer access API and a user has not specified
     * {@code -Dio.netty.noPreferDirect} option.
     */
    public static boolean directBufferPreferred() {
        return DIRECT_BUFFER_PREFERRED;
    }

    /**
     * Returns the maximum memory reserved for direct buffer allocation.
     */
    public static long maxDirectMemory() {
        return DIRECT_MEMORY_LIMIT;
    }

    /**
     * Returns the current memory reserved for direct buffer allocation.
     * This method returns -1 in case that a value is not available.
     *
     * @see #maxDirectMemory()
     */
    public static long usedDirectMemory() {
        return DIRECT_MEMORY_COUNTER != null ? DIRECT_MEMORY_COUNTER.get() : -1;
    }

    /**
     * Returns the temporary directory.
     */
    public static File tmpdir() {
        return TMPDIR;
    }

    /**
     * Returns the bit mode of the current VM (usually 32 or 64.)
     */
    public static int bitMode() {
        return BIT_MODE;
    }

    /**
     * Return the address size of the OS.
     * 4 (for 32 bits systems ) and 8 (for 64 bits systems).
     */
    public static int addressSize() {
        return ADDRESS_SIZE;
    }

    public static long allocateMemory(long size) {
        return PlatformDependent0.allocateMemory(size);
    }

    public static void freeMemory(long address) {
        PlatformDependent0.freeMemory(address);
    }

    public static long reallocateMemory(long address, long newSize) {
        return PlatformDependent0.reallocateMemory(address, newSize);
    }

    /**
     * Raises an exception bypassing compiler checks for checked exceptions.
     */
    public static void throwException(Throwable t) {
        if (hasUnsafe()) {
            PlatformDependent0.throwException(t);
        } else {
            PlatformDependent.<RuntimeException>throwException0(t);
        }
    }

    @SuppressWarnings("unchecked")
    private static <E extends Throwable> void throwException0(Throwable t) throws E {
        throw (E) t;
    }

    /**
     * Creates a new fastest {@link ConcurrentMap} implementation for the current platform.
     */
    public static <K, V> ConcurrentMap<K, V> newConcurrentHashMap() {
        return new ConcurrentHashMap<K, V>();
    }

    /**
     * Creates a new fastest {@link LongCounter} implementation for the current platform.
     */
    public static LongCounter newLongCounter() {
        if (javaVersion() >= 8) {
            return new LongAdderCounter();
        } else {
            return new AtomicLongCounter();
        }
    }

    /**
     * Creates a new fastest {@link ConcurrentMap} implementation for the current platform.
     */
    public static <K, V> ConcurrentMap<K, V> newConcurrentHashMap(int initialCapacity) {
        return new ConcurrentHashMap<K, V>(initialCapacity);
    }

    /**
     * Creates a new fastest {@link ConcurrentMap} implementation for the current platform.
     */
    public static <K, V> ConcurrentMap<K, V> newConcurrentHashMap(int initialCapacity, float loadFactor) {
        return new ConcurrentHashMap<K, V>(initialCapacity, loadFactor);
    }

    /**
     * Creates a new fastest {@link ConcurrentMap} implementation for the current platform.
     */
    public static <K, V> ConcurrentMap<K, V> newConcurrentHashMap(
            int initialCapacity, float loadFactor, int concurrencyLevel) {
        return new ConcurrentHashMap<K, V>(initialCapacity, loadFactor, concurrencyLevel);
    }

    /**
     * Creates a new fastest {@link ConcurrentMap} implementation for the current platform.
     */
    public static <K, V> ConcurrentMap<K, V> newConcurrentHashMap(Map<? extends K, ? extends V> map) {
        return new ConcurrentHashMap<K, V>(map);
    }

    /**
     * Try to deallocate the specified direct {@link ByteBuffer}. Please note this method does nothing if
     * the current platform does not support this operation or the specified buffer is not a direct buffer.
     */
    public static void freeDirectBuffer(ByteBuffer buffer) {
        CLEANER.freeDirectBuffer(buffer);
    }

    public static long directBufferAddress(ByteBuffer buffer) {
        return PlatformDependent0.directBufferAddress(buffer);
    }

    public static ByteBuffer directBuffer(long memoryAddress, int size) {
        if (PlatformDependent0.hasDirectBufferNoCleanerConstructor()) {
            return PlatformDependent0.newDirectBuffer(memoryAddress, size);
        }
        throw new UnsupportedOperationException(
                "sun.misc.Unsafe or java.nio.DirectByteBuffer.<init>(long, int) not available");
    }

    public static Object getObject(Object object, long fieldOffset) {
        return PlatformDependent0.getObject(object, fieldOffset);
    }

    public static int getInt(Object object, long fieldOffset) {
        return PlatformDependent0.getInt(object, fieldOffset);
    }

    static void safeConstructPutInt(Object object, long fieldOffset, int value) {
        PlatformDependent0.safeConstructPutInt(object, fieldOffset, value);
    }

    public static int getIntVolatile(long address) {
        return PlatformDependent0.getIntVolatile(address);
    }

    public static void putIntOrdered(long adddress, int newValue) {
        PlatformDependent0.putIntOrdered(adddress, newValue);
    }

    public static byte getByte(long address) {
        return PlatformDependent0.getByte(address);
    }

    public static short getShort(long address) {
        return PlatformDependent0.getShort(address);
    }

    public static int getInt(long address) {
        return PlatformDependent0.getInt(address);
    }

    public static long getLong(long address) {
        return PlatformDependent0.getLong(address);
    }

    public static byte getByte(byte[] data, int index) {
        return PlatformDependent0.getByte(data, index);
    }

    public static byte getByte(byte[] data, long index) {
        return PlatformDependent0.getByte(data, index);
    }

    public static short getShort(byte[] data, int index) {
        return PlatformDependent0.getShort(data, index);
    }

    public static int getInt(byte[] data, int index) {
        return PlatformDependent0.getInt(data, index);
    }

    public static int getInt(int[] data, long index) {
        return PlatformDependent0.getInt(data, index);
    }

    public static long getLong(byte[] data, int index) {
        return PlatformDependent0.getLong(data, index);
    }

    public static long getLong(long[] data, long index) {
        return PlatformDependent0.getLong(data, index);
    }

    private static long getLongSafe(byte[] bytes, int offset) {
        if (BIG_ENDIAN_NATIVE_ORDER) {
            return (long) bytes[offset] << 56 |
                    ((long) bytes[offset + 1] & 0xff) << 48 |
                    ((long) bytes[offset + 2] & 0xff) << 40 |
                    ((long) bytes[offset + 3] & 0xff) << 32 |
                    ((long) bytes[offset + 4] & 0xff) << 24 |
                    ((long) bytes[offset + 5] & 0xff) << 16 |
                    ((long) bytes[offset + 6] & 0xff) <<  8 |
                    (long) bytes[offset + 7] & 0xff;
        }
        return (long) bytes[offset] & 0xff |
                ((long) bytes[offset + 1] & 0xff) << 8 |
                ((long) bytes[offset + 2] & 0xff) << 16 |
                ((long) bytes[offset + 3] & 0xff) << 24 |
                ((long) bytes[offset + 4] & 0xff) << 32 |
                ((long) bytes[offset + 5] & 0xff) << 40 |
                ((long) bytes[offset + 6] & 0xff) << 48 |
                (long) bytes[offset + 7] << 56;
    }

    private static int getIntSafe(byte[] bytes, int offset) {
        if (BIG_ENDIAN_NATIVE_ORDER) {
            return bytes[offset] << 24 |
                    (bytes[offset + 1] & 0xff) << 16 |
                    (bytes[offset + 2] & 0xff) << 8 |
                    bytes[offset + 3] & 0xff;
        }
        return bytes[offset] & 0xff |
                (bytes[offset + 1] & 0xff) << 8 |
                (bytes[offset + 2] & 0xff) << 16 |
                bytes[offset + 3] << 24;
    }

    private static short getShortSafe(byte[] bytes, int offset) {
        if (BIG_ENDIAN_NATIVE_ORDER) {
            return (short) (bytes[offset] << 8 | (bytes[offset + 1] & 0xff));
        }
        return (short) (bytes[offset] & 0xff | (bytes[offset + 1] << 8));
    }

    /**
     * Identical to {@link PlatformDependent0#hashCodeAsciiCompute(long, int)} but for {@link CharSequence}.
     */
    private static int hashCodeAsciiCompute(CharSequence value, int offset, int hash) {
        if (BIG_ENDIAN_NATIVE_ORDER) {
            return hash * HASH_CODE_C1 +
                    // Low order int
                    hashCodeAsciiSanitizeInt(value, offset + 4) * HASH_CODE_C2 +
                    // High order int
                    hashCodeAsciiSanitizeInt(value, offset);
        }
        return hash * HASH_CODE_C1 +
                // Low order int
                hashCodeAsciiSanitizeInt(value, offset) * HASH_CODE_C2 +
                // High order int
                hashCodeAsciiSanitizeInt(value, offset + 4);
    }

    /**
     * Identical to {@link PlatformDependent0#hashCodeAsciiSanitize(int)} but for {@link CharSequence}.
     */
    private static int hashCodeAsciiSanitizeInt(CharSequence value, int offset) {
        if (BIG_ENDIAN_NATIVE_ORDER) {
            // mimic a unsafe.getInt call on a big endian machine
            return (value.charAt(offset + 3) & 0x1f) |
                   (value.charAt(offset + 2) & 0x1f) << 8 |
                   (value.charAt(offset + 1) & 0x1f) << 16 |
                   (value.charAt(offset) & 0x1f) << 24;
        }
        return (value.charAt(offset + 3) & 0x1f) << 24 |
               (value.charAt(offset + 2) & 0x1f) << 16 |
               (value.charAt(offset + 1) & 0x1f) << 8 |
               (value.charAt(offset) & 0x1f);
    }

    /**
     * Identical to {@link PlatformDependent0#hashCodeAsciiSanitize(short)} but for {@link CharSequence}.
     */
    private static int hashCodeAsciiSanitizeShort(CharSequence value, int offset) {
        if (BIG_ENDIAN_NATIVE_ORDER) {
            // mimic a unsafe.getShort call on a big endian machine
            return (value.charAt(offset + 1) & 0x1f) |
                    (value.charAt(offset) & 0x1f) << 8;
        }
        return (value.charAt(offset + 1) & 0x1f) << 8 |
                (value.charAt(offset) & 0x1f);
    }

    /**
     * Identical to {@link PlatformDependent0#hashCodeAsciiSanitize(byte)} but for {@link CharSequence}.
     */
    private static int hashCodeAsciiSanitizeByte(char value) {
        return value & 0x1f;
    }

    public static void putByte(long address, byte value) {
        PlatformDependent0.putByte(address, value);
    }

    public static void putShort(long address, short value) {
        PlatformDependent0.putShort(address, value);
    }

    public static void putInt(long address, int value) {
        PlatformDependent0.putInt(address, value);
    }

    public static void putLong(long address, long value) {
        PlatformDependent0.putLong(address, value);
    }

    public static void putByte(byte[] data, int index, byte value) {
        PlatformDependent0.putByte(data, index, value);
    }

    public static void putByte(Object data, long offset, byte value) {
        PlatformDependent0.putByte(data, offset, value);
    }

    public static void putShort(byte[] data, int index, short value) {
        PlatformDependent0.putShort(data, index, value);
    }

    public static void putInt(byte[] data, int index, int value) {
        PlatformDependent0.putInt(data, index, value);
    }

    public static void putLong(byte[] data, int index, long value) {
        PlatformDependent0.putLong(data, index, value);
    }

    public static void putObject(Object o, long offset, Object x) {
        PlatformDependent0.putObject(o, offset, x);
    }

    public static long objectFieldOffset(Field field) {
        return PlatformDependent0.objectFieldOffset(field);
    }

    public static void copyMemory(long srcAddr, long dstAddr, long length) {
        PlatformDependent0.copyMemory(srcAddr, dstAddr, length);
    }

    public static void copyMemory(byte[] src, int srcIndex, long dstAddr, long length) {
        PlatformDependent0.copyMemory(src, BYTE_ARRAY_BASE_OFFSET + srcIndex, null, dstAddr, length);
    }

    public static void copyMemory(byte[] src, int srcIndex, byte[] dst, int dstIndex, long length) {
        PlatformDependent0.copyMemory(src, BYTE_ARRAY_BASE_OFFSET + srcIndex,
                                      dst, BYTE_ARRAY_BASE_OFFSET + dstIndex, length);
    }

    public static void copyMemory(long srcAddr, byte[] dst, int dstIndex, long length) {
        PlatformDependent0.copyMemory(null, srcAddr, dst, BYTE_ARRAY_BASE_OFFSET + dstIndex, length);
    }

    public static void setMemory(byte[] dst, int dstIndex, long bytes, byte value) {
        PlatformDependent0.setMemory(dst, BYTE_ARRAY_BASE_OFFSET + dstIndex, bytes, value);
    }

    public static void setMemory(long address, long bytes, byte value) {
        PlatformDependent0.setMemory(address, bytes, value);
    }

    /**
     * Allocate a new {@link ByteBuffer} with the given {@code capacity}. {@link ByteBuffer}s allocated with
     * this method <strong>MUST</strong> be deallocated via {@link #freeDirectNoCleaner(ByteBuffer)}.
     */
    public static ByteBuffer allocateDirectNoCleaner(int capacity) {
        assert USE_DIRECT_BUFFER_NO_CLEANER;

        incrementMemoryCounter(capacity);
        try {
            return PlatformDependent0.allocateDirectNoCleaner(capacity);
        } catch (Throwable e) {
            decrementMemoryCounter(capacity);
            throwException(e);
            return null;
        }
    }

    /**
     * Reallocate a new {@link ByteBuffer} with the given {@code capacity}. {@link ByteBuffer}s reallocated with
     * this method <strong>MUST</strong> be deallocated via {@link #freeDirectNoCleaner(ByteBuffer)}.
     */
    public static ByteBuffer reallocateDirectNoCleaner(ByteBuffer buffer, int capacity) {
        assert USE_DIRECT_BUFFER_NO_CLEANER;

        int len = capacity - buffer.capacity();
        incrementMemoryCounter(len);
        try {
            return PlatformDependent0.reallocateDirectNoCleaner(buffer, capacity);
        } catch (Throwable e) {
            decrementMemoryCounter(len);
            throwException(e);
            return null;
        }
    }

    /**
     * This method <strong>MUST</strong> only be called for {@link ByteBuffer}s that were allocated via
     * {@link #allocateDirectNoCleaner(int)}.
     */
    public static void freeDirectNoCleaner(ByteBuffer buffer) {
        assert USE_DIRECT_BUFFER_NO_CLEANER;

        int capacity = buffer.capacity();
        PlatformDependent0.freeMemory(PlatformDependent0.directBufferAddress(buffer));
        decrementMemoryCounter(capacity);
    }

    public static boolean hasAlignDirectByteBuffer() {
        return hasUnsafe() || PlatformDependent0.hasAlignSliceMethod();
    }

    public static ByteBuffer alignDirectBuffer(ByteBuffer buffer, int alignment) {
        if (!buffer.isDirect()) {
            throw new IllegalArgumentException("Cannot get aligned slice of non-direct byte buffer.");
        }
        if (PlatformDependent0.hasAlignSliceMethod()) {
            return PlatformDependent0.alignSlice(buffer, alignment);
        }
        if (hasUnsafe()) {
            long address = directBufferAddress(buffer);
            long aligned = align(address, alignment);
            buffer.position((int) (aligned - address));
            return buffer.slice();
        }
        // We don't have enough information to be able to align any buffers.
        throw new UnsupportedOperationException("Cannot align direct buffer. " +
                "Needs either Unsafe or ByteBuffer.alignSlice method available.");
    }

    public static long align(long value, int alignment) {
        return Pow2.align(value, alignment);
    }

    private static void incrementMemoryCounter(int capacity) {
        if (DIRECT_MEMORY_COUNTER != null) {
            long newUsedMemory = DIRECT_MEMORY_COUNTER.addAndGet(capacity);
            if (newUsedMemory > DIRECT_MEMORY_LIMIT) {
                DIRECT_MEMORY_COUNTER.addAndGet(-capacity);
                throw new OutOfDirectMemoryError("failed to allocate " + capacity
                        + " byte(s) of direct memory (used: " + (newUsedMemory - capacity)
                        + ", max: " + DIRECT_MEMORY_LIMIT + ')');
            }
        }
    }

    private static void decrementMemoryCounter(int capacity) {
        if (DIRECT_MEMORY_COUNTER != null) {
            long usedMemory = DIRECT_MEMORY_COUNTER.addAndGet(-capacity);
            assert usedMemory >= 0;
        }
    }

    public static boolean useDirectBufferNoCleaner() {
        return USE_DIRECT_BUFFER_NO_CLEANER;
    }

    /**
     * Compare two {@code byte} arrays for equality. For performance reasons no bounds checking on the
     * parameters is performed.
     *
     * @param bytes1 the first byte array.
     * @param startPos1 the position (inclusive) to start comparing in {@code bytes1}.
     * @param bytes2 the second byte array.
     * @param startPos2 the position (inclusive) to start comparing in {@code bytes2}.
     * @param length the amount of bytes to compare. This is assumed to be validated as not going out of bounds
     * by the caller.
     */
    public static boolean equals(byte[] bytes1, int startPos1, byte[] bytes2, int startPos2, int length) {
        if (javaVersion() > 8 && (startPos2 | startPos1 | (bytes1.length - length) | bytes2.length - length) == 0) {
            return Arrays.equals(bytes1, bytes2);
        }
        return !hasUnsafe() || !unalignedAccess() ?
                  equalsSafe(bytes1, startPos1, bytes2, startPos2, length) :
                  PlatformDependent0.equals(bytes1, startPos1, bytes2, startPos2, length);
    }

    /**
     * Determine if a subsection of an array is zero.
     * @param bytes The byte array.
     * @param startPos The starting index (inclusive) in {@code bytes}.
     * @param length The amount of bytes to check for zero.
     * @return {@code false} if {@code bytes[startPos:startsPos+length)} contains a value other than zero.
     */
    public static boolean isZero(byte[] bytes, int startPos, int length) {
        return !hasUnsafe() || !unalignedAccess() ?
                isZeroSafe(bytes, startPos, length) :
                PlatformDependent0.isZero(bytes, startPos, length);
    }

    /**
     * Compare two {@code byte} arrays for equality without leaking timing information.
     * For performance reasons no bounds checking on the parameters is performed.
     * <p>
     * The {@code int} return type is intentional and is designed to allow cascading of constant time operations:
     * <pre>
     *     byte[] s1 = new {1, 2, 3};
     *     byte[] s2 = new {1, 2, 3};
     *     byte[] s3 = new {1, 2, 3};
     *     byte[] s4 = new {4, 5, 6};
     *     boolean equals = (equalsConstantTime(s1, 0, s2, 0, s1.length) &
     *                       equalsConstantTime(s3, 0, s4, 0, s3.length)) != 0;
     * </pre>
     * @param bytes1 the first byte array.
     * @param startPos1 the position (inclusive) to start comparing in {@code bytes1}.
     * @param bytes2 the second byte array.
     * @param startPos2 the position (inclusive) to start comparing in {@code bytes2}.
     * @param length the amount of bytes to compare. This is assumed to be validated as not going out of bounds
     * by the caller.
     * @return {@code 0} if not equal. {@code 1} if equal.
     */
    public static int equalsConstantTime(byte[] bytes1, int startPos1, byte[] bytes2, int startPos2, int length) {
        return !hasUnsafe() || !unalignedAccess() ?
                  ConstantTimeUtils.equalsConstantTime(bytes1, startPos1, bytes2, startPos2, length) :
                  PlatformDependent0.equalsConstantTime(bytes1, startPos1, bytes2, startPos2, length);
    }

    /**
     * Calculate a hash code of a byte array assuming ASCII character encoding.
     * The resulting hash code will be case insensitive.
     * @param bytes The array which contains the data to hash.
     * @param startPos What index to start generating a hash code in {@code bytes}
     * @param length The amount of bytes that should be accounted for in the computation.
     * @return The hash code of {@code bytes} assuming ASCII character encoding.
     * The resulting hash code will be case insensitive.
     */
    public static int hashCodeAscii(byte[] bytes, int startPos, int length) {
        return !hasUnsafe() || !unalignedAccess() ?
                hashCodeAsciiSafe(bytes, startPos, length) :
                PlatformDependent0.hashCodeAscii(bytes, startPos, length);
    }

    /**
     * Calculate a hash code of a byte array assuming ASCII character encoding.
     * The resulting hash code will be case insensitive.
     * <p>
     * This method assumes that {@code bytes} is equivalent to a {@code byte[]} but just using {@link CharSequence}
     * for storage. The upper most byte of each {@code char} from {@code bytes} is ignored.
     * @param bytes The array which contains the data to hash (assumed to be equivalent to a {@code byte[]}).
     * @return The hash code of {@code bytes} assuming ASCII character encoding.
     * The resulting hash code will be case insensitive.
     */
    public static int hashCodeAscii(CharSequence bytes) {
        final int length = bytes.length();
        final int remainingBytes = length & 7;
        int hash = HASH_CODE_ASCII_SEED;
        // Benchmarking shows that by just naively looping for inputs 8~31 bytes long we incur a relatively large
        // performance penalty (only achieve about 60% performance of loop which iterates over each char). So because
        // of this we take special provisions to unroll the looping for these conditions.
        if (length >= 32) {
            for (int i = length - 8; i >= remainingBytes; i -= 8) {
                hash = hashCodeAsciiCompute(bytes, i, hash);
            }
        } else if (length >= 8) {
            hash = hashCodeAsciiCompute(bytes, length - 8, hash);
            if (length >= 16) {
                hash = hashCodeAsciiCompute(bytes, length - 16, hash);
                if (length >= 24) {
                    hash = hashCodeAsciiCompute(bytes, length - 24, hash);
                }
            }
        }
        if (remainingBytes == 0) {
            return hash;
        }
        int offset = 0;
        if (remainingBytes != 2 & remainingBytes != 4 & remainingBytes != 6) { // 1, 3, 5, 7
            hash = hash * HASH_CODE_C1 + hashCodeAsciiSanitizeByte(bytes.charAt(0));
            offset = 1;
        }
        if (remainingBytes != 1 & remainingBytes != 4 & remainingBytes != 5) { // 2, 3, 6, 7
            hash = hash * (offset == 0 ? HASH_CODE_C1 : HASH_CODE_C2)
                    + hashCodeAsciiSanitize(hashCodeAsciiSanitizeShort(bytes, offset));
            offset += 2;
        }
        if (remainingBytes >= 4) { // 4, 5, 6, 7
            return hash * ((offset == 0 | offset == 3) ? HASH_CODE_C1 : HASH_CODE_C2)
                    + hashCodeAsciiSanitizeInt(bytes, offset);
        }
        return hash;
    }

    private static final class Mpsc {
        private static final boolean USE_MPSC_CHUNKED_ARRAY_QUEUE;

        private Mpsc() {
        }

        static {
            Object unsafe = null;
            if (hasUnsafe()) {
                // jctools goes through its own process of initializing unsafe; of
                // course, this requires permissions which might not be granted to calling code, so we
                // must mark this block as privileged too
                unsafe = AccessController.doPrivileged(new PrivilegedAction<Object>() {
                    @Override
                     public Object run() {
                         // force JCTools to initialize unsafe
                         return UnsafeAccess.UNSAFE;
                     }
                 });
             }

             if (unsafe == null) {
                 logger.debug("org.jctools-core.MpscChunkedArrayQueue: unavailable");
                 USE_MPSC_CHUNKED_ARRAY_QUEUE = false;
             } else {
                 logger.debug("org.jctools-core.MpscChunkedArrayQueue: available");
                 USE_MPSC_CHUNKED_ARRAY_QUEUE = true;
             }
         }

         static <T> Queue<T> newMpscQueue(final int maxCapacity) {
             // Calculate the max capacity which can not be bigger than MAX_ALLOWED_MPSC_CAPACITY.
             // This is forced by the MpscChunkedArrayQueue implementation as will try to round it
             // up to the next power of two and so will overflow otherwise.
             final int capacity = max(min(maxCapacity, MAX_ALLOWED_MPSC_CAPACITY), MIN_MAX_MPSC_CAPACITY);
             return newChunkedMpscQueue(MPSC_CHUNK_SIZE, capacity);
         }

         static <T> Queue<T> newChunkedMpscQueue(final int chunkSize, final int capacity) {
             return USE_MPSC_CHUNKED_ARRAY_QUEUE ? new MpscChunkedArrayQueue<T>(chunkSize, capacity)
                     : new MpscChunkedAtomicArrayQueue<T>(chunkSize, capacity);
         }

         static <T> Queue<T> newMpscQueue() {
             return USE_MPSC_CHUNKED_ARRAY_QUEUE ? new MpscUnboundedArrayQueue<T>(MPSC_CHUNK_SIZE)
                                                 : new MpscUnboundedAtomicArrayQueue<T>(MPSC_CHUNK_SIZE);
         }
     }

     /**
      * Create a new {@link Queue} which is safe to use for multiple producers (different threads) and a single
      * consumer (one thread!).
      * @return A MPSC queue which may be unbounded.
      */
     public static <T> Queue<T> newMpscQueue() {
         return Mpsc.newMpscQueue();
     }

     /**
      * Create a new {@link Queue} which is safe to use for multiple producers (different threads) and a single
      * consumer (one thread!).
      */
     public static <T> Queue<T> newMpscQueue(final int maxCapacity) {
         return Mpsc.newMpscQueue(maxCapacity);
     }

     /**
      * Create a new {@link Queue} which is safe to use for multiple producers (different threads) and a single
      * consumer (one thread!).
      * The queue will grow and shrink its capacity in units of the given chunk size.
      */
     public static <T> Queue<T> newMpscQueue(final int chunkSize, final int maxCapacity) {
         return Mpsc.newChunkedMpscQueue(chunkSize, maxCapacity);
     }

     /**
      * Create a new {@link Queue} which is safe to use for single producer (one thread!) and a single
      * consumer (one thread!).
      */
     public static <T> Queue<T> newSpscQueue() {
         return hasUnsafe() ? new SpscLinkedQueue<T>() : new SpscLinkedAtomicQueue<T>();
     }

     /**
      * Create a new {@link Queue} which is safe to use for multiple producers (different threads) and a single
      * consumer (one thread!) with the given fixes {@code capacity}.
      */
     public static <T> Queue<T> newFixedMpscQueue(int capacity) {
         return hasUnsafe() ? new MpscArrayQueue<T>(capacity) : new MpscAtomicArrayQueue<T>(capacity);
     }

     /**
      * Return the {@link ClassLoader} for the given {@link Class}.
      */
     public static ClassLoader getClassLoader(final Class<?> clazz) {
         return PlatformDependent0.getClassLoader(clazz);
     }

     /**
      * Return the context {@link ClassLoader} for the current {@link Thread}.
      */
     public static ClassLoader getContextClassLoader() {
         return PlatformDependent0.getContextClassLoader();
     }

     /**
      * Return the system {@link ClassLoader}.
      */
     public static ClassLoader getSystemClassLoader() {
         return PlatformDependent0.getSystemClassLoader();
     }

     /**
      * Returns a new concurrent {@link Deque}.
      */
     @SuppressJava6Requirement(reason = "Usage guarded by java version check")
     public static <C> Deque<C> newConcurrentDeque() {
         if (javaVersion() < 7) {
             return new LinkedBlockingDeque<C>();
         } else {
             return new ConcurrentLinkedDeque<C>();
         }
     }

     /**
      * Return a {@link Random} which is not-threadsafe and so can only be used from the same thread.
      */
     public static Random threadLocalRandom() {
         return RANDOM_PROVIDER.current();
     }

     private static boolean isWindows0() {
         boolean windows = "windows".equals(NORMALIZED_OS);
         if (windows) {
             logger.debug("Platform: Windows");
         }
         return windows;
     }

     private static boolean isOsx0() {
         boolean osx = "osx".equals(NORMALIZED_OS);
         if (osx) {
             logger.debug("Platform: MacOS");
         }
         return osx;
     }

     private static boolean maybeSuperUser0() {
         String username = SystemPropertyUtil.get("user.name");
         if (isWindows()) {
             return "Administrator".equals(username);
         }
         // Check for root and toor as some BSDs have a toor user that is basically the same as root.
         return "root".equals(username) || "toor".equals(username);
     }

     private static Throwable unsafeUnavailabilityCause0() {
         if (isAndroid()) {
             logger.debug("sun.misc.Unsafe: unavailable (Android)");
             return new UnsupportedOperationException("sun.misc.Unsafe: unavailable (Android)");
         }

         if (isIkvmDotNet()) {
             logger.debug("sun.misc.Unsafe: unavailable (IKVM.NET)");
             return new UnsupportedOperationException("sun.misc.Unsafe: unavailable (IKVM.NET)");
         }

         Throwable cause = PlatformDependent0.getUnsafeUnavailabilityCause();
         if (cause != null) {
             return cause;
         }

         try {
             boolean hasUnsafe = PlatformDependent0.hasUnsafe();
             logger.debug("sun.misc.Unsafe: {}", hasUnsafe ? "available" : "unavailable");
             return hasUnsafe ? null : PlatformDependent0.getUnsafeUnavailabilityCause();
         } catch (Throwable t) {
             logger.trace("Could not determine if Unsafe is available", t);
             // Probably failed to initialize PlatformDependent0.
             return new UnsupportedOperationException("Could not determine if Unsafe is available", t);
         }
     }

     /**
      * Returns {@code true} if the running JVM is either <a href="https://developer.ibm.com/javasdk/">IBM J9</a> or
      * <a href="https://www.eclipse.org/openj9/">Eclipse OpenJ9</a>, {@code false} otherwise.
      */
     public static boolean isJ9Jvm() {
         return IS_J9_JVM;
     }

     private static boolean isJ9Jvm0() {
         String vmName = SystemPropertyUtil.get("java.vm.name", "").toLowerCase();
         return vmName.startsWith("ibm j9") || vmName.startsWith("eclipse openj9");
     }

     /**
      * Returns {@code true} if the running JVM is <a href="https://www.ikvm.net">IKVM.NET</a>, {@code false} otherwise.
      */
     public static boolean isIkvmDotNet() {
         return IS_IVKVM_DOT_NET;
     }

     private static boolean isIkvmDotNet0() {
         String vmName = SystemPropertyUtil.get("java.vm.name", "").toUpperCase(Locale.US);
         return vmName.equals("IKVM.NET");
     }

     private static Pattern getMaxDirectMemorySizeArgPattern() {
         // Pattern's is immutable so it's always safe published
         Pattern pattern = MAX_DIRECT_MEMORY_SIZE_ARG_PATTERN;
         if (pattern == null) {
             pattern = Pattern.compile("\\s*-XX:MaxDirectMemorySize\\s*=\\s*([0-9]+)\\s*([kKmMgG]?)\\s*$");
             MAX_DIRECT_MEMORY_SIZE_ARG_PATTERN =  pattern;
         }
         return pattern;
     }

     /**
      * Compute an estimate of the maximum amount of direct memory available to this JVM.
      * <p>
      * The computation is not cached, so you probably want to use {@link #maxDirectMemory()} instead.
      * <p>
      * This will produce debug log output when called.
      *
      * @return The estimated max direct memory, in bytes.
      */
     public static long estimateMaxDirectMemory() {
         long maxDirectMemory = PlatformDependent0.bitsMaxDirectMemory();
         if (maxDirectMemory > 0) {
             return maxDirectMemory;
         }

         ClassLoader systemClassLoader = null;
         try {
             systemClassLoader = getSystemClassLoader();

             // When using IBM J9 / Eclipse OpenJ9 we should not use VM.maxDirectMemory() as it not reflects the
             // correct value.
             // See:
             //  - https://github.com/netty/netty/issues/7654
             String vmName = SystemPropertyUtil.get("java.vm.name", "").toLowerCase();
             if (!vmName.startsWith("ibm j9") &&
                     // https://github.com/eclipse/openj9/blob/openj9-0.8.0/runtime/include/vendor_version.h#L53
                     !vmName.startsWith("eclipse openj9")) {
                 // Try to get from sun.misc.VM.maxDirectMemory() which should be most accurate.
                 Class<?> vmClass = Class.forName("sun.misc.VM", true, systemClassLoader);
                 Method m = vmClass.getDeclaredMethod("maxDirectMemory");
                 maxDirectMemory = ((Number) m.invoke(null)).longValue();
             }
         } catch (Throwable ignored) {
             // Ignore
         }

         if (maxDirectMemory > 0) {
             return maxDirectMemory;
         }

         try {
             // Now try to get the JVM option (-XX:MaxDirectMemorySize) and parse it.
             // Note that we are using reflection because Android doesn't have these classes.
             Class<?> mgmtFactoryClass = Class.forName(
                     "java.lang.management.ManagementFactory", true, systemClassLoader);
             Class<?> runtimeClass = Class.forName(
                     "java.lang.management.RuntimeMXBean", true, systemClassLoader);

             Object runtime = mgmtFactoryClass.getDeclaredMethod("getRuntimeMXBean").invoke(null);

             @SuppressWarnings("unchecked")
             List<String> vmArgs = (List<String>) runtimeClass.getDeclaredMethod("getInputArguments").invoke(runtime);

             Pattern maxDirectMemorySizeArgPattern = getMaxDirectMemorySizeArgPattern();

             for (int i = vmArgs.size() - 1; i >= 0; i --) {
                 Matcher m = maxDirectMemorySizeArgPattern.matcher(vmArgs.get(i));
                 if (!m.matches()) {
                     continue;
                 }

                 maxDirectMemory = Long.parseLong(m.group(1));
                 switch (m.group(2).charAt(0)) {
                     case 'k': case 'K':
                         maxDirectMemory *= 1024;
                         break;
                     case 'm': case 'M':
                         maxDirectMemory *= 1024 * 1024;
                         break;
                     case 'g': case 'G':
                         maxDirectMemory *= 1024 * 1024 * 1024;
                         break;
                     default:
                         break;
                 }
                 break;
             }
         } catch (Throwable ignored) {
             // Ignore
         }

         if (maxDirectMemory <= 0) {
             maxDirectMemory = Runtime.getRuntime().maxMemory();
             logger.debug("maxDirectMemory: {} bytes (maybe)", maxDirectMemory);
         } else {
             logger.debug("maxDirectMemory: {} bytes", maxDirectMemory);
         }

         return maxDirectMemory;
     }

     private static File tmpdir0() {
         File f;
         try {
             f = toDirectory(SystemPropertyUtil.get("io.netty.tmpdir"));
             if (f != null) {
                 logger.debug("-Dio.netty.tmpdir: {}", f);
                 return f;
             }

             f = toDirectory(SystemPropertyUtil.get("java.io.tmpdir"));
             if (f != null) {
                 logger.debug("-Dio.netty.tmpdir: {} (java.io.tmpdir)", f);
                 return f;
             }

             // This shouldn't happen, but just in case ..
             if (isWindows()) {
                 f = toDirectory(System.getenv("TEMP"));
                 if (f != null) {
                     logger.debug("-Dio.netty.tmpdir: {} (%TEMP%)", f);
                     return f;
                 }

                 String userprofile = System.getenv("USERPROFILE");
                 if (userprofile != null) {
                     f = toDirectory(userprofile + "\\AppData\\Local\\Temp");
                     if (f != null) {
                         logger.debug("-Dio.netty.tmpdir: {} (%USERPROFILE%\\AppData\\Local\\Temp)", f);
                         return f;
                     }

                     f = toDirectory(userprofile + "\\Local Settings\\Temp");
                     if (f != null) {
                         logger.debug("-Dio.netty.tmpdir: {} (%USERPROFILE%\\Local Settings\\Temp)", f);
                         return f;
                     }
                 }
             } else {
                 f = toDirectory(System.getenv("TMPDIR"));
                 if (f != null) {
                     logger.debug("-Dio.netty.tmpdir: {} ($TMPDIR)", f);
                     return f;
                 }
             }
         } catch (Throwable ignored) {
             // Environment variable inaccessible
         }

         // Last resort.
         if (isWindows()) {
             f = new File("C:\\Windows\\Temp");
         } else {
             f = new File("/tmp");
         }

         logger.warn("Failed to get the temporary directory; falling back to: {}", f);
         return f;
     }

     @SuppressWarnings("ResultOfMethodCallIgnored")
     private static File toDirectory(String path) {
         if (path == null) {
             return null;
         }

         File f = new File(path);
         f.mkdirs();

         if (!f.isDirectory()) {
             return null;
         }

         try {
             return f.getAbsoluteFile();
         } catch (Exception ignored) {
             return f;
         }
     }

     private static int bitMode0() {
         // Check user-specified bit mode first.
         int bitMode = SystemPropertyUtil.getInt("io.netty.bitMode", 0);
         if (bitMode > 0) {
             logger.debug("-Dio.netty.bitMode: {}", bitMode);
             return bitMode;
         }

         // And then the vendor specific ones which is probably most reliable.
         bitMode = SystemPropertyUtil.getInt("sun.arch.data.model", 0);
         if (bitMode > 0) {
             logger.debug("-Dio.netty.bitMode: {} (sun.arch.data.model)", bitMode);
             return bitMode;
         }
         bitMode = SystemPropertyUtil.getInt("com.ibm.vm.bitmode", 0);
         if (bitMode > 0) {
             logger.debug("-Dio.netty.bitMode: {} (com.ibm.vm.bitmode)", bitMode);
             return bitMode;
         }

         // os.arch also gives us a good hint.
         String arch = SystemPropertyUtil.get("os.arch", "").toLowerCase(Locale.US).trim();
         if ("amd64".equals(arch) || "x86_64".equals(arch)) {
             bitMode = 64;
         } else if ("i386".equals(arch) || "i486".equals(arch) || "i586".equals(arch) || "i686".equals(arch)) {
             bitMode = 32;
         }

         if (bitMode > 0) {
             logger.debug("-Dio.netty.bitMode: {} (os.arch: {})", bitMode, arch);
         }

         // Last resort: guess from VM name and then fall back to most common 64-bit mode.
         String vm = SystemPropertyUtil.get("java.vm.name", "").toLowerCase(Locale.US);
         Pattern bitPattern = Pattern.compile("([1-9][0-9]+)-?bit");
         Matcher m = bitPattern.matcher(vm);
         if (m.find()) {
             return Integer.parseInt(m.group(1));
         } else {
             return 64;
         }
     }

     private static int addressSize0() {
         if (!hasUnsafe()) {
             return -1;
         }
         return PlatformDependent0.addressSize();
     }

     private static long byteArrayBaseOffset0() {
         if (!hasUnsafe()) {
             return -1;
         }
         return PlatformDependent0.byteArrayBaseOffset();
     }

     private static boolean equalsSafe(byte[] bytes1, int startPos1, byte[] bytes2, int startPos2, int length) {
         final int end = startPos1 + length;
         for (; startPos1 < end; ++startPos1, ++startPos2) {
             if (bytes1[startPos1] != bytes2[startPos2]) {
                 return false;
             }
         }
         return true;
     }

     private static boolean isZeroSafe(byte[] bytes, int startPos, int length) {
         final int end = startPos + length;
         for (; startPos < end; ++startPos) {
             if (bytes[startPos] != 0) {
                 return false;
             }
         }
         return true;
     }

     /**
      * Package private for testing purposes only!
      */
     static int hashCodeAsciiSafe(byte[] bytes, int startPos, int length) {
         int hash = HASH_CODE_ASCII_SEED;
         final int remainingBytes = length & 7;
         final int end = startPos + remainingBytes;
         for (int i = startPos - 8 + length; i >= end; i -= 8) {
             hash = PlatformDependent0.hashCodeAsciiCompute(getLongSafe(bytes, i), hash);
         }
         switch(remainingBytes) {
         case 7:
             return ((hash * HASH_CODE_C1 + hashCodeAsciiSanitize(bytes[startPos]))
                           * HASH_CODE_C2 + hashCodeAsciiSanitize(getShortSafe(bytes, startPos + 1)))
                           * HASH_CODE_C1 + hashCodeAsciiSanitize(getIntSafe(bytes, startPos + 3));
         case 6:
             return (hash * HASH_CODE_C1 + hashCodeAsciiSanitize(getShortSafe(bytes, startPos)))
                          * HASH_CODE_C2 + hashCodeAsciiSanitize(getIntSafe(bytes, startPos + 2));
         case 5:
             return (hash * HASH_CODE_C1 + hashCodeAsciiSanitize(bytes[startPos]))
                          * HASH_CODE_C2 + hashCodeAsciiSanitize(getIntSafe(bytes, startPos + 1));
         case 4:
             return hash * HASH_CODE_C1 + hashCodeAsciiSanitize(getIntSafe(bytes, startPos));
         case 3:
             return (hash * HASH_CODE_C1 + hashCodeAsciiSanitize(bytes[startPos]))
                          * HASH_CODE_C2 + hashCodeAsciiSanitize(getShortSafe(bytes, startPos + 1));
         case 2:
             return hash * HASH_CODE_C1 + hashCodeAsciiSanitize(getShortSafe(bytes, startPos));
         case 1:
             return hash * HASH_CODE_C1 + hashCodeAsciiSanitize(bytes[startPos]);
         default:
             return hash;
         }
     }

     public static String normalizedArch() {
         return NORMALIZED_ARCH;
     }

     public static String normalizedOs() {
         return NORMALIZED_OS;
     }

     public static Set<String> normalizedLinuxClassifiers() {
         return LINUX_OS_CLASSIFIERS;
     }

     @SuppressJava6Requirement(reason = "Guarded by version check")
     public static File createTempFile(String prefix, String suffix, File directory) throws IOException {
         if (javaVersion() >= 7) {
             if (directory == null) {
                 return Files.createTempFile(prefix, suffix).toFile();
             }
             return Files.createTempFile(directory.toPath(), prefix, suffix).toFile();
         }
         final File file;
         if (directory == null) {
             file = File.createTempFile(prefix, suffix);
         } else {
             file = File.createTempFile(prefix, suffix, directory);
         }

         // Try to adjust the perms, if this fails there is not much else we can do...
         if (!file.setReadable(false, false)) {
             throw new IOException("Failed to set permissions on temporary file " + file);
         }
         if (!file.setReadable(true, true)) {
             throw new IOException("Failed to set permissions on temporary file " + file);
         }
         return file;
     }

     /**
      * Adds only those classifier strings to <tt>dest</tt> which are present in <tt>allowed</tt>.
      *
      * @param allowed          allowed classifiers
      * @param dest             destination set
      * @param maybeClassifiers potential classifiers to add
      */
     private static void addClassifier(Set<String> allowed, Set<String> dest, String... maybeClassifiers) {
         for (String id : maybeClassifiers) {
             if (allowed.contains(id)) {
                 dest.add(id);
             }
         }
     }

     private static String normalizeOsReleaseVariableValue(String value) {
         // Variable assignment values may be enclosed in double or single quotes.
         return value.trim().replaceAll("[\"']", "");
     }

     private static String normalize(String value) {
         return value.toLowerCase(Locale.US).replaceAll("[^a-z0-9]+", "");
     }

     private static String normalizeArch(String value) {
         value = normalize(value);
         if (value.matches("^(x8664|amd64|ia32e|em64t|x64)$")) {
             return "x86_64";
         }
         if (value.matches("^(x8632|x86|i[3-6]86|ia32|x32)$")) {
             return "x86_32";
         }
         if (value.matches("^(ia64|itanium64)$")) {
             return "itanium_64";
         }
         if (value.matches("^(sparc|sparc32)$")) {
             return "sparc_32";
         }
         if (value.matches("^(sparcv9|sparc64)$")) {
             return "sparc_64";
         }
         if (value.matches("^(arm|arm32)$")) {
             return "arm_32";
         }
         if ("aarch64".equals(value)) {
             return "aarch_64";
         }
         if ("riscv64".equals(value)) {
             // os.detected.arch is riscv64 for RISC-V, no underscore
             return "riscv64";
         }
         if (value.matches("^(ppc|ppc32)$")) {
             return "ppc_32";
         }
         if ("ppc64".equals(value)) {
             return "ppc_64";
         }
         if ("ppc64le".equals(value)) {
             return "ppcle_64";
         }
         if ("s390".equals(value)) {
             return "s390_32";
         }
         if ("s390x".equals(value)) {
             return "s390_64";
         }
         if ("loongarch64".equals(value)) {
             return "loongarch_64";
         }

         return "unknown";
     }

     private static String normalizeOs(String value) {
         value = normalize(value);
         if (value.startsWith("aix")) {
             return "aix";
         }
         if (value.startsWith("hpux")) {
             return "hpux";
         }
         if (value.startsWith("os400")) {
             // Avoid the names such as os4000
             if (value.length() <= 5 || !Character.isDigit(value.charAt(5))) {
                 return "os400";
             }
         }
         if (value.startsWith("linux")) {
             return "linux";
         }
         if (value.startsWith("macosx") || value.startsWith("osx") || value.startsWith("darwin")) {
             return "osx";
         }
         if (value.startsWith("freebsd")) {
             return "freebsd";
         }
         if (value.startsWith("openbsd")) {
             return "openbsd";
         }
         if (value.startsWith("netbsd")) {
             return "netbsd";
         }
         if (value.startsWith("solaris") || value.startsWith("sunos")) {
             return "sunos";
         }
         if (value.startsWith("windows")) {
             return "windows";
         }

         return "unknown";
     }

     private static final class AtomicLongCounter extends AtomicLong implements LongCounter {
         private static final long serialVersionUID = 4074772784610639305L;

         @Override
         public void add(long delta) {
             addAndGet(delta);
         }

         @Override
         public void increment() {
             incrementAndGet();
         }

         @Override
         public void decrement() {
             decrementAndGet();
         }

         @Override
         public long value() {
             return get();
         }
     }

     private interface ThreadLocalRandomProvider {
         Random current();
     }

     private PlatformDependent() {
         // only static method supported
     }
 }