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    • foundation.icon.ee.util.xxhash.UnsafeAccess Maven / Gradle / Ivy

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    /*
 * Copyright 2021 ICON Foundation
 * Copyright 2014 Higher Frequency Trading http://www.higherfrequencytrading.com
 *
 * Licensed 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
 *
 *     http://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 foundation.icon.ee.util.xxhash;

import sun.misc.Unsafe;

import java.lang.reflect.Field;
import java.nio.ByteOrder;

import static java.nio.ByteOrder.LITTLE_ENDIAN;
import static java.nio.ByteOrder.nativeOrder;

class UnsafeAccess extends Access {
    static final boolean NATIVE_LITTLE_ENDIAN = nativeOrder() == LITTLE_ENDIAN;
    static long unsignedInt(int i) {
        return i & 0xFFFFFFFFL;
    }

    static int unsignedShort(int s) {
        return s & 0xFFFF;
    }

    static int unsignedByte(int b) {
        return b & 0xFF;
    }

    static final UnsafeAccess INSTANCE;
    private static final Access INSTANCE_NON_NATIVE;

    // for test only
    static final UnsafeAccess OLD_INSTANCE = NATIVE_LITTLE_ENDIAN
                                             ? new OldUnsafeAccessLittleEndian()
                                             : new OldUnsafeAccessBigEndian();

    static final Unsafe UNSAFE;

    static final long BOOLEAN_BASE;
    static final long BYTE_BASE;
    static final long CHAR_BASE;
    static final long SHORT_BASE;
    static final long INT_BASE;
    static final long LONG_BASE;

    static final byte TRUE_BYTE_VALUE;
    static final byte FALSE_BYTE_VALUE;

    static {
        try {
            Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
            theUnsafe.setAccessible(true);
            UNSAFE = (Unsafe) theUnsafe.get(null);

            BOOLEAN_BASE = UNSAFE.arrayBaseOffset(boolean[].class);
            BYTE_BASE = UNSAFE.arrayBaseOffset(byte[].class);
            CHAR_BASE = UNSAFE.arrayBaseOffset(char[].class);
            SHORT_BASE = UNSAFE.arrayBaseOffset(short[].class);
            INT_BASE = UNSAFE.arrayBaseOffset(int[].class);
            LONG_BASE = UNSAFE.arrayBaseOffset(long[].class);

            TRUE_BYTE_VALUE = (byte)UNSAFE.getInt(new boolean[] {true, true, true, true},
                                                  BOOLEAN_BASE);
            FALSE_BYTE_VALUE = (byte)UNSAFE.getInt(new boolean[] {false, false, false, false},
                                                  BOOLEAN_BASE);
        } catch (final Exception e) {
            throw new AssertionError(e);
        }

        boolean hasGetByte = true;
        try {
            UNSAFE.getByte(new byte[1], BYTE_BASE);
        } catch (final Throwable ignore) {
            // Unsafe in pre-Nougat Android does not have getByte(), fall back to workround
            hasGetByte = false;
        }

        INSTANCE = hasGetByte ? new UnsafeAccess() : OLD_INSTANCE;
        INSTANCE_NON_NATIVE = Access.newDefaultReverseAccess(INSTANCE);
    }

    private UnsafeAccess() {}

    @Override
    public long getLong(Object input, long offset) {
        return UNSAFE.getLong(input, offset);
    }

    @Override
    public long getUnsignedInt(Object input, long offset) {
        return unsignedInt(getInt(input, offset));
    }

    @Override
    public int getInt(Object input, long offset) {
        return UNSAFE.getInt(input, offset);
    }

    @Override
    public int getUnsignedShort(Object input, long offset) {
        return unsignedShort(getShort(input, offset));
    }

    @Override
    public int getShort(Object input, long offset) {
        return UNSAFE.getShort(input, offset);
    }

    @Override
    public int getUnsignedByte(Object input, long offset) {
        return unsignedByte(getByte(input, offset));
    }

    @Override
    public int getByte(Object input, long offset) {
        return UNSAFE.getByte(input, offset);
    }

    @Override
    public ByteOrder byteOrder(Object input) {
        return ByteOrder.nativeOrder();
    }

    @Override
    protected Access reverseAccess() {
        return INSTANCE_NON_NATIVE;
    }

    private static class OldUnsafeAccessLittleEndian extends UnsafeAccess {
        @Override
        public int getShort(final Object input, final long offset) {
            return UNSAFE.getInt(input, offset - 2) >> 16;
        }

        @Override
        public int getByte(final Object input, final long offset) {
            return UNSAFE.getInt(input, offset - 3) >> 24;
        }
    }

    private static class OldUnsafeAccessBigEndian extends UnsafeAccess {
        @Override
        public int getShort(final Object input, final long offset) {
            return (int)(short)UNSAFE.getInt(input, offset - 2);
        }

        @Override
        public int getByte(final Object input, final long offset) {
            return (int)(byte)UNSAFE.getInt(input, offset - 3);
        }
    }
}
    
    
    
    

    




    
    
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