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 *  Copyright (c) 2014-2019 Appsicle
 *  Copyright (c) 2019-2020 QuestDB
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 *  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
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package io.questdb.std;

import io.questdb.std.ex.FatalError;

import java.lang.reflect.Field;
import java.util.concurrent.atomic.AtomicLong;

public final class Unsafe {
    public static final long INT_OFFSET;
    public static final long INT_SCALE;
    public static final long LONG_OFFSET;
    public static final long LONG_SCALE;
    static final AtomicLong MEM_USED = new AtomicLong(0);
    private static final sun.misc.Unsafe UNSAFE;
    private static final AtomicLong MALLOC_COUNT = new AtomicLong(0);
    private static final AtomicLong FREE_COUNT = new AtomicLong(0);

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

            INT_OFFSET = Unsafe.getUnsafe().arrayBaseOffset(int[].class);
            INT_SCALE = msb(Unsafe.getUnsafe().arrayIndexScale(int[].class));

            LONG_OFFSET = Unsafe.getUnsafe().arrayBaseOffset(long[].class);
            LONG_SCALE = msb(Unsafe.getUnsafe().arrayIndexScale(long[].class));

        } catch (Exception e) {
            throw new FatalError(e);
        }
    }

    private Unsafe() {
    }

    public static long arrayGetVolatile(long[] array, int index) {
        assert index > -1 && index < array.length;
        return Unsafe.getUnsafe().getLongVolatile(array, LONG_OFFSET + (index << LONG_SCALE));
    }

    public static void arrayPutOrdered(long[] array, int index, long value) {
        assert index > -1 && index < array.length;
        Unsafe.getUnsafe().putOrderedLong(array, LONG_OFFSET + (index << LONG_SCALE), value);
    }

    public static long calloc(long size) {
        long ptr = malloc(size);
        getUnsafe().setMemory(ptr, size, (byte) 0);
        return ptr;
    }

    public static boolean cas(Object o, long offset, long expected, long value) {
        return UNSAFE.compareAndSwapLong(o, offset, expected, value);
    }

    public static boolean cas(Object o, long offset, int expected, int value) {
        return UNSAFE.compareAndSwapInt(o, offset, expected, value);
    }

    public static boolean cas(long[] array, int index, long expected, long value) {
        assert index > -1 && index < array.length;
        return Unsafe.cas(array, Unsafe.LONG_OFFSET + (((long) index) << Unsafe.LONG_SCALE), expected, value);
    }

    public static void free(long ptr, long size) {
        getUnsafe().freeMemory(ptr);
        FREE_COUNT.incrementAndGet();
        recordMemAlloc(-size);
    }

    public static boolean getBool(long address) {
        return UNSAFE.getByte(address) == 1;
    }

    public static long getFieldOffset(Class clazz, String name) {
        try {
            Field f = clazz.getDeclaredField(name);
//            f.setAccessible(true);
            return UNSAFE.objectFieldOffset(f);
        } catch (NoSuchFieldException e) {
            throw new RuntimeException(e);
        }
    }

    public static long getFreeCount() {
        return FREE_COUNT.get();
    }

    public static long getMallocCount() {
        return MALLOC_COUNT.get();
    }

    public static long getMemUsed() {
        return MEM_USED.get();
    }

    public static sun.misc.Unsafe getUnsafe() {
        return UNSAFE;
    }

    public static long malloc(long size) {
        long ptr = getUnsafe().allocateMemory(size);
        recordMemAlloc(size);
        MALLOC_COUNT.incrementAndGet();
        return ptr;
    }

    public static long realloc(long address, long oldSize, long newSize) {
        long ptr = getUnsafe().reallocateMemory(address, newSize);
        recordMemAlloc(-oldSize + newSize);
        return ptr;
    }

    static void recordMemAlloc(long size) {
        MEM_USED.addAndGet(size);
    }

    private static int msb(int value) {
        return 31 - Integer.numberOfLeadingZeros(value);
    }
}