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 *
 *  http://www.apache.org/licenses/LICENSE-2.0
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 *  distributed under the License is distributed on an "AS IS" BASIS,
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package io.questdb.std;

public class DirectLongLongMaxHeap implements DirectLongLongHeap {
    private final int capacity;
    private final Cursor cursor = new Cursor();
    private final int memoryTag;
    private long ptr;
    private int size;

    public DirectLongLongMaxHeap(int capacity, int memoryTag) {
        this.capacity = capacity;
        this.memoryTag = memoryTag;
        this.ptr = Unsafe.malloc(16L * capacity, memoryTag);
        this.size = 0;
    }

    @Override
    public void add(long index, long value) {
        // fast path
        if (size == capacity && Unsafe.getUnsafe().getLong(ptr + 16L * (size - 1)) >= value) {
            return;
        }
        // slow path
        int p = binSearch(value);
        if (p < capacity - 1) {
            Vect.memmove(ptr + 16L * (p + 1), ptr + 16L * p, 16L * (capacity - p - 1));
        }
        Unsafe.getUnsafe().putLong(ptr + 16L * p, value);
        Unsafe.getUnsafe().putLong(ptr + 16L * p + 8, index);
        size = Math.min(capacity, size + 1);
    }

    @Override
    public void clear() {
        size = 0;
        cursor.toTop();
    }

    @Override
    public void close() {
        if (ptr != 0) {
            ptr = Unsafe.free(ptr, 16L * capacity, memoryTag);
            size = 0;
        }
    }

    @Override
    public int getCapacity() {
        return capacity;
    }

    @Override
    public Cursor getCursor() {
        return cursor;
    }

    @Override
    public void reopen() {
        if (ptr == 0) {
            ptr = Unsafe.malloc(16L * capacity, memoryTag);
        }
        clear();
    }

    @Override
    public int size() {
        return size;
    }

    @SuppressWarnings("StatementWithEmptyBody")
    private int binSearch(long v) {
        int low = 0;
        int high = size;

        while (high - low > 65) {
            int mid = (low + high - 1) >>> 1;
            long midVal = Unsafe.getUnsafe().getLong(ptr + 16L * mid);

            if (midVal > v) {
                low = mid + 1;
            } else if (midVal < v) {
                high = mid;
            } else {
                while (++mid < high && Unsafe.getUnsafe().getLong(ptr + 16L * mid) == v) {
                }
                return mid;
            }
        }
        return scanSearch(v, low);
    }

    private int scanSearch(long v, int low) {
        for (int i = low; i < size; i++) {
            if (Unsafe.getUnsafe().getLong(ptr + 16L * i) < v) {
                return i;
            }
        }
        return size;
    }

    public class Cursor implements DirectLongLongHeap.Cursor {
        private int pos = -1;

        @Override
        public boolean hasNext() {
            return ++pos < size;
        }

        @Override
        public long index() {
            return Unsafe.getUnsafe().getLong(ptr + 16L * pos + 8);
        }

        @Override
        public void toTop() {
            pos = -1;
        }

        @Override
        public long value() {
            return Unsafe.getUnsafe().getLong(ptr + 16L * pos);
        }
    }
}