/*
 * 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 com.facebook.presto.common.array;

// Note: this code was forked from fastutil (http://fastutil.di.unimi.it/)
// Copyright (C) 2010-2013 Sebastiano Vigna
final class BigArrays
{
    private BigArrays() {}

    /**
     * Initial number of segments to support in array.
     */
    public static final int INITIAL_SEGMENTS = 1024;

    /**
     * The shift used to compute the segment associated with an index (equivalently, the logarithm of the segment size).
     */
    public static final int SEGMENT_SHIFT = 10;

    /**
     * Size of a single segment of a BigArray
     */
    public static final int SEGMENT_SIZE = 1 << SEGMENT_SHIFT;

    /**
     * The mask used to compute the offset associated to an index.
     */
    public static final int SEGMENT_MASK = SEGMENT_SIZE - 1;

    /**
     * Computes the segment associated with a given index.
     *
     * @param index an index into a big array.
     * @return the associated segment.
     */
    @SuppressWarnings("NumericCastThatLosesPrecision")
    public static int segment(long index)
    {
        return (int) (index >>> SEGMENT_SHIFT);
    }

    /**
     * Computes the offset associated with a given index.
     *
     * @param index an index into a big array.
     * @return the associated offset (in the associated {@linkplain #segment(long) segment}).
     */
    @SuppressWarnings("NumericCastThatLosesPrecision")
    public static int offset(long index)
    {
        return (int) (index & SEGMENT_MASK);
    }
}
