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QuestDB is High Performance Time Series Database

There is a newer version: 3.3.3

/*******************************************************************************
 *    ___                  _   ____  ____
 *   / _ \ _   _  ___  ___| |_|  _ \| __ )
 *  | | | | | | |/ _ \/ __| __| | | |  _ \
 *  | |_| | |_| |  __/\__ \ |_| |_| | |_) |
 *   \__\_\\__,_|\___||___/\__|____/|____/
 *
 * Copyright (C) 2014-2016 Appsicle
 *
 * This program is free software: you can redistribute it and/or  modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see .
 *
 ******************************************************************************/

package com.questdb.misc;

public final class Hash {
    private Hash() {
    }

    /**
     * Restricts hashCode() of the underlying char sequence to be no greater than max.
     *
     * @param s   char sequence
     * @param max max value of hashCode()
     * @return power of 2 integer
     */
    public static int boundedHash(CharSequence s, int max) {
        return s == null ? -1 : (Chars.hashCode(s) & 0xFFFFFFF) & max;
    }

    /**
     * Calculates positive integer hash of memory pointer using Java hashcode() algorithm.
     *
     * @param address memory pointer
     * @param len     memory length in bytes
     * @return hash code
     */
    public static int hashMem(final long address, int len) {
        int hash = 0;
        long end = address + len;
        long p = address;
        while (end - p > 1) {
            hash = (hash << 5) - hash + Unsafe.getUnsafe().getChar(p);
            p += 2;
        }

        if (p < end) {
            hash = (hash << 5) - hash + Unsafe.getUnsafe().getByte(p);
        }

        return hash < 0 ? -hash : hash;
    }
}