org.apache.jena.atlas.lib.BitsInt Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of jena-base Show documentation
This module contains non-RDF library code and the common system runtime.
There is a newer version: 5.2.0
/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.jena.atlas.lib;

// NB shifting is "mod 32" -- <<32 is a no-op (not a clear).
// http://mindprod.com/jgloss/masking.html

/** Utilities for manipulating a bit pattern which are held in a 32 bit int.
 *  @see BitsLong
 */
public final class BitsInt
{
    private BitsInt() {}

    private static final int IntLen = Integer.SIZE ;

    /** Extract the value packed into bits start (inclusive) and finish (exclusive).
     *  The value is returned in the low part of the returned int.
     *  The low bit is bit zero.
     * @param bits
     * @param start
     * @param finish
     * @return int
     */

    public static final
    int unpack(int bits, int start, int finish)
    {
        check(start, finish) ;
        if ( finish == 0 ) return 0 ;
        // Remove top bits by moving up.  Clear bottom bits by them moving down.
        return (bits<<(IntLen-finish)) >>> ((IntLen-finish)+start) ;
    }

    /** Place the value into the bit pattern between start and finish
     *  and returns the new int.  Leaves other bits alone.
     * @param bits
     * @param value
     * @param start
     * @param finish
     * @return int
     */
    public static final
    int pack(int bits, int value, int start, int finish)
    {
        check(start, finish) ;
        bits = clear$(bits, start, finish) ;
        int mask = mask(start, finish) ;
        bits = bits | ((value<>> (IntLen-finish+start) ) << start  ;
    }

    private static final
    int mask$(int bitIndex)
    {
        return 1 << bitIndex ;
    }

    private static final
    int mask$(int start, int finish)
    {
        if ( finish == 0 )
            // Valid args; start is zero and so the mask is zero.
            return 0 ;
        int mask = -1 ;
        return mask << (IntLen-finish) >>> (IntLen-finish+start) << start ;
    }

    private static final
    int maskZero$(int bitIndex)
    {
        return ~mask$(bitIndex);
    }

    private static final
    int maskZero$(int start, int finish)
    {
        return ~mask$(start, finish) ;
    }

    private static final
    void check(int bitIndex)
    {
        if ( bitIndex < 0 || bitIndex >= IntLen ) throw new IllegalArgumentException("Illegal bit index: "+bitIndex) ;
    }

    private static final
    void check(int start, int finish)
    {
        if ( start < 0 || start >= IntLen ) throw new IllegalArgumentException("Illegal start: "+start) ;
        if ( finish < 0 || finish > IntLen ) throw new IllegalArgumentException("Illegal finish: "+finish) ;
        if ( start > finish )  throw new IllegalArgumentException("Illegal range: ("+start+", "+finish+")") ;
    }
}