Tools.cs

// AForge Math Library
// AForge.NET framework
// http://www.aforgenet.com/framework/
//
// Copyright © Andrew Kirillov, 2005-2009
// andrew.kirillov@aforgenet.com
//

namespace AForge.Math
{
    using System;

    /// <summary>
    /// Set of tool functions.
    /// </summary>
    /// 
    /// <remarks>The class contains different utility functions.</remarks>
    /// 
    public static class Tools
    {
        /// <summary>
        /// Calculates power of 2.
        /// </summary>
        /// 
        /// <param name="power">Power to raise in.</param>
        /// 
        /// <returns>Returns specified power of 2 in the case if power is in the range of
        /// [0, 30]. Otherwise returns 0.</returns>
        /// 
        public static int Pow2( int power )
        {
            return ( ( power >= 0 ) && ( power <= 30 ) ) ? ( 1 << power ) : 0;
        }

        /// <summary>
        /// Checks if the specified integer is power of 2.
        /// </summary>
        /// 
        /// <param name="x">Integer number to check.</param>
        /// 
        /// <returns>Returns <b>true</b> if the specified number is power of 2.
        /// Otherwise returns <b>false</b>.</returns>
        /// 
        public static bool IsPowerOf2( int x )
        {
            return ( x > 0 ) ? ( ( x & ( x - 1 ) ) == 0 ) : false;
        }

        /// <summary>
        /// Get base of binary logarithm.
        /// </summary>
        /// 
        /// <param name="x">Source integer number.</param>
        /// 
        /// <returns>Power of the number (base of binary logarithm).</returns>
        /// 
        public static int Log2( int x )
        {
            if ( x <= 65536 )
            {
                if ( x <= 256 )
                {
                    if ( x <= 16 )
                    {
                        if ( x <= 4 )
                        {
                            if ( x <= 2 )
                            {
                                if ( x <= 1 )
                                    return 0;
                                return 1;
                            }
                            return 2;
                        }
                        if ( x <= 8 )
                            return 3;
                        return 4;
                    }
                    if ( x <= 64 )
                    {
                        if ( x <= 32 )
                            return 5;
                        return 6;
                    }
                    if ( x <= 128 )
                        return 7;
                    return 8;
                }
                if ( x <= 4096 )
                {
                    if ( x <= 1024 )
                    {
                        if ( x <= 512 )
                            return 9;
                        return 10;
                    }
                    if ( x <= 2048 )
                        return 11;
                    return 12;
                }
                if ( x <= 16384 )
                {
                    if ( x <= 8192 )
                        return 13;
                    return 14;
                }
                if ( x <= 32768 )
                    return 15;
                return 16;
            }

            if ( x <= 16777216 )
            {
                if ( x <= 1048576 )
                {
                    if ( x <= 262144 )
                    {
                        if ( x <= 131072 )
                            return 17;
                        return 18;
                    }
                    if ( x <= 524288 )
                        return 19;
                    return 20;
                }
                if ( x <= 4194304 )
                {
                    if ( x <= 2097152 )
                        return 21;
                    return 22;
                }
                if ( x <= 8388608 )
                    return 23;
                return 24;
            }
            if ( x <= 268435456 )
            {
                if ( x <= 67108864 )
                {
                    if ( x <= 33554432 )
                        return 25;
                    return 26;
                }
                if ( x <= 134217728 )
                    return 27;
                return 28;
            }
            if ( x <= 1073741824 )
            {
                if ( x <= 536870912 )
                    return 29;
                return 30;
            }
            return 31;
        }
    }
}