/* * CVS identifier: * * $Id: MathUtil.java,v 1.15 2001/09/14 08:48:51 grosbois Exp $ * * Class: MathUtil * * Description: Utility mathematical methods * * * * COPYRIGHT: * * This software module was originally developed by Raphaël Grosbois and * Diego Santa Cruz (Swiss Federal Institute of Technology-EPFL); Joel * Askelöf (Ericsson Radio Systems AB); and Bertrand Berthelot, David * Bouchard, Félix Henry, Gerard Mozelle and Patrice Onno (Canon Research * Centre France S.A) in the course of development of the JPEG2000 * standard as specified by ISO/IEC 15444 (JPEG 2000 Standard). This * software module is an implementation of a part of the JPEG 2000 * Standard. Swiss Federal Institute of Technology-EPFL, Ericsson Radio * Systems AB and Canon Research Centre France S.A (collectively JJ2000 * Partners) agree not to assert against ISO/IEC and users of the JPEG * 2000 Standard (Users) any of their rights under the copyright, not * including other intellectual property rights, for this software module * with respect to the usage by ISO/IEC and Users of this software module * or modifications thereof for use in hardware or software products * claiming conformance to the JPEG 2000 Standard. Those intending to use * this software module in hardware or software products are advised that * their use may infringe existing patents. The original developers of * this software module, JJ2000 Partners and ISO/IEC assume no liability * for use of this software module or modifications thereof. No license * or right to this software module is granted for non JPEG 2000 Standard * conforming products. JJ2000 Partners have full right to use this * software module for his/her own purpose, assign or donate this * software module to any third party and to inhibit third parties from * using this software module for non JPEG 2000 Standard conforming * products. This copyright notice must be included in all copies or * derivative works of this software module. * * Copyright (c) 1999/2000 JJ2000 Partners. * */ using System; namespace CSJ2K.j2k.util { /// <summary> This class contains a collection of utility methods fro mathematical /// operations. All methods are static. /// /// </summary> public class MathUtil { /// <summary> Method that calculates the floor of the log, base 2, of 'x'. The /// calculation is performed in integer arithmetic, therefore, it is exact. /// /// </summary> /// <param name="x">The value to calculate log2 on. /// /// </param> /// <returns> floor(log(x)/log(2)), calculated in an exact way. /// /// </returns> public static int log2(int x) { int y, v; // No log of 0 or negative if (x <= 0) { throw new System.ArgumentException("" + x + " <= 0"); } // Calculate log2 (it's actually floor log2) v = x; y = - 1; while (v > 0) { v >>= 1; y++; } return y; } } }