libcaca/cucul/math.c

/*
 *  libcucul      Canvas for ultrafast compositing of Unicode letters
 *  Copyright (c) 2002-2006 Sam Hocevar <sam@zoy.org>
 *                All Rights Reserved
 *
 *  $Id$
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the Do What The Fuck You Want To
 *  Public License, Version 2, as published by Sam Hocevar. See
 *  http://sam.zoy.org/wtfpl/COPYING for more details.
 */

/*
 *  This file contains simple mathematical routines.
 */

#include "config.h"

#if !defined(__KERNEL__)
#   include <stdlib.h>
#endif

#include "cucul.h"
#include "cucul_internals.h"

/** \brief Generate a random integer within a range.
 *
 *  \param min The lower bound of the integer range.
 *  \param max The upper bound of the integer range.
 *  \return A random integer comprised between \p min and \p max, inclusive.
 */
int cucul_rand(int min, int max)
{
    return min + (int)((1.0*(max-min+1)) * rand() / (RAND_MAX+1.0));
}

/** \brief Approximate a square root, using Newton's method to avoid
 *         costly floating point calculations.
 *
 *  \param a A positive integer.
 *  \return The approximate square root of \p a.
 */
unsigned int cucul_sqrt(unsigned int a)
{
    if(a == 0)
        return 0;

    if(a < 1000000000)
    {
        unsigned int x = a < 10 ? 1
                       : a < 1000 ? 10
                       : a < 100000 ? 100
                       : a < 10000000 ? 1000
                       : 10000;

        /* Newton's method. Three iterations would be more than enough. */
        x = (x * x + a) / x / 2;
        x = (x * x + a) / x / 2;
        x = (x * x + a) / x / 2;
        x = (x * x + a) / x / 2;

        return x;
    }

    return 2 * cucul_sqrt(a / 4);
}