source: libcaca/trunk/cucul/math.c @ 769

Last change on this file since 769 was 769, checked in by Sam Hocevar, 15 years ago
  • Removed \file directives from all files except caca.h and cucul.h, to remove redundencies in the Doxygen documentation.
  • Property svn:keywords set to Id
File size: 1.7 KB
Line 
1/*
2 *  libcucul      Canvas for ultrafast compositing of Unicode letters
3 *  Copyright (c) 2002-2006 Sam Hocevar <sam@zoy.org>
4 *                All Rights Reserved
5 *
6 *  $Id: math.c 769 2006-04-14 07:30:53Z sam $
7 *
8 *  This library is free software; you can redistribute it and/or
9 *  modify it under the terms of the Do What The Fuck You Want To
10 *  Public License, Version 2, as published by Sam Hocevar. See
11 *  http://sam.zoy.org/wtfpl/COPYING for more details.
12 */
13
14/*
15 *  This file contains simple mathematical routines.
16 */
17
18#include "config.h"
19
20#if !defined(__KERNEL__)
21#   include <stdlib.h>
22#endif
23
24#include "cucul.h"
25#include "cucul_internals.h"
26
27/**
28 * \brief Generate a random integer within a range.
29 *
30 * \param min The lower bound of the integer range.
31 * \param max The upper bound of the integer range.
32 * \return A random integer comprised between \p min and \p max, inclusive.
33 */
34int cucul_rand(int min, int max)
35{
36    return min + (int)((1.0*(max-min+1)) * rand() / (RAND_MAX+1.0));
37}
38
39/**
40 * \brief Approximate a square root, using Newton's method to avoid
41 *        costly floating point calculations.
42 *
43 * \param a A positive integer.
44 * \return The approximate square root of \p a.
45 */
46unsigned int cucul_sqrt(unsigned int a)
47{
48    if(a == 0)
49        return 0;
50
51    if(a < 1000000000)
52    {
53        unsigned int x = a < 10 ? 1
54                       : a < 1000 ? 10
55                       : a < 100000 ? 100
56                       : a < 10000000 ? 1000
57                       : 10000;
58
59        /* Newton's method. Three iterations would be more than enough. */
60        x = (x * x + a) / x / 2;
61        x = (x * x + a) / x / 2;
62        x = (x * x + a) / x / 2;
63        x = (x * x + a) / x / 2;
64
65        return x;
66    }
67
68    return 2 * cucul_sqrt(a / 4);
69}
70
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