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