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1 // Copyright (c) 1997-2009 Nokia Corporation and/or its subsidiary(-ies). |
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2 // All rights reserved. |
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3 // This component and the accompanying materials are made available |
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4 // under the terms of "Eclipse Public License v1.0" |
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5 // which accompanies this distribution, and is available |
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6 // at the URL "http://www.eclipse.org/legal/epl-v10.html". |
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7 // |
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8 // Initial Contributors: |
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9 // Nokia Corporation - initial contribution. |
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10 // |
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11 // Contributors: |
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12 // |
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13 // Description: |
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14 // FUNCTION |
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15 // <<rand>>, <<srand>>---pseudo-random numbers |
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16 // INDEX |
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17 // rand |
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18 // INDEX |
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19 // srand |
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20 // INDEX |
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21 // _rand_r |
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22 // INDEX |
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23 // _srand_r |
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24 // ANSI_SYNOPSIS |
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25 // |
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26 |
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27 // #include <stdlib.h> |
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28 // int rand(void); |
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29 // void srand(unsigned int <[seed]>); |
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30 // int _rand_r(void *<[reent]>); |
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31 // void _srand_r(void *<[reent]>, unsigned int <[seed]>); |
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32 // TRAD_SYNOPSIS |
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33 // #include <stdlib.h> |
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34 // int rand(); |
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35 // void srand(<[seed]>) |
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36 // unsigned int <[seed]>; |
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37 // int _rand_r(<[reent]>); |
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38 // char *<[reent]> |
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39 // void _srand_r(<[data]>,<[seed]>) |
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40 // char *<[reent]>; |
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41 // unsigned int <[seed]>; |
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42 // <<rand>> returns a different integer each time it is called; each |
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43 // integer is chosen by an algorithm designed to be unpredictable, so |
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44 // that you can use <<rand>> when you require a random number. |
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45 // The algorithm depends on a static variable called the ``random seed''; |
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46 // starting with a given value of the random seed always produces the |
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47 // same sequence of numbers in successive calls to <<rand>>. |
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48 // You can set the random seed using <<srand>>; it does nothing beyond |
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49 // storing its argument in the static variable used by <<rand>>. You can |
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50 // exploit this to make the pseudo-random sequence less predictable, if |
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51 // you wish, by using some other unpredictable value (often the least |
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52 // significant parts of a time-varying value) as the random seed before |
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53 // beginning a sequence of calls to <<rand>>; or, if you wish to ensure |
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54 // (for example, while debugging) that successive runs of your program |
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55 // use the same ``random'' numbers, you can use <<srand>> to set the same |
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56 // random seed at the outset. |
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57 // <<_rand_r>> and <<_srand_r>> are reentrant versions of <<rand>> and |
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58 // <<srand>>. The extra argument <[reent]> is a pointer to a reentrancy |
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59 // structure. |
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60 // RETURNS |
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61 // <<rand>> returns the next pseudo-random integer in sequence; it is a |
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62 // number between <<0>> and <<RAND_MAX>> (inclusive). |
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63 // <<srand>> does not return a result. |
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64 // PORTABILITY |
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65 // <<rand>> is required by ANSI, but the algorithm for pseudo-random |
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66 // number generation is not specified; therefore, even if you use |
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67 // the same random seed, you cannot expect the same sequence of results |
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68 // on two different systems. |
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69 // <<rand>> requires no supporting OS subroutines. |
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70 // |
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71 |
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72 #include <e32math.h> |
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73 #include <stdlib_r.h> |
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74 |
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75 extern "C" { |
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76 |
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77 /** |
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78 Reentrant versions of rand() |
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79 @param ptr |
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80 */ |
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81 EXPORT_C int _rand_r(struct _reent *ptr) |
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82 { |
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83 return Math::Rand(*(TInt64*)ptr->_next); |
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84 } |
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85 |
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86 /** |
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87 Reentrant versions of srand() |
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88 @param ptr |
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89 @param seed |
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90 */ |
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91 EXPORT_C void _srand_r (struct _reent *ptr, unsigned int seed) |
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92 { |
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93 ptr->_next[0] = seed; |
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94 ptr->_next[1] = seed; |
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95 } |
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96 |
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97 /** |
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98 Returns a different integer each time it is called; each |
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99 integer is chosen by an algorithm designed to be unpredictable, so |
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100 that you can use <<rand>> when you require a random number. |
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101 @return the next pseudo-random integer in sequence; it is a |
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102 number between 0 and RAND_MAX (inclusive). |
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103 */ |
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104 EXPORT_C int rand (void) |
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105 { |
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106 return _rand_r (_REENT); |
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107 } |
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108 |
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109 /** |
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110 Sets the random seed. |
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111 @param seed seed |
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112 */ |
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113 EXPORT_C void srand (unsigned int seed) |
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114 { |
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115 _srand_r (_REENT, seed); |
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116 } |
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117 |
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118 } // extern "C" |