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1 /* GStreamer |
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2 * Copyright (C) 2008 Sebastian Dröge <sebastian.droege@collabora.co.uk> |
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3 * |
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4 * gstfastrandom.h: Fast, bad PNRG |
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5 * |
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6 * This library is free software; you can redistribute it and/or |
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7 * modify it under the terms of the GNU Library General Public |
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8 * License as published by the Free Software Foundation; either |
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9 * version 2 of the License, or (at your option) any later version. |
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10 * |
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11 * This library is distributed in the hope that it will be useful, |
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12 * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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14 * Library General Public License for more details. |
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15 * |
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16 * You should have received a copy of the GNU Library General Public |
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17 * License along with this library; if not, write to the |
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18 * Free Software Foundation, Inc., 59 Temple Place - Suite 330, |
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19 * Boston, MA 02111-1307, USA. |
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20 */ |
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21 |
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22 #include <glib.h> |
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23 |
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24 #ifndef __GST_FAST_RANDOM__ |
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25 #define __GST_FAST_RANDOM__ |
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26 |
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27 /* transform [0..2^32] -> [0..1] */ |
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28 #define GST_RAND_DOUBLE_TRANSFORM 2.3283064365386962890625e-10 |
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29 |
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30 /* This is the base function, implementing a linear congruential generator |
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31 * and returning a pseudo random number between 0 and 2^32 - 1. |
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32 */ |
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33 static inline guint32 |
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34 gst_fast_random_uint32 () |
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35 { |
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36 static guint32 state = 0xdeadbeef; |
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37 |
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38 return (state = state * 1103515245 + 12345); |
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39 } |
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40 |
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41 static inline guint32 |
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42 gst_fast_random_uint32_range (gint32 start, gint32 end) |
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43 { |
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44 guint64 tmp = gst_fast_random_uint32 (); |
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45 |
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46 tmp = (tmp * (end - start)) / G_MAXUINT32 + start; |
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47 |
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48 return (guint32) tmp; |
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49 } |
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50 |
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51 static inline gint32 |
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52 gst_fast_random_int32 (void) |
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53 { |
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54 return (gint32) gst_fast_random_uint32 (); |
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55 } |
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56 |
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57 static inline gint32 |
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58 gst_fast_random_int32_range (gint32 start, gint32 end) |
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59 { |
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60 gint64 tmp = gst_fast_random_uint32 (); |
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61 |
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62 tmp = (tmp * (end - start)) / G_MAXUINT32 + start; |
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63 |
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64 return (gint32) tmp; |
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65 } |
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66 |
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67 static inline gdouble |
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68 gst_fast_random_double (void) |
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69 { |
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70 gdouble ret; |
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71 |
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72 ret = gst_fast_random_uint32 () * GST_RAND_DOUBLE_TRANSFORM; |
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73 ret = (ret + gst_fast_random_uint32 ()) * GST_RAND_DOUBLE_TRANSFORM; |
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74 |
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75 if (ret >= 1.0) |
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76 return gst_fast_random_double (); |
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77 |
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78 return ret; |
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79 } |
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80 |
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81 static inline gdouble |
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82 gst_fast_random_double_range (gdouble start, gdouble end) |
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83 { |
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84 return gst_fast_random_double () * (end - start) + start; |
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85 } |
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86 |
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87 #undef GST_RAND_DOUBLE_TRANSFORM |
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88 |
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89 #endif /* __GST_FAST_RANDOM__ */ |
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90 |