/* GStreamer * Copyright (C) 2008 Sebastian Dröge <sebastian.droege@collabora.co.uk> * * gstfastrandom.h: Fast, bad PNRG * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Library General Public * License as published by the Free Software Foundation; either * version 2 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Library General Public License for more details. * * You should have received a copy of the GNU Library General Public * License along with this library; if not, write to the * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, * Boston, MA 02110-1301, USA. */ #include <glib.h> #ifndef __GST_FAST_RANDOM__ #define __GST_FAST_RANDOM__ /* transform [0..2^32] -> [0..1] */ #define GST_RAND_DOUBLE_TRANSFORM 2.3283064365386962890625e-10 /* This is the base function, implementing a linear congruential generator * and returning a pseudo random number between 0 and 2^32 - 1. */ static inline guint32 gst_fast_random_uint32 (void) { static guint32 state = 0xdeadbeef; return (state = state * 1103515245 + 12345); } static inline guint32 gst_fast_random_uint32_range (gint32 start, gint32 end) { guint64 tmp = gst_fast_random_uint32 (); tmp = (tmp * (end - start)) / G_MAXUINT32 + start; return (guint32) tmp; } static inline gint32 gst_fast_random_int32 (void) { return (gint32) gst_fast_random_uint32 (); } static inline gint32 gst_fast_random_int32_range (gint32 start, gint32 end) { gint64 tmp = gst_fast_random_uint32 (); tmp = (tmp * (end - start)) / G_MAXUINT32 + start; return (gint32) tmp; } static inline gdouble gst_fast_random_double (void) { gdouble ret; ret = gst_fast_random_uint32 () * GST_RAND_DOUBLE_TRANSFORM; ret = (ret + gst_fast_random_uint32 ()) * GST_RAND_DOUBLE_TRANSFORM; if (ret >= 1.0) return gst_fast_random_double (); return ret; } static inline gdouble gst_fast_random_double_range (gdouble start, gdouble end) { return gst_fast_random_double () * (end - start) + start; } #undef GST_RAND_DOUBLE_TRANSFORM #endif /* __GST_FAST_RANDOM__ */