/* 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., 59 Temple Place - Suite 330,

 * Boston, MA 02111-1307, 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 ()

{

  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__ */