crypto: add decoding flag to options.

[ffmpeg] / libavutil / lfg.c

diff --git a/libavutil/lfg.c b/libavutil/lfg.c
index e876d18fefb6641f8a0e40de3c328b6efbaa23af..7fab806f8c4baf56725f1400ed6ba09b0203f45b 100644 (file)
--- a/libavutil/lfg.c
+++ b/libavutil/lfg.c
@@ -2,27 +2,30 @@
  * Lagged Fibonacci PRNG
  * Copyright (c) 2008 Michael Niedermayer
  *
- * This file is part of FFmpeg.
+ * This file is part of Libav.
  *
- * FFmpeg is free software; you can redistribute it and/or
+ * Libav is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
- * FFmpeg is distributed in the hope that it will be useful,
+ * Libav 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
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
- * License along with FFmpeg; if not, write to the Free Software
+ * License along with Libav; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #include <inttypes.h>
+#include <limits.h>
+#include <math.h>
 #include "lfg.h"
 #include "md5.h"
 #include "intreadwrite.h"
+#include "attributes.h"
 
 void av_cold av_lfg_init(AVLFG *c, unsigned int seed){
     uint8_t tmp[16]={0};
@@ -39,9 +42,24 @@ void av_cold av_lfg_init(AVLFG *c, unsigned int seed){
     c->index=0;
 }
 
+void av_bmg_get(AVLFG *lfg, double out[2])
+{
+    double x1, x2, w;
+
+    do {
+        x1 = 2.0/UINT_MAX*av_lfg_get(lfg) - 1.0;
+        x2 = 2.0/UINT_MAX*av_lfg_get(lfg) - 1.0;
+        w = x1*x1 + x2*x2;
+    } while (w >= 1.0);
+
+    w = sqrt((-2.0 * log(w)) / w);
+    out[0] = x1 * w;
+    out[1] = x2 * w;
+}
+
 #ifdef TEST
 #include "log.h"
-#include "common.h"
+#include "timer.h"
 
 int main(void)
 {
@@ -59,6 +77,24 @@ int main(void)
         STOP_TIMER("624 calls of av_lfg_get");
     }
     av_log(NULL, AV_LOG_ERROR, "final value:%X\n", x);
+
+    /* BMG usage example */
+    {
+        double mean   = 1000;
+        double stddev = 53;
+
+        av_lfg_init(&state, 42);
+
+        for (i = 0; i < 1000; i += 2) {
+            double bmg_out[2];
+            av_bmg_get(&state, bmg_out);
+            av_log(NULL, AV_LOG_INFO,
+                   "%f\n%f\n",
+                   bmg_out[0] * stddev + mean,
+                   bmg_out[1] * stddev + mean);
+        }
+    }
+
     return 0;
 }
 #endif