AVR32: optimisations for intreadwrite.h

[ffmpeg] / libavutil / lfg.h

diff --git a/libavutil/lfg.h b/libavutil/lfg.h
index 0882faab0207a49c1ea90839549a1c9ff7061dc8..3250c18e794295e6dd4575b913e70fecd9a3822e 100644 (file)
--- a/libavutil/lfg.h
+++ b/libavutil/lfg.h
@@ -19,8 +19,8 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-#ifndef FFMPEG_LFG_H
-#define FFMPEG_LFG_H
+#ifndef AVUTIL_LFG_H
+#define AVUTIL_LFG_H
 
 typedef struct {
     unsigned int state[64];
@@ -29,9 +29,26 @@ typedef struct {
 
 void av_lfg_init(AVLFG *c, unsigned int seed);
 
+/**
+ * Gets the next random unsigned 32-bit number using an ALFG.
+ *
+ * Please also consider a simple LCG like state= state*1664525+1013904223,
+ * it may be good enough and faster for your specific use case.
+ */
 static inline unsigned int av_lfg_get(AVLFG *c){
     c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63];
     return c->state[c->index++ & 63];
 }
 
-#endif //FFMPEG_LFG_H
+/**
+ * Gets the next random unsigned 32-bit number using a MLFG.
+ *
+ * Please also consider av_lfg_get() above, it is faster.
+ */
+static inline unsigned int av_mlfg_get(AVLFG *c){
+    unsigned int a= c->state[(c->index-55) & 63];
+    unsigned int b= c->state[(c->index-24) & 63];
+    return c->state[c->index++ & 63] = 2*a*b+a+b;
+}
+
+#endif /* AVUTIL_LFG_H */