eval: add function to access the current "wallclock" time.

Reviewed-by: Stefano Sabatini <stefasab@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/eval.texi

@@ -163,6 +163,9 @@ note, when you have the derivatives at y instead of 0
 taylor(expr, x-y) can be used
 When the series does not converge the results are undefined.
 
+@item time(0)
+The the current (wallclock) time in seconds
+
 @item root(expr, max)
 Finds x where f(x)=0 in the interval 0..max.
 f() must be continuous or the result is undefined.

libavutil/eval.c

@@ -32,6 +32,7 @@
 #include "eval.h"
 #include "log.h"
 #include "mathematics.h"
+#include "time.h"
 
 typedef struct Parser {
     const AVClass *class;
@@ -156,6 +157,11 @@ struct AVExpr {
     double *var;
 };
 
+static double etime(double v)
+{
+    return av_gettime() * 0.000001;
+}
+
 static double eval_expr(Parser *p, AVExpr *e)
 {
     switch (e->type) {
@@ -377,6 +383,7 @@ static int parse_primary(AVExpr **e, Parser *p)
     else if (strmatch(next, "exp"   )) d->a.func0 = exp;
     else if (strmatch(next, "log"   )) d->a.func0 = log;
     else if (strmatch(next, "abs"   )) d->a.func0 = fabs;
+    else if (strmatch(next, "time"  )) d->a.func0 = etime;
     else if (strmatch(next, "squish")) d->type = e_squish;
     else if (strmatch(next, "gauss" )) d->type = e_gauss;
     else if (strmatch(next, "mod"   )) d->type = e_mod;

libavutil/version.h

@@ -76,7 +76,7 @@
 
 #define LIBAVUTIL_VERSION_MAJOR  52
 #define LIBAVUTIL_VERSION_MINOR  15
-#define LIBAVUTIL_VERSION_MICRO 100
+#define LIBAVUTIL_VERSION_MICRO 101
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
                                                LIBAVUTIL_VERSION_MINOR, \