support SI and some non SI prefixes

Originally committed as revision 6284 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/eval.c

@@ -64,6 +64,28 @@ static int strmatch(const char *s, const char *prefix){
     return 1;
 }
 
+static int8_t si_prefixes['z' - 'E' + 1]={
+    ['y'-'E']= -24,
+    ['z'-'E']= -21,
+    ['a'-'E']= -18,
+    ['f'-'E']= -15,
+    ['p'-'E']= -12,
+    ['n'-'E']= - 9,
+    ['u'-'E']= - 6,
+    ['m'-'E']= - 3,
+    ['c'-'E']= - 2,
+    ['d'-'E']= - 1,
+    ['h'-'E']=   2,
+    ['k'-'E']=   3,
+    ['M'-'E']=   6,
+    ['G'-'E']=   9,
+    ['T'-'E']=  12,
+    ['P'-'E']=  15,
+    ['E'-'E']=  18,
+    ['Z'-'E']=  21,
+    ['Y'-'E']=  24,
+};
+
 static double evalPrimary(Parser *p){
     double d, d2=NAN;
     char *next= p->s;
@@ -72,6 +94,18 @@ static double evalPrimary(Parser *p){
     /* number */
     d= strtod(p->s, &next);
     if(next != p->s){
+        if(*next >= 'E' && *next <= 'z'){
+            int e= si_prefixes[*next - 'E'];
+            if(e){
+                if(next[1] == 'i'){
+                    d*= pow( 2, e/0.3);
+                    next+=2;
+                }else{
+                    d*= pow(10, e);
+                    next++;
+                }
+            }
+        }
         p->s= next;
         return d;
     }