Modify some functions to alleviate overflow / precision errors

'session_frame_to_track_frame()' and its complement, 'track_frame_to_session_frame()' both accept a double and an ARDOUR::framepost_t (int64_t). For convenience these both get converted to long double. However, the functions are often called with very large values (ARDOUR::max_framepos). When this happens, rounding and precision errors can cause overflow issues. This is an attempt to alleviate that problem. Not sure if it's strictly necessary to accommodate negative values - but I'm assuming these could happen if 'speed' was negative (reverse play?)

This is the reason why 'Select All Objects' (and similar functionality) don't work for some users.

diff --git a/libs/ardour/ardour/types.h b/libs/ardour/ardour/types.h
index 17e0b0d7e493bfbd3542105b2a74da0eaed956fd..08fe0ef75bc1239378a1ec99c8a8148dcc195cf0 100644 (file)
--- a/libs/ardour/ardour/types.h
+++ b/libs/ardour/ardour/types.h
@@ -713,13 +713,30 @@ LIBARDOUR_API std::ostream& operator<<(std::ostream& o, const ARDOUR::MeterLineU
 static inline ARDOUR::framepos_t
 session_frame_to_track_frame (ARDOUR::framepos_t session_frame, double speed)
 {
-       return (ARDOUR::framepos_t) ((long double) session_frame * (long double) speed);
+       long double result = (long double) session_frame * (long double) speed;
+
+       if (result >= (long double) ARDOUR::max_framepos) {
+               return ARDOUR::max_framepos;
+       } else if (result <= (long double) (ARDOUR::max_framepos) * (ARDOUR::framepos_t)(-1)) {
+               return (ARDOUR::max_framepos * (ARDOUR::framepos_t)(-1));
+       } else {
+               return result;
+       }
 }
 
 static inline ARDOUR::framepos_t
 track_frame_to_session_frame (ARDOUR::framepos_t track_frame, double speed)
 {
-       return (ARDOUR::framepos_t) ((long double) track_frame / (long double) speed);
+       /* NB - do we need a check for speed == 0 ??? */ 
+       long double result = (long double) track_frame / (long double) speed;
+
+       if (result >= (long double) ARDOUR::max_framepos) {
+               return ARDOUR::max_framepos;
+       } else if (result <= (long double) (ARDOUR::max_framepos) * (ARDOUR::framepos_t)(-1)) {
+               return (ARDOUR::max_framepos * (ARDOUR::framepos_t)(-1));
+       } else {
+               return result;
+       }
 }
 
 /* for now, break the rules and use "using" to make this "global" */