Resume rounding error fixes (patch #783078 by Harold Toler)

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@3978 a1c6a512-1295-4272-9138-f99709370657

1 files changed, 7 insertions, 4 deletions

diff --git a/firmware/mpeg.c b/firmware/mpeg.c
index cc514ba..9d6718d 100644
--- a/firmware/mpeg.c
+++ b/firmware/mpeg.c
@@ -337,17 +337,20 @@ static void set_elapsed(struct mp3entry* id3)
 
             remainder = id3->offset - (relpos * (id3->filesize / 256));
 
-            /* set time for this percent */
-            id3->elapsed = i * id3->length / 100;
+            /* set time for this percent (divide before multiply to prevent
+               overflow on long files. loss of precision is negligible on
+               short files) */
+            id3->elapsed = i * (id3->length / 100);
 
             /* calculate remainder time */
             plen = (nextpos - relpos) * (id3->filesize / 256);
-            id3->elapsed += (((remainder * 100) / plen) * id3->length) / 10000;
+            id3->elapsed += (((remainder * 100) / plen) *
+                             (id3->length / 10000));
         }
         else {
             /* no TOC exists. set a rough estimate using average bitrate */
             int tpk = id3->length / (id3->filesize / 1024);
-            id3->elapsed = id3->offset * tpk / 1024;
+            id3->elapsed = id3->offset / 1024 * tpk;
         }
     }
     else