Fixing data abort (pc in strchr). when scrolling a big playlist very fast.

Change-Id: Ibe00a11592a18d320682cce755e48ce701ff5b4a
Reviewed-on: http://gerrit.rockbox.org/281
Reviewed-by: Thomas Martitz <kugel@rockbox.org>
Tested-by: Thomas Martitz <kugel@rockbox.org>

1 files changed, 41 insertions, 5 deletions

diff --git a/apps/playlist_viewer.c b/apps/playlist_viewer.c
index 68732ad..5479ba4 100644
--- a/apps/playlist_viewer.c
+++ b/apps/playlist_viewer.c
@@ -175,12 +175,21 @@ static void playlist_buffer_load_entries(struct playlist_buffer *pb, int index,
     pb->num_loaded = i;
 }
 
+/* playlist_buffer_load_entries_screen()
+ *      This function is called when the currently selected item gets too close
+ *      to the start or the end of the loaded part of the playlis, or when
+ *      the list callback requests a playlist item that has not been loaded yet
+ *
+ *      reference_track is either the currently selected track, or the track that
+ *      has been requested by the callback, and has not been loaded yet.
+ */
 static void playlist_buffer_load_entries_screen(struct playlist_buffer * pb,
-                                                enum direction direction)
+                                                enum direction direction,
+                                                int reference_track)
 {
     if (direction == FORWARD)
     {
-        int min_start = viewer.selected_track-2*screens[0].getnblines();
+        int min_start = reference_track-2*screens[0].getnblines();
         while (min_start < 0)
             min_start += viewer.num_tracks;
         min_start %= viewer.num_tracks;
@@ -188,7 +197,7 @@ static void playlist_buffer_load_entries_screen(struct playlist_buffer * pb,
     }
     else
     {
-        int max_start = viewer.selected_track+2*screens[0].getnblines();
+        int max_start = reference_track+2*screens[0].getnblines();
         max_start %= viewer.num_tracks;
         playlist_buffer_load_entries(pb, max_start, BACKWARD);
     }
@@ -266,6 +275,31 @@ static struct playlist_entry * playlist_buffer_get_track(struct playlist_buffer
                                                          int index)
 {
     int buffer_index = playlist_buffer_get_index(pb, index);
+    /* Make sure that we are not returning an invalid pointer.
+       In some cases, when scrolling really fast, it could happen that a reqested track
+       has not been pre-loaded */
+    if (buffer_index < 0) {
+        playlist_buffer_load_entries_screen(&viewer.buffer,
+                    pb->direction == FORWARD ? BACKWARD : FORWARD,
+                    index);
+
+    } else if (buffer_index >= pb->num_loaded) {
+        playlist_buffer_load_entries_screen(&viewer.buffer,
+                    pb->direction,
+                    index);
+    }
+    buffer_index = playlist_buffer_get_index(pb, index);
+    if (buffer_index < 0 || buffer_index >= pb->num_loaded) {
+        /* This really shouldn't happen. If this happens, then
+           the name_buffer is probably too small to store enough
+           titles to fill the screen, and preload data in the short
+           direction.
+          
+           If this happens then scrolling performance will probably
+           be quite low, but it's better then having Data Abort errors */
+        playlist_buffer_load_entries(pb, index, FORWARD);
+        buffer_index = playlist_buffer_get_index(pb, index);
+    }
     return &(pb->tracks[buffer_index]);
 }
 
@@ -425,7 +459,8 @@ static bool update_playlist(bool force)
             global_status.resume_offset = -1;
             return false;
         }
-        playlist_buffer_load_entries_screen(&viewer.buffer, FORWARD);
+        playlist_buffer_load_entries_screen(&viewer.buffer, FORWARD,
+                          viewer.selected_track);
         if (viewer.buffer.num_loaded <= 0)
         {
             global_status.resume_index = -1;
@@ -679,7 +714,8 @@ enum playlist_viewer_result playlist_viewer_ex(const char* filename)
                     viewer.selected_track);
             if (reload)
                 playlist_buffer_load_entries_screen(&viewer.buffer,
-                    button == ACTION_STD_NEXT ? FORWARD : BACKWARD);
+                    button == ACTION_STD_NEXT ? FORWARD : BACKWARD,
+                    viewer.selected_track);
             if (reload || viewer.moving_track >= 0)
                 gui_synclist_draw(&playlist_lists);
         }