experimental: make init_edges calls safe

src/intra_edge.rs

@@ -81,16 +81,6 @@ struct ModeSelMem {
     pub nt: *mut EdgeTip,
 }
 
-unsafe fn init_edges(node: *mut EdgeNode, bl: BlockLevel, edge_flags: EdgeFlags) {
-    if bl == BL_8X8 {
-        let nt = &mut *(node as *mut EdgeTip);
-        init_edges_tip(nt, edge_flags)
-    } else {
-        let nwc = &mut *(node as *mut EdgeBranch);
-        init_edges_branch(nwc, bl, edge_flags)
-    }
-}
-
 fn init_edges_tip(nt: &mut EdgeTip, edge_flags: EdgeFlags) {
     let node = &mut nt.node;
 
@@ -167,20 +157,25 @@ unsafe fn init_mode_node(
     top_has_right: bool,
     left_has_bottom: bool,
 ) {
-    init_edges(
-        &mut nwc.node,
+    // this is an invariant: this function is only called with BL_128X128 and BL_64X64.
+    // then this function recurses, decreasing the block level at each step, until bottoming out
+    // at BL_16x16.
+    assert!(bl != BL_8X8);
+
+    init_edges_branch(
+        nwc,
         bl,
         EdgeFlags::ALL_TOP_HAS_RIGHT.select(top_has_right)
             | EdgeFlags::ALL_LEFT_HAS_BOTTOM.select(left_has_bottom),
     );
+
     if bl == BL_16X16 {
         let nt = slice::from_raw_parts_mut(mem.nt, nwc.split.len());
         mem.nt = mem.nt.offset(nt.len() as isize);
         for (n, (split, nt)) in iter::zip(&mut nwc.split, nt).enumerate() {
             *split = &mut nt.node;
-            init_edges(
-                &mut nt.node,
-                bl + 1,
+            init_edges_tip(
+                nt,
                 EdgeFlags::ALL_TOP_HAS_RIGHT.select(!(n == 3 || (n == 1 && !top_has_right)))
                     | EdgeFlags::ALL_LEFT_HAS_BOTTOM.select(n == 0 || (n == 2 && left_has_bottom)),
             );