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zipper_algebra: further specialize grafting #62

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61 changes: 41 additions & 20 deletions src/experimental/zipper_algebra.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -515,13 +515,11 @@ where
Out: ZipperWriting<V, A>,
{
if *lhs_grafts != ByteMask::EMPTY {
out.graft_masked_branches(lhs, *lhs_grafts, false);
*lhs_grafts = ByteMask::EMPTY;
do_graft(out, lhs, std::mem::take(lhs_grafts));
}

if *rhs_grafts != ByteMask::EMPTY {
out.graft_masked_branches(rhs, *rhs_grafts, false);
*rhs_grafts = ByteMask::EMPTY;
do_graft(out, rhs, std::mem::take(rhs_grafts));
}
}

Expand Down Expand Up @@ -731,18 +729,15 @@ where
Out: ZipperWriting<V, A>,
{
if *lhs_grafts != ByteMask::EMPTY {
out.graft_masked_branches(lhs, *lhs_grafts, false);
*lhs_grafts = ByteMask::EMPTY;
do_graft(out, lhs, std::mem::take(lhs_grafts));
}

if *mid_grafts != ByteMask::EMPTY {
out.graft_masked_branches(mid, *mid_grafts, false);
*mid_grafts = ByteMask::EMPTY;
do_graft(out, mid, std::mem::take(mid_grafts));
}

if *rhs_grafts != ByteMask::EMPTY {
out.graft_masked_branches(rhs, *rhs_grafts, false);
*rhs_grafts = ByteMask::EMPTY;
do_graft(out, rhs, std::mem::take(rhs_grafts));
}
}

Expand Down Expand Up @@ -1016,23 +1011,19 @@ fn zipper_merge4<P, V, Z0, Z1, Z2, Z3, Out, A>(
Out: ZipperWriting<V, A>,
{
if *z0_grafts != ByteMask::EMPTY {
out.graft_masked_branches(z0, *z0_grafts, false);
*z0_grafts = ByteMask::EMPTY;
do_graft(out, z0, std::mem::take(z0_grafts));
}

if *z1_grafts != ByteMask::EMPTY {
out.graft_masked_branches(z1, *z1_grafts, false);
*z1_grafts = ByteMask::EMPTY;
do_graft(out, z1, std::mem::take(z1_grafts));
}

if *z2_grafts != ByteMask::EMPTY {
out.graft_masked_branches(z2, *z2_grafts, false);
*z2_grafts = ByteMask::EMPTY;
do_graft(out, z2, std::mem::take(z2_grafts));
}

if *z3_grafts != ByteMask::EMPTY {
out.graft_masked_branches(z3, *z3_grafts, false);
*z3_grafts = ByteMask::EMPTY;
do_graft(out, z3, std::mem::take(z3_grafts));
}
}

Expand Down Expand Up @@ -1631,6 +1622,37 @@ fn with_k<const K: usize, T, R>(
f(refs)
}

fn do_graft<V, A, Z, Out>(dst: &mut Out, src: &Z, grafts: ByteMask)
where
V: Clone + Send + Sync,
A: Allocator,
Out: ZipperWriting<V, A>,
Z: ZipperInfallibleSubtries<V, A>,
{
match grafts.count_bits() {
0 => {}
1 => {
let byte = grafts.indexed_bit::<true>(0).expect("one bit set");
dst.descend_to_byte(byte);
dst.graft_src_at(src, &[byte]);
dst.ascend_byte();
}
2 => {
let first_byte = grafts.indexed_bit::<true>(0).expect("some bit set");
dst.descend_to_byte(first_byte);
dst.graft_src_at(src, &[first_byte]);
dst.ascend_byte();
let second_byte = grafts.next_bit(first_byte).expect("two bits set");
dst.descend_to_byte(second_byte);
dst.graft_src_at(src, &[second_byte]);
dst.ascend_byte();
}
_ => {
dst.graft_masked_branches(src, grafts, false);
}
}
}

// - The function is fully monomorphized over `Z` and `N` and uses a bitmask (`active`)
// to track participating zippers.
// - Small frontiers (`k ≤ 4`) are dispatched to specialized implementations
Expand Down Expand Up @@ -1674,8 +1696,7 @@ where
{
for_each_bit(active, |i| {
if grafts[i] != ByteMask::EMPTY {
out.graft_masked_branches(&zs[i], grafts[i], false);
grafts[i] = ByteMask::EMPTY;
do_graft(out, &zs[i], std::mem::take(&mut grafts[i]));
}
});
}
Expand Down