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net/art: make Table.Get alloc-free

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Updates #7781

Signed-off-by: David Anderson <danderson@tailscale.com>
This commit is contained in:
David Anderson 2023-07-24 11:26:44 -07:00 committed by Dave Anderson
parent b76d8a88ae
commit 125b982ba5
1 changed files with 14 additions and 2 deletions
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16
net/art/table.go
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@ -45,13 +45,25 @@ func (t *Table[T]) init() {
// no route matched.
func (t *Table[T]) Get(addr netip.Addr) *T {
t.init()
st := &t.v4
// Ideally we would use addr.AsSlice here, but AsSlice is just
// barely complex enough that it can't be inlined, and that in
// turn causes the slice to escape to the heap. Using As16 and
// manual slicing here helps the compiler keep Get alloc-free.
rawAddr := addr.As16()
var (
st *strideTable[T]
bs []byte
)
if addr.Is6() {
st = &t.v6
bs = rawAddr[:]
} else {
st = &t.v4
bs = rawAddr[12:]
}
i := 0
bs := addr.AsSlice()
// With path compression, we might skip over some address bits while walking
// to a strideTable leaf. This means the leaf answer we find might not be
// correct, because path compression took us down the wrong subtree. When