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overlaps.go
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/
overlaps.go
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package bart
import "github.com/bits-and-blooms/bitset"
// overlapsRec returns true if any IP in the nodes n or o overlaps.
func (n *node[V]) overlapsRec(o *node[V]) bool {
nPfxLen := len(n.prefixes)
oPfxLen := len(o.prefixes)
nChildLen := len(n.children)
oChildLen := len(o.children)
// ##############################
// 1. Test if any routes overlaps
// ##############################
// special case, overlapsPrefix is faster
if nPfxLen == 1 && nChildLen == 0 {
// get the single prefix from n
idx, _ := n.prefixesBitset.NextSet(0)
return o.overlapsPrefix(idxToPfx(idx))
}
// special case, overlapsPrefix is faster
if oPfxLen == 1 && oChildLen == 0 {
// get the single prefix from o
idx, _ := o.prefixesBitset.NextSet(0)
return n.overlapsPrefix(idxToPfx(idx))
}
// full cross check
if nPfxLen > 0 && oPfxLen > 0 {
if n.overlapsRoutes(o) {
return true
}
}
// ####################################
// 2. Test if routes overlaps any child
// ####################################
if nPfxLen > 0 && oChildLen > 0 {
if n.overlapsChildsIn(o) {
return true
}
}
// symmetric reverse
if oPfxLen > 0 && nChildLen > 0 {
if o.overlapsChildsIn(n) {
return true
}
}
// ################################################################
// 3. rec-descent call for childs with same octet in nodes n and o
// ################################################################
// stop condition, n or o have no childs
if nChildLen == 0 || oChildLen == 0 {
return false
}
if oChildLen == 1 {
return n.overlapsOneChildIn(o)
}
if nChildLen == 1 {
return o.overlapsOneChildIn(n)
}
// stop condition, no child with identical octet in n and o
if n.childrenBitset.IntersectionCardinality(o.childrenBitset) == 0 {
return false
}
return n.overlapsSameChildsRec(o)
}
// overlapsRoutes, test if n overlaps o prefixes and vice versa
func (n *node[V]) overlapsRoutes(o *node[V]) bool {
// one node has just one prefix, use bitset algo
if len(n.prefixes) == 1 {
return o.overlapsOneRouteIn(n)
}
// one node has just one prefix, use bitset algo
if len(o.prefixes) == 1 {
return n.overlapsOneRouteIn(o)
}
// some prefixes are identical, trivial overlap
if n.prefixesBitset.IntersectionCardinality(o.prefixesBitset) > 0 {
return true
}
// make full cross check
nOK := true
oOK := true
var nIdx, oIdx uint
// zip, range over n and o together to help chance on its way
for nOK || oOK {
if nOK {
// does any route in o overlap this prefix from n
if nIdx, nOK = n.prefixesBitset.NextSet(nIdx); nOK {
if o.lpmTest(nIdx) {
return true
}
nIdx++
}
}
if oOK {
// does any route in n overlap this prefix from o
if oIdx, oOK = o.prefixesBitset.NextSet(oIdx); oOK {
if n.lpmTest(oIdx) {
return true
}
oIdx++
}
}
}
return false
}
// overlapsChildsIn, test if prefixes in n overlaps child octets in o.
func (n *node[V]) overlapsChildsIn(o *node[V]) bool {
pfxLen := len(n.prefixes)
childLen := len(o.children)
// heuristic, compare benchmarks
// when will re range over the children and when will we do bitset calc?
magicNumber := 15
doRange := childLen < magicNumber || pfxLen > magicNumber
// do range over, not so many childs and maybe to many prefixes
if doRange {
var oAddr uint
ok := true
for ok {
// does any route in o overlap this child from n
if oAddr, ok = o.childrenBitset.NextSet(oAddr); ok {
if n.lpmTest(hostIndex(byte(oAddr))) {
return true
}
oAddr++
}
}
return false
}
// do bitset intersection, alloted route table with child octets
// maybe to many childs ro range over or not so many prefixes to
// build the alloted routing table from them
// make allot table with prefixes as bitsets, bitsets are precalculated
// just union the bitsets to one bitset (allot table) for all prefixes
// in this node
// gimmick, don't allocate, can't use bitset.New()
prefixBacking := make([]uint64, 8)
prefixRoutes := bitset.From(prefixBacking)
idxBacking := make([]uint, maxNodePrefixes)
for _, idx := range n.allStrideIndexes(idxBacking) {
a8 := allotLookupTbl[idx]
prefixRoutes.InPlaceUnion(bitset.From(a8[:]))
}
// shift children bitset by firstHostIndex
c8 := make([]uint64, 8)
copy(c8[4:], o.childrenBitset.Bytes()) // 4*64= 256
hostRoutes := bitset.From(c8)
return prefixRoutes.IntersectionCardinality(hostRoutes) > 0
}
// overlapsSameChildsRec, find same octets with bitset intersection.
// rec-descent with same child octet in n an o,
func (n *node[V]) overlapsSameChildsRec(o *node[V]) bool {
// gimmicks, clone a bitset without heap allocation
// 4*64=256, maxNodeChildren
a4 := make([]uint64, 4)
copy(a4, n.childrenBitset.Bytes())
nChildrenBitsetCloned := bitset.From(a4)
// intersect in place the child bitsets from n and o
nChildrenBitsetCloned.InPlaceIntersection(o.childrenBitset)
// gimmick, don't allocate
addrBuf := [maxNodeChildren]uint{}
_, allCommonChilds := nChildrenBitsetCloned.NextSetMany(0, addrBuf[:])
// range over all child addrs, common in n and o
for _, addr := range allCommonChilds {
oChild := o.getChild(byte(addr))
nChild := n.getChild(byte(addr))
// rec-descent with same child
if nChild.overlapsRec(oChild) {
return true
}
}
return false
}
func (n *node[V]) overlapsOneChildIn(o *node[V]) bool {
// get the single addr and child
addr, _ := o.childrenBitset.NextSet(0)
oChild := o.children[0]
if nChild := n.getChild(byte(addr)); nChild != nil {
return nChild.overlapsRec(oChild)
}
return false
}
func (n *node[V]) overlapsOneRouteIn(o *node[V]) bool {
// get the single prefix from o
idx, _ := o.prefixesBitset.NextSet(0)
// 1. Test if any route in this node overlaps prefix?
if n.lpmTest(idx) {
return true
}
// 2. Test if prefix overlaps any route in this node
// use bitset intersection with alloted stride table instead of range loops
// precalculated allotment for idx (complete binary tree as bitset)
pfxBuf := allotLookupTbl[idx]
allotedPrefixRoutes := bitset.From(pfxBuf[:])
// use bitset intersection instead of range loops
return allotedPrefixRoutes.IntersectionCardinality(n.prefixesBitset) > 0
}
// overlapsPrefix returns true if node overlaps with prefix.
func (n *node[V]) overlapsPrefix(octet byte, pfxLen int) bool {
// 1. Test if any route in this node overlaps prefix?
idx := pfxToIdx(octet, pfxLen)
if n.lpmTest(idx) {
return true
}
// 2. Test if prefix overlaps any route in this node
// use bitset intersection with alloted stride table instead of range loops
// precalculated allotment for idx (complete binary tree as bitset)
allotmentForIdx := allotLookupTbl[idx]
allotedPrefixRoutes := bitset.From(allotmentForIdx[:])
// use bitset intersection instead of range loops
if allotedPrefixRoutes.IntersectionCardinality(n.prefixesBitset) != 0 {
return true
}
// 3. Test if prefix overlaps any child in this node
// use bitsets intersection instead of range loops
// shift children bitset by firstHostIndex
c8 := make([]uint64, 8)
copy(c8[4:], n.childrenBitset.Bytes()) // 4*64= 256
hostRoutes := bitset.From(c8)
// use bitsets intersection instead of range loops
return allotedPrefixRoutes.IntersectionCardinality(hostRoutes) != 0
}