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list.go
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list.go
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/*
* Copyright (C) 2020-2022, IrineSistiana
*
* This file is part of mosdns.
*
* mosdns is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* mosdns is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package netlist
import (
"fmt"
"net/netip"
"sort"
)
// List is a list of netip.Prefix. It stores all netip.Prefix in one single slice
// and use binary search.
// It is suitable for large static cidr search.
type List struct {
// stores valid and masked netip.Prefix(s)
e []netip.Prefix
sorted bool
}
// NewList returns a *List.
func NewList() *List {
return &List{
e: make([]netip.Prefix, 0),
}
}
func mustValid(l []netip.Prefix) {
for i, prefix := range l {
if !prefix.IsValid() {
panic(fmt.Sprintf("invalid prefix at #%d", i))
}
}
}
// Append appends new netip.Prefix(s) to the list.
// This modified the list. Caller must call List.Sort() before calling List.Contains()
func (list *List) Append(newNet ...netip.Prefix) {
for i, n := range newNet {
addr := to6(n.Addr())
bits := n.Bits()
if n.Addr().Is4() {
bits += 96
}
newNet[i] = netip.PrefixFrom(addr, bits).Masked()
}
mustValid(newNet)
list.e = append(list.e, newNet...)
list.sorted = false
}
// Sort sorts the list, this must be called after
// list being modified and before calling List.Contains().
func (list *List) Sort() {
if list.sorted {
return
}
sort.Sort(list)
out := make([]netip.Prefix, 0)
for i, n := range list.e {
if i == 0 {
out = append(out, n)
} else {
lv := &out[len(out)-1]
switch {
case n.Addr() == lv.Addr():
if n.Bits() < lv.Bits() {
*lv = n
}
case !lv.Contains(n.Addr()):
out = append(out, n)
}
}
}
list.e = out
list.sorted = true
}
// Len implements sort Interface.
func (list *List) Len() int {
return len(list.e)
}
// Less implements sort Interface.
func (list *List) Less(i, j int) bool {
return list.e[i].Addr().Less(list.e[j].Addr())
}
// Swap implements sort Interface.
func (list *List) Swap(i, j int) {
list.e[i], list.e[j] = list.e[j], list.e[i]
}
func (list *List) Match(addr netip.Addr) bool {
return list.Contains(addr)
}
// Contains reports whether the list includes the given netip.Addr.
func (list *List) Contains(addr netip.Addr) bool {
if !list.sorted {
panic("list is not sorted")
}
if !addr.IsValid() {
return false
}
addr = to6(addr)
i, j := 0, len(list.e)
for i < j {
h := int(uint(i+j) >> 1) // avoid overflow when computing h
if list.e[h].Addr().Compare(addr) <= 0 {
i = h + 1
} else {
j = h
}
}
if i == 0 {
return false
}
return list.e[i-1].Contains(addr)
}
func to6(addr netip.Addr) netip.Addr {
if addr.Is6() {
return addr
}
return netip.AddrFrom16(addr.As16())
}