113 lines
2.7 KiB
Go
113 lines
2.7 KiB
Go
package iplist
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import (
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"encoding/binary"
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"io"
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"net"
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)
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// The packed format is an 8 byte integer of the number of ranges. Then 20
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// bytes per range, consisting of 4 byte packed IP being the lower bound IP of
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// the range, then 4 bytes of the upper, inclusive bound, 8 bytes for the
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// offset of the description from the end of the packed ranges, and 4 bytes
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// for the length of the description. After these packed ranges, are the
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// concatenated descriptions.
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const (
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packedRangesOffset = 8
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packedRangeLen = 20
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)
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func (me *IPList) WritePacked(w io.Writer) (err error) {
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descOffsets := make(map[string]int64, len(me.ranges))
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descs := make([]string, 0, len(me.ranges))
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var nextOffset int64
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// This is a little monadic, no?
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write := func(b []byte, expectedLen int) {
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if err != nil {
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return
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}
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var n int
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n, err = w.Write(b)
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if err != nil {
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return
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}
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if n != expectedLen {
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panic(n)
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}
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}
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var b [8]byte
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binary.LittleEndian.PutUint64(b[:], uint64(len(me.ranges)))
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write(b[:], 8)
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for _, r := range me.ranges {
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write(r.First.To4(), 4)
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write(r.Last.To4(), 4)
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descOff, ok := descOffsets[r.Description]
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if !ok {
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descOff = nextOffset
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descOffsets[r.Description] = descOff
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descs = append(descs, r.Description)
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nextOffset += int64(len(r.Description))
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}
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binary.LittleEndian.PutUint64(b[:], uint64(descOff))
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write(b[:], 8)
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binary.LittleEndian.PutUint32(b[:], uint32(len(r.Description)))
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write(b[:4], 4)
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}
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for _, d := range descs {
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write([]byte(d), len(d))
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}
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return
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}
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func NewFromPacked(b []byte) PackedIPList {
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return PackedIPList(b)
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}
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type PackedIPList []byte
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var _ Ranger = PackedIPList{}
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func (me PackedIPList) len() int {
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return int(binary.LittleEndian.Uint64(me[:8]))
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}
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func (me PackedIPList) NumRanges() int {
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return me.len()
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}
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func (me PackedIPList) getFirst(i int) net.IP {
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off := packedRangesOffset + packedRangeLen*i
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return net.IP(me[off : off+4])
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}
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func (me PackedIPList) getRange(i int) (ret Range) {
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rOff := packedRangesOffset + packedRangeLen*i
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last := me[rOff+4 : rOff+8]
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descOff := int(binary.LittleEndian.Uint64(me[rOff+8:]))
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descLen := int(binary.LittleEndian.Uint32(me[rOff+16:]))
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descOff += packedRangesOffset + packedRangeLen*me.len()
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ret = Range{
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me.getFirst(i),
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net.IP(last),
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string(me[descOff : descOff+descLen]),
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}
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return
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}
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func (me PackedIPList) Lookup(ip net.IP) (r Range, ok bool) {
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ip4 := ip.To4()
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if ip4 == nil {
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// If the IP list was built successfully, then it only contained IPv4
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// ranges. Therefore no IPv6 ranges are blocked.
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if ip.To16() == nil {
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r = Range{
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Description: "bad IP",
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}
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ok = true
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}
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return
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}
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return lookup(me.getFirst, me.getRange, me.len(), ip4)
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}
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