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