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v2fly/infra/conf/geodata/memconservative/decode.go
2022-01-02 15:16:23 +00:00

106 lines
2.9 KiB
Go

package memconservative
import (
"errors"
"io"
"strings"
"google.golang.org/protobuf/encoding/protowire"
"github.com/v2fly/v2ray-core/v5/common/platform/filesystem"
)
var (
errFailedToReadBytes = errors.New("failed to read bytes")
errFailedToReadExpectedLenBytes = errors.New("failed to read expected length of bytes")
errInvalidGeodataFile = errors.New("invalid geodata file")
errInvalidGeodataVarintLength = errors.New("invalid geodata varint length")
errCodeNotFound = errors.New("code not found")
)
func emitBytes(f io.ReadSeeker, code string) ([]byte, error) {
count := 1
isInner := false
tempContainer := make([]byte, 0, 5)
var result []byte
var advancedN uint64 = 1
var geoDataVarintLength, codeVarintLength, varintLenByteLen uint64 = 0, 0, 0
Loop:
for {
container := make([]byte, advancedN)
bytesRead, err := f.Read(container)
if err == io.EOF {
return nil, errCodeNotFound
}
if err != nil {
return nil, errFailedToReadBytes
}
if bytesRead != len(container) {
return nil, errFailedToReadExpectedLenBytes
}
switch count {
case 1, 3: // data type ((field_number << 3) | wire_type)
if container[0] != 10 { // byte `0A` equals to `10` in decimal
return nil, errInvalidGeodataFile
}
advancedN = 1
count++
case 2, 4: // data length
tempContainer = append(tempContainer, container...)
if container[0] > 127 { // max one-byte-length byte `7F`(0FFF FFFF) equals to `127` in decimal
advancedN = 1
goto Loop
}
lenVarint, n := protowire.ConsumeVarint(tempContainer)
if n < 0 {
return nil, errInvalidGeodataVarintLength
}
tempContainer = nil
if !isInner {
isInner = true
geoDataVarintLength = lenVarint
advancedN = 1
} else {
isInner = false
codeVarintLength = lenVarint
varintLenByteLen = uint64(n)
advancedN = codeVarintLength
}
count++
case 5: // data value
if strings.EqualFold(string(container), code) {
count++
offset := -(1 + int64(varintLenByteLen) + int64(codeVarintLength))
f.Seek(offset, 1) // back to the start of GeoIP or GeoSite varint
advancedN = geoDataVarintLength // the number of bytes to be read in next round
} else {
count = 1
offset := int64(geoDataVarintLength) - int64(codeVarintLength) - int64(varintLenByteLen) - 1
f.Seek(offset, 1) // skip the unmatched GeoIP or GeoSite varint
advancedN = 1 // the next round will be the start of another GeoIPList or GeoSiteList
}
case 6: // matched GeoIP or GeoSite varint
result = container
break Loop
}
}
return result, nil
}
func Decode(filename, code string) ([]byte, error) {
f, err := filesystem.NewFileSeeker(filename)
if err != nil {
return nil, newError("failed to open file: ", filename).Base(err)
}
defer f.Close()
geoBytes, err := emitBytes(f, code)
if err != nil {
return nil, err
}
return geoBytes, nil
}