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package resolver
import (
"encoding/binary"
"fmt"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/crypto"
)
/*
Resolver implements the Ethereum DNS mapping
NameReg : Domain Name (or Code hash of Contract) -> Content Hash
UrlHint : Content Hash -> Url Hint
The resolver is meant to be called by the roundtripper transport implementation
of a url scheme
*/
const (
urlHintContractAddress = "urlhint"
nameRegContractAddress = "nameReg"
)
type Resolver struct {
backend Backend
urlHintContractAddress string
nameRegContractAddress string
}
type Backend interface {
StorageAt(string, string) string
}
func New(eth Backend, uhca, nrca string) *Resolver {
return &Resolver{eth, uhca, nrca}
}
func (self *Resolver) NameToContentHash(name string) (chash common.Hash, err error) {
// look up in nameReg
key := storageAddress(0, common.Hex2Bytes(name))
hash := self.backend.StorageAt(self.nameRegContractAddress, key)
copy(chash[:], common.Hex2Bytes(hash))
return
}
func (self *Resolver) ContentHashToUrl(chash common.Hash) (uri string, err error) {
// look up in nameReg
key := storageAddress(0, chash[:])
uri = self.backend.StorageAt(self.urlHintContractAddress, key)
l := len(uri)
for (l > 0) && (uri[l-1] == 0) {
l--
}
uri = uri[:l]
if l == 0 {
err = fmt.Errorf("GetURLhint: URL hint not found")
}
return
}
func (self *Resolver) NameToUrl(name string) (uri string, hash common.Hash, err error) {
// look up in urlHint
hash, err = self.NameToContentHash(name)
if err != nil {
return
}
uri, err = self.ContentHashToUrl(hash)
return
}
func storageAddress(varidx uint32, key []byte) string {
data := make([]byte, 64)
binary.BigEndian.PutUint32(data[28:32], varidx)
copy(data[32:64], key[0:32])
return common.Bytes2Hex(crypto.Sha3(data))
}
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