package resolver import ( "encoding/binary" "fmt" "github.com/ethereum/go-ethereum/common" "github.com/ethereum/go-ethereum/core" "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 = core.ContractAddrURLhint NameRegContractAddress = core.ContractAddrHashReg ) 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(1, common.Hex2BytesFixed(name, 32)) hash := self.backend.StorageAt("0x"+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(2, chash[:]) hex := self.backend.StorageAt("0x"+self.urlHintContractAddress, key) uri = string(common.Hex2Bytes(hex[2:])) 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[60:64], varidx) copy(data[0:32], key[0:32]) return "0x" + common.Bytes2Hex(crypto.Sha3(data)) }