package resolver import ( "encoding/binary" "fmt" "github.com/ethereum/go-ethereum/common" "github.com/ethereum/go-ethereum/crypto" xe "github.com/ethereum/go-ethereum/xeth" ) /* Resolver implements the Ethereum DNS mapping HashReg : Key Hash (hash of domain name or contract code) -> Content Hash UrlHint : Content Hash -> Url Hint The resolver is meant to be called by the roundtripper transport implementation of a url scheme */ // contract addresses will be hardcoded after they're created var URLHintContractAddress string = "0000000000000000000000000000000000000000000000000000000000001234" var HashRegContractAddress string = "0000000000000000000000000000000000000000000000000000000000005678" func CreateContracts(xeth *xe.XEth, addr string) { var err error URLHintContractAddress, err = xeth.Transact(addr, "", "100000000000", "1000000", "100000", ContractCodeURLhint) if err != nil { panic(err) } HashRegContractAddress, err = xeth.Transact(addr, "", "100000000000", "1000000", "100000", ContractCodeHashReg) if err != nil { panic(err) } } type Resolver struct { backend Backend urlHintContractAddress string hashRegContractAddress string } type Backend interface { StorageAt(string, string) string } func New(eth Backend, uhca, nrca string) *Resolver { return &Resolver{eth, uhca, nrca} } func (self *Resolver) KeyToContentHash(khash common.Hash) (chash common.Hash, err error) { // look up in hashReg key := storageAddress(storageMapping(storageIdx2Addr(1), khash[:])) hash := self.backend.StorageAt(self.hashRegContractAddress, key) if hash == "0x0" || len(hash) < 3 { err = fmt.Errorf("GetHashReg: content hash not found") return } copy(chash[:], common.Hex2BytesFixed(hash[2:], 32)) return } func (self *Resolver) ContentHashToUrl(chash common.Hash) (uri string, err error) { // look up in URL reg var str string = " " var idx uint32 for len(str) > 0 { mapaddr := storageMapping(storageIdx2Addr(1), chash[:]) key := storageAddress(storageFixedArray(mapaddr, storageIdx2Addr(idx))) hex := self.backend.StorageAt(self.urlHintContractAddress, key) str = string(common.Hex2Bytes(hex[2:])) l := len(str) for (l > 0) && (str[l-1] == 0) { l-- } str = str[:l] uri = uri + str idx++ } if len(uri) == 0 { err = fmt.Errorf("GetURLhint: URL hint not found") } return } func (self *Resolver) KeyToUrl(key common.Hash) (uri string, hash common.Hash, err error) { // look up in urlHint hash, err = self.KeyToContentHash(key) if err != nil { return } uri, err = self.ContentHashToUrl(hash) return } func storageIdx2Addr(varidx uint32) []byte { data := make([]byte, 32) binary.BigEndian.PutUint32(data[28:32], varidx) return data } func storageMapping(addr, key []byte) []byte { data := make([]byte, 64) copy(data[0:32], key[0:32]) copy(data[32:64], addr[0:32]) return crypto.Sha3(data) } func storageFixedArray(addr, idx []byte) []byte { var carry byte for i := 31; i >= 0; i-- { var b byte = addr[i] + idx[i] + carry if b < addr[i] { carry = 1 } else { carry = 0 } addr[i] = b } return addr } func storageAddress(addr []byte) string { return common.ToHex(addr) }