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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
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
*/
const (
URLHintContractAddress = core.ContractAddrURLhint
HashRegContractAddress = core.ContractAddrHashReg
)
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(1, khash[:])
hash := self.backend.StorageAt("0x"+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
key := storageAddress(1, 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) 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 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))
}
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