1 files changed, 128 insertions, 0 deletions
diff --git a/common/resolver/resolver.go b/common/resolver/resolver.go
new file mode 100644
index 000000000..1e6d03ffb
--- /dev/null
+++ b/common/resolver/resolver.go
@@ -0,0 +1,128 @@
+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)
+}