3 files changed, 252 insertions, 0 deletions
diff --git a/common/resolver/contracts.go b/common/resolver/contracts.go
new file mode 100644
index 000000000..4aad95e43
--- /dev/null
+++ b/common/resolver/contracts.go
@@ -0,0 +1,36 @@
+package resolver
+
+const ( // built-in contracts address and code
+	ContractCodeURLhint = "0x60c180600c6000396000f30060003560e060020a90048063300a3bbf14601557005b6024600435602435604435602a565b60006000f35b6000600084815260200190815260200160002054600160a060020a0316600014806078575033600160a060020a03166000600085815260200190815260200160002054600160a060020a0316145b607f5760bc565b336000600085815260200190815260200160002081905550806001600085815260200190815260200160002083610100811060b657005b01819055505b50505056"
+	/*
+		contract URLhint {
+			function register(uint256 _hash, uint8 idx, uint256 _url) {
+				if (owner[_hash] == 0 || owner[_hash] == msg.sender) {
+					owner[_hash] = msg.sender;
+					url[_hash][idx] = _url;
+				}
+			}
+			mapping (uint256 => address) owner;
+			mapping (uint256 => uint256[256]) url;
+		}
+	*/
+
+	ContractCodeHashReg = "0x609880600c6000396000f30060003560e060020a9004806331e12c2014601f578063d66d6c1014602b57005b6025603d565b60006000f35b6037600435602435605d565b60006000f35b600054600160a060020a0316600014605357605b565b336000819055505b565b600054600160a060020a031633600160a060020a031614607b576094565b8060016000848152602001908152602001600020819055505b505056"
+	/*
+		   contract HashReg {
+			function setowner() {
+				if (owner == 0) {
+					owner = msg.sender;
+				}
+			}
+		   	function register(uint256 _key, uint256 _content) {
+				if (msg.sender == owner) {
+		   			content[_key] = _content;
+				}
+		   	}
+			address owner;
+		   	mapping (uint256 => uint256) content;
+		   }
+	*/
+
+)
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)
+}
diff --git a/common/resolver/resolver_test.go b/common/resolver/resolver_test.go
new file mode 100644
index 000000000..f5eb51437
--- /dev/null
+++ b/common/resolver/resolver_test.go
@@ -0,0 +1,88 @@
+package resolver
+
+import (
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+type testBackend struct {
+	// contracts mock
+	contracts map[string](map[string]string)
+}
+
+var (
+	text     = "test"
+	codehash = common.StringToHash("1234")
+	hash     = common.BytesToHash(crypto.Sha3([]byte(text)))
+	url      = "bzz://bzzhash/my/path/contr.act"
+)
+
+func NewTestBackend() *testBackend {
+	self := &testBackend{}
+	self.contracts = make(map[string](map[string]string))
+
+	self.contracts[HashRegContractAddress] = make(map[string]string)
+	key := storageAddress(storageMapping(storageIdx2Addr(1), codehash[:]))
+	self.contracts[HashRegContractAddress][key] = hash.Hex()
+
+	self.contracts[URLHintContractAddress] = make(map[string]string)
+	mapaddr := storageMapping(storageIdx2Addr(1), hash[:])
+
+	key = storageAddress(storageFixedArray(mapaddr, storageIdx2Addr(0)))
+	self.contracts[URLHintContractAddress][key] = common.ToHex([]byte(url))
+	key = storageAddress(storageFixedArray(mapaddr, storageIdx2Addr(1)))
+	self.contracts[URLHintContractAddress][key] = "0x00"
+
+	return self
+}
+
+func (self *testBackend) StorageAt(ca, sa string) (res string) {
+	c := self.contracts[ca]
+	if c == nil {
+		return
+	}
+	res = c[sa]
+	return
+}
+
+func TestKeyToContentHash(t *testing.T) {
+	b := NewTestBackend()
+	res := New(b, URLHintContractAddress, HashRegContractAddress)
+
+	got, err := res.KeyToContentHash(codehash)
+	if err != nil {
+		t.Errorf("expected no error, got %v", err)
+	} else {
+		if got != hash {
+			t.Errorf("incorrect result, expected %x, got %x: ", hash.Hex(), got.Hex())
+		}
+	}
+}
+
+func TestContentHashToUrl(t *testing.T) {
+	b := NewTestBackend()
+	res := New(b, URLHintContractAddress, HashRegContractAddress)
+	got, err := res.ContentHashToUrl(hash)
+	if err != nil {
+		t.Errorf("expected no error, got %v", err)
+	} else {
+		if string(got) != url {
+			t.Errorf("incorrect result, expected %v, got %s: ", url, string(got))
+		}
+	}
+}
+
+func TestKeyToUrl(t *testing.T) {
+	b := NewTestBackend()
+	res := New(b, URLHintContractAddress, HashRegContractAddress)
+	got, _, err := res.KeyToUrl(codehash)
+	if err != nil {
+		t.Errorf("expected no error, got %v", err)
+	} else {
+		if string(got) != url {
+			t.Errorf("incorrect result, expected %v, got %s: ", url, string(got))
+		}
+	}
+}