plugeth/common/resolver/resolver.go

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package resolver
import (
"encoding/binary"
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"fmt"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/logger/glog"
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)
/*
Resolver implements the Ethereum DNS mapping
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HashReg : Key Hash (hash of domain name or contract code) -> Content Hash
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UrlHint : Content Hash -> Url Hint
The resolver is meant to be called by the roundtripper transport implementation
of a url scheme
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*/
// // contract addresses will be hardcoded after they're created
var UrlHintContractAddress, HashRegContractAddress string
const (
txValue = "0"
txGas = "100000"
txGasPrice = "1000000000000"
)
func abi(s string) string {
return common.ToHex(crypto.Sha3([]byte(s))[:4])
}
var (
registerContentHashAbi = abi("register(uint256,uint256)")
registerUrlAbi = abi("register(uint256,uint8,uint256)")
setOwnerAbi = abi("setowner()")
)
type Backend interface {
StorageAt(string, string) string
Transact(fromStr, toStr, nonceStr, valueStr, gasStr, gasPriceStr, codeStr string) (string, error)
}
type Resolver struct {
backend Backend
}
func New(eth Backend) *Resolver {
return &Resolver{eth}
}
// for testing and play temporarily
// ideally the HashReg and UrlHint contracts should be in the genesis block
// if we got build-in support for natspec/contract info
// there should be only one of these officially endorsed
// addresses as constants
// TODO: could get around this with namereg, check
func (self *Resolver) CreateContracts(addr common.Address) (err error) {
HashRegContractAddress, err = self.backend.Transact(addr.Hex(), "", "", txValue, txGas, txGasPrice, ContractCodeHashReg)
if err != nil {
return
}
UrlHintContractAddress, err = self.backend.Transact(addr.Hex(), "", "", txValue, txGas, txGasPrice, ContractCodeURLhint)
glog.V(logger.Detail).Infof("HashReg @ %v\nUrlHint @ %v\n", HashRegContractAddress, UrlHintContractAddress)
return
}
// called as first step in the registration process on HashReg
func (self *Resolver) SetOwner(address common.Address) (txh string, err error) {
return self.backend.Transact(
address.Hex(),
HashRegContractAddress,
"", txValue, txGas, txGasPrice,
setOwnerAbi,
)
}
// registers some content hash to a key/code hash
// e.g., the contract Info combined Json Doc's ContentHash
// to CodeHash of a contract or hash of a domain
// kept
func (self *Resolver) RegisterContentHash(address common.Address, codehash, dochash common.Hash) (txh string, err error) {
_, err = self.SetOwner(address)
if err != nil {
return
}
codehex := common.Bytes2Hex(codehash[:])
dochex := common.Bytes2Hex(dochash[:])
data := registerContentHashAbi + codehex + dochex
return self.backend.Transact(
address.Hex(),
HashRegContractAddress,
"", txValue, txGas, txGasPrice,
data,
)
}
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// registers a url to a content hash so that the content can be fetched
// address is used as sender for the transaction and will be the owner of a new
// registry entry on first time use
// FIXME: silently doing nothing if sender is not the owner
// note that with content addressed storage, this step is no longer necessary
// it could be purely
func (self *Resolver) RegisterUrl(address common.Address, hash common.Hash, url string) (txh string, err error) {
hashHex := common.Bytes2Hex(hash[:])
var urlHex string
urlb := []byte(url)
var cnt byte
n := len(urlb)
for n > 0 {
if n > 32 {
n = 32
}
urlHex = common.Bytes2Hex(urlb[:n])
urlb = urlb[n:]
n = len(urlb)
bcnt := make([]byte, 32)
bcnt[31] = cnt
data := registerUrlAbi +
hashHex +
common.Bytes2Hex(bcnt) +
common.Bytes2Hex(common.Hex2BytesFixed(urlHex, 32))
txh, err = self.backend.Transact(
address.Hex(),
UrlHintContractAddress,
"", txValue, txGas, txGasPrice,
data,
)
if err != nil {
return
}
cnt++
}
return
}
func (self *Resolver) Register(address common.Address, codehash, dochash common.Hash, url string) (txh string, err error) {
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_, err = self.RegisterContentHash(address, codehash, dochash)
if err != nil {
return
}
return self.RegisterUrl(address, dochash, url)
}
// resolution is costless non-transactional
// implemented as direct retrieval from db
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func (self *Resolver) KeyToContentHash(khash common.Hash) (chash common.Hash, err error) {
// look up in hashReg
at := common.Bytes2Hex(common.FromHex(HashRegContractAddress))
key := storageAddress(storageMapping(storageIdx2Addr(1), khash[:]))
hash := self.backend.StorageAt(at, key)
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if hash == "0x0" || len(hash) < 3 {
err = fmt.Errorf("content hash not found for '%v'", khash.Hex())
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return
}
copy(chash[:], common.Hex2BytesFixed(hash[2:], 32))
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return
}
// retrieves the url-hint for the content hash -
// if we use content addressed storage, this step is no longer necessary
func (self *Resolver) ContentHashToUrl(chash common.Hash) (uri string, err error) {
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// 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(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 for '%v'", chash.Hex())
}
return
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}
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func (self *Resolver) KeyToUrl(key common.Hash) (uri string, hash common.Hash, err error) {
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// look up in urlHint
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hash, err = self.KeyToContentHash(key)
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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)
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copy(data[0:32], key[0:32])
copy(data[32:64], addr[0:32])
sha := crypto.Sha3(data)
return sha
}
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)
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}