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// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package backends
import (
"encoding/json"
"fmt"
"math/big"
"sync"
"sync/atomic"
"github.com/ethereum/go-ethereum/accounts/abi/bind"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/rlp"
"github.com/ethereum/go-ethereum/rpc"
)
// This nil assignment ensures compile time that rpcBackend implements bind.ContractBackend.
var _ bind.ContractBackend = (*rpcBackend)(nil)
// rpcBackend implements bind.ContractBackend, and acts as the data provider to
// Ethereum contracts bound to Go structs. It uses an RPC connection to delegate
// all its functionality.
//
// Note: The current implementation is a blocking one. This should be replaced
// by a proper async version when a real RPC client is created.
type rpcBackend struct {
client rpc.Client // RPC client connection to interact with an API server
autoid uint32 // ID number to use for the next API request
lock sync.Mutex // Singleton access until we get to request multiplexing
}
// NewRPCBackend creates a new binding backend to an RPC provider that can be
// used to interact with remote contracts.
func NewRPCBackend(client rpc.Client) bind.ContractBackend {
return &rpcBackend{
client: client,
}
}
// request is a JSON RPC request package assembled internally from the client
// method calls.
type request struct {
JSONRPC string `json:"jsonrpc"` // Version of the JSON RPC protocol, always set to 2.0
ID int `json:"id"` // Auto incrementing ID number for this request
Method string `json:"method"` // Remote procedure name to invoke on the server
Params []interface{} `json:"params"` // List of parameters to pass through (keep types simple)
}
// response is a JSON RPC response package sent back from the API server.
type response struct {
JSONRPC string `json:"jsonrpc"` // Version of the JSON RPC protocol, always set to 2.0
ID int `json:"id"` // Auto incrementing ID number for this request
Error json.RawMessage `json:"error"` // Any error returned by the remote side
Result json.RawMessage `json:"result"` // Whatever the remote side sends us in reply
}
// request forwards an API request to the RPC server, and parses the response.
//
// This is currently painfully non-concurrent, but it will have to do until we
// find the time for niceties like this :P
func (b *rpcBackend) request(method string, params []interface{}) (json.RawMessage, error) {
b.lock.Lock()
defer b.lock.Unlock()
// Ugly hack to serialize an empty list properly
if params == nil {
params = []interface{}{}
}
// Assemble the request object
req := &request{
JSONRPC: "2.0",
ID: int(atomic.AddUint32(&b.autoid, 1)),
Method: method,
Params: params,
}
if err := b.client.Send(req); err != nil {
return nil, err
}
res := new(response)
if err := b.client.Recv(res); err != nil {
return nil, err
}
if len(res.Error) > 0 {
return nil, fmt.Errorf("remote error: %s", string(res.Error))
}
return res.Result, nil
}
// ContractCall implements ContractCaller.ContractCall, delegating the execution of
// a contract call to the remote node, returning the reply to for local processing.
func (b *rpcBackend) ContractCall(contract common.Address, data []byte, pending bool) ([]byte, error) {
// Pack up the request into an RPC argument
args := struct {
To common.Address `json:"to"`
Data string `json:"data"`
}{
To: contract,
Data: common.ToHex(data),
}
// Execute the RPC call and retrieve the response
block := "latest"
if pending {
block = "pending"
}
res, err := b.request("eth_call", []interface{}{args, block})
if err != nil {
return nil, err
}
var hex string
if err := json.Unmarshal(res, &hex); err != nil {
return nil, err
}
// Convert the response back to a Go byte slice and return
return common.FromHex(hex), nil
}
// PendingAccountNonce implements ContractTransactor.PendingAccountNonce, delegating
// the current account nonce retrieval to the remote node.
func (b *rpcBackend) PendingAccountNonce(account common.Address) (uint64, error) {
res, err := b.request("eth_getTransactionCount", []interface{}{account.Hex(), "pending"})
if err != nil {
return 0, err
}
var hex string
if err := json.Unmarshal(res, &hex); err != nil {
return 0, err
}
nonce, ok := new(big.Int).SetString(hex, 0)
if !ok {
return 0, fmt.Errorf("invalid nonce hex: %s", hex)
}
return nonce.Uint64(), nil
}
// SuggestGasPrice implements ContractTransactor.SuggestGasPrice, delegating the
// gas price oracle request to the remote node.
func (b *rpcBackend) SuggestGasPrice() (*big.Int, error) {
res, err := b.request("eth_gasPrice", nil)
if err != nil {
return nil, err
}
var hex string
if err := json.Unmarshal(res, &hex); err != nil {
return nil, err
}
price, ok := new(big.Int).SetString(hex, 0)
if !ok {
return nil, fmt.Errorf("invalid price hex: %s", hex)
}
return price, nil
}
// EstimateGasLimit implements ContractTransactor.EstimateGasLimit, delegating
// the gas estimation to the remote node.
func (b *rpcBackend) EstimateGasLimit(sender common.Address, contract *common.Address, value *big.Int, data []byte) (*big.Int, error) {
// Pack up the request into an RPC argument
args := struct {
From common.Address `json:"from"`
To *common.Address `json:"to"`
Value *rpc.HexNumber `json:"value"`
Data string `json:"data"`
}{
From: sender,
To: contract,
Data: common.ToHex(data),
Value: rpc.NewHexNumber(value),
}
// Execute the RPC call and retrieve the response
res, err := b.request("eth_estimateGas", []interface{}{args})
if err != nil {
return nil, err
}
var hex string
if err := json.Unmarshal(res, &hex); err != nil {
return nil, err
}
estimate, ok := new(big.Int).SetString(hex, 0)
if !ok {
return nil, fmt.Errorf("invalid estimate hex: %s", hex)
}
return estimate, nil
}
// SendTransaction implements ContractTransactor.SendTransaction, delegating the
// raw transaction injection to the remote node.
func (b *rpcBackend) SendTransaction(tx *types.Transaction) error {
data, err := rlp.EncodeToBytes(tx)
if err != nil {
return err
}
res, err := b.request("eth_sendRawTransaction", []interface{}{common.ToHex(data)})
if err != nil {
return err
}
var hex string
if err := json.Unmarshal(res, &hex); err != nil {
return err
}
return nil
}
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