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