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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 (
"math/big"
"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"
"golang.org/x/net/context"
)
// 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.
type rpcBackend struct {
client *rpc.Client // RPC client connection to interact with an API server
}
// 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}
}
// HasCode implements ContractVerifier.HasCode by retrieving any code associated
// with the contract from the remote node, and checking its size.
func (b *rpcBackend) HasCode(ctx context.Context, contract common.Address, pending bool) (bool, error) {
block := "latest"
if pending {
block = "pending"
}
var hex string
err := b.client.CallContext(ctx, &hex, "eth_getCode", contract, block)
if err != nil {
return false, err
}
return len(common.FromHex(hex)) > 0, 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(ctx context.Context, contract common.Address, data []byte, pending bool) ([]byte, error) {
args := struct {
To common.Address `json:"to"`
Data string `json:"data"`
}{
To: contract,
Data: common.ToHex(data),
}
block := "latest"
if pending {
block = "pending"
}
var hex string
err := b.client.CallContext(ctx, &hex, "eth_call", args, block)
if err != nil {
return nil, err
}
return common.FromHex(hex), nil
}
// PendingAccountNonce implements ContractTransactor.PendingAccountNonce, delegating
// the current account nonce retrieval to the remote node.
func (b *rpcBackend) PendingAccountNonce(ctx context.Context, account common.Address) (uint64, error) {
var hex rpc.HexNumber
err := b.client.CallContext(ctx, &hex, "eth_getTransactionCount", account.Hex(), "pending")
if err != nil {
return 0, err
}
return hex.Uint64(), nil
}
// SuggestGasPrice implements ContractTransactor.SuggestGasPrice, delegating the
// gas price oracle request to the remote node.
func (b *rpcBackend) SuggestGasPrice(ctx context.Context) (*big.Int, error) {
var hex rpc.HexNumber
if err := b.client.CallContext(ctx, &hex, "eth_gasPrice"); err != nil {
return nil, err
}
return (*big.Int)(&hex), nil
}
// EstimateGasLimit implements ContractTransactor.EstimateGasLimit, delegating
// the gas estimation to the remote node.
func (b *rpcBackend) EstimateGasLimit(ctx context.Context, sender common.Address, contract *common.Address, value *big.Int, data []byte) (*big.Int, error) {
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
var hex rpc.HexNumber
err := b.client.CallContext(ctx, &hex, "eth_estimateGas", args)
if err != nil {
return nil, err
}
return (*big.Int)(&hex), nil
}
// SendTransaction implements ContractTransactor.SendTransaction, delegating the
// raw transaction injection to the remote node.
func (b *rpcBackend) SendTransaction(ctx context.Context, tx *types.Transaction) error {
data, err := rlp.EncodeToBytes(tx)
if err != nil {
return err
}
return b.client.CallContext(ctx, nil, "eth_sendRawTransaction", common.ToHex(data))
}
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