w3

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 Go to latest Published: Feb 18, 2022 License: MIT Imports: 14 Imported by: 20

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w3

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W3 Gopher

Package w3 implements a modular and fast Ethereum JSON RPC client with first-class ABI support.

  • Modular API allows to create custom RPC method integrations that can be used alongside the methods implemented by the package.
  • Batch request support significantly reduces the duration of requests to both remote and local endpoints.
  • ABI bindings are specified for individual functions using Solidity syntax. No need for abigen and ABI JSON files.

w3 is closely linked to go-ethereum and uses a variety of its types, such as common.Address or types.Transaction.

Install

go get github.com/lmittmann/w3@latest

Getting Started

Connect to an RPC endpoint via HTTP, WebSocket, or IPC using Dial or MustDial.

// Connect (or panic on error)
client := w3.MustDial("https://cloudflare-eth.com")
defer client.Close()

Batch Requests

Batch request support in the Client allows to send multiple RPC requests in a single HTTP request. The speed gains to remote endpoints are huge. Fetching 100 blocks in a single batch request with w3 is ~80x faster compared to sequential requests with ethclient.

Example: Request the nonce and balance of an address in a single request

var (
	addr = w3.A("0x000000000000000000000000000000000000c0Fe")

	nonce   uint64
	balance big.Int
)

err := client.Call(
	eth.Nonce(addr).Returns(&nonce),
	eth.Balance(addr).Returns(&balance),
)

ABI Bindings

ABI bindings in w3 are specified for individual functions using Solidity syntax and are usable for any contract that supports that function.

Example: ABI binding for the ERC20-function balanceOf

funcBalanceOf := w3.MustNewFunc("balanceOf(address)", "uint256")

A Func can be used to

Reading Contracts

Func's can be used with eth.CallFunc in the client to read contract data.

var (
	weth9 = w3.A("0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2")
	dai   = w3.A("0x6B175474E89094C44Da98b954EedeAC495271d0F")

	weth9Balance big.Int
	daiBalance   big.Int
)

err := client.Call(
	eth.CallFunc(funcBalanceOf, weth9, addr).Returns(&weth9Balance),
	eth.CallFunc(funcBalanceOf, dai, addr).Returns(&daiBalance),
)

Custom RPC Methods

Custom RPC methods can be called with the w3 client by creating a core.Caller implementation. The w3/module/eth package can be used as implementation reference.

RPC Methods

List of supported RPC methods.

eth
Method Go Code
eth_blockNumber eth.BlockNumber().Returns(blockNumber *big.Int)
eth_call eth.Call(msg ethereum.CallMsg).Returns(output *[]byte)
eth.CallFunc(fn core.Func, contract common.Address, args ...interface{}).Returns(returns ...interface{})
eth_chainId eth.ChainID().Returns(chainID *uint64)
eth_gasPrice eth.GasPrice().Returns(gasPrice *big.Int)
eth_getBalance eth.Balance(addr common.Address).Returns(balance *big.Int)
eth_getBlockByHash eth.BlockByHash(hash common.Hash).Returns(block *types.Block)
eth.BlockByHash(hash common.Hash).ReturnsRAW(block *eth.RPCBlock)
eth.HeaderByHash(hash common.Hash).Returns(header *types.Header)
eth.HeaderByHash(hash common.Hash).ReturnsRAW(header *eth.RPCHeader)
eth_getBlockByNumber eth.BlockByNumber(number *big.Int).Returns(block *types.Block)
eth.BlockByNumber(number *big.Int).ReturnsRAW(block *eth.RPCBlock)
eth.HeaderByNumber(number *big.Int).Returns(header *types.Header)
eth.HeaderByNumber(number *big.Int).ReturnsRAW(header *eth.RAWHeader)
eth_getCode eth.Code(addr common.Address).Returns(code *[]byte)
eth_getLogs eth.Logs(q ethereum.FilterQuery).Returns(logs *[]types.Log)
eth_getStorageAt eth.StorageAt(addr common.Address, slot common.Hash).Returns(storage *common.Hash)
eth_getTransactionByHash eth.TransactionByHash(hash common.Hash).Returns(tx *types.Transaction)
eth.TransactionByHash(hash common.Hash).ReturnsRAW(tx *eth.RPCTransaction)
eth_getTransactionCount eth.Nonce(addr common.Address).Returns(nonce *uint64)
eth_getTransactionReceipt eth.TransactionReceipt(hash common.Hash).Returns(receipt *types.Receipt)
eth.TransactionReceipt(hash common.Hash).ReturnsRAW(receipt *eth.RPCReceipt)
eth_sendRawTransaction eth.SendTransaction(tx *types.Transaction).Returns(hash *common.Hash)
eth.SendRawTransaction(rawTx []byte).Returns(hash *common.Hash)
Third Party RPC Method Packages
Package Description
github.com/lmittmann/flashbots Package flashbots implements RPC API bindings for the Flashbots relay and mev-geth.

Documentation

Overview

Package w3 implements a modular and fast Ethereum JSON RPC client with first-class ABI support.

Index

Examples

Constants

This section is empty.

Variables

View Source 
var (
	// ErrRequestCreation is returned by Client.CallCtx and Client.Call when the
	// creation of the RPC request failes.
	ErrRequestCreation = errors.New("w3: request creation failed")

	// ErrResponseHandling is returned by Client.CallCtx and Client.Call when
	// the handeling of the RPC response failes.
	ErrResponseHandling = errors.New("w3: response handling failed")
)
View Source 
var (
	ErrInvalidABI       = errors.New("w3: invalid ABI")
	ErrArgumentMismatch = errors.New("w3: argument mismatch")
	ErrReturnsMismatch  = errors.New("w3: returns mismatch")
	ErrInvalidType      = errors.New("w3: invalid type")
	ErrEvmRevert        = errors.New("w3: evm reverted")
)
View Source 
var (
	Big0     = big.NewInt(0)
	Big1     = big.NewInt(1)
	Big2     = big.NewInt(2)
	BigGwei  = big.NewInt(1_000000000)
	BigEther = big.NewInt(1_000000000_000000000)
)

Common big.Int's.

Functions

func A 

func A(hexAddress string) common.Address

A returns an address from a hexstring. It is short for common.HexToAddress(…).

func APtr 

func APtr(hexAddress string) *common.Address

APtr returns an address pointer from a hexstring. The returned address is nil, if the hexstring address equals the zero address 0x00…00.

func B 

func B(hexBytes string) []byte

B returns a byte slice from a hexstring. It is short for common.FromHex(…).

func FromWei 

func FromWei(wei *big.Int, decimals uint8) string

FromWei returns the given Wei as decimal with the given number of decimals.

Example 
package main

import (
	"fmt"
	"math/big"

	"github.com/lmittmann/w3"
)

func main() {
	wei := big.NewInt(1_230000000_000000000)
	fmt.Printf("%s Ether\n", w3.FromWei(wei, 18))
}

Output:

1.23 Ether

func H 

func H(hexHash string) common.Hash

H returns a hash from a hexstring. It is short for common.HexToHash(…).

func I 

func I(strInt string) *big.Int

I returns a big.Int from a number string in decimal or hex format. Nil is returned if the number parsing fails.

I supports the units "ether" or "eth" and "gwei" for decimal number strings. E.g.: 

w3.I("1 ether")   -> 1000000000000000000
w3.I("1.2 ether") -> 1200000000000000000

Fractional digits that exceed the units maximum number of fractional digits are ignored. E.g.: 

w3.I("0.000000123456 gwei") -> 123
Example 
package main

import (
	"fmt"

	"github.com/lmittmann/w3"
)

func main() {
	fmt.Printf("%v wei\n", w3.I("0x2b98d99b09e3c000"))
	fmt.Printf("%v wei\n", w3.I("3141500000000000000"))
	fmt.Printf("%v wei\n", w3.I("3.1415 ether"))
	fmt.Printf("%v wei\n", w3.I("31.415 gwei"))
}

Output:

3141500000000000000 wei
3141500000000000000 wei
3141500000000000000 wei
31415000000 wei

func Keccak 

func Keccak(data []byte) common.Hash

Keccak returns the Keccak256 hash of data. It is short for crypto.Keccak256Hash(…)

Types

type Client 

type Client struct {
	// contains filtered or unexported fields
}

Client represents a connection to an RPC endpoint.

func Dial 

func Dial(rawurl string) (*Client, error)

Dial returns a new Client connected to the URL rawurl. An error is returned if the connection establishment failes.

The supported URL schemes are "http", "https", "ws" and "wss". If rawurl is a file name with no URL scheme, a local IPC socket connection is established.

Example 
package main

import (
	"fmt"

	"github.com/lmittmann/w3"
)

func main() {
	client, err := w3.Dial("https://cloudflare-eth.com")
	if err != nil {
		fmt.Printf("Failed to connect to RPC endpoint: %v\n", err)
		return
	}
	defer client.Close()
}

Output:

func MustDial 

func MustDial(rawurl string) *Client

MustDial is like Dial but panics if the connection establishment failes.

Example 
package main

import (
	"github.com/lmittmann/w3"
)

func main() {
	client := w3.MustDial("https://cloudflare-eth.com")
	defer client.Close()
}

Output:

func NewClient 

func NewClient(client *rpc.Client) *Client

NewClient returns a new Client given an rpc.Client client.

func (*Client) Call 

func (c *Client) Call(calls ...core.Caller) error

Call is like CallCtx with ctx equal to context.Background().

Example 
package main

import (
	"fmt"
	"math/big"

	"github.com/lmittmann/w3"
	"github.com/lmittmann/w3/module/eth"
)

func main() {
	// Connect to RPC endpoint (or panic on error) and
	// close the connection when you are done.
	client := w3.MustDial("https://cloudflare-eth.com")
	defer client.Close()

	var (
		addr  = w3.A("0x000000000000000000000000000000000000dEaD")
		weth9 = w3.A("0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2")

		// Declare a Smart Contract function using Solidity syntax,
		// no "abigen" and ABI JSON file needed.
		balanceOf = w3.MustNewFunc("balanceOf(address)", "uint256")

		// Declare variables for the RPC responses.
		ethBalance   big.Int
		weth9Balance big.Int
	)

	// Do batch request (both RPC requests are send in the same
	// HTTP request).
	if err := client.Call(
		eth.Balance(addr).Returns(&ethBalance),
		eth.CallFunc(balanceOf, weth9, addr).Returns(&weth9Balance),
	); err != nil {
		fmt.Printf("Request failed: %v\n", err)
		return
	}

	fmt.Printf("Combined balance: %v wei",
		new(big.Int).Add(&ethBalance, &weth9Balance),
	)
}

Output:

func (*Client) CallCtx 

func (c *Client) CallCtx(ctx context.Context, calls ...core.Caller) error

CallCtx creates the final RPC request, sends it, and handles the RPC response.

An error is returned if RPC request creation, networking, or RPC response handeling fails.

func (*Client) Close 

func (c *Client) Close() error

Close closes the RPC connection and cancels any in-flight requests.

Close implements the io.Closer interface.

type Event added in v0.3.0 

type Event struct {
	Signature string        // Event signature
	Topic0    common.Hash   // Hash of event signature (Topic 0)
	Args      abi.Arguments // Arguments
}

Event represents a Smart Contract event decoder.

func MustNewEvent added in v0.3.0 

func MustNewEvent(signature string) *Event

MustNewEvent is like NewEvent but panics if the signature parsing fails.

func NewEvent added in v0.3.0 

func NewEvent(signature string) (*Event, error)

NewEvent returns a new Smart Contract event log decoder from the given Solidity event signature.

An error is returned if the signature parsing fails.

func (*Event) DecodeArgs added in v0.3.0 

func (e *Event) DecodeArgs(log *types.Log, args ...interface{}) error

DecodeArgs decodes the topics and data of the given log to the given args.

DecodeArgs is insensitiv to indexed fields.

Example 
package main

import (
	"fmt"
	"math/big"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/lmittmann/w3"
)

func main() {
	var (
		eventTransfer = w3.MustNewEvent("Transfer(address from, address to, uint256 value)")
		log           = &types.Log{
			Address: w3.A("0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2"),
			Topics: []common.Hash{
				w3.H("0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"),
				w3.H("0x000000000000000000000000000000000000000000000000000000000000c0fe"),
				w3.H("0x000000000000000000000000000000000000000000000000000000000000dead"),
			},
			Data: w3.B("0x0000000000000000000000000000000000000000000000001111d67bb1bb0000"),
		}

		from  common.Address
		to    common.Address
		value big.Int
	)

	if err := eventTransfer.DecodeArgs(log, &from, &to, &value); err != nil {
		fmt.Printf("Failed to decode event log: %v\n", err)
		return
	}
	fmt.Printf("Transferred %s WETH9 from %s to %s", w3.FromWei(&value, 18), from, to)
}

Output:

Transferred 1.23 WETH9 from 0x000000000000000000000000000000000000c0Fe to 0x000000000000000000000000000000000000dEaD

type Func added in v0.1.1 

type Func struct {
	Signature string        // Function signature
	Selector  [4]byte       // 4-byte selector
	Args      abi.Arguments // Input arguments
	Returns   abi.Arguments // Output returns
}

Func represents a Smart Contract function ABI binding.

Func implements the core.Func interface.

func MustNewFunc 

func MustNewFunc(signature, returns string) *Func

MustNewFunc is like NewFunc but panics if the signature or returns parsing fails.

func NewFunc 

func NewFunc(signature, returns string) (*Func, error)

NewFunc returns a new Smart Contract function ABI binding from the given Solidity function signature and its returns.

An error is returned if the signature or returns parsing fails.

Example 
package main

import (
	"fmt"
	"math/big"

	"github.com/ethereum/go-ethereum/common"
	"github.com/lmittmann/w3"
)

func main() {
	// ABI binding to the balanceOf function of an ERC20 Token.
	funcBalanceOf, _ := w3.NewFunc("balanceOf(address)", "uint256")

	// Optionally names can be specified for function arguments. This is
	// especially useful for more complex functions with many arguments.
	funcBalanceOf, _ = w3.NewFunc("balanceOf(address who)", "uint256 amount")

	// ABI-encode the functions args.
	input, _ := funcBalanceOf.EncodeArgs(w3.A("0xAb5801a7D398351b8bE11C439e05C5B3259aeC9B"))
	fmt.Printf("balanceOf input: 0x%x\n", input)

	// ABI-decode the functions args from a given input.
	var (
		who common.Address
	)
	funcBalanceOf.DecodeArgs(input, &who)
	fmt.Printf("balanceOf args: %v\n", who)

	// ABI-decode the functions output.
	var (
		output = w3.B("0x000000000000000000000000000000000000000000000000000000000000c0fe")
		amount = new(big.Int)
	)
	funcBalanceOf.DecodeReturns(output, amount)
	fmt.Printf("balanceOf returns: %v\n", amount)
}

Output:

balanceOf input: 0x70a08231000000000000000000000000ab5801a7d398351b8be11c439e05c5b3259aec9b
balanceOf args: 0xAb5801a7D398351b8bE11C439e05C5B3259aeC9B
balanceOf returns: 49406

func (*Func) DecodeArgs added in v0.1.1 

func (f *Func) DecodeArgs(input []byte, args ...interface{}) error

DecodeArgs ABI-decodes the given input to the given args.

func (*Func) DecodeReturns added in v0.1.1 

func (f *Func) DecodeReturns(output []byte, returns ...interface{}) error

DecodeReturns ABI-decodes the given output to the given returns.

func (*Func) EncodeArgs added in v0.1.1 

func (f *Func) EncodeArgs(args ...interface{}) ([]byte, error)

EncodeArgs ABI-encodes the given args and prepends the Func's 4-byte selector.

Source Files

View all Source files

Directories

Path Synopsis
internal
abi
module
eth
Package eth implements RPC API bindings for methods in the "eth" namespace.
 Package eth implements RPC API bindings for methods in the "eth" namespace.
Package rpctest provides utilities for testing RPC methods.
 Package rpctest provides utilities for testing RPC methods.

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