README

@ethereumjs/common

Resources common to all EthereumJS implementations.

Note: this README reflects the state of the library from v2.0.0 onwards. See README from the standalone repository for an introduction on the last preceding release.

INSTALL

npm install @ethereumjs/common

USAGE

All parameters can be accessed through the Common class which can be required through the main package and instantiated either with just the chain (e.g. 'mainnet') or the chain together with a specific hardfork provided.

If no hardfork is provided, the common is initialized with the default hardfork.

Current DEFAULT_HARDFORK: istanbul

Here are some simple usage examples:

import Common from '@ethereumjs/common'

// Instantiate with the chain (and the default hardfork)
const c = new Common({ chain: 'ropsten' })
c.param('gasPrices', 'ecAddGas') // 500

// Chain and hardfork provided
c = new Common({ chain: 'ropsten', hardfork: 'byzantium' })
c.param('pow', 'minerReward') // 3000000000000000000

// Instantiate with an EIP activated
const c = new Common({ chain: 'mainnet', eips: [2537] })

// Access genesis data for Ropsten network
c.genesis().hash // 0x41941023680923e0fe4d74a34bdac8141f2540e3ae90623718e47d66d1ca4a2d

// Get bootstrap nodes for chain/network
c.bootstrapNodes() // Array with current nodes

If the initializing library only supports a certain range of hardforks you can use the supportedHardforks option to restrict hardfork access on the Common instance:

const c = new Common({
  chain: 'ropsten',
  supportedHardforks: ['byzantium', 'constantinople', 'petersburg'],
})

This will e.g. throw an error when a param is requested for an unsupported hardfork and like this prevents unpredicted behaviour.

For an improved developer experience, there are Chain and Hardfork enums available:

import Common, { Chain, Hardfork } from '@ethereumjs/common'

// Chain provided by Chain enum
const c = new Common({ chain: Chain.Mainnet })

// Chain provided by Chain enum, hardfork provided by Hardfork enum
const c = new Common({ chain: Chain.Ropsten, hardfork: Hardfork.Byzantium })

API

See the API documentation for a full list of functions for accessing specific chain and depending hardfork parameters. There are also additional helper functions like paramByBlock (topic, name, blockNumber) or hardforkIsActiveOnBlock (hardfork, blockNumber) to ease blockNumber based access to parameters.

API Docs

EVENTS

The Common class is implemented as an EventEmitter and is emitting the following events on which you can react within your code:

SETUP

Chains

The chain can be set in the constructor like this:

const c = new Common({ chain: 'ropsten' })

Or optionally with the Chain enum:

import Common, { Chain } from '@ethereumjs/common'

const c = new Common({ chain: Chain.Ropsten })

Supported chains:

mainnet (Chain.Mainnet)
ropsten (Chain.Ropsten)
rinkeby (Chain.Rinkeby)
kovan (Chain.Kovan)
goerli (Chain.Goerli)
sepolia (Chain.Sepolia) (v2.6.1+)
Private/custom chain parameters

The following chain-specific parameters are provided:

name
chainId
networkId
consensusType (e.g. pow or poa)
consensusAlgorithm (e.g. ethash or clique)
consensusConfig (depends on consensusAlgorithm, e.g. period and epoch for clique)
genesis block header values
hardforks block numbers
bootstrapNodes list
dnsNetworks list (EIP-1459-compliant list of DNS networks for peer discovery)

To get an overview of the different parameters have a look at one of the chain-specifc files like mainnet.json in the chains directory, or to the Chain type in ./src/types.ts.

Working with private/custom chains

There are two distinct APIs available for setting up custom(ized) chains.

Basic Chain Customization / Predefined Custom Chains

There is a dedicated Common.custom() static constructor which allows for an easy instantiation of a Common instance with somewhat adopted chain parameters, with the main use case to adopt on instantiating with a deviating chain ID (you can use this to adopt other chain parameters as well though). Instantiating a custom common instance with its own chain ID and inheriting all other parameters from mainnet can now be as easily done as:

const common = Common.custom({ chainId: 1234 })

The custom() method also takes a string as a first input (instead of a dictionary). This can be used in combination with the CustomChain enum dict which allows for the selection of predefined supported custom chains for an easier Common setup of these supported chains:

const common = Common.custom(CustomChain.ArbitrumRinkebyTestnet)

The following custom chains are currently supported:

PolygonMainnet
PolygonMumbai
ArbitrumRinkebyTestnet
xDaiChain
OptimisticKovan
OptimisticEthereum

Common instances created with this simplified custom() constructor can't be used in all usage contexts (the HF configuration is very likely not matching the actual chain) but can be useful for specific use cases, e.g. for sending a tx with @ethereumjs/tx to an L2 network (see the Tx library README for a complete usage example).

Activate with a single custom Chain setup

If you want to initialize a Common instance with a single custom chain which is then directly activated you can pass a dictionary - conforming to the parameter format described above - with your custom chain values to the constructor using the chain parameter or the setChain() method, here is some example:

import myCustomChain from './[PATH]/myCustomChain.json'
const common = new Common({ chain: myCustomChain })

Initialize using customChains Array

A second way for custom chain initialization is to use the customChains constructor option. This option comes with more flexibility and allows for an arbitrary number of custom chains to be initialized on a common instance in addition to the already supported ones. It also allows for an activation-independent initialization, so you can add your chains by adding to the customChains array and either directly use the chain option to activate one of the custom chains passed or activate a build in chain (e.g. mainnet) and switch to other chains - including the custom ones - by using Common.setChain().

import myCustomChain1 from './[PATH]/myCustomChain1.json'
import myCustomChain2 from './[PATH]/myCustomChain2.json'
// Add two custom chains, initial mainnet activation
const common1 = new Common({ chain: 'mainnet', customChains: [ myCustomChain1, myCustomChain2 ] })
// Somewhat later down the road...
common1.setChain('customChain1')
// Add two custom chains, activate customChain1
const common1 = new Common({ chain: 'customChain1', customChains: [ myCustomChain1, myCustomChain2 ] })

It is also possible (v2.5.0+) to pass in a custom genesis state file (see e.g. src/genesisStates/goerli.json for an example on the format needed) along with the custom chain configuration:

import myCustomChain1 from '[PATH_TO_MY_CHAINS]/myCustomChain1.json'
import chain1GenesisState from '[PATH_TO_GENESIS_STATES]/chain1GenesisState.json'
const common = new Common({ chain: 'myCustomChain1', customChains: [ [ myCustomChain1, chain1GenesisState ] ]})

Accessing the genesis state can be done as follows:

const genesisState = common.genesisState()

This now also provides direct access to custom genesis states passed into Common as described above. The old Common-separate genesisStateByName() and genesisStateById() functions are now deprecated and usage should be avoided.

Hardforks

The hardfork can be set in constructor like this:

const c = new Common({ chain: 'ropsten', hardfork: 'byzantium' })

Or optionally with the Hardfork enum:

import Common, { Chain, Hardfork } from '@ethereumjs/common'

const c = new Common({
  chain: Chain.Ropsten,
  hardfork: Hardfork.Byzantium,
})

Active Hardforks

There are currently parameter changes by the following past and future hardfork by the library supported:

chainstart (Hardfork.Chainstart)
homestead (Hardfork.Homestead)
dao (Hardfork.Dao)
tangerineWhistle (Hardfork.TangerineWhistle)
spuriousDragon (Hardfork.SpuriousDragon)
byzantium (Hardfork.Byzantium)
constantinople (Hardfork.Constantinople)
petersburg (Hardfork.Petersburg) (aka constantinopleFix, apply together with constantinople)
istanbul (Hardfork.Instanbul) (DEFAULT_HARDFORK (v2.0.0 release series))
muirGlacier (Hardfork.MuirGlacier)
berlin (Hardfork.Berlin) (since v2.2.0)
london (Hardfork.London) (since v2.4.0)
merge (Hardfork.Merge) (since v2.5.0, experimental)

Future Hardforks

The next upcoming HF shanghai is currently not yet supported by this library.

Parameter Access

For hardfork-specific parameter access with the param() and paramByBlock() functions you can use the following topics:

gasConfig
gasPrices
vm
pow

See one of the hardfork files like byzantium.json in the hardforks directory for an overview. For consistency, the chain start (chainstart) is considered an own hardfork.

The hardfork-specific json files only contain the deltas from chainstart and shouldn't be accessed directly until you have a specific reason for it.

EIPs

Starting with the v2.0.0 release of the library, EIPs are now native citizens within the library and can be activated like this:

const c = new Common({ chain: Chain.Mainnet, eips: [2537] })

The following EIPs are currently supported:

EIP-1559: Fee market change for ETH 1.0 chain
EIP-2315: Simple subroutines for the EVM
EIP-2537: BLS precompiles
EIP-2565: ModExp gas cost
EIP-2718: Transaction Types
EIP-2929: gas cost increases for state access opcodes
EIP-2930: Optional accesss list tx type
EIP-3198: Base fee Opcode
EIP-3529: Reduction in refunds
EIP-3541: Reject new contracts starting with the 0xEF byte
EIP-3554: Difficulty Bomb Delay to December 2021 (only PoW networks)
EIP-3675: Upgrade consensus to Proof-of-Stake (experimental)
EIP-3855: Push0 opcode (v2.6.1+)

Bootstrap Nodes

You can use common.bootstrapNodes() function to get nodes for a specific chain/network.

EthereumJS

See our organizational documentation for an introduction to EthereumJS as well as information on current standards and best practices.

If you want to join for work or do improvements on the libraries have a look at our contribution guidelines.

LICENSE

MIT

Usage no npm install needed!