# SYNOPSIS

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# ETHEREUMJS-COMMON
Resources common to all Ethereum implementations

Succeeds the old [ethereum/common](https://github.com/ethereumjs/common/) library.

# 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.

Here are some simple usage examples:

```javascript
const Common = require('ethereumjs-common')

// Instantiate with only the chain
let c = new Common('ropsten')
c.param('gasPrices', 'ecAddGas', 'byzantium') // 500

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

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

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

It is encouraged to also explicitly set the ``supportedHardforks`` if the initializing library
only supports a certain range of ``hardforks``:

```javascript
let c = new Common('ropsten', null, ['byzantium', 'constantinople'])
```

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

# 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](./docs/index.md)


# Hardfork Params

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

- ``chainstart``
- ``homestead``
- ``dao``
- ``tangerineWhistle``
- ``spuriousDragon``
- ``byzantium``
- ``constantinople`` (Draft)
- ``hybridCasper`` (Draft)


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

- ``gasConfig``
- ``gasPrices``
- ``vm``
- ``pow``
- ``casper``
- ``sharding``

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.

Note: The list of ``gasPrices`` and gas price changes on hardforks is consistent 
but not complete, so there are currently gas price values missing (PRs welcome!).

# Chain Params

Supported chains:

- ``mainnet``
- ``ropsten``
- ``rinkeby``
- ``kovan``

The following chain-specific parameters are provided:

- ``name``
- ``chainId``
- ``networkId``
- ``genesis`` block header values
- ``hardforks`` block numbers
- ``bootstrapNodes`` list

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.

# Bootstrap Nodes

There is no separate config file for bootstrap nodes like in the old ``ethereum-common`` library.
Instead use the ``common.bootstrapNodes()`` function to get nodes for a specific chain/network.

# Genesis States

Network-specific genesis files are located in the ``genesisStates`` folder.

Due to the large file sizes genesis states are not directly included in the ``index.js`` file
but have to be accessed directly, e.g.:

```
const mainnetGenesisState = require('ethereumjs-common/genesisStates/mainnet')
```

# LICENSE
[MIT](https://opensource.org/licenses/MIT)