SYNOPSIS

Implements Ethereum's VM in Javascript.

Fork Support

The VM currently supports the following hardfork rules:

• Byzantium
• Constantinople
• Petersburg (default)
• Istanbul (DRAFT)

If you are still looking for a Spurious Dragon compatible version of this library install the latest of the 2.2.x series (see Changelog).

Istanbul Harfork Support

With the v4.0.0 release we are starting to add implementations of EIPs being candidates or accepted for inclusion within the Istanbul hardfork. You can activate a preliminary Istanbul VM by using the istanbul hardfork option flag.

Currently supported Istanbul EIPs:

• EIP-1108 (Candidate): alt_bn128 Gas Cost Reductions, see PR #540

Note that this is highly experimental and solely meant for experimental purposes, since Istanbul scope is not yet finalized and most EIPs are still in a DRAFT state and likely subject to updates and changes.

A final Istanbul VM will be released along a major version bump to likely v5.0.0 or v6.0.0.

Have a look at the corresponding issue to follow the discussion and current state on Istanbul planning.

INSTALL

npm install ethereumjs-vm

USAGE

const BN = require('bn.js')
var VM = require('ethereumjs-vm').default

// Create a new VM instance
// For explicity setting the HF use e.g. `new VM({ hardfork: 'petersburg' })`
const vm = new VM()

const STOP = '00'
const ADD = '01'
const PUSH1 = '60'

// Note that numbers added are hex values, so '20' would be '32' as decimal e.g.
const code = [PUSH1, '03', PUSH1, '05', ADD, STOP]

vm.on('step', function(data) {
  console.log(`Opcode: ${data.opcode.name}\tStack: ${data.stack}`)
})

vm.runCode({
  code: Buffer.from(code.join(''), 'hex'),
  gasLimit: new BN(0xffff),
})
  .then(results => {
    console.log('Returned : ' + results.returnValue.toString('hex'))
    console.log('gasUsed  : ' + results.gasUsed.toString())
  })
  .catch(err => console.log('Error    : ' + err))

Example

This projects contain the following examples:

1. ./examples/run-blockchain: Loads tests data, including accounts and blocks, and runs all of them in the VM.
2. ./examples/run-code-browser: Show how to use this library in a browser.
3. ./examples/run-solidity-contract: Compiles a Solidity contract, and calls constant and non-constant functions.
4. ./examples/run-transactions-complete: Runs a contract-deployment transaction and then calls one of its functions.
5. ./examples/decode-opcodes: Decodes a binary EVM program into its opcodes.

All of the examples have their own README.md explaining how to run them.

BROWSER

To build for standalone use in the browser, install browserify and check run-transactions-simple example. This will give you a global variable EthVM to use. The generated file will be at ./examples/run-transactions-simple/build.js.

API

VM

For documentation on VM instantiation, exposed API and emitted events see generated API docs.

StateManger

The API for the StateManager is currently in Beta, separate documentation can be found here, see also release notes from the v2.5.0 VM release for details on the StateManager rewrite.

Internal Structure

The VM processes state changes at many levels.

• runBlockchain
  • for every block, runBlock
• runBlock
  • for every tx, runTx
  • pay miner and uncles
• runTx
  • check sender balance
  • check sender nonce
  • runCall
  • transfer gas charges
• runCall
  • checkpoint state
  • transfer value
  • load code
  • runCode
  • materialize created contracts
  • revert or commit checkpoint
• runCode
  • iterate over code
  • run op codes
  • track gas usage
• OpFns
  • run individual op code
  • modify stack
  • modify memory
  • calculate fee

The opFns for CREATE, CALL, and CALLCODE call back up to runCall.

DEVELOPMENT

Developer documentation - currently mainly with information on testing and debugging - can be found here.

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

MPL-2.0