@ethereumjs/statemanager

Library to provide high level access to Ethereum State

Installation

To obtain the latest version, simply require the project using npm:

npm install @ethereumjs/statemanager

Note: this library was part of the @ethereumjs/vm package up till VM v5.

Usage

Introduction

The StateManager provides high-level access and manipulation methods to and for the Ethereum state, thinking in terms of accounts or contract code rather then the storage operations of the underlying data structure (e.g. a Trie).

The library includes a TypeScript interface StateManager to ensure a unified interface (e.g. when passed to the VM), a concrete Trie-based DefaultStateManager implementation, as well as an RPCStateManager implementation that sources state and history data from an external JSON-RPC provider.

It also includes a checkpoint/revert/commit mechanism to either persist or revert state changes and provides a sophisticated caching mechanism under the hood to reduce the need for direct state accesses.

DefaultStateManager

Usage example

// ./examples/basicUsage.ts

import { Account, Address } from '@ethereumjs/util'
import { DefaultStateManager } from '@ethereumjs/statemanager'
import { hexToBytes } from '@ethereumjs/util'

const main = async () => {
  const stateManager = new DefaultStateManager()
  const address = new Address(hexToBytes('0xa94f5374fce5edbc8e2a8697c15331677e6ebf0b'))
  const account = new Account(BigInt(0), BigInt(1000))
  await stateManager.checkpoint()
  await stateManager.putAccount(address, account)
  await stateManager.commit()
  await stateManager.flush()

  // Account at address 0xa94f5374fce5edbc8e2a8697c15331677e6ebf0b has balance 1000
  console.log(
    `Account at address ${address.toString()} has balance ${
      (await stateManager.getAccount(address))?.balance
    }`
  )
}
main()

Account, Storage and Code Caches

Starting with the v2 release and complemented by the v2.1 release the StateManager comes with a significantly more elaborate caching mechanism for account, storage and code caches.

There are now two cache options available: an unbounded cache (CacheType.ORDERED_MAP) for short-lived usage scenarios (this one is the default cache) and a fixed-size cache (CacheType.LRU) for a long-lived large cache scenario.

Caches now "survive" a flush operation and especially long-lived usage scenarios will benefit from increased performance by a growing and more "knowing" cache leading to less and less trie reads.

Have a loot at the extended CacheOptions on how to use and leverage the new cache system.

Instantiating from a Proof

The DefaultStateManager has a static constructor fromProof that accepts one or more EIP-1186 proofs and will instantiate a DefaultStateManager with a partial trie containing the state provided by the proof(s). Be aware that this constructor accepts the StateManagerOpts dictionary as a third parameter (i.e. stateManager.fromProof(proof, safe, opts)). Therefore, if you need to use a customized trie (e.g. one that does not use key hashing) or specify caching options, you can pass them in here. If you do instantiate a trie and pass it into the fromProof constructor, you also need to instantiate the trie using the corresponding fromProof constructor to ensure the state root matches when the proof data is added to the trie. See this test for more details.

See below example for common usage:

// ./examples/fromProofInstantiation.ts

import { Address } from '@ethereumjs/util'
import { DefaultStateManager } from '@ethereumjs/statemanager'
import { hexToBytes } from '@ethereumjs/util'

const main = async () => {
  // setup `stateManager` with some existing address
  const stateManager = new DefaultStateManager()
  const contractAddress = new Address(hexToBytes('0xa94f5374fce5edbc8e2a8697c15331677e6ebf0b'))
  const byteCode = hexToBytes('0x67ffffffffffffffff600160006000fb')
  const storageKey1 = hexToBytes(
    '0x0000000000000000000000000000000000000000000000000000000000000001'
  )
  const storageKey2 = hexToBytes(
    '0x0000000000000000000000000000000000000000000000000000000000000002'
  )
  const storageValue1 = hexToBytes('0x01')
  const storageValue2 = hexToBytes('0x02')

  await stateManager.putContractCode(contractAddress, byteCode)
  await stateManager.putContractStorage(contractAddress, storageKey1, storageValue1)
  await stateManager.putContractStorage(contractAddress, storageKey2, storageValue2)

  const proof = await stateManager.getProof(contractAddress)
  const proofWithStorage = await stateManager.getProof(contractAddress, [storageKey1, storageKey2])
  const partialStateManager = await DefaultStateManager.fromProof(proof)

  // To add more proof data, use `addProofData`
  await partialStateManager.addProofData(proofWithStorage)
  console.log(await partialStateManager.getContractCode(contractAddress)) // contract bytecode is not included in proof
  console.log(
    await partialStateManager.getContractStorage(contractAddress, storageKey1),
    storageValue1
  ) // should match
  console.log(
    await partialStateManager.getContractStorage(contractAddress, storageKey2),
    storageValue2
  ) // should match

  const accountFromNewSM = await partialStateManager.getAccount(contractAddress)
  const accountFromOldSM = await stateManager.getAccount(contractAddress)
  console.log(accountFromNewSM, accountFromOldSM) // should match

  const slot1FromNewSM = await stateManager.getContractStorage(contractAddress, storageKey1)
  const slot2FromNewSM = await stateManager.getContractStorage(contractAddress, storageKey2)
  console.log(slot1FromNewSM, storageValue1) // should match
  console.log(slot2FromNewSM, storageValue2) // should match
}
main()

RPCStateManager

The RPCStateManager can be be used with any JSON-RPC provider that supports the eth namespace. Instantiate the VM and pass in an RPCStateManager to run transactions against accounts sourced from the provider or to run blocks pulled from the provider at any specified block height.

A simple example of usage:

// ./examples/rpcStateManager.ts

import { Address } from '@ethereumjs/util'
import { RPCStateManager } from '@ethereumjs/statemanager'

const main = async () => {
  try {
    const provider = 'https://path.to.my.provider.com'
    const stateManager = new RPCStateManager({ provider, blockTag: 500000n })
    const vitalikDotEth = Address.fromString('0xd8da6bf26964af9d7eed9e03e53415d37aa96045')
    const account = await stateManager.getAccount(vitalikDotEth)
    console.log('Vitalik has a current ETH balance of ', account?.balance)
  } catch (e) {
    console.log(e.message) // fetch fails because provider url is not real. please replace provider with a valid rpc url string.
  }
}
main()

Note: Usage of this StateManager can cause a heavy load regarding state request API calls, so be careful (or at least: aware) if used in combination with a JSON-RPC provider connecting to a third-party API service like Infura!

Points on RPCStateManager usage

Instantiating the EVM

In order to have an EVM instance that supports the BLOCKHASH opcode (which requires access to block history), you must instantiate both the RPCStateManager and the RpcBlockChain and use that when initalizing your EVM instance as below:

// ./examples/evm.ts

import { RPCStateManager, RPCBlockChain } from '@ethereumjs/statemanager'
import { EVM } from '@ethereumjs/evm'

const main = async () => {
  try {
    const provider = 'https://path.to.my.provider.com'
    const blockchain = new RPCBlockChain(provider)
    const blockTag = 1n
    const state = new RPCStateManager({ provider, blockTag })
    const evm = new EVM({ blockchain, stateManager: state }) // note that evm is ready to run BLOCKHASH opcodes (over RPC)
  } catch (e) {
    console.log(e.message) // fetch would fail because provider url is not real. please replace provider with a valid rpc url string.
  }
}
main()

Note: Failing to provide the RPCBlockChain instance when instantiating the EVM means that the BLOCKHASH opcode will fail to work correctly during EVM execution.

Provider selection

• The provider you select must support the eth_getProof, eth_getCode, and eth_getStorageAt RPC methods.
• Not all providers support retrieving state from all block heights so refer to your provider's documentation. Trying to use a block height not supported by your provider (e.g. any block older than the last 256 for CloudFlare) will result in RPC errors when using the state manager.

Block Tag selection

• You have to pass a block number or earliest in the constructor that specifies the block height you want to pull state from.
• The latest/pending values supported by the Ethereum JSON-RPC are not supported as longer running scripts run the risk of state values changing as blocks are mined while your script is running.
• If using a very recent block as your block tag, be aware that reorgs could occur and potentially alter the state you are interacting with.
• If you want to rerun transactions from block X or run block X, you need to specify the block tag as X-1 in the state manager constructor to ensure you are pulling the state values at the point in time the transactions or block was run.

Potential gotchas

• The RPC State Manager cannot compute valid state roots when running blocks as it does not have access to the entire Ethereum state trie so can not compute correct state roots, either for the account trie or for storage tries.
• If you are replaying mainnet transactions and an account or account storage is touched by multiple transactions in a block, you must replay those transactions in order (with regard to their position in that block) or calculated gas will likely be different than actual gas consumed.

Further reference

Refer to this test script for complete examples of running transactions and blocks in the vm with data sourced from a provider.

StatelessVerkleStateManager (experimental)

There is a new StatelessVerkleStateManager integrated into the code base. This state manager is very experimental and meant to be used for connecting to early Verkle Tree test networks (Kaustinen). This state manager is not yet sufficiently tested and APIs are not yet stable and it therefore should not be used in production.

See PRs around Verkle in our monorepo for an entrypoint if you are interested in our current Verkle related work.

WASM Crypto Support

This library by default uses JavaScript implementations for the basic standard crypto primitives like hashing for underlying trie keys. See @ethereumjs/common README for instructions on how to replace with e.g. a more performant WASM implementation by using a shared common instance.

Browser

With the breaking release round in Summer 2023 we have added hybrid ESM/CJS builds for all our libraries (see section below) and have eliminated many of the caveats which had previously prevented a frictionless browser usage.

It is now easily possible to run a browser build of one of the EthereumJS libraries within a modern browser using the provided ESM build. For a setup example see ./examples/browser.html.

API

Docs

Generated TypeDoc API Documentation

Hybrid CJS/ESM Builds

With the breaking releases from Summer 2023 we have started to ship our libraries with both CommonJS (cjs folder) and ESM builds (esm folder), see package.json for the detailed setup.

If you use an ES6-style import in your code files from the ESM build will be used:

import { EthereumJSClass } from '@ethereumjs/[PACKAGE_NAME]'

If you use Node.js specific require, the CJS build will be used:

const { EthereumJSClass } = require('@ethereumjs/[PACKAGE_NAME]')

Using ESM will give you additional advantages over CJS beyond browser usage like static code analysis / Tree Shaking which CJS can not provide.

Buffer -> Uint8Array

With the breaking releases from Summer 2023 we have removed all Node.js specific Buffer usages from our libraries and replace these with Uint8Array representations, which are available both in Node.js and the browser (Buffer is a subclass of Uint8Array).

We have converted existing Buffer conversion methods to Uint8Array conversion methods in the @ethereumjs/util bytes module, see the respective README section for guidance.

BigInt Support

Starting with v1 the usage of BN.js for big numbers has been removed from the library and replaced with the usage of the native JS BigInt data type (introduced in ES2020).

Please note that number-related API signatures have changed along with this version update and the minimal build target has been updated to ES2020.

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 carry out improvements on the libraries, please review our contribution guidelines first.

License

MPL-2.0