@ethereumjs/statemanager

@ethereumjs/statemanager

Note: this README has been updated containing the changes from our next breaking release round [UNRELEASED] targeted for Summer 2023. See the README files from the maintenance-v6 branch for documentation matching our latest releases.

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) as well as a concrete Trie-based implementation DefaultStateManager as well as an EthersStateManager implementation that sources state and history data from an external ethers 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 Example

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

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 and Storage Caches

Starting with the v2 release the StateManager comes with a significantly more elaborate caching mechanism for account and storage 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.

EthersStateManager

First, a simple example of usage:

import { Account, Address } from '@ethereumjs/util'
import { EthersStateManager } from '@ethereumjs/statemanager'
import { ethers } from 'ethers'

const provider = new ethers.providers.JsonRpcProvider('https://path.to.my.provider.com')
const stateManager = new EthersStateManager({ 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)

The EthersStateManager can be be used with an ethers JsonRpcProvider or one of its subclasses. Instantiate the VM and pass in an EthersStateManager to run transactions against accounts sourced from the provider or to run blocks pulled from the provider at any specified block height.

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 an Ethers provider connecting to a third-party API service like Infura!

Points on usage:

Provider selection

• If you don't have access to a provider, you can use the CloudFlareProvider from the @ethersproject/providers module to get a quickstart.
• 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 Ethers 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.

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