Extracting Read/Write Sets of State Variables from an Ethereum Smart Contract

As Ethereum-based decentralized applications (dApps) continue to grow in popularity, understanding how they store data on-chain is becoming increasingly important. In this article, we will explore methods for extracting read and write sets of state variables from a smart contract written in Solidity.

Understanding Ethereum State

In an Ethereum smart contract, state is represented as an object that stores data. Each object can have multiple properties (state variables) that can be accessed using either dot notation or parentheses notation. For example:

pragma solidity ^0,8,0;
contract MyContract {
uint public counter; // read-only variable
mapping(address => uint) public annotation; // map user addresses to counters
function incrementCounter() public payable {
counter += 1;
}
function updateMemo(address _user, uint amount) public {
memo[_user] = amount;
}
}

In this example, the variable counter is a read-only property that can be accessed using dot notation (“MyContract.counter”). The memo map is also a read-only property that can be accessed using parentheses (“MyContract.memo[“user”]).

• Get all properties: Usesolhint get-variables orsolc get-variable-counts ` to retrieve a list of all contract properties (state variables).

• Use reflection

  

  : You can use Solidity’s reflection functionality (solc –reflection) to inspect and modify the contract’s state variables at runtime.

Example: Extracting read-only and write-only state variables

Assuming we have an Ethereum smart contract named “MyContract” with a read-only variable “counter” and a write-only set “note”, we can use the following steps:

• Get all properties using solhint get-variables MyContract:

$ solhint get-variables MyContract
Counter: uint
Note: mapping (address => uint)

• Inspect and modify the contract state variables at runtime using Solidity’s reflection functionality (“solc –reflection”) with the following command:

$ solc --reflection --print-vars MyContract

Read-only variable
Counter (uint)

Write-only set
note: mapping (address => uint)

Take Note that the “–print-vars” flag is used to print all contract variables, including read-write and internal variables.

Conclusion

Extracting read and write sets of state variables from an Ethereum smart contract requires Solidity’s reflection functionality, solhint, and possibly manual inspection using Solscan or other tools. Understanding how to use these methods will help you better analyze and understand the behavior of your Ethereum smart contracts.

Recommendations

• Use solhint get-variables to retrieve a list of all contract properties (state variables).

• Use Solidity’s reflection functionality (“solc –reflection”) with the “–print-vars” flag to inspect and modify contract state variables at runtime.

• Consider using Solscan or other tools to help identify and extract information about your smart contracts.