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

As the popularity of Ethereum-based decentralized applications (dApps) continues to grow, understanding how they store data on-chain has become increasingly important. In this article, we’ll 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), which are accessed using dot notation or bracket notation. For example:

pragma solidity ^0.8.0;


contract MyContract { {

    uint public counter; // read-only variable

    mapping ( address => uint ) public memo ; // map of user addresses to counters


    function incrementCounter() public payable {

        counter += 1;

    } } }


    function updateMemo ( address _user , uint amount ) public { {

        memo[_user] = amount;

    } } }

} } }

In this example, the counter variable 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 bracket notation (MyContract.memo["user"]).

Extracting Read and Write Sets of State Variables

To extract read and write sets of state variables from an Ethereum smart contract, you’ll need to use the following approaches:

• Get all properties: Use solhint get-variables or solc get-variable-counts to retrieve a list of all properties (state variables) in the contract.

• 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 and Write Sets of State Variables

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

• Get all properties using solhint get-variables MyContract:

$ solhint get-variables MyContract

Counter : uint

Memo : mapping ( address => uint )

• Inspect and modify the contract’s 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 set

  memo : mapping ( address => uint ) ;

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

Conclusion

Extracting read and write sets of state variables from an Ethereum smart contract requires a combination of Solidity’s reflection functionality, solhint, and possibly manual inspection using Solscan or other tools. By understanding how to use these techniques, you’ll be able to better analyze and understand the behavior of your own Ethereum smart contracts.

Recommendations

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

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

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