The gas.rs Module

The gas.rs module in this Rust EVM implementation manages the concept of "gas" within the Ethereum network. In Ethereum, "gas" signifies the computational effort needed to execute operations, whether a simple transfer of ether or the execution of a smart contract function. Each operation carries a gas cost, and transactions must specify the maximum amount of gas they are willing to consume.

Data Structures

• Gas Struct

  The Gas struct represents the gas state for a particular operation or transaction. The struct is defined as follows:

  Fields in Gas Struct

  • limit: The maximum amount of gas allowed for the operation or transaction.
  • all_used_gas: The total gas used, inclusive of memory expansion costs.
  • used: The gas used, excluding memory expansion costs.
  • memory: The gas used for memory expansion.
  • refunded: The gas refunded. Certain operations in Ethereum allow for gas refunds, up to half the gas used by a transaction.

Methods of the Gas Struct

The Gas struct also includes several methods to manage the gas state. Here's a brief summary of their functions:

• new: Creates a new Gas instance with a specified gas limit and zero usage and refunds.
• limit, memory, refunded, spend, remaining: These getters return the current state of the corresponding field.
• erase_cost: Decreases the gas usage by a specified amount.
• record_refund: Increases the refunded gas by a specified amount.
• record_cost: Increases the used gas by a specified amount. It also checks for gas limit overflow. If the new total used gas would exceed the gas limit, it returns false and doesn't change the state.
• record_memory: This method works similarly to record_cost, but specifically for memory expansion gas. It only updates the state if the new memory gas usage is greater than the current usage.
• gas_refund: Increases the refunded gas by a specified amount.