Ethereum: Difference between `tx.gasprice`, `assembly { gasPrice := gasprice() }` and `block.basefee`

Understanding Gas Price Output in Ethereum Contracts

When working with Ethereum contracts, especially those that use built-in assembly or interact with external APIs like «gasprice()», accurate implementation can be crucial in distinguishing between two seemingly similar values. In this article, we will delve into the variables tx.gasprice and assembly { gasPrice := gasprice() }, exploring their differences and how they affect the operation of your contract.

tx.gasprice

The variable tx.gasprice represents the estimated gas price for a transaction on the Ethereum network. This value is calculated by the Ethereum Virtual Machine (EVM) based on a variety of factors, including:

• Network congestion

• Transaction gas limit

• Contract execution time

Calling gasprice() within an included assembly block or as part of the contract initialization code returns this estimated gas price.

assembly { gasPrice := gasprice() }

The keyword assembly' is used to define a function that takes no arguments and has a single return statement. When this function is executed inside an assembly, it calculates the expected gas price for the transaction and assigns its value to the local variablegasPrice''. This approach allows you to efficiently cache gas prices without directly accessing the EVM functiongasprice()''.

• Cache performance

  : By storing gas price calculations in a single variable, you can optimize cache hits and reduce memory allocation time. In contrast, if you store the result of`gasprice()» directly in an inside assembly block, you have to allocate memory for it each time.

• Gas calculation efficiency: Due to the EVM architecture, calculating gas prices from scratch each time incurs a significant performance cost. By caching these calculations, you can improve the speed of contract execution and reduce latency.

Code Example

Here is an example of how you can use both variables in a contract:

pragma hardness ^0,8,0;
contract GasPriceExample {
// Store gas price calculations for efficient performance
uint256 private _gasPrices = 0;
assembly {
// Calculate approximate gas prices for cached values
call @borderGasprice()[] memory txGases {
// Example: Calculate approximate gas prices using inline assembly
let gasPrice := gasprice()
// Store the result in a local variable for efficient caching
_gasPrices := gasPrices + (gasPrice - 1)
}
}
function borderGasprice() public pure returns (uint256) {
// Example: Simulate a cache miss by calculating gas prices from scratch
uint256 gasPrice = 10; // Estimated gas price
assembly {
// Calculate the expected gas price using the EVM gas pricing algorithm
gasPrice := gas(1, gasPrice)
}
return gasPrice;
}
function calculateGasPrice(uint256 txGases) public net return (uint256) {
// Example: Use the included assembly to maintain cache and reuse previous calculations
uint256 cachedGasPrice = _gasPrices; // Use cached value if available
assembly {
// Calculate the expected gas price using cached value or direct calculation
let gasPrice := gas(txGases, 1)
// Assign the calculated gas price to a local variable for efficient caching
cachedGasPrice := (cachedGasPrice - 1) + gasPrice
}
return cachedGasPrice;
}
}

In this example, we show how both variables can be used effectively in an Ethereum contract.

ETHEREUM FAIL PARSE JSON