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Ethereum: Is it possible to emit generic events using assembly?

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Ethereum: Is it possible to create public events using Assembly?

As part of our ongoing efforts to improve and expand the Ethereum blockchain, we are exploring innovative solutions to improve the performance, scalability and usability of decentralized applications (dApps). One area that has generated considerable interest is the use of assembly languages ​​to create generic events. In this article, we will look at the possibility of using Assembly to create shared events in the Ethereum blockchain.

Background

Before we get into the details, let’s briefly summarize what’s going on in a high-level context. When an ERC-721 smart contract delegates its functions to another contract (known as a “controller”) via proxies or updated templates, it needs to generate various types of events to notify other contracts of state changes. These events can be triggered by various conditions, such as state, ownership, or contract metadata changes.

Ethereum Event Broadcast Mechanism

In Ethereum, events are broadcast using a combination of assembly language programming and smart contracts such as Solidity (the language used for most ERC-721 contracts). The event broadcast process involves several stages:

  • Contract call

    : When an event is triggered, the calling contract executes a call to its own functions (e.g. transfer or updateBalance).

  • Intermediate dispatch

    : The intermediate code runs on the Ethereum Virtual Machine (EVM) and generates a dispatch operation that triggers the correct function.

  • Function execution: The called function is executed, which may include broadcasting new events.

Collection of generic events

To create common events using assembly, we need to understand how the EVM communicates with Solidity code. We can use the call' command in Solidity to call a function and then manipulate the stack to generate a dispatcher for the assembly that triggers the specific event.

Here is a simplified example of how we can collect a generic event:

solidity

contract My contract {

// Definition of a generic event contract

struct Events {

uint256[] ids;

string[] messageStrings;

}

function emitEvent(uint256 id, string message) public {

// Create an array to store the event data

event memory events = Events({

ids: new uint256[](id),

messageStrings: new string[](message.length)

});

// Push the event data onto the stack

for (uint256 i = 0; i < id; i++) {

events.ids[i] = id;

events.messageStrings[i] = msg.value.toString();

}

// Create a dispatch assembly to run the correct function

assembly {

// Get the current state of the contract storage

let value := mstore(0, myContractStorage)

// Put the new event data on the stack

push(value, events.id)

push(value, events.messageStrings)

// Call function for event processing

call(myContract, "myFunction", 0, abi.encode(value))

}

}

// Example of a function that handles a general event

function myFunction(uint256 id) public payable {

// Processing a new event in the stack

if (id == 1) {

// Do something with the event data

require(msg.value >= 10, "Insufficient funds")

}

}

}

`

In this example, we define anEventsstructure to store event data. We then create a dispatch assembly that places theidsandmessageStringsfields on the stack before calling the function (myFunction`) to process the new event.

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