Ethereum. Is there a way to know the storage space needed by my smart contract?

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How can I quantify how much storage space (approximately) do I need for Ethereum transactions? Is it per function/ transaction or how is it calculated? any leads on this is appreciated. I am trying to quantify the storage space needed for the transactions created by my smart contract...

blockchain smartcontracts ethereum storage transactions
1 Answers

How to calculate the data field size

(when you're sending a transaction calling a smart contract function)

The data field value could be divided into three parts:

  • 0x
  • 4 bytes (8 hex characters) - This is the function signature, it identifies the function that you are going to call.
    • The value is first 4 bytes of keccak256 hash of the function name and argument types. Example: transfer(address,uint256) => a9059cbb
  • the rest of data - Arguments passed into the function.

The easiest way is to use a library that calculates the size for you. :) For example web3js function encodeFunctionCall().

Example:

const result = web3.eth.abi.encodeFunctionCall({
    name: 'transfer',
    type: 'function',
    inputs: [{
        type: 'address',
        name: ''
    },{
        type: 'uint256',
        name: ''
    }]
}, ['0x1231231231231231231231231231231231231231', '1']);
console.log(result);

Returns

0xa9059cbb00000000000000000000000012312312312312312312312312312312312312310000000000000000000000000000000000000000000000000000000000000001
  • a9059cbb is the function signature
  • 0000000000000000000000001231231231231231231231231231231231231231 is the address type (256bit, 64 hex chars) first argument
  • 0000000000000000000000000000000000000000000000000000000000000001 is the uint256 type (256bit, 64 hex chars) second argument

So the result is 0x and 136 hex characters, which makes 68 bytes.

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