Inputs and outputs have typed ABI shapes with different call-data framing.
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Build a transfer call from typed fieldsStep 1 / 4
The standard transfer interface takes an address and a raw integer amount. This diagram uses address one and amount one hundred.
The standard transfer interface takes an address and a raw integer amount. This diagram uses address one and amount one hundred.Keccak-256 of the canonical signature supplies the first four bytes. The transfer selector is a9059cbb.An address is twenty bytes. Standard ABI encoding adds twelve zero bytes on the left to fill one thirty-two-byte word.The integer one hundred is hex 64, left-padded in word one. Selector plus two words produces sixty-eight bytes of standard calldata.
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Inputs belong to a chosen function
A standard external function request begins with a selector followed by its encoded arguments. Canonical parameter types are part of the selector’s signature.
Outputs omit that selector prefix
Ordinary ABIreturn data encodes the declared results without prepending the function’s four-byte selector. Decode it using the known output schema rather than treating it as another function call.
Names are documentation, types are representation
Return names can improve readability. They do not make the raw bytes self-describing or guarantee a particular implementation is honest. Multiple results can have a tuple-like encoding.
Check direction before decoding
Know whether bytes are calldata, return data, event data or revert data. The surrounding interface determines framing. A decoder choosing the wrong direction can produce nonsense or reject valid bytes.
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// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;
contract LearningExample {
function split(uint256 x)
external pure returns (uint256 half, uint256 remainder)
{
return (x / 2, x % 2);
}
}
The two returned integers are ABI-encoded without a function selector prefix.
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Do ordinary ABI return values prepend the called function selector?
Function calldata and return data use different framing.