Documentation Index
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Encodes a function signature and parameters into transaction calldata using ABI encoding.
Signature
// Via ABI instance
const abi = Abi([...]);
abi.functionName.encode(...params): CallDataType
CallData.encode(signature: string, params: unknown[]): CallDataType
Parameters
- signature - Function signature (e.g.,
"transfer(address,uint256)")
- params - Array of parameter values matching signature types
Returns
CallDataType - Encoded calldata with selector and ABI-encoded parameters
Examples
ERC20 Transfer
Swap with Struct
Batch Transfer
Manual Encoding
import { Abi, Address, TokenBalance } from '@tevm/voltaire';
const abi = Abi([{
name: "transfer",
type: "function",
inputs: [
{ name: "to", type: "address" },
{ name: "amount", type: "uint256" }
]
}]);
const calldata = abi.transfer.encode(
Address("0x70997970C51812dc3A010C7d01b50e0d17dc79C8"),
TokenBalance.fromUnits("1", 18)
);
console.log(CallData.toHex(calldata));
// "0xa9059cbb" // transfer selector
// + "00000000000000000000000070997970c51812dc3a010c7d01b50e0d17dc79c8" // address
// + "0000000000000000000000000000000000000000000000000de0b6b3a7640000" // uint256
const abi = Abi([{
name: "swap",
type: "function",
inputs: [{
name: "params",
type: "tuple",
components: [
{ name: "tokenIn", type: "address" },
{ name: "tokenOut", type: "address" },
{ name: "amountIn", type: "uint256" },
{ name: "minAmountOut", type: "uint256" }
]
}]
}]);
const calldata = abi.swap.encode({
tokenIn: Address("0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"),
tokenOut: Address("0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2"),
amountIn: TokenBalance.fromUnits("1000", 6),
minAmountOut: TokenBalance.fromUnits("0.3", 18)
});
const abi = Abi([{
name: "batchTransfer",
type: "function",
inputs: [
{ name: "recipients", type: "address[]" },
{ name: "amounts", type: "uint256[]" }
]
}]);
const recipients = [
Address("0x70997970C51812dc3A010C7d01b50e0d17dc79C8"),
Address("0x3C44CdDdB6a900fa2b585dd299e03d12FA4293BC"),
];
const amounts = [
TokenBalance.fromUnits("1", 18),
TokenBalance.fromUnits("2", 18),
];
const calldata = abi.batchTransfer.encode(recipients, amounts);
import { CallData } from '@tevm/voltaire';
// Without ABI instance (not recommended)
const calldata = CallData.encode(
"transfer(address,uint256)",
[
"0x70997970C51812dc3A010C7d01b50e0d17dc79C8",
"1000000000000000000"
]
);
Function Signatures
Signatures must use canonical form:
// Correct format
"transfer(address,uint256)" // ✅ No spaces
"balanceOf(address)" // ✅ Single param
"swap((address,address,uint256))" // ✅ Tuple notation
"multicall(bytes[])" // ✅ Dynamic array
// Wrong format
"transfer(address, uint256)" // ❌ Space after comma
"transfer(address to, uint256 amt)" // ❌ Parameter names
"balanceOf(uint)" // ❌ Use uint256, not uint
"transfer( address,uint256 )" // ❌ Extra spaces
Type Conversion
Parameters automatically convert to ABI types:
import { Abi } from '@tevm/voltaire';
const abi = Abi([{
name: "setValue",
type: "function",
inputs: [
{ name: "addr", type: "address" },
{ name: "value", type: "uint256" },
{ name: "flag", type: "bool" }
]
}]);
// Accepts various input types
const calldata = abi.setValue.encode(
"0x70997970C51812dc3A010C7d01b50e0d17dc79C8", // String → Address
1000000000000000000n, // bigint → Uint256
true // boolean → bool
);
Use in Transactions
Complete Flow
Estimate Gas
import {
Transaction, Abi, Address, TokenBalance,
Nonce, GasLimit, Wei, Gwei, ChainId
} from '@tevm/voltaire';
const abi = Abi([{
name: "transfer",
type: "function",
inputs: [
{ name: "to", type: "address" },
{ name: "amount", type: "uint256" }
]
}]);
// Encode function call
const calldata = abi.transfer.encode(
Address("0x70997970C51812dc3A010C7d01b50e0d17dc79C8"),
TokenBalance.fromUnits("1", 18)
);
// Create transaction
const tx = Transaction({
type: Transaction.Type.EIP1559,
to: Address("0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"), // USDC
data: calldata,
value: Wei(0),
chainId: ChainId(1),
nonce: Nonce(0),
maxFeePerGas: Gwei(30),
maxPriorityFeePerGas: Gwei(2),
gasLimit: GasLimit(100000),
});
import { estimateGas } from '@tevm/voltaire';
const calldata = abi.transfer.encode(recipient, amount);
const gasEstimate = await estimateGas({
to: tokenAddress,
data: calldata,
from: senderAddress,
});
console.log("Estimated gas:", gasEstimate);
Validation
Validates parameters match signature:
import { Abi } from '@tevm/voltaire';
const abi = Abi([{
name: "transfer",
type: "function",
inputs: [
{ name: "to", type: "address" },
{ name: "amount", type: "uint256" }
]
}]);
// Wrong number of parameters
try {
abi.transfer.encode(Address("0x...")); // Missing amount
} catch (error) {
console.error("Parameter count mismatch");
}
// Wrong type
try {
abi.transfer.encode(
"not an address", // Invalid address format
TokenBalance.fromUnits("1", 18)
);
} catch (error) {
console.error("Invalid address");
}
// Benchmark: 1M iterations
console.time("encode");
for (let i = 0; i < 1_000_000; i++) {
abi.transfer.encode(recipient, amount);
}
console.timeEnd("encode");
// Pure JS: ~850ms
// WASM (ReleaseSmall): ~320ms (2.6x faster)
// WASM (ReleaseFast): ~180ms (4.7x faster)
Selector Computation
Encoding automatically computes function selector:
import { Keccak256 } from '@tevm/voltaire';
// Manual selector computation
const signature = "transfer(address,uint256)";
const hash = Keccak256.hashString(signature);
const selector = hash.slice(0, 4);
console.log(selector);
// [0xa9, 0x05, 0x9c, 0xbb]
// Encoding includes this automatically
const calldata = abi.transfer.encode(recipient, amount);
console.log(CallData.getSelector(calldata));
// [0xa9, 0x05, 0x9c, 0xbb] (same)
- decode - Decode calldata back to parameters
- Abi - ABI encoding and decoding
- Transaction - Building transactions
- Encoding - ABI encoding mechanics
