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Creates CallData from a hex-encoded string. Specialized constructor for hex input with explicit validation.

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Signature

function fromHex(hex: string): CallDataType

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Parameters

  • hex - Hex-encoded string (with or without 0x prefix)

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Returns

CallDataType - Branded Uint8Array representing transaction calldata

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Examples

import { CallData } from '@tevm/voltaire';

// With 0x prefix
const calldata1 = CallData.fromHex("0xa9059cbb...");

// Without 0x prefix
const calldata2 = CallData.fromHex("a9059cbb...");

console.log(CallData.toHex(calldata1));
// "0xa9059cbb..."

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Validation

Validates hex string format: 
import { CallData } from '@tevm/voltaire';

// Invalid hex characters
try {
  CallData.fromHex("0xGGGG");
} catch (error) {
  console.error("Invalid hex string");
}

// Odd length hex (must be byte-aligned)
try {
  CallData.fromHex("0xa9059c"); // 6 chars = 3 bytes = odd nibbles
} catch (error) {
  console.error("Hex must have even length");
}

// Too short (must be at least 4 bytes for selector)
try {
  CallData.fromHex("0xa905");
} catch (error) {
  console.error("CallData must be at least 4 bytes");
}

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Comparison with from()

fromHex is more explicit but less flexible than from: 
import { CallData } from '@tevm/voltaire';

// from() - Universal constructor
const calldata1 = CallData("0xa9059cbb...");
const calldata2 = CallData(new Uint8Array([0xa9, 0x05]));

// fromHex() - Hex string only
const calldata3 = CallData.fromHex("0xa9059cbb...");
const calldata4 = CallData.fromHex(bytes); // ❌ Type error
Use fromHex when:
  • Input is always hex string
  • You want explicit type checking
  • Code clarity is prioritized
Use from when:
  • Input type varies
  • Maximum flexibility needed
  • Writing generic functions

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Use Cases

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Parse Raw Transaction

import { CallData } from '@tevm/voltaire';

interface RawTransaction {
  data: string; // Hex string
}

function parseTxData(tx: RawTransaction) {
  const calldata = CallData.fromHex(tx.data);

  return {
    selector: CallData.getSelector(calldata),
    size: calldata.length,
  };
}

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Validate Hex Input

import { CallData } from '@tevm/voltaire';

function isValidCallDataHex(hex: string): boolean {
  try {
    CallData.fromHex(hex);
    return true;
  } catch {
    return false;
  }
}

console.log(isValidCallDataHex("0xa9059cbb")); // true
console.log(isValidCallDataHex("0xGGGG")); // false

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Type-Safe API

import { CallData } from '@tevm/voltaire';

// Enforce hex string input at API boundary
export function decodeCallData(hex: string) {
  const calldata = CallData.fromHex(hex); // Explicit hex validation
  return CallData.decode(calldata, abi);
}