> ## Documentation Index
> Fetch the complete documentation index at: https://voltaire.tevm.sh/llms.txt
> Use this file to discover all available pages before exploring further.

# Overview

> Contract creation bytecode (constructor + runtime)

## Type Definition

[Branded](/getting-started/branded-types) [`Uint8Array`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array) representing contract creation bytecode deployed during contract creation transactions.

```typescript theme={null}
import type { brand } from '@tevm/voltaire/brand';

export type InitCodeType = Uint8Array & {
  readonly [brand]: "InitCode";
};
```

Init code contains:

1. Constructor logic
2. Constructor arguments (if any)
3. Runtime bytecode (returned by constructor)

## Quick Reference

<Tabs>
  <Tab title="Create">
    ```typescript theme={null}
    import * as InitCode from '@tevm/voltaire/InitCode';

    // From hex string
    const init = InitCode.from("0x608060405234801561001057600080fd5b50...");

    // From Uint8Array
    const init = InitCode.from(new Uint8Array([0x60, 0x80, ...]));
    ```
  </Tab>

  <Tab title="Extract">
    ```typescript theme={null}
    // Extract runtime code at known offset
    const runtime = InitCode.extractRuntime(init, constructorLength);

    // Estimate gas cost
    const gas = InitCode.estimateGas(init);
    console.log(`Creation gas: ${gas}`);
    ```
  </Tab>
</Tabs>

## API Methods

### Constructors

* [`from(value)`](./from) - Create from hex string or Uint8Array
* [`fromHex(hex)`](./fromHex) - Parse hex string (with or without 0x prefix)

### Analysis

* [`extractRuntime(init, offset)`](./extractRuntime) - Extract runtime code at offset
* [`estimateGas(init)`](./estimateGas) - Estimate creation gas cost

### Utilities

* [`toHex(init)`](./toHex) - Convert to hex string
* [`equals(a, b)`](./equals) - Compare equality

## Usage Patterns

### Deploying Contract

```typescript theme={null}
import * as InitCode from '@tevm/voltaire/InitCode';

// Get init code from compilation output
const init = InitCode.from(compiledOutput.bytecode);

// Estimate gas
const estimatedGas = InitCode.estimateGas(init);
console.log(`Estimated gas: ${estimatedGas}`);

// Deploy
const tx = await signer.sendTransaction({
  data: InitCode.toHex(init),
  gasLimit: estimatedGas + 50000n, // Add buffer
});
```

### Analyzing Creation Bytecode

```typescript theme={null}
import * as InitCode from '@tevm/voltaire/InitCode';
import * as Bytecode from '@tevm/voltaire/Bytecode';

const init = InitCode.from(creationBytecode);

// Analyze constructor
const analysis = Bytecode.analyze(init);
console.log(`Constructor instructions: ${analysis.instructions.length}`);

// Find constructor length (usually ends with RETURN or STOP)
// then extract runtime code
const runtime = InitCode.extractRuntime(init, constructorLength);
```

### Gas Estimation

```typescript theme={null}
import * as InitCode from '@tevm/voltaire/InitCode';

const init = InitCode.from("0x608060405234801561001057600080fd5b50...");

// Base gas cost (data + creation)
const gas = InitCode.estimateGas(init);

// Gas breakdown:
// - 21000: Base transaction cost
// - 32000: CREATE operation
// - 16 per non-zero byte
// - 4 per zero byte
console.log(`Total creation gas: ${gas}`);
```

## Related

* [ContractCode](/primitives/contract-code) - Deployed contract bytecode
* [RuntimeCode](/primitives/runtime-code) - Pure runtime bytecode
* [Bytecode](/primitives/bytecode) - General bytecode analysis
* [Transaction](/primitives/transaction) - Transaction types

## Specification

* [Ethereum Yellow Paper](https://ethereum.github.io/yellowpaper/paper.pdf) - Contract creation semantics
* [EVM Opcodes](https://www.evm.codes/) - CREATE and CREATE2 operations
* [EIP-2028](https://eips.ethereum.org/EIPS/eip-2028) - Calldata gas cost reduction