# Types & Constants

Everything the package exports besides the [`Rollup`](/cmio/reference/rollup) class (the `RollupError` class is documented under [Errors](#errors)). All types are importable with `import type`:

```ts twoslash
import type {
    AddressLike,
    AdvanceRequest,
    BytesLike,
    DelegateCallVoucher,
    GioResponse,
    Hex,
    InspectRequest,
    RollupRequest,
    RunHandlers,
    U256Like,
    Voucher,
} from '@deroll/cmio';
```

## Input types

Three "like" types describe what the binding accepts and converts automatically — see [byte and number conventions](/cmio/guide/emitting-outputs#byte-and-number-conventions). Hex strings are `Hex` (`` `0x${string}` ``), structurally identical to viem's `Hex`/`Address`:

| Type | Accepts | Used for |
| --- | --- | --- |
| `BytesLike` | `Hex`, `Buffer`, `Uint8Array` | payloads, gio ids |
| `AddressLike` | `Hex`, `Buffer`, `Uint8Array` (20 bytes) | voucher destinations |
| `U256Like` | `bigint`, `number`, `Hex`, `Uint8Array` (32 bytes) | voucher values |

## Output argument types

The two voucher emitters take a named options object, importable for typing helpers that build outputs:

* `Voucher` — argument of [`emitVoucher`](/cmio/reference/emit-voucher): `destination` (`AddressLike`), optional `value` (`U256Like`, default `0n`) and `payload` (`BytesLike`, default empty).
* `DelegateCallVoucher` — argument of [`emitDelegateCallVoucher`](/cmio/reference/emit-delegate-call-voucher): `destination` (`AddressLike`) and optional `payload` (`BytesLike`). No `value` — `DELEGATECALL` cannot transfer ether.

```ts twoslash
import type { Voucher, DelegateCallVoucher } from '@deroll/cmio';

const voucher: Voucher = {
    destination: '0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266',
    value: 1_000_000_000_000_000_000n,
};

const delegateCall: DelegateCallVoucher = {
    destination: '0x5FbDB2315678afecb367f032d93F642f64180aa3',
};
```

## Request types

[`finish`](/cmio/reference/finish) returns `RollupRequest`, the discriminated union of:

* `AdvanceRequest` — `type: 'advance'` plus the input metadata (`chainId`, `appContract`, `msgSender`, `blockNumber`, `blockTimestamp`, `prevRandao`, `index`) and `payload`.
* `InspectRequest` — `type: 'inspect'` and `payload`.

```ts twoslash
import { Rollup } from '@deroll/cmio';
const rollup = new Rollup();
// ---cut---
const request = rollup.finish();
if (request.type === 'advance') {
    request.index;
    //       ^?
}
```

## Handler types

`RunHandlers` is the parameter of [`run`](/cmio/reference/run) — an optional `advance` and `inspect` handler, each receiving `(request, rollup)` and returning `boolean | void`, possibly wrapped in a `Promise`.

## Response types

`GioResponse` is returned by [`gio`](/cmio/reference/gio): `{ responseCode: number, responseData: Buffer }`.

## Constants

```ts twoslash
import { ADDRESS_LENGTH, U256_LENGTH } from '@deroll/cmio';

ADDRESS_LENGTH;
// ^?

U256_LENGTH;
// ^?
```

## Errors

Failed libcmt calls throw a `RollupError` (a subclass of `Error`) with two extra properties:

| Property | Type | Meaning |
| --- | --- | --- |
| `errno` | `number` | The negative errno from libcmt (e.g. `-16` for `EBUSY`) |
| `syscall` | `string` | The libcmt call that failed (e.g. `cmt_rollup_init`) |

`RollupError` is exported as a value, so it can be caught with `instanceof`:

```ts twoslash
import { Rollup, RollupError } from '@deroll/cmio';

try {
    new Rollup();
} catch (error) {
    if (error instanceof RollupError) {
        error.errno;
        //    ^?
    }
}
```

Argument validation failures throw plain `TypeError` / `RangeError` before reaching the device.