# StreamingApi

**Kind:** Class

**Source:** [`src/utils/stream.ts`](https://github.com/honojs/hono/blob/main/src/utils/stream.ts#L6)

**Part of:** [Utils](subsystem-src-utils)

`StreamingApi` coordinates streamed output, delayed work, piping, and cancellation in `src/utils/stream.ts`. It exposes async write methods alongside abort handling so callers can stop work when the stream is no longer active.

## Methods

| Method | Signature | Returns |
|---|---|---|
| `write` | `write(input: Uint8Array | string)` | `Promise<StreamingApi>` |
| `writeln` | `writeln(input: string)` | `Promise<StreamingApi>` |
| `sleep` | `sleep(ms: number)` | `Promise<unknown>` |
| `close` | `close()` | `void` |
| `pipe` | `pipe(body: ReadableStream)` | `void` |
| `onAbort` | `onAbort(listener: () => void | Promise<void>)` | `void` |
| `abort` | `abort()` | `void` |

## Properties

| Property | Type |
|---|---|
| `responseReadable` | `ReadableStream` |
| `aborted` | `boolean` |
| `closed` | `boolean` |

## When something fails

- `StreamingApi` handles failure in 2 places: it discards it silently in all 2.

## Diagram

```mermaid
graph LR
  Caller --> StreamingApi
  StreamingApi --> Write[write / writeln]
  StreamingApi --> Delay[sleep]
  StreamingApi --> Pipe[pipe]
  StreamingApi --> Abort[onAbort / abort]
  StreamingApi --> Close[close]
```

## Usage

```ts
import type { StreamingApi } from "./utils/stream";

async function handleStream(stream: StreamingApi) {
  stream.onAbort(() => {
    console.log("Stream aborted");
  });

  await stream.write();
  await stream.writeln();

  await stream.sleep();

  stream.close();
}
```

## AI Coding Instructions

- Await `write()` and `writeln()` before dependent streamed work.
- Register `onAbort()` handlers before starting long-running work.
- Stop pending work when an abort handler runs; do not continue writing after cancellation.
- Call `close()` when streaming is complete.
- Keep stream lifecycle handling in the caller that owns the request or response.

## Used by

2 references from 2 files. Each is a place in this repository where the symbol is actually used — go read one rather than trusting an example.

### Imported by (2)

- `SSEMessage` — `src/helper/streaming/sse.ts`:6
- `stream` — `src/helper/streaming/stream.ts`:7