zb0002, err = dc.ReadArrayHeader()
			if err != nil {
				err = msgp.WrapError(err, "ObjSizes")
				return
			}
			if zb0002 != uint32(dataUsageBucketLen) {
				err = msgp.ArrayError{Wanted: uint32(dataUsageBucketLen), Got: zb0002}
				return
			}
			for za0001 := range z.ObjSizes {
				z.ObjSizes[za0001], err = dc.ReadUint64()
				if err != nil {

* `read(size)`：按指定数量的字节或字符（`size` (`int`)）读取文件内容；
* `seek(offset)`：移动至文件 `offset` （`int`）字节处的位置；
    * 例如，`await myfile.seek(0) ` 移动到文件开头；
    * 执行 `await myfile.read()` 后，需再次读取已读取内容时，这种方法特别好用；
* `close()`：关闭文件。

因为上述方法都是 `async` 方法，要搭配「await」使用。

例如，在 `async` *路径操作函数* 内，要用以下方式读取文件内容：

```Python
contents = await myfile.read()
```

在普通 `def` *路径操作函数*  内，则可以直接访问 `UploadFile.file`，例如：

```Python

    return value


@app.websocket("/ws")
async def get_value_by_ws(
    websocket: WebSocket, value: int = Depends(extract_value_from_http_connection)
):
    await websocket.accept()
    await websocket.send_json(value)
    await websocket.close()


client = TestClient(app)


def test_value_extracting_by_http():
    response = client.get("/http")
    assert response.status_code == 200

Подробности о синтаксисе `async def` для *функций-обработчиков пути* и немного фона об асинхронном коде, конкурентности и параллелизме.

## Нет времени? { #in-a-hurry }

<abbr title="too long; didn't read – слишком длинно; не читал"><strong>TL;DR:</strong></abbr>

Если вы используете сторонние библиотеки, которые нужно вызывать с `await`, например:

```Python
results = await some_library()
```

@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket, session: SessionDep):
    await websocket.accept()
    for item in session:
        await websocket.send_text(f"{item}")


@app.websocket("/ws-broken")
async def websocket_endpoint_broken(websocket: WebSocket, session: BrokenSessionDep):
    await websocket.accept()
    for item in session:
        await websocket.send_text(f"{item}")  # pragma no cover


client = TestClient(app)

    cookie_or_token: str = Depends(get_cookie_or_token),
):
    await websocket.accept()
    while True:
        data = await websocket.receive_text()
        await websocket.send_text(
            f"Session cookie or query token value is: {cookie_or_token}"
        )
        if q is not None:
            await websocket.send_text(f"Query parameter q is: {q}")

    await websocket.accept()  # pragma: no cover
    await websocket.send_text(f"Item: {item_id}")  # pragma: no cover
    await websocket.close()  # pragma: no cover


@sub_app.websocket("/ws/{item_id}")
async def subapp_websocket_endpoint(websocket: WebSocket, item_id: int):
    await websocket.accept()  # pragma: no cover
    await websocket.send_text(f"Item: {item_id}")  # pragma: no cover

          return false;
        } else {
          long now = System.nanoTime();
          NANOSECONDS.timedWait(lock, nanos);
          nanos -= System.nanoTime() - now; // subtract the actual time we waited
        }
      }
    }
  }

  /**
   * Checks if the executor has been shut down and increments the running task count.
   *

  /** Invokes {@code latch.}{@link CountDownLatch#await() await()} uninterruptibly. */
  @J2ktIncompatible
  @GwtIncompatible // concurrency
  public static void awaitUninterruptibly(CountDownLatch latch) {
    boolean interrupted = false;
    try {
      while (true) {
        try {
          latch.await();
          return;
        } catch (InterruptedException e) {

# Concorrência e async / await { #concurrency-and-async-await }

Detalhes sobre a sintaxe `async def` para *funções de operação de rota* e alguns conceitos de código assíncrono, concorrência e paralelismo.

## Com pressa? { #in-a-hurry }

<abbr title="too long; didn't read – muito longo; não li"><strong>TL;DR:</strong></abbr>

Se você estiver utilizando bibliotecas de terceiros que dizem para você chamar as funções com `await`, como:

```Python