* return 0 for streams connected to regular files. However, a
     * stream created from a Named Pipe this method will query the server using a
     * "peek named pipe" operation and return the number of available bytes
     * on the server.
     */
    @Override
    public int available() throws IOException {

            s[i] = s[j];
            s[j] = t;
        }

        i = j = 0;
    }

    /**
     * Encrypts or decrypts data using the RC4 stream cipher.
     * Since RC4 is a stream cipher, the same operation is used for both encryption and decryption.
     *
     * @param src the source data array
     * @param soff the offset in the source array
     * @param slen the length of data to process

     * Applies the upgrade strategy to all eligible POMs.
     *
     * @param context the upgrade context
     * @param pomMap map of all POM files in the project (domtrip Documents)
     * @return the result of the upgrade operation
     */
    UpgradeResult apply(UpgradeContext context, Map<Path, Document> pomMap);

    /**
     * Checks if this strategy is applicable given the current options.
     *
     * @param context the upgrade context

For example, to declare a header of `X-Token` that can appear more than once, you can write:

{* ../../docs_src/header_params/tutorial003_an_py310.py hl[9] *}

If you communicate with that *path operation* sending two HTTP headers like:

```
X-Token: foo
X-Token: bar
```

The response would be like:

```JSON
{
    "X-Token values": [
        "bar",
        "foo"
    ]
}
```

   * </pre>
   *
   * @return a list of {@code ListenableFuture} instances representing the tasks, in the same
   *     sequential order as produced by the iterator for the given task list. If the operation did
   *     not time out, each task will have completed. If it did time out, some of these tasks will
   *     not have completed.
   * @throws RejectedExecutionException {@inheritDoc}

The normal (default) process, is as follows.

A `FastAPI` application (instance) has an `.openapi()` method that is expected to return the OpenAPI schema.

As part of the application object creation, a *path operation* for `/openapi.json` (or for whatever you set your `openapi_url`) is registered.

It just returns a JSON response with the result of the application's `.openapi()` method.

	return info, nil
}

// GetDriveStats returns IO stats of the drive by its major:minor
func GetDriveStats(major, minor uint32) (iostats IOStats, err error) {
	return IOStats{}, errors.New("operation unsupported")

        }
    }

    @Nested
    @DisplayName("WriteBytesWireFormat Tests")
    class WriteBytesWireFormatTests {

        @Test
        @DisplayName("Should always return 0 for write operation")
        void testWriteBytesWireFormat() {
            byte[] buffer = new byte[64];
            int result = notification.writeBytesWireFormat(buffer, 0);
            assertEquals(0, result);

# OpenAPI 回呼 { #openapi-callbacks }

你可以建立一個含有「路徑操作（path operation）」的 API，該操作會觸發對某個「外部 API（external API）」的請求（通常由使用你 API 的同一位開發者提供）。

當你的 API 應用呼叫「外部 API」時發生的過程稱為「回呼（callback）」。因為外部開發者撰寫的軟體會先向你的 API 發出請求，接著你的 API 再「回呼」，也就是向（可能同一位開發者建立的）外部 API 發送請求。

在這種情況下，你可能想要文件化說明該外部 API 應該長什麼樣子。它應該有哪些「路徑操作」、應該接受什麼 body、應該回傳什麼 response，等等。

## 帶有回呼的應用 { #an-app-with-callbacks }

我們用一個例子來看。

想像你開發了一個允許建立發票的應用。

這些發票會有 `id`、`title`（可選）、`customer` 和 `total`。

```
.
├── app
│   ├── __init__.py
│   ├── main.py
│   └── test_main.py
```

ここで、**FastAPI** アプリがある `main.py` ファイルには、他の path operation があります。

エラーを返す可能性のある `GET` オペレーションがあります。

いくつかのエラーを返す可能性のある `POST` オペレーションもあります。

両方の *path operation* には `X-Token` ヘッダーが必要です。

{* ../../docs_src/app_testing/app_b_an_py310/main.py *}

### 拡張版テストファイル { #extended-testing-file }