}

        in 3..4 -> {
          source.readData(data)
        }

        in 5..7 -> {
          data.writeByte('\n'.code) // 'data' on a line of its own.
        }

        in 8..9 -> {
          id = source.readUtf8LineStrict().takeIf { it.isNotEmpty() }
        }

        in 10..12 -> {
          id = null // 'id' on a line of its own.
        }

        in 13..14 -> {

**FastAPI** сам займётся их управлением.

## Провайдер зависимости

Можно создать первую зависимость следующим образом:

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[8:9] *}

Она объявляет необязательный параметр запроса `q` как строку, а затем возвращает его.

Это довольно просто (хотя и не очень полезно), но поможет нам сосредоточиться на том, как работают подзависимости.

O **FastAPI** se encarrega de resolver essas dependências.

## Primeira dependência "injetável"

Você pode criar uma primeira dependência (injetável) dessa forma:

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[8:9] *}

Esse código declara um parâmetro de consulta opcional, `q`, com o tipo `str`, e então retorna esse parâmetro.

Isso é bastante simples (e não muito útil), mas irá nos ajudar a focar em como as subdependências funcionam.

    - [Client Binaries](#client-binaries-5)
    - [Server Binaries](#server-binaries-5)
    - [Node Binaries](#node-binaries-5)
  - [Changelog since v1.8.9](#changelog-since-v189)
    - [Other notable changes](#other-notable-changes-5)
- [v1.8.9](#v189)
  - [Downloads for v1.8.9](#downloads-for-v189)
    - [Client Binaries](#client-binaries-6)
    - [Server Binaries](#server-binaries-6)
    - [Node Binaries](#node-binaries-6)

     */
    @Test
    void testWriteParametersWireFormat() {
        // Given
        int sid = 0x1234;
        int resumeKey = 0x89ABCDEF; // LE expected: EF CD AB 89
        String name = "file.txt";
        Trans2FindNext2 next = new Trans2FindNext2(sid, resumeKey, name);

        int expectedLen = 2 + 2 + 2 + 4 + 2 + name.length() + 1;
        byte[] dst = new byte[expectedLen];

```
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number:
            35:ac:60:46:ad:8d:de:18:dc:0b:f6:98:14:ee:89:e8
        Signature Algorithm: ED25519
        Issuer: CN = consoleAdmin
        Validity
            Not Before: Jul 19 15:08:44 2021 GMT
            Not After : Aug 18 15:08:44 2021 GMT
        Subject: CN = consoleAdmin

Давайте для начала сфокусируемся на зависимостях.

Это просто функция, которая может принимать все те же параметры, что и *функции обработки пути*:
{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[8:9] *}

**И всё.**

**2 строки.**

И теперь она той же формы и структуры, что и все ваши *функции обработки пути*.

	_ = x[ErrMissingFields-83]
	_ = x[ErrMissingCredTag-84]
	_ = x[ErrCredMalformed-85]
	_ = x[ErrInvalidRegion-86]
	_ = x[ErrInvalidServiceS3-87]
	_ = x[ErrInvalidServiceSTS-88]
	_ = x[ErrInvalidRequestVersion-89]
	_ = x[ErrMissingSignTag-90]
	_ = x[ErrMissingSignHeadersTag-91]
	_ = x[ErrMalformedDate-92]
	_ = x[ErrMalformedPresignedDate-93]
	_ = x[ErrMalformedCredentialDate-94]
	_ = x[ErrMalformedExpires-95]

Primero enfoquémonos en la dependencia.

Es solo una función que puede tomar todos los mismos parámetros que una *path operation function* puede tomar:

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[8:9] *}

Eso es todo.

**2 líneas**.

Y tiene la misma forma y estructura que todas tus *path operation functions*.

Let's first focus on the dependency.

It is just a function that can take all the same parameters that a *path operation function* can take:

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[8:9] *}

That's it.

**2 lines**.

And it has the same shape and structure that all your *path operation functions* have.