// If the most recent read or write operation on the buffer was
// not a successful [Buffer.ReadRune], UnreadRune returns an error.  (In this regard
// it is stricter than [Buffer.UnreadByte], which will unread the last byte
// from any read operation.)
func (b *Buffer) UnreadRune() error {
	if b.lastRead <= opInvalid {
		return errors.New("bytes.Buffer: UnreadRune: previous operation was not a successful ReadRune")
	}

Imaginemos que quieres obtener la dirección IP/host del cliente dentro de tu *path operation function*.

Para eso necesitas acceder al request directamente.

{* ../../docs_src/using_request_directly/tutorial001_py39.py hl[1,7:8] *}

Al declarar un parámetro de *path operation function* con el tipo siendo `Request`, **FastAPI** sabrá pasar el `Request` en ese parámetro.

/// tip | Consejo

//
//go:build linux

package bytes_test

import (
	. "bytes"
	"syscall"
	"testing"
)

// This file tests the situation where byte operations are checking
// data very near to a page boundary. We want to make sure those
// operations do not read across the boundary and cause a page
// fault where they shouldn't.

// These tests run only on linux. The code being tested is

También puedes usar `url_for()` dentro de la plantilla, toma como argumentos los mismos que usaría tu *path operation function*.

Entonces, la sección con:

{% raw %}

```jinja
<a href="{{ url_for('read_item', id=id) }}">
```

{% endraw %}

...generará un enlace hacia la misma URL que manejaría la *path operation function* `read_item(id=id)`.

Por ejemplo, con un ID de `42`, esto se renderizaría como:

```html

import java.io.IOException;

import jcifs.smb1.smb1.ACE;
import jcifs.smb1.smb1.SecurityDescriptor;

/**
 * MS-RPC share information retrieval operation.
 *
 * This class implements the Server Service (SRVSVC) ShareGetInfo operation
 * for retrieving detailed information about a network share, including
 * security descriptors.
 */
public class MsrpcShareGetInfo extends srvsvc.ShareGetInfo {

    /**

 *
 * @author mbechler
 */
public class Smb2ReadRequest extends ServerMessageBlock2Request<Smb2ReadResponse> implements RequestWithFileId {

    /**
     * Flag to indicate unbuffered read operation
     */
    public static byte SMB2_READFLAG_READ_UNBUFFERED = 0x1;
    /**
     * Channel type for standard read without RDMA
     */
    public static int SMB2_CHANNEL_NONE = 0x0;
    /**

            NdrBuffer buffer2 = mock(NdrBuffer.class);
            when(buffer2.dec_ndr_short()).thenReturn(75);

            // When: Performing multiple operations
            ndrShort.encode(buffer1);
            ndrShort.decode(buffer2);

            // Then: Should handle both operations correctly
            verify(buffer1).enc_ndr_short(50);
            verify(buffer2).dec_ndr_short();
            assertEquals(75, ndrShort.value);

* feature: funcionalidad
* sponsor: sponsor
* host (in a podcast): host
* request (as in HTTP request): request
* response (as in HTTP response): response
* path operation function: path operation function (do not translate to "función de operación de ruta")
* path operation: path operation (do not translate to "operación de ruta")
* path (as in URL path): path (do not translate to "ruta")
* query (as in URL query): query (do not translate to "consulta")

In this case, this `__call__` is what **FastAPI** will use to check for additional parameters and sub-dependencies, and this is what will be called to pass a value to the parameter in your *path operation function* later.

## Parameterize the instance { #parameterize-the-instance }

And now, we can use `__init__` to declare the parameters of the instance that we can use to "parameterize" the dependency:

Entonces podemos usar la dependencia con:

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[23] *}

/// info | Información

Fíjate que solo estamos declarando una dependencia en la *path operation function*, `query_or_cookie_extractor`.

Pero **FastAPI** sabrá que tiene que resolver `query_extractor` primero, para pasar los resultados de eso a `query_or_cookie_extractor` al llamarlo.

///

```mermaid
graph TB