}

// MarshalXML - StringMap marshals into XML.
func (s *Metadata) MarshalXML(e *xxml.Encoder, start xxml.StartElement) error {
	if s == nil {
		return nil
	}

	if len(s.Items) == 0 {
		return nil
	}

	if err := e.EncodeToken(start); err != nil {
		return err
	}

	for _, item := range s.Items {
		if err := e.Encode(xmlKeyEntry{
			XMLName: xxml.Name{Local: item.Key},
			Value:   item.Value,

                        buf.append(c);
                    } else {
                        try {
                            buf.append(URLEncoder.encode(String.valueOf(c), Constants.UTF_8));
                        } catch (final UnsupportedEncodingException e) {
                            // NOP
                        }
                    }
                }

			} else {
				s += ", \"bitrot_valid\": false"
			}
			if value {
				if utf8.Valid(data) {
					// Encode as JSON string.
					b, err := json.Marshal(string(data))
					if err == nil {
						s += `, "data_string": ` + string(b)
					}
				}
				// Base64 encode.
				s += `, "data_base64": "` + base64.StdEncoding.EncodeToString(data) + `"`
			}
			s += "}"
		}

## Otros middlewares

Hay muchos otros middlewares ASGI.

Por ejemplo:

* <a href="https://github.com/encode/uvicorn/blob/master/uvicorn/middleware/proxy_headers.py" class="external-link" target="_blank">`ProxyHeadersMiddleware` de Uvicorn</a>

    @Override
    public int size() {
        // Context header (16) + name length (4) + padding to 8-byte alignment + data (16)
        return 16 + 4 + 4 + STRUCTURE_SIZE;
    }

    @Override
    public int encode(byte[] dst, int dstIndex) {
        int start = dstIndex;

        // Write context header
        SMBUtil.writeInt4(0, dst, dstIndex); // Next (offset to next context, 0 for last)
        dstIndex += 4;

			t.Fatalf("Test %d: failed to create erasure: %v", i, err)
		}
		encoded, err := erasure.EncodeData(t.Context(), buffer)
		if err != nil {
			t.Fatalf("Test %d: failed to encode data: %v", i, err)
		}

		for j := range encoded[:test.missingData] {
			encoded[j] = nil
		}
		for j := test.dataBlocks; j < test.dataBlocks+test.missingParity; j++ {
			encoded[j] = nil
		}

		if test.reconstructParity {

        // Test encoding/decoding
        byte[] encoded = nic.encode();
        assertNotNull(encoded);
        assertEquals(Smb2ChannelCapabilities.NETWORK_INTERFACE_INFO_SIZE, encoded.length);

        NetworkInterfaceInfo decoded = NetworkInterfaceInfo.decode(encoded, 0);
        assertEquals(nic.getInterfaceIndex(), decoded.getInterfaceIndex());

	if s3Err != ErrNone {
		return s3Err
	}

	// Extract all the signed headers along with its values.
	extractedSignedHeaders, errCode := extractSignedHeaders(pSignValues.SignedHeaders, r)
	if errCode != ErrNone {
		return errCode
	}

	// Check if the metadata headers are equal with signedheaders
	errMetaCode := checkMetaHeaders(extractedSignedHeaders, r)
	if errMetaCode != ErrNone {

        return dstIndex - start;
    }

    @Override
    protected int writeDataWireFormat(final byte[] dst, int dstIndex) {
        final int start = dstIndex;
        dstIndex += this.info.encode(dst, dstIndex);

        /* 6 zeros observed with NT */
        SMBUtil.writeInt8(0L, dst, dstIndex);
        dstIndex += 6;

        /*
         * Also observed 4 byte alignment but we stick

    assertThat(encoding.encode(decoded.getBytes(UTF_8), offset, len)).isEqualTo(encoded);
  }

  private static void testDecodes(BaseEncoding encoding, String encoded, String decoded) {
    assertThat(encoding.canDecode(encoded)).isTrue();
    assertThat(encoding.decode(encoded)).isEqualTo(decoded.getBytes(UTF_8));
  }

  private static void testDecodesByBytes(BaseEncoding encoding, String encoded, byte[] decoded) {