But when the form includes files, it is encoded as `multipart/form-data`. You'll read about handling files in the next chapter.

If you want to read more about these encodings and form fields, head to the <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/POST" class="external-link" target="_blank"><abbr title="Mozilla Developer Network">MDN</abbr> web docs for <code>POST</code></a>.

///

* Decompressing gzip-compressed request bodies.
* Automatically logging all request bodies.

## Handling custom request body encodings

Let's see how to make use of a custom `Request` subclass to decompress gzip requests.

And an `APIRoute` subclass to use that custom request class.

### Create a custom `GzipRequest` class

/// tip

But when the form includes files, it is encoded as `multipart/form-data`. If you use `File`, **FastAPI** will know it has to get the files from the correct part of the body.

If you want to read more about these encodings and form fields, head to the <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/POST" class="external-link" target="_blank"><abbr title="Mozilla Developer Network">MDN</abbr> web docs for <code>POST</code></a>.

///

	// Hex constant 0x20004000000
	MOVD $2199090364416, R5         // 60058001
	// Hex constant 0xFFFFFE0004000000
	MOVD $-2198956146688, R5        // 38a08001
	// TODO: On GOPPC64={power8,power9}, this is preprocessed into MOVD $-1, R5; RLDC R5, $33, $63, R5.
	//       This only captures the MOVD. Should the RLDC be appended to the encoding by the test?
	// Hex constant 0xFFFFFFFE00000001

 * return hex.decode("deadbeef"); // throws an IllegalArgumentException
 * }</pre>
 *
 * <p>It is guaranteed that {@code encoding.decode(encoding.encode(x))} is always equal to {@code
 * x}, but the reverse does not necessarily hold.
 *
 * <table>
 * <caption>Encodings</caption>
 * <tr>
 * <th>Encoding
 * <th>Alphabet
 * <th>{@code char:byte} ratio
 * <th>Default padding
 * <th>Comments
 * <tr>
 * <td>{@link #base16()}

- JWTs used in service account and OIDC authentication are now strictly parsed to confirm that they use compact serialization. Other encodings were not previously accepted, but would result in different unspecific errors. ([#123540](https://github.com/kubernetes/kubernetes/pull/123540), [@enj](https://github.com/enj))

    assertThat(encoding.canDecode(encoded)).isTrue();
    assertThat(encoding.decode(encoded)).isEqualTo(decoded);
  }

  private static void assertFailsToDecode(BaseEncoding encoding, String cannotDecode) {
    assertFailsToDecode(encoding, cannotDecode, null);
  }

  private static void assertFailsToDecode(
      BaseEncoding encoding, String cannotDecode, @Nullable String expectedMessage) {

    assertThat(encoding.canDecode(encoded)).isTrue();
    assertThat(encoding.decode(encoded)).isEqualTo(decoded);
  }

  private static void assertFailsToDecode(BaseEncoding encoding, String cannotDecode) {
    assertFailsToDecode(encoding, cannotDecode, null);
  }

  private static void assertFailsToDecode(
      BaseEncoding encoding, String cannotDecode, @Nullable String expectedMessage) {

        assertFileExistence(dir, filename, true);

        File file = new File(dir, filename);

        String contents = FileUtils.fileRead(file, encoding);

        assertEquals(contentsTest, contents);
    }

    public File createFile(File dir, String filename, String contents, String encoding) throws IOException {

pkg encoding, type BinaryAppender interface { AppendBinary } #62384
pkg encoding, type BinaryAppender interface, AppendBinary([]uint8) ([]uint8, error) #62384
pkg encoding, type TextAppender interface { AppendText } #62384
pkg encoding, type TextAppender interface, AppendText([]uint8) ([]uint8, error) #62384
pkg net/url, method (*URL) AppendBinary([]uint8) ([]uint8, error) #62384
pkg log/slog, method (Level) AppendText([]uint8) ([]uint8, error) #62384