object : DerAdapter<Long> {
      override fun matches(header: DerHeader): Boolean {
        return Adapters.UTC_TIME.matches(header) || Adapters.GENERALIZED_TIME.matches(header)
      }

      override fun fromDer(reader: DerReader): Long {
        val peekHeader =
          reader.peekHeader()
            ?: throw ProtocolException("expected time but was exhausted at $reader")

        return when {

      // Read the header.
      val header = Buffer()
      fileOperator.read(0, header, FILE_HEADER_SIZE)
      val prefix = header.readByteString(PREFIX_CLEAN.size.toLong())
      if (prefix != PREFIX_CLEAN) throw IOException("unreadable cache file")
      val upstreamSize = header.readLong()
      val metadataSize = header.readLong()

      // Read the metadata.

    description="OAuth2 security scheme",
    auto_error=False,
)


class User(BaseModel):
    username: str


def get_current_user(oauth_header: Optional[str] = Security(reusable_oauth2)):
    if oauth_header is None:
        return None
    user = User(username=oauth_header)
    return user


@app.post("/login")
def login(form_data: OAuth2PasswordRequestFormStrict = Depends()):
    return form_data

// For forward compatibility, users that retrieve a Header from Reader.Next,
// mutate it in some ways, and then pass it back to Writer.WriteHeader
// should do so by creating a new Header and copying the fields
// that they are interested in preserving.
type Header struct {
	// Typeflag is the type of header entry.
	// The zero value is automatically promoted to either TypeReg or TypeDir
	// depending on the presence of a trailing slash in Name.

   *
   * Otherwise if the response has a `Content-Type` header that specifies a charset, that is used
   * to determine the charset of the response bytes.
   *
   * Otherwise the response bytes are decoded as UTF-8.
   */
  fun charStream(): Reader =
    reader ?: BomAwareReader(source(), charset()).also {
      reader = it
    }

  /**
   * Returns the response as a string.
   *

	if !reflect.DeepEqual(want,...

        "custom-foo",
        "custom-header",
        "custom-bar",
        "custom-header",
        "custom-baz",
        "custom-header",
      )
    bytesIn.writeByte(0x40) // Literal indexed
    bytesIn.writeByte(0x0a) // Literal name (len = 10)
    bytesIn.writeUtf8("custom-foo")
    bytesIn.writeByte(0x0d) // Literal value (len = 13)
    bytesIn.writeUtf8("custom-header")
    bytesIn.writeByte(0x40) // Literal indexed

	o = msgp.Require(b, z.Msgsize())
	// map header, size 4
	// string "APIVersion"
	o = append(o, 0x84, 0xaa, 0x41, 0x50, 0x49, 0x56, 0x65, 0x72, 0x73, 0x69, 0x6f, 0x6e)
	o = msgp.AppendString(o, z.APIVersion)
	// string "Flags"
	o = append(o, 0xa5, 0x46, 0x6c, 0x61, 0x67, 0x73)
	// map header, size 3
	// string "Filter"
	o = append(o, 0x83, 0xa6, 0x46, 0x69, 0x6c, 0x74, 0x65, 0x72)

// where we keep old *Readers
var readMsgpReaderPool = sync.Pool{New: func() interface{} { return &msgp.Reader{} }}

// mspNewReader returns a *Reader that reads from the provided reader.
// The reader will be buffered.
// Return with readMsgpReaderPoolPut when done.
func msgpNewReader(r io.Reader) *msgp.Reader {
	p := readMsgpReaderPool.Get().(*msgp.Reader)
	if p.R == nil {
		p.R = xbufio.NewReaderSize(r, 4<<10)
	} else {
		p.R.Reset(r)

    ```

!!! info
    The additional header `WWW-Authenticate` with value `Bearer` we are returning here is also part of the spec.

    Any HTTP (error) status code 401 "UNAUTHORIZED" is supposed to also return a `WWW-Authenticate` header.

    In the case of bearer tokens (our case), the value of that header should be `Bearer`.

    You can actually skip that extra header and it would still work.