tokens = need + hdr

		} else { // part of header can be accommodated
			r.opts.HeaderSize -= b - 1
			need = 1 // to ensure we read at least one byte for every Read
			tokens = b
		}
	} else { // all tokens go towards payload
		need = int(math.Min(float64(b), float64(need)))
		tokens = need
	}
	// reduce tokens requested according to availability

```

////

## Die Abhängigkeiten aktualisieren

Aktualisieren Sie `get_current_user`, um den gleichen Token wie zuvor zu erhalten, dieses Mal jedoch unter Verwendung von JWT-Tokens.

Dekodieren Sie den empfangenen Token, validieren Sie ihn und geben Sie den aktuellen Benutzer zurück.

Wenn der Token ungültig ist, geben Sie sofort einen HTTP-Fehler zurück.

//// tab | Python 3.10+

```Python hl_lines="89-106"

        List<String> tokens = new ArrayList<String>();
        for (int i = 0; i < NUM; i++) {
            tokens.add(accessTokenHelper.generateAccessToken());
        }
        for (int i = 0; i < NUM; i++) {
            assertFalse(tokens.get(i).isEmpty());
            for (int j = i + 1; j < NUM; j++) {
                assertFalse(tokens.get(i).equals(tokens.get(j)));
            }
        }
    }

		return nil, &ErrInvalidARN{s}
	}

	tokens := strings.Split(s, ":")
	if len(tokens) != 6 {
		return nil, &ErrInvalidARN{s}
	}

	if tokens[4] == "" || tokens[5] == "" {
		return nil, &ErrInvalidARN{s}
	}

	return &ARN{
		region: tokens[3],
		TargetID: TargetID{
			ID:   tokens[4],
			Name: tokens[5],
		},
	}, nil

	Close()
}

// A Token is a scan token plus its string value.
// A macro is stored as a sequence of Tokens with spaces stripped.
type Token struct {
	ScanToken
	text string
}

// Make returns a Token with the given rune (ScanToken) and text representation.
func Make(token ScanToken, text string) Token {
	// Substitute the substitutes for . and /.
	text = strings.ReplaceAll(text, "\u00B7", ".")

	var tokens []Token
	for _, tok := range macro.tokens {
		if tok.ScanToken != scanner.Ident {
			tokens = append(tokens, tok)
			continue
		}
		substitution := actuals[tok.text]
		if substitution == nil {
			tokens = append(tokens, tok)
			continue
		}
		tokens = append(tokens, substitution...)
	}
	in.Push(NewSlice(in.Base(), in.Line(), tokens))
}

	return nil
}

// parseTargetID - parses string to TargetID.
func parseTargetID(s string) (*TargetID, error) {
	tokens := strings.Split(s, ":")
	if len(tokens) != 2 {
		return nil, fmt.Errorf("invalid TargetID format '%v'", s)
	}

	return &TargetID{
		ID:   tokens[0],
		Name: tokens[1],
	}, nil

{!> ../../docs_src/security/tutorial004.py!}
```

////

## Update the dependencies

Update `get_current_user` to receive the same token as before, but this time, using JWT tokens.

Decode the received token, verify it, and return the current user.

If the token is invalid, return an HTTP error right away.

//// tab | Python 3.10+

```Python hl_lines="90-107"

package lex

import (
	"text/scanner"

	"cmd/internal/src"
)

// A Slice reads from a slice of Tokens.
type Slice struct {
	tokens []Token
	base   *src.PosBase
	line   int
	pos    int
}

func NewSlice(base *src.PosBase, line int, tokens []Token) *Slice {
	return &Slice{
		tokens: tokens,
		base:   base,
		line:   line,
		pos:    -1, // Next will advance to zero.
	}
}

///

## Return the token

The response of the `token` endpoint must be a JSON object.

It should have a `token_type`. In our case, as we are using "Bearer" tokens, the token type should be "`bearer`".

And it should have an `access_token`, with a string containing our access token.