.. index:: single: paseto_helpers
.. _paseto_helpers/0:

.. rst-class:: right

**category**

``paseto_helpers``
==================

Protected PASETO v4 framing, PAE, and encoding helpers.

| **Availability:** 
|    ``logtalk_load(paseto(loader))``

| **Author:** Paulo Moura
| **Version:** 1:0:0
| **Date:** 2026-08-08

| **Compilation flags:**
|    ``static``


| **Uses:**
|    :ref:`base64url_no_padding <base64url_no_padding/0>`
|    :ref:`list <list/0>`

| **Remarks:**
|    (none)

| **Inherited public predicates:**
|    (none)

.. contents::
   :local:
   :backlinks: top

Public predicates
-----------------

(no local declarations; see entity ancestors if any)

Protected predicates
--------------------

.. index:: pae/2
.. _paseto_helpers/0::pae/2:

``pae/2``
^^^^^^^^^

Pre-authentication encodes a list of byte-list pieces.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``pae(Pieces,Encoding)``
| **Mode and number of proofs:**
|    ``pae(+list(list(byte)),-list(byte))`` - ``one``


------------

.. index:: parse_token/4
.. _paseto_helpers/0::parse_token/4:

``parse_token/4``
^^^^^^^^^^^^^^^^^

Strictly parses a canonical v4 token for Purpose and decodes its body and optional footer.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``parse_token(Token,Purpose,Body,Footer)``
| **Mode and number of proofs:**
|    ``parse_token(+atom,+atom,-list(byte),-list(byte))`` - ``one_or_error``

| **Exceptions:**
|    ``Token`` is a variable:
|        ``instantiation_error``
|    ``Token`` is neither a variable nor an atom:
|        ``type_error(atom,Token)``
|    ``Token`` is an atom but does not have the expected PASETO v4 header:
|        ``domain_error(paseto_v4_token,Token)``
|    ``Token`` is a PASETO v4 header but has a malformed compact serialization:
|        ``domain_error(paseto_compact_serialization,malformed)``
|    ``Token`` contains non-canonical base64url data:
|        ``representation_error(base64)``


------------

.. index:: format_token/4
.. _paseto_helpers/0::format_token/4:

``format_token/4``
^^^^^^^^^^^^^^^^^^

Formats a canonical v4 token for Purpose from body and footer bytes.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``format_token(Purpose,Body,Footer,Token)``
| **Mode and number of proofs:**
|    ``format_token(+atom,+list(byte),+list(byte),-atom)`` - ``one``


------------

Private predicates
------------------

(no local declarations; see entity ancestors if any)

Operators
---------

(none)