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.. Generated automatically by doc/tools/make_rst.py in Godot's source tree.
.. DO NOT EDIT THIS FILE, but the HMACContext.xml source instead.
.. The source is found in doc/classes or modules/<name>/doc_classes.

.. _class_HMACContext:

HMACContext
===========

**Inherits:** :ref:`Reference<class_Reference>` **<** :ref:`Object<class_Object>`

Used to create an HMAC for a message using a key.

Description
-----------

The HMACContext class is useful for advanced HMAC use cases, such as streaming the message as it supports creating the message over time rather than providing it all at once.

::

    extends Node
    var ctx = HMACContext.new()
    
    func _ready():
        var key = "supersecret".to_utf8()
        var err = ctx.start(HashingContext.HASH_SHA256, key)
        assert(err == OK)
        var msg1 = "this is ".to_utf8()
        var msg2 = "super duper secret".to_utf8()
        err = ctx.update(msg1)
        assert(err == OK)
        err = ctx.update(msg2)
        assert(err == OK)
        var hmac = ctx.finish()
        print(hmac.hex_encode())

And in C# we can use the following.

::

    using Godot;
    using System;
    using System.Diagnostics;
    
    public class CryptoNode : Node
    {
        private HMACContext ctx = new HMACContext();
        public override void _Ready()
        {
            PoolByteArray key = String("supersecret").to_utf8();
            Error err = ctx.Start(HashingContext.HASH_SHA256, key);
            GD.Assert(err == OK);
            PoolByteArray msg1 = String("this is ").to_utf8();
            PoolByteArray msg2 = String("super duper secret").to_utf8();
            err = ctx.Update(msg1);
            GD.Assert(err == OK);
            err = ctx.Update(msg2);
            GD.Assert(err == OK);
            PoolByteArray hmac = ctx.Finish();
            GD.Print(hmac.HexEncode());
        }
    }

**Note:** Not available in HTML5 exports.

Methods
-------

+-------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+
| :ref:`PoolByteArray<class_PoolByteArray>` | :ref:`finish<class_HMACContext_method_finish>` **(** **)**                                                                                                      |
+-------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+
| :ref:`Error<enum_@GlobalScope_Error>`     | :ref:`start<class_HMACContext_method_start>` **(** :ref:`HashType<enum_HashingContext_HashType>` hash_type, :ref:`PoolByteArray<class_PoolByteArray>` key **)** |
+-------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+
| :ref:`Error<enum_@GlobalScope_Error>`     | :ref:`update<class_HMACContext_method_update>` **(** :ref:`PoolByteArray<class_PoolByteArray>` data **)**                                                       |
+-------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+

Method Descriptions
-------------------

.. _class_HMACContext_method_finish:

- :ref:`PoolByteArray<class_PoolByteArray>` **finish** **(** **)**

Returns the resulting HMAC. If the HMAC failed, an empty :ref:`PoolByteArray<class_PoolByteArray>` is returned.

----

.. _class_HMACContext_method_start:

- :ref:`Error<enum_@GlobalScope_Error>` **start** **(** :ref:`HashType<enum_HashingContext_HashType>` hash_type, :ref:`PoolByteArray<class_PoolByteArray>` key **)**

Initializes the HMACContext. This method cannot be called again on the same HMACContext until :ref:`finish<class_HMACContext_method_finish>` has been called.

----

.. _class_HMACContext_method_update:

- :ref:`Error<enum_@GlobalScope_Error>` **update** **(** :ref:`PoolByteArray<class_PoolByteArray>` data **)**

Updates the message to be HMACed. This can be called multiple times before :ref:`finish<class_HMACContext_method_finish>` is called to append ``data`` to the message, but cannot be called until :ref:`start<class_HMACContext_method_start>` has been called.

.. |virtual| replace:: :abbr:`virtual (This method should typically be overridden by the user to have any effect.)`
.. |const| replace:: :abbr:`const (This method has no side effects. It doesn't modify any of the instance's member variables.)`
.. |vararg| replace:: :abbr:`vararg (This method accepts any number of arguments after the ones described here.)`