[#btck_NotificationInterfaceCallbacks]
= btck_NotificationInterfaceCallbacks
:mrdocs:

A struct for holding the kernel notification callbacks. The user data pointer may be used to point to user‐defined structures to make processing the notifications easier.

== Synopsis

Declared in `<kernel/bitcoinkernel.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
struct btck_NotificationInterfaceCallbacks;
----

== Description

If user_data_destroy is provided, the kernel will automatically call this callback to clean up user_data when the notification interface object is destroyed. If user_data_destroy is NULL, it is the user's responsibility to ensure that the user_data outlives the kernel objects. Notifications can occur even as kernel objects are deleted, so care has to be taken to ensure safe unwinding.

== Data Members

[cols="1,4"]
|===
| Name| Description
| xref:btck_NotificationInterfaceCallbacks/block_tip.adoc[`block_tip`] 
| The chain's tip was updated to the provided block entry.
| xref:btck_NotificationInterfaceCallbacks/fatal_error.adoc[`fatal_error`] 
| An unrecoverable system error encountered by the library.
| xref:btck_NotificationInterfaceCallbacks/flush_error.adoc[`flush_error`] 
| An error encountered when flushing data to disk.
| xref:btck_NotificationInterfaceCallbacks/header_tip.adoc[`header_tip`] 
| A new best block header was added.
| xref:btck_NotificationInterfaceCallbacks/progress.adoc[`progress`] 
| Reports on current block synchronization progress.
| xref:btck_NotificationInterfaceCallbacks/user_data.adoc[`user_data`] 
| Holds a user‐defined opaque structure that is passed to the notification callbacks. If user_data_destroy is also defined ownership of the user_data is passed to the created context options and subsequently context.
| xref:btck_NotificationInterfaceCallbacks/user_data_destroy.adoc[`user_data_destroy`] 
| Frees the provided user data structure.
| xref:btck_NotificationInterfaceCallbacks/warning_set.adoc[`warning_set`] 
| A warning issued by the kernel library during validation.
| xref:btck_NotificationInterfaceCallbacks/warning_unset.adoc[`warning_unset`] 
| A previous condition leading to the issuance of a warning is no longer given.
|===



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