[#ChainstateManager-ActivateSnapshot]
= xref:ChainstateManager.adoc[ChainstateManager]::ActivateSnapshot
:relfileprefix: ../
:mrdocs:

Construct and activate a Chainstate on the basis of UTXO snapshot data.

== Synopsis

Declared in `<validation.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
[[nodiscard]]
xref:util/Result.adoc[util::Result<CBlockIndex*>]
ActivateSnapshot(
    xref:AutoFile.adoc[AutoFile]& coins_file,
    xref:node/SnapshotMetadata.adoc[node::SnapshotMetadata] const& metadata,
    bool in_memory);
----

== Description

Steps:

* Initialize an unused Chainstate.
* Load its `CoinsViews` contents from `coins_file`.
* Verify that the hash of the resulting coinsdb matches the expected hash per assumeutxo chain parameters.
* Wait for our headers chain to include the base block of the snapshot.
* "Fast forward" the tip of the new chainstate to the base of the snapshot.
* Construct the new Chainstate and add it to m_chainstates.

== Return Value

The base block index of the activated snapshot, or an error.

[NOTE]
====
The return value https://en.cppreference.com/cpp/language/attributes/nodiscard[should not be discarded^].
====
== Parameters

[cols="1,4"]
|===
| Name| Description
| *coins_file*
| Serialized UTXO snapshot to load the new chainstate from.
| *metadata*
| Metadata describing the snapshot file.
| *in_memory*
| Whether the new chainstate's databases should be kept in memory only.
|===


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