[#node-BlockManager-GetFirstBlock]
= xref:node.adoc[node]::xref:node/BlockManager.adoc[BlockManager]::GetFirstBlock
:relfileprefix: ../../
:mrdocs:

Returns the earliest block with specified `status_mask` flags set after the latest block _not_ having those flags.

== Synopsis

Declared in `<node/blockstorage.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
[[requires_capability(0x7f2e1b0997e8), requires_capability(0x7f2e26d1af48), requires_capability(0x7f2e375e1028), requires_capability(0x7f2e333683e8), requires_capability(0x7f2e3542f3d8), requires_capability(0x7f2e28a73f38)]]
xref:CBlockIndex.adoc[CBlockIndex] const&
GetFirstBlock(
    xref:CBlockIndex.adoc[CBlockIndex] const& upper_block,
    uint32_t status_mask,
    xref:CBlockIndex.adoc[CBlockIndex] const* lower_block = nullptr) const;
----

== Description

This function starts from `upper_block`, which must have all `status_mask` flags set, and iterates backwards through its ancestors. It continues as long as each block has all `status_mask` flags set, until reaching the oldest ancestor or `lower_block`.

== Return Value

A reference to the earliest block between `upper_block` and `lower_block`, inclusive, such that every block between the returned block and `upper_block` has `status_mask` flags set.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *upper_block*
| The starting block for the search, which must have all `status_mask` flags set.
| *status_mask*
| Bitmask specifying required status flags.
| *lower_block*
| The earliest possible block to return. If null, the search can extend to the genesis block.
|===

== Preconditions

* `upper_block` must have all `status_mask` flags set.
* `lower_block` must be null or an ancestor of `upper_block`


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