[#txindex-02-CreateKeyPrefix]
= xref:txindex-02.adoc[txindex]::CreateKeyPrefix
:relfileprefix: ../
:mrdocs:

Compute the txid‐hash key prefix for a transaction.

== Synopsis

Declared in `<index/txindex_key.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:txindex-02/TxHashKeyPrefix.adoc[TxHashKeyPrefix]
CreateKeyPrefix(
    xref:SipHasher13UJ.adoc[SipHasher13UJ] const& hasher,
    xref:Txid.adoc[Txid] const& txid);
----

== Return Value

The truncated hash prefix used in the hashed txindex key.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *hasher*
| Salted SipHash used to hash the txid.
| *txid*
| Transaction id to hash.
|===


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