[#SignPSBTInput]
= SignPSBTInput
:mrdocs:

Signs a PSBTInput, verifying that all provided data matches what is being signed.

== Synopsis

Declared in `<psbt.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
[[nodiscard]]
xref:util/Expected-0b.adoc[util::Expected<void, common::PSBTError>]
SignPSBTInput(
    xref:SigningProvider.adoc[SigningProvider] const& provider,
    xref:PartiallySignedTransaction.adoc[PartiallySignedTransaction]& psbt,
    int index,
    xref:PrecomputedTransactionData.adoc[PrecomputedTransactionData] const* txdata,
    xref:common/PSBTFillOptions.adoc[common::PSBTFillOptions] const& options,
    xref:SignatureData.adoc[SignatureData]* out_sigdata = nullptr);
----

== Description

txdata should be the output of PrecomputePSBTData (which can be shared across multiple SignPSBTInput calls). If it is nullptr, a dummy signature will be created.

== Return Value

Success, or a PSBTError describing why signing failed.

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

[cols="1,4"]
|===
| Name| Description
| *provider*
| The source of keys and scripts used to sign.
| *psbt*
| The PSBT containing the input.
| *index*
| The index of the input to sign.
| *txdata*
| Precomputed transaction data, or nullptr for a dummy signature.
| *options*
| Options controlling how fields are filled.
| *out_sigdata*
| Optional output receiving the resulting signature data.
|===


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